Introduction
The first Wnt gene was discovered in mouse mammary epithelial tumor cells and was termed int-1 . 1 In time, sequencing would reveal the drosophila homolog of the mouse int-1 proto-oncogene ( Dint-1 ) and the Drosophila segment polarity gene wingless ( Wg ) were identical. Moreover, the discovery that Dint-1 was homologous to Wg added to the notion that int/Wg played an important role in development. 2 The int/Wg family later became known as the Wnt family due to the fusion of the names wingless and integrated. 3 Multiple distinct Wnt signaling pathways have been identified to date, including the canonical (β-catenin-dependent) and the non-canonical (or β-catenin-independent) paths. Non-canonical Wnt signaling can be further divided into the planar cell polarity and Wnt/Ca 2+ paths. 4 As a result of the wide range of diverse biological functions attributed to Wnt signaling, dysregulations can lead to the development of many pathologies. In the past decade, the Wnt pathway has also emerged as a potential target in cancer, disease therapy, and tissue regeneration. While Wnt signaling has been studied for decades and numerous elucidations have been made in that time, there exists a need to compile this information in a cohesive, up-to-date summary. Therein, the purpose of this review is to summarize the current knowledge of Wnt in stem cells, Wnt pathway-associated diseases, and pharmacologic targeting of the Wnt pathway.
Overview of canonical Wnt signaling
The canonical path is the most thoroughly characterized Wnt pathway and is crucial for inducing cell proliferation, differentiation, maturation, and proper body-axis specification ( Fig. 1 ). Canonical Wnt signaling is activated via the Wnt1 class ligands, which include Wnt2, Wnt3, Wnt3a, and Wnt8a. 5 , 6 Canonical Wnt ligands bind to the N-terminal extracellular cysteine-rich domain of Fz or Fzd (Frizzled) receptors as well as LRP5/6 (low-density-lipoprotein-receptor-related proteins 5 and 6) coreceptors. When active, canonical Wnt signaling stimulates target gene transcription via the binding of β-catenin to the TCF/LEF (T-cell factor/lymphoid enhancer factor) family of transcription factors. 7 Moreover, the mammalian TCF/LEF family is composed of four nuclear factors, TCF1, LEF1, TCF3, and TCF4. 8 For a full explanation of the detailed canonical and two non-canonical Wnt signaling pathways, please refer to our other work: The Wnt signaling pathway: Multilayered mediators, molecular basis of signaling circuitry and crosstalk with other major signaling pathways ( Fig. 1 ).
In the absence of Wnt ligands, a destruction complex is responsible for clearing β-catenin ( Fig. 2 ). The destruction complex is composed of adenomatous polyposis coli (APC) protein, Axin, serine/threonine kinase glycogen synthase kinase 3 (GSK-3), casein kinase 1 (CK1), the E3-ubiquitin ligase β-TrCP, and protein phosphatase 2A (PP2A). CK1 first phosphorylates (or “primes”) β-catenin at the Ser45 residue, enabling GSK-3 to phosphorylate the Ser33, Ser37, and Thr41 residues, creating a binding site for β-TrCP. 9 Phosphorylated Ser37 and Ser33 are recognized by the F-box protein β-TrCP for ubiquitination ( Fig. 2 ). 10 β-TrCP complexes with Skp1/cullin machinery to ubiquitinate β-catenin, which leads to its proteasomal degradation. 9
In the absence of β-catenin, the TCF/LEF complex is bound to the transducing-like enhancer protein (TLE/Groucho), which recruits histone deacetylases (HDACs) to repress gene transcription. 11 In the presence of Wnt ligands, Fz receptors and LRP5/6 coreceptors recruit the disheveled protein (Dsh/Dvl), phosphorylating the cytoplasmic tails of LRP5/6. LRP5/6 binds Axin, causing the destruction complex to disassemble and freeing the β-catenin. β-Catenin is stabilized as a result, accumulating in the cytoplasm and translocating to the nucleus to regulate target gene expression. 7 , 12 , 13 , 14 , 15 β-Catenin binding to TCF/LEF displaces TLE/Groucho and recruits histone-modifying activators such as CBP/p300, Pygo, BCL9, and BRG1. 11
Overview of non-canonical Wnt signaling
Non-canonical Wnt signaling functions independent of the cytoplasmic stabilization of β-catenin and is involved in processes such as cell polarization and migration. Non-canonical Wnt is characterized by two unique paths: the Wnt/planar cell polarity (PCP) pathway and the Wnt/Ca 2+ pathway. Moreover, non-canonical Wnt is known to utilize the Wnt5a type ligands which include Wnt4, Wnt5a, Wnt5b, Wnt6, Wnt7a, and Wnt11. 4 , 5 The Wnt/PCP pathway is an important regulator of cellular polarization for proper development and function. 16 On the other hand, the Wnt/Ca 2+ path has been characterized as an important organizer during early embryogenesis. 17
In the Wnt/PCP cascade ( Fig. 3 ), Wnt signaling is transduced through Fzd receptors and co-receptors such as protein tyrosine kinase 7 (PTK7), tyrosine kinase-like orphan receptor (ROR1/ROR2), and tyrosine kinase related receptor (RYK). 18 , 19 , 20 Additionally, the Wnt/PCP pathway is also known to utilize the Celsr1 and Vangl2 receptors, although the exact ligand-receptor binding interactions have not been fully clarified. 21 As a result of Wnt binding to Fzd receptors, Dvl becomes phosphorylated, leading to Inversin (Invs) recruitment. 22 Smad ubiquitination regulatory factor (Smurf) is then recruited by the phosphorylated Dvl to Par6. Smurf is responsible for the ubiquitination of Wnt/PCP antagonizing Prickle, thereby targeting Prickle for proteasomal destruction. 23 Dvl also associates with DAAM (Disheveled-associated activator of morphogenesis), which mediates actin polymerization through the activation of profilin protein. 24 Dvl and DAAM, respectively, stimulate the activation of the GTPases RHOA and Rac1. 25 RHOA, in turn, activates ROCK (Rho kinase). ROCK mediates actin polymerization through its activation of mitogen-activated protein kinase (MRLC). 26 Moreover, Rac1 activates JNK (c-Jun N-terminal kinase) which phosphorylates c-Jun, resulting in c-Jun activation. 27 Furthermore, c-Jun, a well-characterized protein of the activator protein-1 (AP-1) complex, 28 moves to the nucleus in order to initiate target gene expression. 29 JNK also phosphorylates and activates CapZ-interacting protein (CapZIP), which serves to remodel actin filament assembly. 30 Altogether, Wnt/PCP effectors influence the cytoskeletal rearrangements needed for cell polarity and cell motility.
The Wnt/Ca 2+ pathway functions to regulate endoplasmic reticulum (ER) calcium release in order to control intracellular calcium levels ( Fig. 4 ). Wnt/Ca 2+ signaling is primarily initiated by the binding of the Wnt5a ligand and Fzd2 receptor. 31 Wnt/Fzd interaction, along with the Ror1/Ror2 co-receptor, 32 leads to the co-stimulation of Dvl and heterotrimeric G-protein to activate phospholipase C (PLC). 33 PLC cleaves phosphatidylinositol-4,5-bisphosphate (PtdInsP2) into diacylglycerol (DAG) and inositol-1,4,5-trisphosphate (InsP3/IP3). DAG activates protein kinase C (PKC) to stimulate CDC42. 21 CDC42 serves to mediate cellular polarity during development. 34 , 35 InsP3 binds to InsP3R receptors on the ER surface, initiating the release of Ca 2+ ions, thereby increasing cytoplasmic levels of calcium. 21 The calcium sensor stromal interaction molecule 1/2 (STIM1/2) detects decreases in lumen ER Ca 2+ concentration before activation of the Orai family proteins to mediate store-operated Ca 2+ entry. 36 Sarcoplasmic/ER Ca 2+ ATPases (SERCAs) also pump Ca 2+ back from the cytosol into the ER. 21 Increased cytoplasmic Ca 2+ concentration activates the phosphatase calcineurin as well as calcium calmodulin-mediated kinase II (CAMKII). Calcineurin activates the nuclear factor of activated T cells (NFAT), leading to target gene transcription. 37 , 38 CAMKII activates TGFβ-activated protein kinase 1 (TAK1), 39 which then activates Nemo-like kinase (NLK). NLK is responsible for the phosphorylation of TCF, thereby inhibiting the formation of the B-catenin/TCF complex and preventing gene transcription. 40
Wnt secretion and extracellular regulators
The human genome encodes 19 glycoprotein Wnt ligands, 350–400 amino acids in length, that are capable of binding Fzd receptors to trigger complex signaling cascades. 14 , 41 The specificity of the Wnt ligands depends on the cell-specific context and the receptors and downstream molecules expressed. 42 In addition to glycosylation, Wnt proteins also undergo post-translational palmitoylation via the membrane-bound O-acyltransferase Porcupine (PORCN) in the endoplasmic reticulum. 43 For example, Wnt3a requires Porc-dependent palmitoylation at Ser209 prior to secretion. 44 In order to be secreted, Wnt proteins must also be bound to the carrier protein Wntless (Wls), also known as Evenness interrupted (Evi), and escorted from the Golgi apparatus to the plasma membrane for secretion. 45 After delivering Wnt proteins to the plasma membrane, the retromer complex recycles Wls from endocytic vesicles for return back to the Golgi. 46
A number of extracellular regulators capable of modulating Wnt signaling have been identified. Wnt antagonists include secreted Frizzled-related proteins (sFRP), Wnt inhibitory factor (Wif-1), Cerberus, Dickkopf (DKK), and Wise/sclerostin (SOST) families. 47 Dickkopf family proteins and SOST bind to the LRP5/6 co-receptor to prevent the binding to Wnt. 48 , 49 Wif-1, Cerberus, and members of the sFRP family sequester Wnts in the extracellular space to prevent the triggering of signaling. 50 , 51 , 52 On the other hand, two families of proteins are known to activate canonical Wnt signaling: Norrin and R-spondin (Rspo). 47 Rspo ligands potentiate Wnt signaling through interaction with LGR4/5 and inhibition of Rnf43/Znrf3 (a transmembrane E3 ubiquitin ligase) mediated degradation of Fzd. 53 , 54 , 55 Interestingly, it was recently demonstrated that Rspo2 and Rspo3, but not Rspo1 or Rspo4, can potentiate WNT/β-catenin signaling in the absence of LGRs. 56 Furthermore, Norrin is a unique non-Wnt ligand that binds to Fz receptor subtype-4 (Fz4) in order to activate the canonical pathway in an LRP5-dependent manner. 57
Wnt signaling in stem cell self-renewal and lineage differentiation
Stem cells are a group of unspecialized cells that usually arise from a single cell and are responsible for tissue development and regeneration. 58 They are capable of self-renewal into at least one identical daughter cell, preserving the stem cell pool throughout life. Moreover, self-renewal involves cell division accompanied by maintenance of an undifferentiated state. 59 Stem cells are organized at the apex of a developmental hierarchy and are capable of differentiation towards more specialized cell types. Through the process of differentiation, developmental potency is reduced at each step of maturity. 60 As a result of their biological capabilities, stem cells have been extensively studied and characterized due to widespread interest in their use for disease research. 61 , 62 , 63 In this review, we discuss the current evidence that canonical and non-canonical Wnt signaling cascades play important roles in stem cells of various tissues.
Wnt signaling in embryonic stem cells
Embryonic stem cells (ESCs) are pluripotent cells, commonly derived from the inner cell mass of pre-implantation embryos, that are capable of generating all 3 germ layers (ectoderm, endoderm, and mesoderm). 64 Moreover, ESCs exist in two distinct states of pluripotency. Naïve pluripotent stem cells (PSC) correspond to an earlier developmental state and resemble cells from the preimplantation embryo. By contrast, primed PSCs resemble a later developmental stage found in the post-implantation epiblast. 65 Xu et al recently discovered naïve human ESCs (hESCs) secrete Wnts that activate autocrine or paracrine Wnt/β-catenin signaling to promote efficient self-renewal as well as prevent the transition to the primed state. The authors demonstrated that recombinant canonical Wnt3a, but not non-canonical Wnt5a, rescues self-renewal in naïve hESCs affected by inhibited Wnt secretion. While Wnt/β-catenin signaling is an important factor regulating the self-renewal of naïve hESCs, it was not required for the expression of pluripotency markers. Furthermore, it was discovered that the inhibition of Wnt/β-catenin signaling induced protein and metabolic changes associated with the naïve to primed state transition in hESCs. 66
The role of Wnt signaling in ESC self-renewal and differentiation remains complex. Many studies have reported that Wnt/β-catenin signaling is a key player in mouse ESC (mESC) self-renewal and maintenance of pluripotency. 67 , 68 , 69 However, there are conflicting reports on the role of Wnt signaling in the self-renewal of human ESCs. Sato et al found that Wnt pathway activation by 6-bromoindirubin-3′-oxime (BIO), a pharmacological inhibitor of glycogen synthase kinase-3β (GSK3β), sufficiently maintained self-renewal in both hESCs and mESCs. Canonical Wnt activation also maintained an undifferentiated phenotype in both types of ESCs, as well as preserved the expression of the pluripotent state-specific transcription factors Oct-3/4, Rex-1, and Nanog. 70 By contrast, Dravid et al demonstrated that the addition of recombinant Wnt3a to undifferentiated human ESCs led not only to cell proliferation but also differentiation. Subsequent reporter assays revealed Wnt/β-catenin-mediated transcriptional activation was minimal in undifferentiated hESCs but greatly up-regulated during differentiation. 71 Similarly, further study has demonstrated that activation of Wnt/β-catenin signaling in hESCs does not promote self-renewal, but rather, drives the induction of mesoderm lineage genes. 72 Consistent with these findings, other studies have also shown Wnt signaling is required for ESC meso/endodermal differentiation. 73 , 74
The embryonic stem cell cycle is unique in that it is composed mainly of the S phase with a short G1 phase. Evidence suggests that as ESCs differentiate, their cell cycle structure changes to incorporate a significantly longer G1 phase. 75 , 76 De Jaime-Soguero et al sought to determine whether canonical Wnt/TCF1 activity controls the cell cycle of mESCs. The authors activated the Wnt pathway by treating mESCs with the GSK3β inhibitor BIO, and in contrast to the known mitogenic effects of canonical Wnt signaling on somatic stem cells, 77 they found that canonical Wnt induced the expression of negative regulators of the cell cycle. This occurred via TCF1 recruitment at the promoter regions of cell cycle repressor genes such as the Ink4/Arf locus . Wnt/TCF1 signaling in mESCs, thereby increasing the expression of tumor suppressors such as Cdkn2a (p16Ink4a, p19Arf) and Cdkn2b (p15Ink4b), leading to a reduction of cell proliferation and an increase in the number of cells in G1. 78 Taken together, these findings suggest that Wnt/TCF1 activity triggers an antiproliferative effect in mESCs without perturbing pluripotency. Evenness interrupted (Evi), also known as wntless, is a Wnt-binding protein required for the secretion of Wnt ligands. 79 Through the generation of Evi-deficient and Evi-overexpressing mESCs (modeling Wnt depleted and overexpressed lines respectively), it was discovered that autocrine Wnt signaling is necessary for mESC survival and genomic stability. Thereby, the inhibition of autocrine Wnt signaling in mESCs resulted in mitotic defects, suggesting Wnt signaling plays an important role in chromosomal stability. 80
Wnt signaling in hematopoietic stem cells
Hematopoietic stem cells (HSCs) reside primarily in the bone-marrow (BM) microenvironment and give rise to a variety of blood and immune cells. 81 Interactions between HSCs and the niche constituents regulate the careful balance between self-renewal and lineage differentiation. Hematopoietic stem cells and progenitor cells (HSPCs) are divided into three multipotent populations: long-term hematopoietic stem cells (LT-HSCs), short-term hematopoietic stem cells (ST-HSCs), and multipotent progenitor cells (MPPs). MPP populations give rise to two oligopotent progenitor cell lines, common lymphoid progenitors (CLPs) and common myeloid progenitors (CMPs). 82 Moreover, hematopoietic development occurs in two distinct phases: primitive and definitive. Primitive hematopoiesis occurs early in development and primarily generates nucleated embryonic erythrocytes that sustain an organism during early development. On the other hand, definitive hematopoiesis gives rise to all HSPCs, which are the source of mature blood and immune cells. 83 Sturgeon et al conducted a study of Wnt/β-catenin in human pluripotent stem cells (hPSCs) to discern the role of Wnt signaling in deriving primitive and definitive hematopoietic progenitors in vitro . Measured by T-cell differentiation potential, they found Wnt signaling inhibits primitive hematopoiesis but appears to enhance definitive hematopoiesis. 84 Interestingly, studies of mouse embryonic stem cells revealed Wnt signaling stimulates the specification of the nucleated primitive erythroid lineage within the blood islands of the yolk sac. Primitive erythrocytes are the predominant circulating blood cells in the fetus until enucleated erythrocytes can be produced by the fetal liver. 85 , 86
A number of studies have implicated both the canonical and non-canonical Wnt signaling pathways in the maintenance of HSCs ( Fig. 5 ). Canonical Wnt signaling via Wnt3a has been shown to play a role in HSC self-renewal capability, whereby, Wnt3a deficiency led to reductions in both the number of HSCs in fetal mouse liver and long-term repopulation capacity, as measured by secondary transplantation assays. 87 It was found that the overexpression of activated β-catenin expanded the pool of HSCs in culture. By contrast, the ectopic expression of Wnt pathway inhibitors, an Fz ligand-binding domain or Axin, reduced both HSC growth in vitro and reconstitution in vivo . 88 Sugimura et al investigated the role of non-canonical Wnt signaling in HSC self-renewal and maintenance via Flamingo ( Fmi ) and Frizzled ( Fz ) 8 knockout. Fmi is known to regulate Fz8 distribution at the interface between HSCs and N-cadherin + osteoblasts that enrich osteoprogenitors. They discovered that Fmi and Fz8 knockout resulted in the decline of quiescent LT-HSC populations, indicating non-canonical Wnt signaling plays an important role in the maintenance of LT-HSCs. Mechanistically, the authors determined that non-canonical Wnt signaling, mediated by Fmi and Fz8, maintains quiescent long-term HSCs by suppressing the Ca 2+ NFAT interferon-gamma (IFNγ) pathway and by antagonizing canonical Wnt signaling. 89 Moreover, Wnt5a has been shown to induce HSC quiescence through the activation of the non-canonical pathway as well as inhibit Wnt3a-mediated canonical Wnt signaling. 90 An additional study revealed Wnt5a acts through the Ryk receptor to induce HSC quiescence and enhance short-term and long-term hematopoietic repopulation. 91 Further study of the non-canonical Ryk receptor found that Ryk-deficient HSCs from fetal liver exhibited diminished quiescence, leading to proliferation-induced apoptosis and decreased self-renewal. 92
The role of Wnt signaling in lymphopoiesis is an area of interest. Studies have shown that Wnt/β-catenin signaling and β-catenin/TCF interaction are required for normal T-cell development. 93 , 94 Similarly, Hossain et al demonstrated the significance of the interaction between β-catenin and TCF in transgenic mice expressing ICAT (an inhibitor of β-catenin and TCF). ICAT expression resulted in increased susceptibility of thymocytes and activated T-cells to apoptosis. These results suggest that in adult mice, disruption of β-catenin and TCF interaction hinders T-cell survival. 95 Malhotra et al reported differing effects of canonical and non-canonical Wnt ligands on B-cell development. Canonical Wnt signaling, through Wnt3a, inhibited B-cell lymphopoiesis and promoted the retention of HSC markers. On the other hand, Wnt5a, which may oppose the canonical path or act via the non-canonical cascade, increased B-cell lymphopoiesis. 96 When coupled to β-catenin, lymphoid enhancer-binding factor 1 (LEF1) functions as an important nuclear mediator of Wnt signaling. 97 Moreover, LEF1 has been shown to be transiently expressed during the early stages of B lymphocyte differentiation. 98 It was also discovered that Wnt5a regulates B-cell proliferation and acts as a tumor suppressor through the non-canonical Wnt/Ca 2+ pathway. Wnt5a hemizygous mice developed myeloid leukemias and B-cell lymphomas and displayed loss of Wnt5a function in tumor tissue. Moreover, the deletion or loss of expression of the Wnt5a gene was noted in human primary leukemias, highlighting the role of Wnt5a as a tumor suppressor in hematopoietic malignancies. 99 Wilson et al showed that conditional elimination of canonical Wnt effector c-Myc in mouse BM resulted in cytopenia, the accumulation of self-renewing HSCs in situ , and failure of normal HSC differentiation. 100 These results suggest c-Myc controls the balance between HSC self-renewal and differentiation in the BM niche.
Interestingly, while several studies have implicated canonical Wnt signaling in lymphopoiesis, others report no defects following the deletion of β-catenin. Using the Mx1-Cre system, Cobas et al inactivated β-catenin in murine BM progenitor cells. Surprisingly, they observed that BM chimeras showed no defects in hematopoiesis or lymphopoiesis despite the absence of β-catenin. 101 In a subsequent experiment, Koch et al examined whether the persistence of normal hematopoiesis and lymphopoiesis could be explained by the compensatory function of γ-catenin, a close homolog of β-catenin. However, double-deficient β- and γ-catenin HSCs did not exhibit an impaired ability to differentiate into all myeloid, erythroid, and lymphoid lineages. 102 In contrast to a previous study, these results suggested canonical Wnt signaling (through β- or γ-catenin) is not essential for hematopoiesis or lymphopoiesis. In accordance with this notion, Jeannet et al also showed that hematopoiesis and lymphopoiesis were found to be normal in the absence of β- and γ-catenin. However, unexpectedly, ex vivo reporter assays showed Wnt signal transmission was maintained in double-deficient HSCs, 103 suggesting redundancy of Wnt signaling molecules or perhaps that HSCs may still transduce canonical Wnt signals despite the loss of β- and γ-catenin via alternative or compensatory pathways.
Wnt signaling mesenchymal stem cells
Mesenchymal stem cells (MSCs) are multipotent stromal cells found in several tissues such as bone, cartilage, and fat. MSCs have the ability to self-renew and also exhibit multilineage differentiation into osteocytes, chondrocytes, and adipocytes. 104 Human MSCs are commonly isolated from adult tissues, namely from bone marrow and adipose. 105 , 106 MSC multi-lineage specification is controlled by several pathways, one of which is Wnt signaling ( Fig. 6 ). 107 Shen et al showed the overexpression of microRNA 1–2 in mouse-derived bone-marrow MSCs led to their differentiation into cardiomyocytes via the activation of Wnt/β-catenin signaling. 108 Wnt signaling also plays an important role in the regulation of chondrogenesis. Noncanonical Wnt signaling via Wnt5a was shown to be important to the chondrogenic differentiation of MSCs. In a rabbit model, Wnt5a enhanced cartilage formation, collagen fiber rearrangement, and glycosaminoglycan and collagen deposition in vivo . 109 Misexpression of Wnt5a in developing chicken limb resulted in a delay of chondrocyte maturation as well as growth plate shortening. 110 Wnt3a plays a dual role in modulating chondrogenesis. When acting via the canonical Wnt pathway, Wnt3a promotes MSC proliferation. By contrast, Wnt3a inhibits MSC chondrogenesis via the CaMKII-mediated non-canonical Wnt pathway. 111
Wnt signaling is an important regulator of osteoblast differentiation and skeletal development ( Fig. 6 ). Sclerostin is a small protein expressed by the SOST gene located on the chromosomal region 17q12-21 which codes for sclerostin. Expressed by mature osteocytes but not by early osteocytes or osteoblasts, sclerostin binds to the Wnt co-receptors LRP5/6, thereby antagonizing Wnt signaling with the effect of inhibiting the bone formation and indirectly promoting bone resorption. 49 , 112 The deletion of β-catenin in early osteoblast progenitors and precursors led to a failure of osteoblast differentiation as well as a conversion to a chondrocyte fate. 113 Studies have found that Wnt/β-catenin signaling via the Wnt10b ligand facilitates osteogenesis and increases bone mass, as supported by findings that the deletion of Wnt10b leads to the reduction of trabecular bone mass, bone mineral density, and serum osteocalcin. 114 , 115 It was also revealed that Wnt10b-null mice exhibit age-dependent loss of bone mass as well as a reduction in the number of bone marrow-derived mesenchymal progenitors. 116
Wnt3a and Wnt1 are also capable of stimulating osteoblastogenesis through β-catenin activation. 117 The canonical Wnt pathway is known to up-regulate the expression of the Cbfa1/Runx2 transcription factor required for osteoblastogenesis. 118 Wnt7a enhances the differentiation of MSCs into osteoblasts via enhancing TCF-1 binding to the promoter region of Runx2. 119 Wnt11 increases the expression of Rspo2 as well as osteoblast-associated genes Dmp1 (dentin matrix protein 1), Phex (phosphate-regulating endopeptidase homolog), and Bsp (bone sialoprotein). 120 Moreover, β-catenin deletion from differentiated osteoblasts has been shown to lead to osteopenia. By contrast, Wnt/β-catenin signaling regulates the osteoblast expression of osteoprotegerin, an inhibitor of osteoclast differentiation and function. 121 Axin2 -knockout mice experienced significantly increased trabecular bone mass, osteoblast proliferation, along with decreased osteoclast formation. These results demonstrate the negative regulation of bone remodeling by Axin2. 122 Interestingly, non-canonical Wnt5a cooperates with Wnt/β-catenin signaling to promote osteoblastogenesis via the up-regulation of Lrp5/6 in osteoblast lineage cells. 123
Crosstalk between the bone morphogenetic protein (BMP) and Wnt/β-catenin signaling pathways stimulates osteoblast differentiation and bone formation. 124 Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-beta (TGF-β) family of cytokines and are vital in embryogenesis and homeostasis, and are known to induce bone formation. 125 BMP2 stimulates LRP5 expression and inhibits β-TrCP expression, leading to an increase in β-catenin levels in osteoblasts and the promotion of osteogenic differentiation. BMP2 also increases expression of the canonical Wnt ligands Wnt1, Wnt3a, and Wnt4 and exhibits a cooperative effect with Wnt3a to increase transcription of osteogenic genes ( Id1 , Dlx5 , Msx2 , Osx , and Runx2 ). 126 , 127 Furthermore, Wnt11 is known to promote the BMP-induced expression of alkaline phosphatase and mineralization. 120 Tang et al determined Wnt3a and BMP9 act synergistically to induce alkaline phosphatase (ALP) activity in MSCs. The knockdown of β-catenin also showed that the BMP9-induced osteogenic differentiation of MSCs depended on functional canonical Wnt signaling. 128 BMP signaling may also restrict Wnt signaling through induction of SOST, as He et al found that BMP receptor type 1a (BMPr1a) induces the expression of SOST to limit cancellous bone accrual. 129
The formation of osteoblasts (osteogenesis) occurs at the expense of adipocyte differentiation (adipogenesis) and is regulated by canonical Wnt/β-catenin signaling. Wnt10b was found to shift cell fate toward the osteoblast lineage by induction of the osteoblastogenic transcription factors Runx2, Dlx5, and osterix. Moreover, Wnt10b also suppresses the adipogenic transcription factors peroxisome proliferator-activated receptor (PPARγ) and CCAAT/enhancer-binding protein a (C/EBPa). 115 , 130 The non-canonical Wnt5a ligand inhibits PPARγ activation, thereby suppressing adipogenesis and promoting the osteogenic differentiation of MSCs. Wnt5a deficiency in osteoblast-lineage cells in mice has been shown to cause low bone mass. 123 Prior to differentiation into mature adipocytes, MSCs must first differentiate into an intermediate cell type called preadipocytes. 131 Evidence suggests Wnt signaling promotes stem cell maintenance, rather than differentiation, of preadipocytes in adipose tissue, with Wnt10a and Wnt6 ligands shown to have similar effects. Cawthorne et al demonstrated that overexpression of Wnt10a resulted in stabilized β-catenin, suppression of preadipocyte differentiation as well as the stimulation of osteoblast formation. The authors found that the knockdown of endogenous Wnt6 is associated with greater preadipocyte differentiation and impaired osteoblastogenesis. 132 Furthermore, human preadipocytes secrete the Wnt antagonist Dkk1 to promote differentiation into adipocytes during early adipogenesis. 133 Pygo2 is a nuclear component of Wnt signaling believed to promote β-catenin-LEF1/TCF transcriptional activation. 134 Xie et al identified that Pygo2 expression and Wnt/β-catenin signaling declined during preadipocyte differentiation into adipocytes. Furthermore, the authors demonstrated that ectopic expression of Pygo2 reduced adipocyte differentiation. 135 Song et al sought to determine whether interrupting Wnt signaling via knockout of β-catenin from osteoblasts would promote bone marrow adiposity. The authors conducted knockout of β-catenin in mouse preosteoblasts and conducted lineage tracing, both in vivo and in vitro , to find that the loss of β-catenin from preosteoblasts caused a cell-fate shift of these cells from osteoblasts to adipocytes. Thereby, the observed cell-fate switch contributed to an increase in bone marrow adiposity and low bone mass in knockout mice. 136
By contrast, Wnt inhibition has been shown to play a role in adipogenesis. The Wnt/β-catenin inhibitor sFRP1 is endogenously expressed by mature adipocytes in human adipose tissue and several sFRPs are associated with adipocyte dysfunction in obesity. 137 Mori et al demonstrated that sFRP5 inhibition of Wnt signaling in a mouse model suppressed adipocyte mitochondrial metabolism to stimulate maximal adipocyte growth. By contrast, the authors found that mice lacking sFRP5 were resistant to adipocyte growth despite a diet intended to induce obesity. 138 Increased levels of circulating sFRP2 have been linked to increased adipose tissue mass as well as vascular endothelial growth factor (VEGF) expression, suggesting sFRP2 may play a role in regulating adipose tissue blood supply and expansion. 139 Lagathu et al discovered that sFRP1 expression in human adipose tissue peaked in patients with mild obesity, but gradually fell in those with morbidly obese. 140 Furthermore, a novel role for Axin2 in adipogenesis has also been described, as it was discovered that the adipogenic transcription factor PPARγ transcriptionally activates the destruction complex member Axin2, thereby impairing Wnt signaling via β-catenin degradation. 141
Wnt signaling intestinal stem cells
The intestine is the body's primary site of nutrient uptake. Furthermore, intestinal epithelial cells greatly contribute to the maintenance of the symbiotic relationship between gut microbiota and the host by constructing mucosal barriers. 142 , 143 The single-layered intestinal epithelium is exposed to continuous mechanical, chemical, and biological insults and necessary tissue replenishment is fueled by continuously dividing intestinal stem cells (ICSs) that reside at the bottom of crypts. 144 The Wnt target gene and transmembrane receptor, Lgr5, has been identified as a stem cell marker for cycling crypt base columnar cells (CBCs). 145 CBCs may either self-renew or give rise to specialized cell types (including the absorptive enterocytes and secretory goblet cells, Paneth cells, and enteroendocrine cells). 146 Moreover, CBCs generate rapidly proliferating transit-amplifying (TA) cells that move upwards from the crypt base. During their upward migration, TA cells differentiate into specialized cell lineages, eventually moving from the crypt area to the villus. 147 A notable exception to this upward migration is the antimicrobial Paneth cell, which travels downward to the base during its differentiation. 148 Usually located at the +4 position from the crypt base, label-retaining cells (LRCs) are functionally distinct from crypt base stem cells. LRCs are slow-cycling, quiescent stem cells that have been shown to be precursors of the secretory Paneth and enteroendocrine cell lineages. Moreover, LRCs are capable of rapid proliferation following damage. 149
The Wnt pathway is an important regulator of crypt homeostasis, as active Wnt signaling is believed to stimulate crypt stem cell proliferation ( Fig. 7 ). 150 The loss of Wnt effector TCF4 leads to the depletion of the intestinal stem cell compartment, as mice lacking TCF4 were born with intestinal epithelium composed entirely of differentiated, non-dividing villus cells. 151 Consistent with these findings and in support of the notion that canonical Wnt signals are crucial for ISC homeostasis, ectopic expression of the Wnt inhibitor Dkk1 in transgenic mice led to the loss of Lgr5-expressing crypt stem cells as well as cells of the secretory lineages. 152 On the other hand, constitutive activation of the B-catenin/TCF4 complex via the loss of the APC tumor suppressor transforms the colonic epithelium, leading to colorectal carcinogenesis. 153 Crypt stem cells receive Wnt3 signals from neighboring daughter Paneth cells. Wnt3 from Paneth cells takes part in a signaling loop, as its expression is necessary for Paneth cell induction and maturation. 154 Moreover, culturing of Lgr5 stem cells with Paneth cells or exogenous Wnt3a has been shown to improve growth efficiency. 155 Interestingly, Farin et al demonstrated Wnt3 was dispersible for the maintenance of ISCs in vivo , suggesting the redundancy of Wnt signals from other sources in ISC homeostasis. By contrast, Wnt3 was required for the growth of cultured crypt organoids in vitro and exogenous Wnt2b supplementation, or co-culture with mesenchymal cells restored organoid growth. 156 Foxl1-expressing mesenchymal cells have been identified as an essential source of Wnt2b, Wnt4, Wnt5a, and Wnt-activating Rspo3 within the intestinal stem cell niche. Aoki and colleagues demonstrated that diphtheria toxin-mediated loss of Foxl1 cells resulted in the shortening of the intestine as well as decreased epithelial cell proliferation, villi length, and crypt depth. 157
Wnt signaling has also been implicated in intestinal epithelium regeneration following damage. CD44 is both a Wnt target gene and a positive regulator, modulating LRP6 membrane localization and activation. 158 CD44 knockout in intestinal epithelium had the effect of reducing Wnt/β-catenin signaling in the crypts, thereby reducing the expression of Wnt target genes as well as the number of Paneth cells. Moreover, mice lacking CD44 were given dextran sulfate sodium (DSS)-induced colitis and showed more severe intestinal inflammation and delayed regeneration. 159 With these results, Walter et al demonstrated the importance of CD44 and Wnt signal to intestinal epithelial regeneration. Inflammation frequently involves the production of tumor necrosis factor (TNF) by macrophages. 160 Bradford et al investigated the role of TNF signaling on Wnt/β-catenin-mediated intestinal stem and progenitor cell expansion in mouse models. They found that TNF-deficient mice exhibited impaired Wnt/β-catenin signaling, less intestinal epithelial cell proliferation, and increased cell apoptosis. TNF-deficient mice given chronic DSS-induced colitis also exhibited delayed ulcer healing and more mucosal inflammation, suggesting TNF and Wnt/β-catenin signaling contribute to the intestinal epithelial healing process following injury. 161 Besides, the ablation of epithelial WNT secretion diminished crypt expansion and ISC activation following rotavirus-induced epithelial cell injury, supporting the importance of Wnt signals in injury repair. 162 Additionally, stem cells ensure homeostasis and chromosomal stability by preserving telomere length through the use of telomerase reverse transcriptase (TERT). 163 Distinguished from the previously described Lgr5 + ISCs and +4 label-retaining stem cells, TERT + intestinal stem cells are slowly cycling cells capable of regeneration upon tissue injury and differentiation into all intestinal cell types. 164 Wnt signaling is crucial for TERT + stem cell activation in response to tissue injury, as β-catenin knockout has been shown to impair the irradiation-induced quiescence exit of TERT + stem cells, subsequently hindering intestinal epithelial regeneration. 165
Wnt signaling neural stem cells
Neural stem cells (NSCs) are a group of progenitor cells that give rise to the neural and glial cell components of the central nervous system (CNS). Adult NSCs may either undergo self-renewal to maintain the population of multipotent progenitors or they may differentiate into specialized cell types. Notably, NSCs are present in the CNS during embryonic development as well as in the adult brains of mammals. There are two neurogenic niches of the mammalian brain where NSCs are known to reside: the subventricular zone (SVZ) lining the lateral ventricles of the cerebral cortex and the subgranular zone (SGZ) in the dentate gyrus of the hippocampus. 166 , 167 , 168 Similarly, adult neurogenesis is restricted in the mammalian brain to the SGZ and SVZ regions. 169 A lineage-tracing experiment with Axin2 conducted on developing mouse embryos found that early ectodermal, neuroepithelial, and radial glial cells of the central nervous system are Wnt/β-catenin responsive. The authors also discovered that progeny from Axin2 + cells gave rise to populations of adult neural stem cells in the SVZ and dentate gyrus of the hippocampus. 170 These results are consistent with the notion Wnt signaling is involved in neural stem and progenitor cell development. It has also been reported that Wnt signaling is implicated in the self-renewal of neural progenitors. Kalani et al demonstrated the addition of soluble Wnt protein increased stem cell clonal outgrowth in cultures of multipotent Wnt-responsive cells isolated from the SVX of developing E14.5 mouse brain. Cell treatment with exogenous Wnt3a protein led to a twofold increase in colony initiation efficiency. In contrast, the addition of Wnt inhibitor Dkk resulted in a fivefold decrease in colony initiation, 171 indicating Wnt signaling is required for the efficient cloning and expansion of developing neural progenitors. TLX (also known as NR2E1) is a known regulator of NSC self-renewal and neurogenesis. 172 Qu et al demonstrated that TLX activates the canonical Wnt pathway via Wnt7a in adult mouse NSCs. Moreover, lentiviral transduction of active beta-catenin in neurogenic areas of TLX-null murine brains led to increased cell proliferation. By contrast, the deletion of Wnt7a or lentiviral transduction of Wnt inhibitor axin resulted in decreased proliferation of progenitor cells in adult neurogenic regions, 173 demonstrating the importance of Wnt/β-catenin to NSC proliferation and self-renewal.
Wnt signaling regulates multiple aspects of adult hippocampal neurogenesis. Rodent and human adult hippocampal progenitors (AHPs) both produce endogenous Wnt proteins as well as possess the intracellular components necessary to respond to Wnt signals. Moreover, the cessation of endogenous Wnt signaling via the application of Wnt antagonists, axin, or truncated cadherin (β-catenin sequestration), decreased the population of hippocampal progenitor cells while an increased fraction committed to a cell fate. 174 These findings suggest autocrine Wnt signaling serves to maintain multipotent rodent and human neural hippocampal progenitor cells. Moreover, Wnt5a has been shown to play a role in adult hippocampal neurogenesis by activating the non-canonical Wnt pathway. The Wnt5a ligand is expressed in the axons of developing rat hippocampal neurons, where it is involved in neural differentiation and synaptic modulation. 175 Moreover, Wnt5a knockdown was found to impair neuronal differentiation of hippocampal progenitors both in vivo and in vitro . Activated by the Wnt5a ligand, the non-canonical Wnt/JNK and Wnt/CaMKII pathways were found to be key players in the neuronal differentiation of progenitor cells in the adult hippocampus. 176 In addition, it was found that paracrine Wnt3 secreted from hippocampal astrocytes promoted neuronal differentiation via the canonical Wnt/β-catenin pathway. The overexpression of Wnt3 caused an increase in AHP neurogenesis in vitro and in vivo . Conversely, blocking Wnt3 signaling in AHPs reduced neurogenesis in vitro and abolished it in vivo . 177 A further study discovered the deletion of Wnt3a in developing mouse brains resulted in the under-proliferation of progenitor cells resulting in a tiny or altogether missing hippocampus. 178 Moreover, Okamoto et al showed that Wnt3 production by hippocampal astrocytes decreases with age and correlates with impaired neurogenic differentiation. 179 Together, these findings suggest Wnt signaling is crucial for the normal growth of the hippocampus.
Wnt signaling in epidermal stem cells
Skin is the largest organ in the body and is constituted of three primary layers, the epidermis, the dermis, and the hypodermis. Multipotent epidermal stem cells (SCs) reside in the stratum basalis (basal cell layer) of the epidermis as well as within hair follicles (HFs). 180 , 181 Wnt/β-catenin signaling has been shown to play a crucial role in epidermal SC development and maintenance. Neural induction is the developmental process by which cells from the ectoderm acquire a neural fate as opposed to an epidermal cell fate. 182 In a study of neural and epidermal fates in chick embryos, Edlund et al discovered that Wnt signaling leads to a block of neural specification and the induction of epidermal lineage. Specifically, the authors found Wnt signals block the response of ectoderm to fibroblast growth factor (FGF) signals, permitting the expression of bone morphogenetic proteins (BMPs) to direct cells toward an epidermal fate. On the other hand, a lack of exposure of ectoderm to Wnt signals permits cell response to FGFs, thereby inducing a neural fate. 183 Wnt signaling is also implicated in epidermal stratification. In a mouse model ablating GPR177, a trans-membrane cargo protein required for Wnt secretion, 184 Zhu et al demonstrated epidermal production of Wnts is essential for the formation of the spinous layer of the epidermis. Moreover, the authors found that signaling of epidermal Wnt to the underlying dermis activated a BMP-FGF signaling cascade required for the epidermal stratification process. 185
Hair is unique to mammals and serves several functions including thermoregulation, protection, and sensory activity. Hair follicles give rise to terminally differentiated keratinocytes, comprising the hair shaft. 186 HFs themselves develop from thickenings in ectodermal tissue called placodes (also known as hair germs or buds depending on the developmental stage). 187 HF morphogenesis can be broadly classified into three phases, induction, organogenesis, and cytodifferentiation. 188 Wnt/β-catenin plays a role during the induction phase early in HF morphogenesis as Wnt signals have been found to be critical in placode formation. To determine whether WNT signals are required for the initiation of follicular development, Andl et al ectopically expressed the Wnt inhibitor Dkk1 in the skin of transgenic mice. The authors found this resulted in a complete failure of placode formation. 189 Moreover, investigating the importance of Wnt/β-catenin in mouse fetuses, Atit et al found that dorsal hair placodes were absent in β-catenin loss-of-function mutants. 190 Together, these results support the notion that β-catenin is required for the induction of hair placodes.
HF regeneration occurs via repetitive cycles of growth (anagen), apoptosis-driven regression (catagen), and rest (telogen). 191 The bulge region of HFs, a convex protrusion of the outer root sheath in the most distal permanent portion of the follicle, houses multipotent bulge stem cells. Upon activation, bulge stem cells proliferate, forming the hair germ, and extend downwards to the dermal papilla at the base of the follicle. Activated matrix keratinocytes that have migrated out of the bulge to colonize the matrix area will terminally differentiate into cell lineages of the hair shaft and the inner root sheath. 186 The HF bulge is normally a Wnt-restricted environment during the telogen phase of the hair follicle cycle, with microarrays showing the expression of Wnt-inhibitory factors. Despite this, bulge stem cells express several Frizzled receptors (Fzd3, F2d7, and Fzd2), elucidating their potential to receive Wnt signals. 192 These findings could explain how bulge cells, in relative quiescence and in the absence of Wnt/β-catenin signals, may maintain an undifferentiated state.
Moreover, it was discovered that Wnt/β-catenin is a crucial player in bulge stem cell lineage. The absence of β-catenin in bulge stem cells led to their failure to differentiate into follicular keratinocytes. Instead, they adopted an epidermal phenotype. 193 Furthermore, LEF1 has been shown to be crucial for the development of hair follicles. 194 , 195 In a study of gain of function mutations and inducible loss of function mutations, Lowry et al demonstrated that β-catenin-mediated activation of LEF1/TCF complexes and subsequent up-regulation of target genes led to the conversion of transiently amplifying cells to activated cells of the newly developing hair follicle. 196 Wnt signaling is also involved in the promotion of the anagen growth phase. A study regulating β-catenin expression in the skin of a murine model showed that chronic β-catenin activation in telogen HFs resulted in an exaggerated anagen phase. On the other hand, transient activation of β-catenin in telogen follicles produced a normal anagen, indicating Wnt/β-catenin signaling has a critical role in the promotion of the telogen-anagen transition. 197
Wnt signaling in cancer stem cells
Cancer stem cells (CSCs) represent a subset of tumor cells that are capable of tumor initiation, stem cell-like self-renewal, proliferation, and aberrant differentiation to heterogeneous cancer cell types. 198 , 199 The CSC model remains somewhat controversial, as not all cancers express CSC markers. 200 CSCs are also unique among tumor cells as they are known to be resistant to many anti-cancer treatments. 201 , 202 CSCs exist at the top of the tumor cell hierarchy and reside in the CSC niche within the tumor microenvironment. The CSC niche, composed of bone marrow-derived stromal cells as well as normal tissues, 203 is responsible for maintaining CSC properties, providing protection from the immune system, and facilitating metastasis. 204 CSCs have been implicated in driving tumor metastasis by induction of the epithelial–mesenchymal transition (EMT). The transition to migratory mesenchymal cells allows for enhanced tumor invasion and secondary site colonization. 205 Another characteristic of CSCs is their utilization of similar signaling pathways and gene expression patterns as normal stem cells to promote malignant growth. 206 Aberrant regulation of canonical and non-canonical WNT signaling occurs in many human malignancies. 207 As a result, mutations to the Wnt pathway play important roles in the induction of various cancers. 11 Dysregulated Wnt/β-catenin signaling also plays a role in cancer cell resistance to cytotoxic chemotherapy. 208 , 209 In this portion of the review, we will discuss the evidence that Wnt signaling is an important regulator of CSC biology.
Leucine rich repeat containing G protein-coupled receptor 5 (LGR5) is a cell surface GPCR that binds R-spondin ligands and activates the Frizzled/LRP6 complex together with Wnt ligands. Thereby, LGR5 and R-spondin ligands function to modulate Wnt signaling. 210 LGR5 was recently identified as a CSC marker 211 and is known to be up-regulated in many human cancers such as breast, gastric, cervical, and colorectal cancers. 212 , 213 , 214 , 215 Notably, LGR5 was found to promote CSC self-renewal and tumorigenicity in breast cancer through activation of Wnt/β-catenin signaling. 212 Furthermore, elevated LGR5 expression in cervical cancer stem cells resulted in increased tumor sphere-forming efficiency in addition to conferring chemoresistance to cisplatin treatment. 214
A key characteristic of normal stem cell and CSC maintenance is the ability to ensure chromosomal stability by preserving telomere length through the use of TERT, a catalytic subunit of telomerase. 163 A link between TERT and Wnt/β-catenin signaling has been described whereby β-catenin regulates TERT expression in a variety of cell lines. 216 , 217 , 218 Activation of the Wnt/β-catenin pathway via Wnt3a has been shown to enhance leukemic stem/progenitor cell self-renewal potential in acute myeloid leukemia (AML) and acute T-lymphoblastic leukemia (T-ALL) cell lines. 219 Furthermore, Cai et al demonstrated that blocking Wnt signaling with DKK-1 reduced the self-renewing capacity of tumorsphere stem cells from MKN-45 human gastric cancer cells. By contrast, the addition of lithium chloride improved gastric cancer cell renewal capacity, indicating a role for Wnt signaling in the maintenance of gastric cancer stem cells. 220 Wnt/β-catenin signaling has been implicated in the self-renewal and expansion of hepatocellular carcinoma (HCC)-initiating cells with stem/progenitor features. 221 Interestingly, it was found that the expression of non-canonical Wnt5a inhibited the effects of Wnt/β-catenin signaling in HCC cells. 222
Wnt signaling up-regulates transcriptional factors which facilitate EMT induction and tumor metastasis. Among these, slug (also known as snail2) and snail (snail1) belong to the snail family of transcriptional factors and are known as major EMT inducers expressed in breast, ovarian, and colon cancers. 223 Wu et al demonstrated the link between canonical Wnt signaling and slug activity. In the absence of Wnt/β-catenin signaling, the cytosolic slug is phosphorylated by GSK3β and subsequently undergoes β-Trcp1 dependent ubiquitination and proteasomal degradation. When present, Wnt signaling inhibited GSK3β-mediated phosphorylation, thereby stabilizing the slug and permitting the induction of EMT programs. 224 Twist is a key transcriptional factor for the initiation of EMT in breast cancer. 225 Howe et al demonstrated that Twist expression is up-regulated in murine mammary epithelial cells in response to Wnt1. The authors observed elevated Twist in nearly 70% of mammary tumors in Wnt1 transgenic mice. 226 Altogether, these findings indicate a link between Wnt1 and twist expression contributing to mammary tumorigenesis. Moreover, the non-canonical ligands Wnt5a/Wnt5b and Fzd2 receptors are highly expressed in metastatic breast liver, lung, and colon cancer cell lines. Wnt5a/5b binds to Fzd2 receptors, leading to the phosphorylation of transcription factor and driver of EMT, STAT3. 227 Wnt5a has also been linked to EMT in ovarian and nasopharyngeal cancers. 228 , 229 On the other hand, the role of Wnt5a is complex as Cheng et al demonstrated Wnt5a inhibited cell proliferation and EMT in colon cancer cells. 230
Studies have described a relationship between non-coding microRNAs (miRs) and Wnt signaling in CSCs. Whereby, miRs provide intrinsic modulation of Wnt signaling, and are implicated in CSC maintenance of stem cell traits. For example, assays revealed miR-217 expression was increased in HCC tissues and cells. MiR-217 induced stem cell-like traits in HCC cells through the activation of Wnt signaling via the targeting of Wnt inhibitor DKK1. 231 Moreover, miR-1207 is up-regulated in ovarian cancer cells and promotes stem cell traits by activating Wnt signaling via the targeting of negative Wnt regulators SFRP1, AXIN2, and ICAT. 232 Lastly, miR-21 expression is increased in colon cancer cells and induces stemness via the suppression of transforming growth factor β receptor 2 (TGFβR2) as well as increases in levels of β-catenin, TCF/LEF activity, c-Myc expression, and cyclin-D1 expression. 233
Wnt signaling in human diseases
Wnt signaling has a wide range of functions in development. As mentioned previously, the canonical pathway is vital for inducing cell proliferation, differentiation, maturation, as well as proper body-axis specification. On the other hand, the non-canonical pathway is involved in cell polarization and migration. Both the canonical and non-canonical pathways perform a wide array of functions across species, and their dysregulation can lead to numerous diseases. Several genetic changes in Wnt signaling components can cause human diseases ( Table 1 ). Although not exhaustive, we will cover many important diseases in this section, with a particular focus on the more thoroughly understood canonical Wnt signaling pathway.
Table 1
List of genetic diseases caused by mutations in the Wnt pathway.
| Implicated member of the Wnt pathway | Associated disease |
| APC | Familial adenomatous polyposis |
| Axin2 | Colorectal cancer |
| Axin1 | Hepatocellular carcinoma |
| Prostate cancer | |
| DVL1 | Robinow syndrome |
| Fzd4 | Familial exudative vitreoretinopathy |
| Lef1 | Human sebaceous tumors |
| LGR4 | Obesity |
| LRP5 | Osteoporosis pseudoglioma syndrome |
| Early-onset osteoporosis | |
| LRP6 | Early-onset coronary artery disease |
| Late-onset alzheimer's disease | |
| Norrin | Familial exudative vitreoretinopathy |
| Norrie disease | |
| PORCN | Focal dermal hypoplasia |
| RNF43 | Hereditary sessile serrated adenomas |
| Colorectal adenocarcinomas | |
| Sclerostin (SOST) | Sclerosteosis |
| Van Buchem disease | |
| TCF7L2 | Type II diabetes |
| Wnt1 | Osteogenesis imperfecta |
| Early-onset osteoporosis | |
| Wnt3 | Tetra-Amelia |
| Wnt4 | SERKAL syndrome |
| Wnt5a | Robinow syndrome |
| Wnt7a | Fuhrmann syndrome |
| Wnt10B | Oligodontia |
| Early-onset obesity | |
| Wnt11 | Hepatocellular carcinoma |
Wnt signaling in cancer
Control of Wnt signaling is crucial in the prevention of a diverse range of cancers ( Fig. 8 ). 234 , 235 Moreover, mutations of Wnt pathway members can lead to EMT, unchecked cell proliferation, and metastasis. Overexpression of Wnt pathway members FZD7, LRP6, and TCF7 has been observed in triple-negative breast cancer (TNBC). 236 TNBC is an aggressive variant of breast cancer that lacks the expression of estrogen receptors, progesterone receptors, and human epidermal growth factor receptors (HER-2) seen in other breast cancer subtypes. 237 Moreover, transcriptional knockdown of LRP6 or FZD7 has been shown to reduce TNBC tumor growth in vivo . 238 APC is an important component of the β-catenin destruction complex in canonical Wnt signaling. Mutations in APC have been characterized by familial adenomatous polyposis, a hereditary condition involving thousands of colonic polyps. 239 However, somatic mutations in a single APC gene are responsible for over 80% of colorectal tumors, and over 60% in those with two APC gene mutations. 240 APC is expressed in the basolateral membrane of colorectal epithelial cells and is suggested to cause apoptosis to control cell death and regulate cell number. APC functions as a tumor-suppressing “gatekeeper” gene of colonic epithelial cell proliferation, maintaining cell number, and preventing uninhibited cell division. This may also explain how APC mutations do not result in cancer in other organs despite being ubiquitously expressed. 241 Overall, the loss of APC causes constitutive activation of the β-catenin/TCF4 complex, which can lead to the transformation of colonic epithelium. 242
Axin proteins are negative regulators of Wnt/β-catenin signaling and help comprise the β-catenin destruction complex. Mutations in Axin2, leading to the stabilization of β-catenin and activation of Wnt/β-catenin signaling, have been linked to CRC susceptibility. 243 , 244 Yet, findings by Wu et al suggest the role of Axin2 may be more complex. Axin2 was actually found to promote CRC oncogenesis in mice by up-regulating the transcriptional repressor Snail1, leading to increased EMT and metastasis. Interestingly, these findings suggest that rather than acting as a tumor suppressor, Axin2 may be involved in promoting oncogenic activity. 245 Mutations in Axin1, on the other hand, have been associated with HCC and prostate cancer. 246 , 247
Perhaps unsurprisingly, mutations in the β-catenin gene are also associated with cancer. Mutations that removed the Ser/Thr regulatory residues on the N-terminus of β-catenin were found in CRC tumors with intact APC genes. 248 Melanoma was one of the first cancers to be associated with β-catenin dysregulation. 249 However, the exact role of β-catenin in melanoma is unclear, as subsequent studies have linked activated Wnt/β-catenin signaling to decreased proliferation and suppression of invasion. 250 , 251 Furthermore, canonical Wnt signaling has been shown to drive oncogenesis in a number of leukemia subtypes. Wnt signaling components, LEF1 and downstream target cyclin D1, were overexpressed in cell lines of B cell chronic lymphocytic leukemia (CLL), and their expression was associated with defects in cell apoptosis. 252 An examination of Wnt/β-catenin signaling in T-cell acute lymphoblastic leukemia (T-ALL) patients showed that β-catenin was up-regulated in nearly 85% of the childhood T-ALL patients. Moreover, Wnt target genes Axin2, c-Myc, TCF1, and LEF were also highly expressed. When β-catenin was silenced, T-ALL cancer cells showed higher rates of apoptosis. Together, these results suggest Wnt/β-catenin signaling plays a role in a notable subset of T-ALL cancers. 253 Furthermore, Wnt signaling is required for the pathogenesis of AML. A significant portion of AML cases was found to exhibit constitutive activation of Wnt/β-catenin signaling, as well as the aberrant expression of pathway components Wnt1, Wnt2b, and LEF1. 254 A study of the role of LEF1 dysregulation in murine HSCs showed that mice transduced to express LEF1 or a constitutive active LEF1 mutant developed abnormal hematopoietic differentiation leading to AML. 255 Leukemia stem cells (LSC) are a subset of AML cells with stem-like properties of self-renewal and proliferation, as well as the ability to initiate and maintain leukemia in vivo . 256 Wang et al have shown that canonical Wnt signals are required for the self-renewal of LSCs in mouse models of AML. 257 Epigenetic regulation of the Wnt pathway in AML can occur via methylation of Wnt antagonists. Valencia et al used a methylation-specific PCR approach to study the methylation status of a number of Wnt antagonists (including sFRP1, sFRP2, sFRP4, sFRP5, Dkk1, and Dkk3). The authors discovered aberrant methylation of Wnt antagonists in up to 64% of AML marrow samples. 258
One-third of human sebaceous tumors were found to contain inactivating mutations of LEF1, one of the nuclear factors of the TCF/LEF family. The mutations stimulated the expression of sebocyte markers and prevented β-catenin from binding to LEF1 and activating target gene transcription. Interestingly, the LEF1 mutations characterized in human sebaceous tumors are among the first tumor-associated mutations that inactivate Wnt signaling. 259 As previously mentioned, dysregulation of the Wnt pathway may also occur via epigenetic means, as the hypermethylation of the promoter regions of Wnt inhibitors SFRP, DKK, and WIF-1 were associated with a worse prognosis of both ALL and AML. 260 Ring finger protein 43 (RNF43) is a negative regulator of the canonical Wnt pathway, and in the absence of R-spondin ligands, degrades Fzd receptors. 55 RNF43 mutations have been associated with hereditary sessile serrated adenomas (SSAs) and colorectal adenocarcinomas. 261 , 262 Moreover, Non-canonical signaling via Wnt5a/Ror2 activity has been found to enhance the invasiveness of osteosarcoma cells. 263 Non-canonical Wnt11 acts as a tumor suppressor during hepatocarcinogenesis, as the loss of Wnt11 expression led to malignancy via canonical and non-canonical paths. 264
Wnt signaling in bone and skeletal disorders
The Wnt pathway plays a significant role in bone formation and, as will be discussed later in this review, presents a potential target for the development of therapeutics for bone disorders. 41 , 265 , 266 The importance of Wnt signaling in bone formation is highlighted by the SOST gene located on chromosome chromosomal region 17q12-21 which codes for sclerostin. Expressed by mature osteocytes, sclerostin is a small protein that functions as an antagonist of Wnt signaling by binding to the Wnt co-receptors LRP5/6 with the effect of inhibiting bone formation and indirectly promoting bone resorption. Moreover, mutations in SOST can cause sclerosteosis as well as van Buchem disease (VBD). 267 , 268 Sclerosteosis and VBD are rare autosomal recessive sclerosing bone dysplasias that result from bone overgrowth due to osteoblast hyperactivity. Sclerosteosis is known to be caused by loss-of-function mutations in the SOST gene which encodes sclerostin. VBD results from a deletion of regulatory elements for SOST transcription, leading to reduced sclerostin expression. 269
Osteoporosis is a condition characterized by low bone mineral density (BMD) resulting from altered bone microstructure, that ultimately predisposes patients to low-impact, fragility fractures. 270 Osteogenesis imperfecta, also known as brittle bone disease, is marked by the early onset of osteoporosis and increased bone fragility. 271 While most osteogenesis imperfecta cases are caused by dominant mutations to the COL1A1 or COL1A2 genes involved in the production of type-1 collagen, a number of studies have also linked mutations in Wnt1 to autosomal recessive osteogenesis imperfecta. 272 , 273 , 274 Laine et al discovered a heterozygous missense mutation of Wnt1 in adults with dominantly inherited early-onset osteoporosis. 275 Furthermore, a heterozygous missense mutation in LRP5 that reduces the activity of canonical Wnt signaling was linked to juvenile-onset primary osteoporosis, without the features of osteogenesis imperfecta. 276 Yu et al identified autosomal-dominant missense mutations in Wnt10B that were associated with oligodontia, a severe form of tooth agenesis. 277 Furthermore, partial loss of Wnt7A function has been linked to Fuhrmann syndrome, a skeletal dysplasia characterized by limb aplasia or hypoplasia as well as joint abnormalities. 278 Dysregulation of Wnt signaling has not only been implicated in disorders of the axial skeleton. It is well established that Saethre Chotzen Syndrome, 279 characterized by a mutation in the Twist1 gene (a downstream target of Wnt), results in multi-suture craniosynostosis. Behr and colleagues 280 have elegantly demonstrated that canonical Wnt signaling determines cranial suture fate in the mice and perturbations in such signaling, whether via continuous activation or inhibition, yield differential patterns of closure in posterior frontal and sagittal sutures.
Wnt signaling in ocular disorders
In humans, autosomal dominant and recessive loss of function mutations in the Frizzled 4 (Fzd4) receptor cause a disease known as familial exudative vitreoretinopathy (FEVR). The expressivity of the disease can be highly variable but, generally, FEVR results in lack of retinal angiogenesis. This can lead to neovascularization, fibrosis, retinal detachment, and even retinal dysplasia among other symptoms, clarifying the importance of Fzd4 receptors in retinal vascular development. 281 X-linked mutations in the Norrin disease protein ( NDP ) gene, which codes for norrin (a ligand of FZD4), 282 cause X-linked FEVR and Norrie disease. 281 Norrie disease is characterized by retinal hypovascularization, 283 as the lack of Norrin-induced Wnt signaling is integral to proper retinal vascular development. 282 The overactivation of Wnt/β-catenin signaling also plays a role in the development of age-related macular degeneration through increasing angiogenic factors. 284 , 285 Furthermore, LRP5 loss of function mutations has also been linked to osteoporosis pseudoglioma syndrome, a rare disease characterized by reduced bone formation and congenital vision loss. Patients born with osteoporosis pseudoglioma syndrome may experience blindness as well as severe disruptions of ocular structure blood vessel development. 286
Diabetic retinopathy (DR) is a microvascular disease and a major complication of diabetes mellitus (DM). 287 DR is also associated with increased Wnt/B-catenin signaling, as retinal sections taken from DR patients revealed elevated β-catenin and LRP5/6 levels. Moreover, the administration of Dkk1 reduced retinal inflammation caused by pro-inflammatory factors such as ICAM-1 and cyclooxygenase-2. Dkk1 also reduced retinal vascular leakage as well as ischemia-induced retinal neovascularization in DR models. 288 Analysis of the vitreous humor of patients with proliferative diabetic retinopathy revealed a correlation between LRP6 levels and VEGF levels. 289 Moreover, plasma levels of Wnt inhibitor Dkk1 were found to be lower in DR patients than in non-diabetic controls, further implicating Wnt signaling in the pathogenesis of DR. 290 The cornea is the outermost part of the eye and provides both refractive and protective functions. It is a unique tissue without vascularization and maintaining its transparency and avascular nature is important to visual acuity. 291 Corneal neovascularization (CNV) is a sight-threatening condition that involves the growth of blood vessels within the cornea. Insults associated with CNV include hypoxia, infection, inflammation, and chronic contact lens wear. 292 Aberrant Wnt signaling has also been associated with CNV, as components of the Wnt pathway have been shown to be increased in animal models of CNV. Following the induction of suture-induced CNV in rats, phosphorylated LRP6 and nuclear accumulation of β-catenin were found to be increased in endothelial cells and neo-vascularized corneal tissue. 293 Moreover, similar results have been demonstrated in the corneas of mice and rats following alkali burns. 294
Wnt signaling in cardiovascular diseases
Atherosclerosis is an inflammatory disease characterized by the progressive accumulation of lipids and fibrous elements in large arteries, 295 and the Wnt pathway has been implicated in mechanisms contributing to the progression of atherosclerosis. Genetic investigations of families or populations that exhibited early onset coronary artery disease revealed a number of LRP6 mutations associated with the increased risk of elevated low-density-lipoprotein-cholesterol. 296 , 297 , 298 Furthermore, murine and human macrophages and atherosclerotic lesions were found to have elevated levels of Wnt5a expression. 299 Wnt5a contributes to inflammation in atherosclerosis by inducing the gene expression of cyclooxygenase-2 and inflammatory cytokines in human aortic endothelial cells. 300 Dkk-1 is also elevated in atherosclerotic lesions and Ueland et al identified Dkk-1 as a novel mediator in platelet-mediated endothelial cell activation and release of pro-inflammatory cytokines. 301 By contrast, Dkk-3 has been linked to a potential atheroprotective role against atherosclerosis in human subjects. Wherein, Yu et al found that plasma Dkk-3 levels were inversely associated with carotid artery intima-media thickness and carotid atherosclerosis. 302 β-Catenin is capable of up-regulating genes that promote vascular smooth muscle cell proliferation, such as cyclin D1, while also decreasing the level of cell cycle inhibitor p21. 303 Moreover, Wnt4 expression was also found to be elevated in proliferating vascular smooth muscle cells. 304
The Wnt pathway has been shown to be activated following myocardial infarction (MI). Reporter analysis of Wnt signaling in the myocardium following MI, in vivo , showed that active Wnt signaling increased in the cardiomyocytes at the infarct border, from 7 days post-MI onwards. 305 Meyer discerned that the cardiac microenvironment employs non-canonical Wnt signals to activate monocytes after MI. The authors also discovered an up-regulation of Wnt pathway inhibitor Wif1 in cardiomyocytes. Knockout studies revealed the deletion of Wif1 led to more recruited monocytes, increased scar size, and reduced ejection fraction 4 weeks post MI. By contrast, cardiomyocyte-specific Wif1 overexpression attenuated the monocyte response and improved cardiac function after MI. 306 Furthermore, the expression of Wnt pathway inhibitors such as sFRP1 and sFRP5 has been shown to protect against further injury by mitigating the inflammatory response post-MI. When expressed in bone marrow cells (but not cardiomyocytes or endothelial cells), sFRP-1 reduced neutrophil infiltration after ischemia, lessened scar formation, and improved cardiac hemodynamic parameters. 307 Similarly, knockout of sFRP5 in an ischemic heart resulted in greater infiltration of Wnt5a-positive macrophages and increased inflammatory cytokine and chemokine expression compared to wild-type mice. 308
LRP5/Wnt3 signaling has been linked to valvular calcification and stenosis due to osteoblast differentiation in calcified aortic valves. 309 Arrhythmogenic cardiomyopathy (AC) is a disease of life-threatening ventricular arrhythmias and progressive dystrophy of the ventricular myocardium. 310 A role for GSK-3β in the pathogenesis of AC has been described, as it has been shown that GSK-3β localization occurs in intercalated disks of myocardium in mouse models of AC. 311 Wnt signaling has been linked to cardiac remodeling that can result in the progression of heart failure. The inactivation of Wnt inhibiting sFRP1 in the hearts of aged mice led to increased expression of ligands Wnt1, Wnt3, Wnt7b, Wnt16, and Wnt target genes Wisp1 and LEF1. Moreover, sFRP1 knockout mice exhibited ventricular dilation and hypertrophy as well as depressed cardiac function and fibrosis. Further study revealed the down-regulation of sFRP-1 gene expression in human hearts with dilated cardiomyopathy and ischemic cardiomyopathy, suggesting similarity with the phenotype observed in sFRP1 knockout mice. 312 Hou et al discovered that β-catenin is stabilized and translocated to the nucleus of cardiomyocytes in human ischemic and dilated cardiomyopathy, as well as in mouse desmin cardiomyopathy. β-Catenin/transcription factor 7-like 2 (TCF7L2), of the TCF/LEF family of transcription factors, interacts with β-catenin to up-regulate c-Myc, resulting in cardiac hypertrophy. TCF7L2 knockdown was found to suppress these activities, suggesting TCF7L2 mediates the c-Myc up-regulation and abnormal cardiac remodeling seen in heart failure. 313
Wnt signaling in metabolic disorders
Type 2 diabetes mellitus (T2DM) is a common metabolic disorder primarily characterized by two factors, defective insulin secretion by β-cells in the pancreas and the inability of insulin-sensitive tissues to respond appropriately to insulin. 314 TCF7L2, a downstream effector of the Wnt/β-catenin signaling pathway, is a potent risk locus for T2DM. 315 A large human genome review and meta-analysis of different populations found that under a multiplicative genetic model, four variants of TCF7L2 gene are associated with T2DM. The results of this study suggested the TCF7L2 gene may be involved in nearly 1/5 of all T2DM cases. 316 While the exact mechanisms by which TCF7L2 polymorphisms affect T2DM are still not well understood, a number of association studies have helped to elucidate this role. Zhou et al utilized RNA sequencing to identify a TCF7L2-regulated transcriptional network responsible for insulin production and processing in rodent and human pancreatic islets. Wherein, ISL LIM homeobox 1 (Isl1) was found to be the primary target of TCF7L2. Isl1, in turn, mediates proinsulin production and processing via the regulation of PCSK1, PCSK2, SLC30A8, MAFA, PDX1, and NKX6.1. 317 Inactivation of TCF7L2 in the pancreatic pericytes of transgenic mice led to poor glucose tolerance as a result of β-cell dysfunction and impaired glucose-stimulated insulin secretion. These findings were accompanied by the discovery that TCF7L2-dependent pericytic expression of secreted factors such as BMP4 promoted β-cell function. Moreover, exogenous BMP4 rescued the impaired glucose-stimulated insulin secretion of transgenic mice, highlighting the importance of TCF7L2 activity in pancreatic β-cells. 318 Further studies in mice have shown that TCF7L2 loss-of-function in pancreatic β cells results in defective glucose-stimulated insulin secretion and a decrease in β cell mass. 319 , 320
Obesity is characterized by the accumulation of excess energy into white adipose tissue. By contrast, brown adipose tissue (BAT) is primarily energy-dissipating and protects the body from cold through thermogenesis. 321 , 322 The loss of functioning Wnt10B leads to an inability to activate canonical Wnt signaling and block adipogenesis and, as Christodoulides et al discovered, mutations in Wnt10B are associated with early-onset obesity. 323 LGR4, a receptor for R-spondin ligands, has been implicated in energy expenditure by driving the conversion of white fat to brown fat. Wang et al demonstrated that LGR4 homozygous mutant mice exhibit reduced adiposity, greater energy expenditure, and higher expression of BAT markers. Mutant mice also resisted dietary and leptin mutant-induced obesity. Moreover, the ablation of LGR4 potentiated BAT differentiation. The authors also identified a functional low-frequency missense LGR4 variant associated with an increased risk of obesity. 324 Recently, LGR4 gene polymorphisms found in Chinese nuclear families with female children were related to obesity phenotypes, including body mass index and trunk fat mass. 325
Members of the sFRP family act as adipokines and have been associated with adipocyte dysfunction in obesity. 137 sFRP5 is an anti-inflammatory adipokine secreted by adipocytes and its potential role in obesity is an area of interest. In mouse models of obesity and diabetes, sFRP5 was shown to reduce adipose tissue inflammation with the overall effect of improving metabolic dysfunction by sequestering non-canonical Wnt5a and preventing the activation of the JNK pathway in macrophages and adipocytes. 326 Schulte et al discerned that obesity is associated with elevated serum levels of pro-inflammatory Wnt5a in humans. The authors also found that nutritional therapy and weight loss increaseses serum concentrations of sFRP5 in subjects with obesity. 327 A large population-based study discovered that serum sFRP5 was negatively associated with multiple risk factors for T2DM and cardiovascular diseases. At the same time, higher levels of sFRP5 were associated with lower odds of developing prediabetes/T2DM. 328 Another study found that subjects with T2DM exhibited elevated Wnt5a levels that positively correlated with IL-6 and triglyceride concentrations. 329 However, in contrast to results in mice implicating sFRP5 in metabolic dysfunction, Ehrlund et al found that sFRP5 was not actively secreted from human white adipose tissue and its expression was not influenced by obesity. 137 Taken together, these conflicting results suggest that the exact role of sFRP5 in obesity requires further elucidation.
Wnt signaling in neurological disorders
Wnt/β-catenin signals are important for the function of the adult nervous system and are critical for adult neurogenesis and synaptic maintenance. 330 Alzheimer's disease (AD) is a neurodegenerative disease characterized by the presence of amyloid-β plaques tau neurofibrillary tangles. AD patients experience progressive impairment of behavioral and cognitive functions. 331 Genetic analysis revealed variations in LRP6 were associated with late-onset AD, supporting the notion aberrant Wnt signaling is involved in AD. 332 Canonical Wnt signaling inhibition by Dkk1 results in increased GSK3-β activity and decreased cytoplasmic β-catenin protein levels. Similarly, a study of prefrontal lobe structures in AD patients found that brains with AD exhibited decreased β-catenin levels and increased phosphorylation of GSK3β compared to age-matched controls. 333 Neurofibrillary tangles are a characteristic lesion found in AD and are composed of hyper-phosphorylated forms of the microtubule-associated protein tau. 334 Several studies have implicated GSK3-β and GSK3-α as important tau-kinases in AD. 335 , 336 , 337 Moreover, autosomal dominant AD involves mutations of presenilin (PSEN) genes. Takashima et al discovered mutant PSEN1 binds both GSK3β and tau protein and that the association of GSK3-β with mutant PSEN1 prompts the phosphorylation of tau. 338 Furthermore, Purro et al showed that amyloid-β increases the levels of Dkk1 in the hippocampus, which in turn modulates synaptic loss through the dispersal of synaptic components. 339 Further study revealed the induced expression of Dkk1 in the hippocampus of transgenic mouse mode triggers cognitive impairments such as synapse loss as well as learning and memory deficits. However, following the loss of synaptic connectivity, reactivation of the Wnt pathway by cessation of Dkk1 expression notably restored synapse number, synaptic plasticity, and long-term memory. 340 Moreover, the administration of lithium (which rescues the Wnt pathway by inhibiting GSK3-β) and rosiglitazone in mouse models of AD also resulted in spatial memory improvement, possibly due to the reactivation of Wnt signaling. 341
Parkinson's disease (PD) is a common neurodegenerative disorder marked by motor symptoms such as tremors, rigidity, bradykinesia/akinesia, and postural instability. The substantia nigra is a midbrain dopaminergic nucleus crucial for modulating motor movement. Pathologically, PD is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta as well as the deposition of intra-cytoplasmic inclusions (Lewy bodies) containing ubiquitin and α-synuclein (α-syn). 342 Leucine-rich repeat kinase 2 (LRRK2) mutations have been linked with pathologies of α-syn and identified as a genetic risk factor for developing PD. 343 Berwick et al found that over-expressed LRRK2 binds to and represses β-catenin activity, suggesting LRRK2 may contribute to the β-catenin destruction complex. By contrast, the authors showed that the loss of LRRK2 led to increased canonical Wnt signaling both in vitro and in vivo . 344 Together, these results indicate decreased Wnt/β-catenin signaling may play a role in PD pathogenesis. Wnt/β-catenin signaling plays an important role in midbrain dopaminergic (mDA) neuron induction, as Wnt1 regulates the establishment of the dopaminergic progenitors in mammalian ventral midbrain. 345 A previous study has shown that the inactivation of Wnt1 in murine embryonic stem cell lines leads to the loss of the midbrain region. 346 Conversely, expression of ectopic Wnt1 has been shown to induce the overproliferation of precursor cells in the caudal midbrain. 347 Furthermore, Schulte et al have reported Wnt-3a enhances the proliferation of midbrain dopaminergic precursors and that Wnt-5a increases differentiation of mDA cells as well as disheveled phosphorylation. 348 Administration of the neurotoxin 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine (MPTP) induces a PD-like phenotype and MPTP mouse models have been used to replicate the pathophysiology of PD. 349 Interestingly, L'Episcopo et al discovered MPTP-reactive astrocytes express Wnt1 and engage in the rescue of mesencephalic dopaminergic neurons from MPP (the active metabolite of MPTP) induced neurotoxicity. 350 Of note, aging impairs Wnt-mediated self-protection, and neurogenesis/neurorepair capacity in the ventral midbrain, as astrocyte-derived Wnt signaling is down-regulated with age while the expression of endogenous Wnt antagonists such as Dkk1 is up-regulated. 351
Wnt signaling in other human diseases
Wnt signaling is known to play a critical role in embryonic development and has been implicated in a number of developmental disorders. For example, Wnt/β-catenin signaling is necessary for proper lung development. β-Catenin inactivation in mouse foregut endoderm leads to the absence of both the lungs and trachea. By contrast, activated β-catenin has been linked to Nkx2.1 expression, an early marker of trachea and lung development. 352 Bronchopulmonary dysplasia is a chronic lung disease in infants caused by prenatal and/or postnatal injury to developing lungs. It was discovered that Wnt signaling is up-regulated in hyperoxia-induced arrest in alveolar development and subsequent bronchopulmonary dysplasia in neonatal rats. 353 Wnt signaling also plays a major role in nephrogenesis. Failures of Wnt signaling may result in congenital anomalies of the kidney and urinary tract. 354 Furthermore, β-catenin knockout mice exhibited hypoplastic kidneys with reduced renal function, absence of the superficial layer of renal tubules, a thin cortex, and underdeveloped capillary tufts in the glomeruli. 355 Additionally, LRP6 knockout in mouse embryos resulted in hypoplastic kidneys and cyst development. 356 Highlighting the important role of Wnt signaling in human organogenesis, loss of function missense mutations in Wnt4 were described in SERKAL syndrome, an autosomal recessive syndrome characterized by female-to-male sex reversal as well as kidney, adrenal, and lung dysgenesis. 357 Mutations in Fzd1 and Fzd2 are known to cause cleft palate and ventricular septal defects in mice. These mutations also affected neural tube closure and inner ear development. Fzd7 mutations were shown to cause ventricular septal defects but were more commonly associated with a kinked tail phenotype. 358 Loss-of-function mutations in Wnt3 have been linked to Tetra-Amelia, which is characterized by the congenital absence of all four limbs. 359 DVL1 frameshift mutations have been identified and associated with autosomal dominant Robinow syndrome, a rare disorder of mesomelic limb shortening, genital hypoplasia, and distinct facial features. 360 Additionally, missense mutations in Wnt5a have also been associated with Robinow syndrome. 361
Dupuytren's disease is a fibroproliferative disorder that causes the palmar fascia to thicken and shorten. Patients with Dupuytren's present with nodules on the palm that can progress to contracture deformities of the hand. 362 Studies have noted increased β-catenin expression in Dupuytren's disease. 363 , 364 A genome-wide association study identified multiple loci involved in the Wnt signaling pathway that were associated with susceptibility to Dupuytren's disease. Wherein, polymorphisms in Wnt2 , Wnt4 , Wnt7B , R-spo2 , and sFRP4 genes were linked to the process of fibromatosis seen in Dupuytren's. 365 Further study revealed a significantly higher expression of Wnt7B and β-catenin in nodules from Dupuytren's patients compared to controls, adding to the notion of canonical Wnt activation in Dupuytren's. 366 Furthermore, X-linked mutations in PORCN (an o-acyltransferase critical for cellular export of Wnt signaling proteins) are known to cause focal dermal hypoplasia, a multisystem disorder characterized by developmental abnormalities of the skin, skeletal system, eyes, and face. 367 , 368 With respect to other fibrotic diseases, psoriasis is a chronic immune-mediated skin condition characterized by inflammation, uncontrolled keratinocyte proliferation, and erythematous scaly plaques. 369 Studies of lesional and uninvolved psoriatic skin have revealed the increased expression of Wnt5a in psoriatic lesions. 370 , 371 By contrast, the expression of soluble Wnt inhibitors such as WIF-1, sFRP1, sFRP2, sFRP4, and sFRP5 as well as Dkk1, Dkk2, and Dkk3 were down-regulated in psoriatic skin. 371 Together, these results suggest non-canonical signaling via Wnt5a may play a role in the pathogenesis of psoriasis.
Dysregulation of Wnt signaling is also associated with idiopathic pulmonary fibrosis (IPF), a disease characterized by progressive and chronic lung scarring that is detrimental to lung function. Although the exact role of Wnt signaling is not well understood, current research suggests that the crosstalk between Wnt and TGF-β underlies the development of IPF. β-catenin and LRP5 promote fibrosis by increasing TGF-β, while TGF-β can activate canonical Wnt signaling in fibroblasts. 372 However, it has been reported that β-catenin in the alveolar epithelium may be implicated in a protective role against lung fibrosis, so the exact role of Wnt signaling in IPF remains complicated and requires further delineation. 373 Aberrant Wnt signaling is also involved in the development of renal cysts, as the deletion of APC in mice led to increased β-catenin levels and cyst formation. 374
Targeting Wnt signaling as novel therapeutics
Wnt signaling is involved in a multitude of physiological processes and, unsurprisingly, aberrant Wnt signaling is associated with a wide variety of diseases, including cancer. Advances in the understanding of Wnt signaling have enabled the creation of novel therapeutics that target components of the Wnt pathway. There is a wide array of Wnt-targeting therapeutics in preclinical studies or clinical trials that are under development for numerous disease applications. In this review, we will outline the drugs for Wnt-related bone disease that are approved or in clinical trials as well as the anti-cancer therapeutics in preclinical and clinical studies.
Wnt-targeting therapeutics for bone and skeletal diseases
Osteoporosis is a common bone disease characterized by low BMD that predisposes patients to low-impact, fragile fractures. Osteogenesis imperfecta, also known as brittle bone disease, is marked by early-onset osteoporosis, increased bone fragility, bone deformity, and short stature. The risk of developing osteoporosis increases with age and it was estimated osteoporosis causes greater than 8.9 million fractures worldwide each year, with fractures commonly occurring in the hip, vertebrae, and distal forearm. 270 Moreover, the incidence of osteoporotic fracture in women is higher than that in men. 375 Postmenopausal women are susceptible to developing osteoporosis, in particular, due to a decline in estrogen levels and progressive loss of its anti-osteoclastic and osteoanabolic effects. 376 , 377 Osteoporotic fractures can lead to a significant decrease in quality of life, while increasing morbidity and disability. 378 A recent retrospective cohort study of 3992 patients admitted to the hospital due to osteoporotic hip fracture in 17 years reported an increase in mortality for patients with hip fracture and a higher mortality rate in men than in women. Moreover, the risk of death was highest immediately after fracture occurrence. 379 The pain, disability, and costs associated with osteoporosis reflect the essential need for effective measures to prevent fractures. Important contributing factors to the ability of bone to withstand trauma include density, size, micro-, and macro-architecture as well as turnover. 380 Current therapies for osteoporosis include antiresorptive treatments and anabolic drugs. Antiresorptive drugs are more widely utilized and include bisphosphonates (first-line drugs for osteoporosis that work by inducing osteoclasts apoptosis), selective estrogen receptor modulators, and RANKL inhibitors (drugs that inhibit osteoclast activity by direct binding to RANKL). By contrast, current anabolic therapies include parathyroid hormone analogues and the recently approved romosozumab (a monoclonal antibody targeting sclerostin). 381
Due to its role in osteogenesis and bone metabolism, the Wnt pathway presents a promising therapeutic target for the treatment of osteoporosis and osteogenesis imperfecta ( Table 2 ). Encoded by the SOST gene, sclerostin is a small protein that antagonizes Wnt signaling by binding to the Wnt co-receptors LRP5/6 with the effect of inhibiting bone formation and indirectly promoting bone resorption. In this review, we will discuss the monoclonal antibodies targeting sclerostin currently in clinical trials as well as the efficacy and safety of romosozumab (Evenity), the first FDA-approved sclerostin inhibitor for the treatment of osteoporosis in postmenopausal women with a high risk of fracture. Approved by the FDA in 2019, romosozumab is a fully humanized and specific monoclonal IgG2 antibody against sclerostin that works by binding to sclerostin and preventing its inhibition of the Wnt signaling pathway. 382 It is also the first anabolic medication for osteoporosis that increases bone formation while decreasing bone resorption. 383 The Fracture Study in Postmenopausal Women with Osteoporosis (FRAME) phase III study demonstrated that romosozumab treatment was associated with a lower risk of vertebral fracture than placebo at 12 months and, following the transition to Denosumab (a RANKL inhibitor), at 24 months. 384 The romosozumab or Alendronate for Fracture Prevention in Women with Osteoporosis (ARCH) phase III study compared a regimen of romosozumab transitioning to alendronate (bisphosphonate drug) versus an alendronate treatment alone. Results of the trial showed the risk of new vertebral fracture was reduced by 48% in the romosozumab-alendronate group when compared with the alendronate–alendronate group. 385 A phase II study found that romosozumab does not exhibit long-lasting effects after its discontinuation. In the absence of another treatment for osteoporosis, the BMD of study subjects returned to close to baseline 1 year after discontinuation of romosozumab. 386 The primary safety concern of romosozumab use is potential cardiovascular events. Due in part to the results of the ARCH study that showed an imbalance between groups in cardiovascular-related adverse events, a boxed warning for romosozumab was included that outlined the potential risk of MI, stroke, and cardiovascular death associated with romosozumab use. 383
Table 2
List of therapeutic antibodies targeting sclerostin for osteoporosis.
| Drug (Monoclonal Antibody) | Treatment or Indication | Phase of Clinical Trial | Trial Identifier(s) |
| Romosozumab | Postmenopausal Osteoporosis | FDA approved (2019) | NCT01575834 , NCT01631214 , NCT00896532 |
| Osteogenesis Imperfecta | Phase I | NCT04545554 | |
| Blosozumab | Postmenopausal Osteoporosis | Phase II | NCT01742078 , NCT01144377 |
| SHR-1222 | Postmenopausal Osteoporosis | Phase I | NCT04435158 |
| Setrusumab (BPS-804) | Osteogenesis Imperfecta | Phase II | NCT01417091 , NCT03118570 |
Blosozumab is another monoclonal antibody against sclerostin that has undergone clinical trials. Structurally diverse from romosozumab, it is also designed to treat postmenopausal osteoporosis. 381 As of this writing, blosozumab has undergone phase I and II clinical trials. Blosozumab was well tolerated in the phase I study that demonstrated dose-dependent increases in bone formation biomarkers and BMD after single and multiple doses of the drug. 387 The phase II study showed a dose-dependent increase in bone formation markers as well as a reduction in bone resorption, as assessed by CTX (a biochemical marker of bone resorption). Moreover, compared with placebo, blosozumab treatment resulted in significant dose-related increases in the spine, femoral neck, and total hip BMD. Furthermore, mild injection site reactions were reported more frequently with blosozumab compared to placebo. 388 In a follow-up study 1 year after discontinuing treatment, women initially treated with blosozumab 270 mg Q2W and blosozumab 180 mg Q2W showed lumbar spine BMD that remained significantly greater than placebo. 389 SHR-1222 is the newest monoclonal antibody targeting sclerostin in postmenopausal osteoporosis to enter clinical trials. It is currently in its phase I trial and no clinical data has been published up to this point. Setrusumab (BPS-804) is a monoclonal antibody against sclerostin used to treat osteogenesis imperfecta that has been tested in a phase IIa clinical trial. A study of 14 adult patients with osteogenesis imperfecta demonstrated that BPS-804 was generally well tolerated and treatment stimulated bone formation, reduced bone resorption (as measured by CTX levels), and increased lumbar spine BMD (by 4% on day 141 compared with baseline). 390
Anti-cancer therapeutics targeting Wnt signaling
As previously mentioned, aberrations of the Wnt pathway are implicated in numerous cancers. Research in this area has paved the way for the development of anti-cancer therapeutics that target the Wnt pathway. Many have entered clinical trials, either as monotherapies or in combination with chemotherapy ( Table 3 ).
Table 3
List of anti-cancer Wnt-targeting therapeutics.
| Mode of Action | Drug(s) | Cancer (Indication) | Phase | Identifier |
| PORCN Inhibitor | LGK974 | Pancreatic cancer, BRAF mutant CRC, Melanoma, TNBC, HNSCC, Cervical squamous cell cancer, Esophageal squamous cell cancer, Lung squamous cell cancer | Phase I | NCT01351103 |
| WNT974 (with LGX818 and Cetuximab) | Metastatic CRC | Phase I/II | NCT02278133 | |
| ETC-1922159 (single agent and with Pembrolizumab) | Advanced solid tumors | Phase I | NCT02521844 | |
| CGX1321 | GI Cancer | Phase I | NCT03507998 | |
| CGX1321 (with Pembrolizumab or Encorafenib + Cetuximab) | Solid tumors, GI cancer | Phase I | NCT02675946 | |
| RXC004 | Advanced solid tumors | Phase II | NCT04907851 | |
| RXC004 (with Nivolumab) | Advanced solid tumors | Phase I | NCT03447470 | |
| CBP/β-catenin antagonist | PRI-724 | Advanced or metastatic pancreatic adenocarcinoma | Phase I | NCT01764477 |
| PRI-724 | Acute myeloid leukemia, Chronic myeloid leukemia | Phase I/II | NCT01606579 | |
| ROR1- and ROR2-antagonist | Cirmtuzumab | Chronic Lymphocytic Leukemia | Phase I | NCT02222688 |
| Cirmtuzumab (with ibrutinib) | B-cell chronic lymphocytic leukemia, Small lymphocytic lymphoma, Mantle cell lymphoma, Marginal zone lymphoma | Phase I/II | NCT03088878 | |
| Zilovertamab vedotin | Breast cancer, Lung cancer, Pancreatic cancer, Gastric cancer | Phase II | NCT04504916 | |
| CCT301-59 | Solid tumors, Soft tissue sarcoma, Gastric cancer, Pancreatic cancer, Bladder cancer | Phase I | NCT03960060 | |
| Wnt5a peptide mimic | Foxy-5 | Metastatic Breast cancer, Metastatic Colon cancer, Metastatic Prostate cancer | Phase I | NCT02655952 |
| Foxy-5 | Colon cancer | Phase II | NCT03883802 | |
| GSK-3β inhibitor | LY2090314 (with pemetrexed and carboplatin) | Advanced cancer | Phase I | NCT01287520 |
| LY2090314 | Leukemia | Phase II | NCT01214603 | |
| mAb targeting Dkk1 | DKN-01 | Multiple myeloma, Solid tumors, Non-small cell lung cancer | Phase I | NCT01457417 |
| DKN-01 (with lenalidomide/dexamethasone) | Multiple myeloma | Phase I | NCT01711671 | |
| DKN-01 (with Nivolumab) | Advanced Biliary Tract Cancer | Phase II | NCT04057365 | |
| DKN-01 (with Gemcitabine/Cisplatin) | Carcinoma of intrahepatic and extra-hepatic biliary system, Carcinoma of gallbladder, Cholangiocarcinoma | Phase I | NCT02375880 | |
| LRP5/6 antagonist | BI 905677 | Solid tumors | Phase I | NCT03604445 |
| mAb targeting FZD receptors | OMP-18R5 | Solid tumors | Phase I | NCT01345201 |
| OMP-18R5 (with Docetaxel) | Solid tumors | Phase I | NCT01957007 | |
| OMP-18R5 (with Paclitaxel) | Metastatic breast cancer | Phase I | NCT01973309 | |
| OMP-18R5 (with Nab-Paclitaxel and Gemcitabine) | Stage IV pancreatic cancer | Phase I | NCT02005315 | |
| Truncated FZD8 fused to IgG1 Fc | OMP-54F28 | Solid tumors | Phase I | NCT01608867 |
| OMP-54F28 (with Sorafenib) | Hepatocellular cancer | Phase I | NCT02069145 | |
| OMP-54F28 (with Paclitaxel and Carboplatin) | Ovarian cancer | Phase I | NCT02092363 | |
| OMP-54F28 (with Nab-Paclitaxel and Gemcitabine) | Stage IV pancreatic cancer | Phase I | NCT02050178 |
Porcupine (PORCN) inhibitors prevent the post-translational palmitoylation of Wnt ligands. Thereby, PORCN inhibitors work to block the secretion of Wnt ligands and the triggering of Wnt signaling, which can have implications for the control of aberrant cell growth in cancer. 391 Current applications of PORCN inhibitors in clinical trials include solid tumors, gastrointestinal cancers, pancreatic cancer, BRAF-mutant CRC, melanoma, and TNBC among others. The interaction between cAMP response element binding (CREB) binding protein (CBP) and β-catenin is believed to activate genes linked to cell proliferation, 392 and inhibitors are under development. Moreover, small molecule inhibitors of TCF4/β-catenin interaction that prevent the transcription of Wnt target genes have demonstrated anti-tumor activity in preclinical experiments. 393 , 394 Signal transduction through the non-canonical Wnt co-receptor, tyrosine kinase-like orphan receptor (ROR), is overexpressed in a number of hematologic malignancies and solid tumors. β-Catenin independent Wnt/ROR signaling has been linked to processes such as tumor cell proliferation, survival, invasion, or treatment resistance. As a result, targeting ROR1/ROR2 is a point of interest for anti-cancer therapies and several drugs are in clinical trials. 395
Tankyrase enzymes are negative regulators of the β-catenin destruction complex that mediate the ubiquitination and degradation of the scaffolding protein Axin. 396 A number of tankyrase inhibitors have been in development and several have shown promising anti-tumor activity in preclinical experiments. 397 , 398 However, none have entered clinical trials as of this writing. Foxy-5 (a formylated Wnt5A-derived six amino acid peptide) functions as a Wnt5a mimicking peptide that has exhibited anti-metastatic effects in preclinical experiments. 399 , 400 Foxy-5 has also undergone phase I clinical trials for the treatment of metastatic breast, colon, and prostate cancer. LY2090314 is a GSK-3β inhibitor that activates the Wnt/β-catenin pathway. Preclinical studies of LY2090314 have demonstrated the inhibition of tumor growth in melanoma and neuroblastoma. 401 , 402 LY2090314 has also undergone clinical trials both as a single therapy for leukemia and in combination with other chemotherapies for advanced cancers.
Besides small molecule inhibitors, antibody-based therapeutics have also been developed to target Wnt signaling. DKN-01 is an IgG4 monoclonal antibody that targets Dkk1. While the specific mechanism is unknown, Dkk1 is thought to play a role in tumor immune resistance. Elevated levels of Dkk1 have also been associated with poor prognosis in gynecologic and gastroesophageal cancers. 403 Vantictumab (OMP-18R5) is a monoclonal antibody that binds to FZD1, FZD2, FZD5, FZD7, and FZD8 receptors through a conserved epitope within the extracellular domain. Preclinical testing in a xenograft model demonstrated reduced tumor growth and tumor-initiating cell frequency and synergistic activity with other chemotherapeutic agents. 404 OMP-18R5 has undergone phase I clinical trials as both a single therapy and in combination with other agents. Furthermore, OMP-54F28 is a fused protein of truncated FZD8 and IgG1 Fc region that antagonizes Wnt signaling by competing with the native Fzd8 receptor for ligands. Preclinical experiments have demonstrated inhibition of tumor growth in an MMTV-Wnt1-induced tumor model as well as synergy with gemcitabine in a pancreatic cancer xenograft model. 405
Lastly, there are numerous repurposed drugs ( e.g. , niclodamide and pyrvinium) and chemical/natural products ( e.g. , ginsenoside Rg3, resveratrol, and tetrandrine) that have been shown to target various components of Wnt signaling in cancer cells as a part of their modes of action, although they may not exclusively impact Wnt signaling. 235 , 406 , 407 , 408 , 409 , 410 , 411 , 412 , 413 It is thus anticipated more Wnt signaling-targeting chemicals and compounds will be identified and subsequently developed as novel anticancer agents.
Conclusions and future directions
Since its discovery nearly 40 years ago, research into the evolutionarily conserved Wnt pathway has broadened our understanding of stem cell self-renewal, tissue homeostasis, and diseases. Research has also revealed the underlying mechanisms of the canonical and the non-canonical paths. The study of Wnt signaling has not only increased our knowledge of physiological development and homeostasis but also of disease pathology when components of Wnt signaling experience dysregulation. These developments in our understanding of Wnt signaling have paved the way for the creation of novel therapeutics. The development of romosozumab (a monoclonal antibody targeting sclerostin) illustrates the therapeutic potential in targeting the Wnt pathway in human diseases. While many anti-cancer treatments targeting the Wnt pathway have entered the early phases of clinical trials, they face a significant challenge in side effects on normal tissue. As a result, further study is warranted in the area of cancer-specific regulators of Wnt signaling that may prove to be druggable targets of Wnt-associated cancers.
Conflict of interests
All authors declare no conflict of interests.
Funding
The reported work was supported in part by research grants from the National Institutes of Health (No. CA226303 to TCH and No. DE030480 to RRR). JF was supported in part by research grants from the Natural Science Foundation of China (No. 82102696), the 2019 Science and Technology Research Plan Project of Chongqing Education Commission (China) (No. KJQN201900410), and the 2019 Funding for Postdoctoral Research (Chongqing Human Resources and Social Security Bureau No. 298, Chongqing, China). WW was supported by the Medical Scientist Training Program of the National Institutes of Health (No. T32 GM007281). This project was also supported in part by The University of Chicago Cancer Center Support Grant (No. P30CA014599) and the National Center for Advancing Translational Sciences (NCATS) of the National Institutes of Health (No. 5UL1TR002389). TCH was also supported by the Mabel Green Myers Research Endowment Fund and The University of Chicago Orthopaedics Alumni Fund. Funding sources were not involved in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication.
Acknowledgements
The authors wish to apologize to the investigators whose original work cannot be cited in the manuscript due to space constraints.
Footnotes
Peer review under responsibility of Chongqing Medical University.
Contributor Information
Russell R. Reid, Email: rreid@surgery.bsd.uchicago.edu.
Tong-Chuan He, Email: tche@uchicago.edu.
References
1. Nusse R., Varmus H.E. Many tumors induced by the mouse mammary tumor virus contain a provirus integrated in the same region of the host genome. Cell. 1982;31(1):99–109. doi: 10.1016/0092-8674(82)90409-3.
2. Rijsewijk F., Schuermann M., Wagenaar E., Parren P., Weigel D., Nusse R. The Drosophila homolog of the mouse mammary oncogene int-1 is identical to the segment polarity gene wingless. Cell. 1987;50(4):649–657. doi: 10.1016/0092-8674(87)90038-9.
3. Wodarz A., Nusse R. Mechanisms of Wnt signaling in development. Annu Rev Cell Dev Biol. 1998;14:59–88. doi: 10.1146/annurev.cellbio.14.1.59.
4. Hayat R., Manzoor M., Hussain A. Wnt signaling pathway: a comprehensive review. Cell Biol Int. 2022;46(6):863–877. doi: 10.1002/cbin.11797.
5. Chae W.J., Bothwell A.L.M. Canonical and non-canonical Wnt signaling in immune cells. Trends Immunol. 2018;39(10):830–847. doi: 10.1016/j.it.2018.08.006.
6. Yang K., Wang X., Zhang H., et al. The evolving roles of canonical WNT signaling in stem cells and tumorigenesis: implications in targeted cancer therapies. Lab Invest. 2016;96(2):116–136. doi: 10.1038/labinvest.2015.144.
7. He X., Semenov M., Tamai K., Zeng X. LDL receptor-related proteins 5 and 6 in Wnt/beta-catenin signaling: arrows point the way. Development. 2004;131(8):1663–1677. doi: 10.1242/dev.01117.
8. Hrckulak D., Kolar M., Strnad H., Korinek V. TCF/LEF transcription factors: an update from the Internet resources. Cancers. 2016;8(7):70. doi: 10.3390/cancers8070070.
9. Stamos J.L., Weis W.I. The β-catenin destruction complex. Cold Spring Harb Perspect Biol. 2013;5(1):a007898. doi: 10.1101/cshperspect.a007898.
10. Hart M., Concordet J.P., Lassot I., et al. The F-box protein beta-TrCP associates with phosphorylated beta-catenin and regulates its activity in the cell. Curr Biol. 1999;9(4):207–210. doi: 10.1016/s0960-9822(99)80091-8.
11. Zhan T., Rindtorff N., Boutros M. Wnt signaling in cancer. Oncogene. 2017;36(11):1461–1473. doi: 10.1038/onc.2016.304.
12. He T.C., Sparks A.B., Rago C., et al. Identification of c-MYC as a target of the APC pathway. Science. 1998;281(5382):1509–1512. doi: 10.1126/science.281.5382.1509.
13. He T.C., Chan T.A., Vogelstein B., Kinzler K.W. PPARδ is an APC-regulated target of nonsteroidal anti-inflammatory drugs. Cell. 1999;99(3):335–345. doi: 10.1016/s0092-8674(00)81664-5.
14. MacDonald B.T., Tamai K., He X. Wnt/β-catenin signaling: components, mechanisms, and diseases. Dev Cell. 2009;17(1):9–26. doi: 10.1016/j.devcel.2009.06.016.
15. Yang Y. Wnt signaling in development and disease. Cell Biosci. 2012;2(1):14. doi: 10.1186/2045-3701-2-14.
16. Butler M.T., Wallingford J.B. Planar cell polarity in development and disease. Nat Rev Mol Cell Biol. 2017;18(6):375–388. doi: 10.1038/nrm.2017.11.
17. Slusarski D.C., Pelegri F. Calcium signaling in vertebrate embryonic patterning and morphogenesis. Dev Biol. 2007;307(1):1–13. doi: 10.1016/j.ydbio.2007.04.043.
18. Berger H., Wodarz A., Borchers A. PTK7 faces the Wnt in development and disease. Front Cell Dev Biol. 2017;5:31. doi: 10.3389/fcell.2017.00031.
19. Katoh M., Katoh M. Molecular genetics and targeted therapy of WNT-related human diseases. Int J Mol Med. 2017;40(3):587–606. doi: 10.3892/ijmm.2017.3071. (Review)
20. Bovolenta P., Rodriguez J., Esteve P. Frizzled/RYK mediated signalling in axon guidance. Development. 2006;133(22):4399–4408. doi: 10.1242/dev.02592.
21. Xu X., Zhang M., Xu F., Jiang S. Wnt signaling in breast cancer: biological mechanisms, challenges and opportunities. Mol Cancer. 2020;19(1):165. doi: 10.1186/s12943-020-01276-5.
22. Jenny A., Reynolds-Kenneally J., Das G., Burnett M., Mlodzik M. Diego and Prickle regulate Frizzled planar cell polarity signalling by competing for Dishevelled binding. Nat Cell Biol. 2005;7(7):691–697. doi: 10.1038/ncb1271.
23. Narimatsu M., Bose R., Pye M., et al. Regulation of planar cell polarity by Smurf ubiquitin ligases. Cell. 2009;137(2):295–307. doi: 10.1016/j.cell.2009.02.025.
24. Barkó S., Bugyi B., Carlier M.F., et al. Characterization of the biochemical properties and biological function of the formin homology domains of Drosophila DAAM. J Biol Chem. 2010;285(17):13154–13169. doi: 10.1074/jbc.M109.093914.
25. Habas R., Dawid I.B., He X. Coactivation of Rac and Rho by Wnt/Frizzled signaling is required for vertebrate gastrulation. Genes Dev. 2003;17(2):295–309. doi: 10.1101/gad.1022203.
26. Peng Y., Chen Z., Chen Y., et al. ROCK isoforms differentially modulate cancer cell motility by mechanosensing the substrate stiffness. Acta Biomater. 2019;88:86–101. doi: 10.1016/j.actbio.2019.02.015.
27. Coso O.A., Chiariello M., Yu J.C., et al. The small GTP-binding proteins Rac1 and Cdc42 regulate the activity of the JNK/SAPK signaling pathway. Cell. 1995;81(7):1137–1146. doi: 10.1016/s0092-8674(05)80018-2.
28. Meng Q., Xia Y. c-Jun, at the crossroad of the signaling network. Protein Cell. 2011;2(11):889–898. doi: 10.1007/s13238-011-1113-3.
29. Huang L., Jin Y., Feng S., et al. Role of Wnt/β-catenin, Wnt/c-Jun N-terminal kinase and Wnt/Ca2+ pathways in cisplatin-induced chemoresistance in ovarian cancer. Exp Ther Med. 2016;12(6):3851–3858. doi: 10.3892/etm.2016.3885.
30. Eyers C.E., McNeill H., Knebel A., et al. The phosphorylation of CapZ-interacting protein (CapZIP) by stress-activated protein kinases triggers its dissociation from CapZ. Biochem J. 2005;389(Pt 1):127–135. doi: 10.1042/BJ20050387.
31. De A. Wnt/Ca2+ signaling pathway: a brief overview. Acta Biochim Biophys Sin (Shanghai) 2011;43(10):745–756. doi: 10.1093/abbs/gmr079.
32. Grumolato L., Liu G., Mong P., et al. Canonical and noncanonical Wnts use a common mechanism to activate completely unrelated coreceptors. Genes Dev. 2010;24(22):2517–2530. doi: 10.1101/gad.1957710.
33. McQuate A., Latorre-Esteves E., Barria A. A Wnt/calcium signaling cascade regulates neuronal excitability and trafficking of NMDARs. Cell Rep. 2017;21(1):60–69. doi: 10.1016/j.celrep.2017.09.023.
34. Zhang Z., Zhang F., Davis A.K., et al. CDC42 controlled apical-basal polarity regulates intestinal stem cell to transit amplifying cell fate transition via YAP-EGF-mTOR signaling. Cell Rep. 2022;38(2) doi: 10.1016/j.celrep.2021.110009.
35. Osmani N., Vitale N., Borg J.P., Etienne-Manneville S. Scrib controls Cdc42 localization and activity to promote cell polarization during astrocyte migration. Curr Biol. 2006;16(24):2395–2405. doi: 10.1016/j.cub.2006.10.026.
36. Wong H.S.C., Chang W.C. Correlation of clinical features and genetic profiles of stromal interaction molecule 1 (STIM1) in colorectal cancers. Oncotarget. 2015;6(39):42169–42182. doi: 10.18632/oncotarget.5888.
37. Wang H.Y., Malbon C.C. Wnt signaling, Ca2+, and cyclic GMP: visualizing Frizzled functions. Science. 2003;300(5625):1529–1530. doi: 10.1126/science.1085259.
38. Heit J.J., Apelqvist Å.A., Gu X., et al. Calcineurin/NFAT signalling regulates pancreatic β-cell growth and function. Nature. 2006;443(7109):345–349. doi: 10.1038/nature05097.
39. Ishitani T., Kishida S., Hyodo-Miura J., et al. The TAK1-NLK mitogen-activated protein kinase cascade functions in the Wnt-5a/Ca(2+) pathway to antagonize Wnt/beta-catenin signaling. Mol Cell Biol. 2003;23(1):131–139. doi: 10.1128/MCB.23.1.131-139.2003.
40. Ishitani T., Ninomiya-Tsuji J., Nagai S.I., et al. The TAK1-NLK-MAPK-related pathway antagonizes signalling between β-catenin and transcription factor TCF. Nature. 1999;399(6738):798–802. doi: 10.1038/21674.
41. Kim J.H., Liu X., Wang J., et al. Wnt signaling in bone formation and its therapeutic potential for bone diseases. Ther Adv Musculoskelet Dis. 2013;5(1):13–31. doi: 10.1177/1759720X12466608.
42. Colozza G., Koo B.K. Wnt/β-catenin signaling: structure, assembly and endocytosis of the signalosome. Dev Growth Differ. 2021;63(3):199–218. doi: 10.1111/dgd.12718.
43. Proffitt K.D., Virshup D.M. Precise regulation of porcupine activity is required for physiological Wnt signaling. J Biol Chem. 2012;287(41):34167–34178. doi: 10.1074/jbc.M112.381970.
44. Coombs G.S., Yu J., Canning C.A., et al. WLS-dependent secretion of WNT3A requires Ser209 acylation and vacuolar acidification. J Cell Sci. 2010;123(Pt 19):3357–3367. doi: 10.1242/jcs.072132.
45. Nygaard R., Yu J., Kim J., et al. Structural basis of WLS/Evi-mediated Wnt transport and secretion. Cell. 2021;184(1):194–206.e14. doi: 10.1016/j.cell.2020.11.038.
46. Belenkaya T.Y., Wu Y., Tang X., et al. The retromer complex influences Wnt secretion by recycling wntless from endosomes to the trans-Golgi network. Dev Cell. 2008;14(1):120–131. doi: 10.1016/j.devcel.2007.12.003.
47. Cruciat C.M., Niehrs C. Secreted and transmembrane Wnt inhibitors and activators. Cold Spring Harb Perspect Biol. 2013;5(3):a015081. doi: 10.1101/cshperspect.a015081.
48. Bao J., Zheng J.J., Wu D. The structural basis of DKK-mediated inhibition of Wnt/LRP signaling. Sci Signal. 2012;5(224):pe22. doi: 10.1126/scisignal.2003028.
49. Poole K.E., van Bezooijen R.L., Loveridge N., et al. Sclerostin is a delayed secreted product of osteocytes that inhibits bone formation. FASEB J. 2005;19(13):1842–1844. doi: 10.1096/fj.05-4221fje.
50. Malinauskas T., Aricescu A.R., Lu W., Siebold C., Jones E.Y. Modular mechanism of Wnt signaling inhibition by Wnt inhibitory factor 1. Nat Struct Mol Biol. 2011;18(8):886–893. doi: 10.1038/nsmb.2081.
51. Piccolo S., Agius E., Leyns L., et al. The head inducer Cerberus is a multifunctional antagonist of Nodal, BMP and Wnt signals. Nature. 1999;397(6721):707–710. doi: 10.1038/17820.
52. Bovolenta P., Esteve P., Ruiz J.M., Cisneros E., Lopez-Rios J. Beyond Wnt inhibition: new functions of secreted Frizzled-related proteins in development and disease. J Cell Sci. 2008;121(pt 6):737–746. doi: 10.1242/jcs.026096.
53. Ruffner H., Sprunger J., Charlat O., et al. R-Spondin potentiates Wnt/β-catenin signaling through orphan receptors LGR4 and LGR5. PLoS One. 2012;7(7) doi: 10.1371/journal.pone.0040976.
54. Carmon K.S., Gong X., Lin Q., Thomas A., Liu Q. R-spondins function as ligands of the orphan receptors LGR4 and LGR5 to regulate Wnt/beta-catenin signaling. Proc Natl Acad Sci U S A. 2011;108(28):11452–11457. doi: 10.1073/pnas.1106083108.
55. Hao H.X., Xie Y., Zhang Y., et al. ZNRF3 promotes Wnt receptor turnover in an R-spondin-sensitive manner. Nature. 2012;485(7397):195–200. doi: 10.1038/nature11019.
56. Lebensohn A.M., Rohatgi R. R-spondins can potentiate WNT signaling without LGRs. Elife. 2018;7 doi: 10.7554/eLife.33126.
57. Xu Q., Wang Y., Dabdoub A., et al. Vascular development in the retina and inner ear: control by Norrin and Frizzled-4, a high-affinity ligand-receptor pair. Cell. 2004;116(6):883–895. doi: 10.1016/s0092-8674(04)00216-8.
58. Bacakova L., Zarubova J., Travnickova M., et al. Stem cells: their source, potency and use in regenerative therapies with focus on adipose-derived stem cells - a review. Biotechnol Adv. 2018;36(4):1111–1126. doi: 10.1016/j.biotechadv.2018.03.011.
59. Zhang H., Wang Z.Z. Mechanisms that mediate stem cell self-renewal and differentiation. J Cell Biochem. 2008;103(3):709–718. doi: 10.1002/jcb.21460.
60. Zakrzewski W., Dobrzyński M., Szymonowicz M., Rybak Z. Stem cells: past, present, and future. Stem Cell Res Ther. 2019;10(1):68. doi: 10.1186/s13287-019-1165-5.
61. Sterneckert J.L., Reinhardt P., Schöler H.R. Investigating human disease using stem cell models. Nat Rev Genet. 2014;15(9):625–639. doi: 10.1038/nrg3764.
62. Liu C., Oikonomopoulos A., Sayed N., Wu J.C., Wu J.C. Modeling human diseases with induced pluripotent stem cells: from 2D to 3D and beyond. Development. 2018;145(5):dev156166. doi: 10.1242/dev.156166.
63. Rowe R.G., Daley G.Q. Induced pluripotent stem cells in disease modelling and drug discovery. Nat Rev Genet. 2019;20(7):377–388. doi: 10.1038/s41576-019-0100-z.
64. Yamanaka S., Li J., Kania G., et al. Pluripotency of embryonic stem cells. Cell Tissue Res. 2008;331(1):5–22. doi: 10.1007/s00441-007-0520-5.
65. Dodsworth B.T., Hatje K., Rostovskaya M., Flynn R., Meyer C.A., Cowley S.A. Profiling of naïve and primed human pluripotent stem cells reveals state-associated miRNAs. Sci Rep. 2020;10(1) doi: 10.1038/s41598-020-67376-w.
66. Xu Z., Robitaille A.M., Berndt J.D., et al. Wnt/β-catenin signaling promotes self-renewal and inhibits the primed state transition in naïve human embryonic stem cells. Proc Natl Acad Sci U S A. 2016;113(42):E6382–E6390. doi: 10.1073/pnas.1613849113.
67. Hao J., Li T.G., Qi X., Zhao D.F., Zhao G.Q. WNT/β-catenin pathway up-regulates Stat3 and converges on LIF to prevent differentiation of mouse embryonic stem cells. Dev Biol. 2006;290(1):81–91. doi: 10.1016/j.ydbio.2005.11.011.
68. Miyabayashi T., Teo J.L., Yamamoto M., McMillan M., Nguyen C., Kahn M. Wnt/beta-catenin/CBP signaling maintains long-term murine embryonic stem cell pluripotency. Proc Natl Acad Sci U S A. 2007;104(13):5668–5673. doi: 10.1073/pnas.0701331104.
69. Singla D.K., Schneider D.J., LeWinter M.M., Sobel B.E. wnt3a but not wnt11 supports self-renewal of embryonic stem cells. Biochem Biophys Res Commun. 2006;345(2):789–795. doi: 10.1016/j.bbrc.2006.04.125.
70. Sato N., Meijer L., Skaltsounis L., Greengard P., Brivanlou A.H. Maintenance of pluripotency in human and mouse embryonic stem cells through activation of Wnt signaling by a pharmacological GSK-3-specific inhibitor. Nat Med. 2004;10(1):55–63. doi: 10.1038/nm979.
71. Dravid G., Ye Z., Hammond H., et al. Defining the role of Wnt/β-catenin signaling in the survival, proliferation, and self-renewal of human embryonic stem cells. Stem Cells. 2005;23(10):1489–1501. doi: 10.1634/stemcells.2005-0034.
72. Davidson K.C., Adams A.M., Goodson J.M., et al. Wnt/β-catenin signaling promotes differentiation, not self-renewal, of human embryonic stem cells and is repressed by Oct4. Proc Natl Acad Sci U S A. 2012;109(12):4485–4490. doi: 10.1073/pnas.1118777109.
73. Lindsley R.C., Gill J.G., Kyba M., Murphy T.L., Murphy K.M. Canonical Wnt signaling is required for development of embryonic stem cell-derived mesoderm. Development. 2006;133(19):3787–3796. doi: 10.1242/dev.02551.
74. Bakre M.M., Hoi A., Mong J.C., Koh Y.Y., Wong K.Y., Stanton L.W. Generation of multipotential mesendodermal progenitors from mouse embryonic stem cells via sustained Wnt pathway activation. J Biol Chem. 2007;282(43):31703–31712. doi: 10.1074/jbc.M704287200.
75. White J., Dalton S. Cell cycle control of embryonic stem cells. Stem Cell Rev. 2005;1(2):131–138. doi: 10.1385/SCR:1:2:131.
76. Calder A., Roth-Albin I., Bhatia S., et al. Lengthened G1 phase indicates differentiation status in human embryonic stem cells. Stem Cells Dev. 2013;22(2):279–295. doi: 10.1089/scd.2012.0168.
77. Niehrs C., Acebron S.P. Mitotic and mitogenic Wnt signalling. EMBO J. 2012;31(12):2705–2713. doi: 10.1038/emboj.2012.124.
78. De Jaime-Soguero A., Aulicino F., Ertaylan G., et al. Wnt/Tcf1 pathway restricts embryonic stem cell cycle through activation of the Ink4/Arf locus. PLoS Genet. 2017;13(3) doi: 10.1371/journal.pgen.1006682.
79. Koles K., Nunnari J., Korkut C., et al. Mechanism of evenness interrupted (Evi)-exosome release at synaptic boutons. J Biol Chem. 2012;287(20):16820–16834. doi: 10.1074/jbc.M112.342667.
80. Augustin I., Dewi D.L., Hundshammer J., Erdmann G., Kerr G., Boutros M. Autocrine Wnt regulates the survival and genomic stability of embryonic stem cells. Sci Signal. 2017;10(461) doi: 10.1126/scisignal.aah6829.
81. Bryder D., Rossi D.J., Weissman I.L. Hematopoietic stem cells: the paradigmatic tissue-specific stem cell. Am J Pathol. 2006;169(2):338–346. doi: 10.2353/ajpath.2006.060312.
82. Seita J., Weissman I.L. Hematopoietic stem cell: self-renewal versus differentiation. Wiley Interdiscip Rev Syst Biol Med. 2010;2(6):640–653. doi: 10.1002/wsbm.86.
83. Umeda K., Heike T., Yoshimoto M., et al. Development of primitive and definitive hematopoiesis from nonhuman primate embryonic stem cells in vitro. Development. 2004;131(8):1869–1879. doi: 10.1242/dev.01065.
84. Sturgeon C.M., Ditadi A., Awong G., Kennedy M., Keller G. Wnt signaling controls the specification of definitive and primitive hematopoiesis from human pluripotent stem cells. Nat Biotechnol. 2014;32(6):554–561. doi: 10.1038/nbt.2915.
85. Nostro M.C., Cheng X., Keller G.M., Gadue P. Wnt, activin, and BMP signaling regulate distinct stages in the developmental pathway from embryonic stem cells to blood. Cell Stem Cell. 2008;2(1):60–71. doi: 10.1016/j.stem.2007.10.011.
86. Isern J., He Z., Fraser S.T., et al. Single-lineage transcriptome analysis reveals key regulatory pathways in primitive erythroid progenitors in the mouse embryo. Blood. 2011;117(18):4924–4934. doi: 10.1182/blood-2010-10-313676.
87. Luis T.C., Weerkamp F., Naber B.A., et al. Wnt3a deficiency irreversibly impairs hematopoietic stem cell self-renewal and leads to defects in progenitor cell differentiation. Blood. 2009;113(3):546–554. doi: 10.1182/blood-2008-06-163774.
88. Reya T., Duncan A.W., Ailles L., et al. A role for Wnt signalling in self-renewal of haematopoietic stem cells. Nature. 2003;423(6938):409–414. doi: 10.1038/nature01593.
89. Sugimura R., He X.C., Venkatraman A., et al. Noncanonical Wnt signaling maintains hematopoietic stem cells in the niche. Cell. 2012;150(2):351–365. doi: 10.1016/j.cell.2012.05.041.
90. Nemeth M.J., Topol L., Anderson S.M., Yang Y., Bodine D.M. Wnt5a inhibits canonical Wnt signaling in hematopoietic stem cells and enhances repopulation. Proc Natl Acad Sci U S A. 2007;104(39):15436–15441. doi: 10.1073/pnas.0704747104.
91. Povinelli B.J., Nemeth M.J. Wnt5a regulates hematopoietic stem cell proliferation and repopulation through the Ryk receptor. Stem Cells. 2014;32(1):105–115. doi: 10.1002/stem.1513.
92. Famili F., Perez L.G., Naber B.A., Noordermeer J.N., Fradkin L.G., Staal F.J. The non-canonical Wnt receptor Ryk regulates hematopoietic stem cell repopulation in part by controlling proliferation and apoptosis. Cell Death Dis. 2016;7(11):e2479. doi: 10.1038/cddis.2016.380.
93. Schilham M.W., Wilson A., Moerer P., Benaissa-Trouw B.J., Cumano A., Clevers H.C. Critical involvement of Tcf-1 in expansion of thymocytes. J Immunol. 1998;161(8):3984–3991.
94. Staal F.J., Meeldijk J., Moerer P., et al. Wnt signaling is required for thymocyte development and activates Tcf-1 mediated transcription. Eur J Immunol. 2001;31(1):285–293. doi: 10.1002/1521-4141(200101)31:1<285::AID-IMMU285>3.0.CO;2-D.
95. Hossain M.Z., Yu Q., Xu M., Sen J.M. ICAT expression disrupts beta-catenin-TCF interactions and impairs survival of thymocytes and activated mature T cells. Int Immunol. 2008;20(7):925–935. doi: 10.1093/intimm/dxn051.
96. Malhotra S., Baba Y., Garrett K.P., Staal F.J., Gerstein R., Kincade P.W. Contrasting responses of lymphoid progenitors to canonical and noncanonical Wnt signals. J Immunol. 2008;181(6):3955–3964. doi: 10.4049/jimmunol.181.6.3955.
97. Eastman Q., Grosschedl R. Regulation of LEF-1/TCF transcription factors by Wnt and other signals. Curr Opin Cell Biol. 1999;11(2):233–240. doi: 10.1016/s0955-0674(99)80031-3.
98. Reya T., O'Riordan M., Okamura R., et al. Wnt signaling regulates B lymphocyte proliferation through a LEF-1 dependent mechanism. Immunity. 2000;13(1):15–24. doi: 10.1016/s1074-7613(00)00004-2.
99. Liang H., Chen Q., Coles A.H., et al. Wnt5a inhibits B cell proliferation and functions as a tumor suppressor in hematopoietic tissue. Cancer Cell. 2003;4(5):349–360. doi: 10.1016/s1535-6108(03)00268-x.
100. Wilson A., Murphy M.J., Oskarsson T., et al. c-Myc controls the balance between hematopoietic stem cell self-renewal and differentiation. Genes Dev. 2004;18(22):2747–2763. doi: 10.1101/gad.313104.
101. Cobas M., Wilson A., Ernst B., et al. Beta-catenin is dispensable for hematopoiesis and lymphopoiesis. J Exp Med. 2004;199(2):221–229. doi: 10.1084/jem.20031615.
102. Koch U., Wilson A., Cobas M., Kemler R., MacDonald H.R., Radtke F. Simultaneous loss of beta- and gamma-catenin does not perturb hematopoiesis or lymphopoiesis. Blood. 2008;111(1):160–164. doi: 10.1182/blood-2007-07-099754.
103. Jeannet G., Scheller M., Scarpellino L., et al. Long-term, multilineage hematopoiesis occurs in the combined absence of beta-catenin and gamma-catenin. Blood. 2008;111(1):142–149. doi: 10.1182/blood-2007-07-102558.
104. Pittenger M.F., Discher D.E., Péault B.M., Phinney D.G., Hare J.M., Caplan A.I. Mesenchymal stem cell perspective: cell biology to clinical progress. NPJ Regen Med. 2019;4:22. doi: 10.1038/s41536-019-0083-6.
105. Zuk P.A., Zhu M., Mizuno H., et al. Multilineage cells from human adipose tissue: implications for cell-based therapies. Tissue Eng. 2001;7(2):211–228. doi: 10.1089/107632701300062859.
106. Haynesworth S.E., Goshima J., Goldberg V.M., Caplan A.I. Characterization of cells with osteogenic potential from human marrow. Bone. 1992;13(1):81–88. doi: 10.1016/8756-3282(92)90364-3.
107. Etheridge S.L., Spencer G.J., Heath D.J., Genever P.G. Expression profiling and functional analysis of Wnt signaling mechanisms in mesenchymal stem cells. Stem Cells. 2004;22(5):849–860. doi: 10.1634/stemcells.22-5-849.
108. Shen X., Pan B., Zhou H., et al. Differentiation of mesenchymal stem cells into cardiomyocytes is regulated by miRNA-1-2 via WNT signaling pathway. J Biomed Sci. 2017;24(1):29. doi: 10.1186/s12929-017-0337-9.
109. Qi Y., Zhang W., Li G., et al. An oriented-collagen scaffold including Wnt5a promotes osteochondral regeneration and cartilage interface integration in a rabbit model. FASEB J. 2020;34(8):11115–11132. doi: 10.1096/fj.202000280R.
110. Hartmann C., Tabin C.J. Dual roles of Wnt signaling during chondrogenesis in the chicken limb. Development. 2000;127(14):3141–3159. doi: 10.1242/dev.127.14.3141.
111. Qu F., Wang J., Xu N., et al. WNT3A modulates chondrogenesis via canonical and non-canonical Wnt pathways in MSCs. Front Biosci (Landmark Ed) 2013;18(2):493–503. doi: 10.2741/4116.
112. Lewiecki E.M. Role of sclerostin in bone and cartilage and its potential as a therapeutic target in bone diseases. Ther Adv Musculoskelet Dis. 2014;6(2):48–57. doi: 10.1177/1759720X13510479.
113. Rodda S.J., McMahon A.P. Distinct roles for Hedgehog and canonical Wnt signaling in specification, differentiation and maintenance of osteoblast progenitors. Development. 2006;133(16):3231–3244. doi: 10.1242/dev.02480.
114. Bennett C.N., Ouyang H., Ma Y.L., et al. Wnt10b increases postnatal bone formation by enhancing osteoblast differentiation. J Bone Miner Res. 2007;22(12):1924–1932. doi: 10.1359/jbmr.070810.
115. Bennett C.N., Longo K.A., Wright W.S., et al. Regulation of osteoblastogenesis and bone mass by Wnt10b. Proc Natl Acad Sci U S A. 2005;102(9):3324–3329. doi: 10.1073/pnas.0408742102.
116. Stevens J.R., Miranda-Carboni G.A., Singer M.A., Brugger S.M., Lyons K.M., Lane T.F. Wnt10b deficiency results in age-dependent loss of bone mass and progressive reduction of mesenchymal progenitor cells. J Bone Miner Res. 2010;25(10):2138–2147. doi: 10.1002/jbmr.118.
117. Krishnan V., Bryant H.U., Macdougald O.A. Regulation of bone mass by Wnt signaling. J Clin Invest. 2006;116(5):1202–1209. doi: 10.1172/JCI28551.
118. Gaur T., Lengner C.J., Hovhannisyan H., et al. Canonical WNT signaling promotes osteogenesis by directly stimulating Runx2 gene expression. J Biol Chem. 2005;280(39):33132–33140. doi: 10.1074/jbc.M500608200.
119. Yang L., Li Q., Zhang J., et al. Wnt7a promotes the osteogenic differentiation of human mesenchymal stem cells. Int J Mol Med. 2021;47(6):94. doi: 10.3892/ijmm.2021.4927.
120. Friedman M.S., Oyserman S.M., Hankenson K.D. Wnt11 promotes osteoblast maturation and mineralization through R-spondin 2. J Biol Chem. 2009;284(21):14117–14125. doi: 10.1074/jbc.M808337200.
121. Glass D.A., Bialek P., Ahn J.D., et al. Canonical Wnt signaling in differentiated osteoblasts controls osteoclast differentiation. Dev Cell. 2005;8(5):751–764. doi: 10.1016/j.devcel.2005.02.017.
122. Yan Y., Tang D., Chen M., et al. Axin2 controls bone remodeling through the beta-catenin-BMP signaling pathway in adult mice. J Cell Sci. 2009;122(Pt 19):3566–3578. doi: 10.1242/jcs.051904.
123. Okamoto M., Udagawa N., Uehara S., et al. Noncanonical Wnt5a enhances Wnt/β-catenin signaling during osteoblastogenesis. Sci Rep. 2014;4:4493. doi: 10.1038/srep04493.
124. Chen G., Deng C., Li Y.P. TGF-β and BMP signaling in osteoblast differentiation and bone formation. Int J Biol Sci. 2012;8(2):272–288. doi: 10.7150/ijbs.2929.
125. Guo X., Wang X.F. Signaling cross-talk between TGF-β/BMP and other pathways. Cell Res. 2009;19(1):71–88. doi: 10.1038/cr.2008.302.
126. Zhang M., Yan Y., Lim Y.B., et al. BMP-2 modulates beta-catenin signaling through stimulation of Lrp5 expression and inhibition of beta-TrCP expression in osteoblasts. J Cell Biochem. 2009;108(4):896–905. doi: 10.1002/jcb.22319.
127. Rodríguez-Carballo E., Ulsamer A., Susperregui A.R., et al. Conserved regulatory motifs in osteogenic gene promoters integrate cooperative effects of canonical Wnt and BMP pathways. J Bone Miner Res. 2011;26(4):718–729. doi: 10.1002/jbmr.260.
128. Tang N., Song W.X., Luo J., et al. BMP-9-induced osteogenic differentiation of mesenchymal progenitors requires functional canonical Wnt/beta-catenin signalling [published correction appears in J Cell Mol Med. 2023 Apr;27(8):1155-1156] J Cell Mol Med. 2009;13(8B):2448–2464. doi: 10.1111/j.1582-4934.2008.00569.x.
129. He G., Shi Y., Lim J., Bellido T., Ni J., Long F. Differential involvement of Wnt signaling in Bmp regulation of cancellous versus periosteal bone growth. Bone Res. 2017;5 doi: 10.1038/boneres.2017.16.
130. Kang S., Bennett C.N., Gerin I., Rapp L.A., Hankenson K.D., Macdougald O.A. Wnt signaling stimulates osteoblastogenesis of mesenchymal precursors by suppressing CCAAT/enhancer-binding protein alpha and peroxisome proliferator-activated receptor gamma. J Biol Chem. 2007;282(19):14515–14524. doi: 10.1074/jbc.M700030200.
131. Sengenès C., Lolmède K., Zakaroff-Girard A., Busse R., Bouloumié A. Preadipocytes in the human subcutaneous adipose tissue display distinct features from the adult mesenchymal and hematopoietic stem cells. J Cell Physiol. 2005;205(1):114–122. doi: 10.1002/jcp.20381.
132. Cawthorn W.P., Bree A.J., Yao Y., et al. Wnt6, Wnt10a and Wnt10b inhibit adipogenesis and stimulate osteoblastogenesis through a β-catenin-dependent mechanism. Bone. 2012;50(2):477–489. doi: 10.1016/j.bone.2011.08.010.
133. Christodoulides C., Laudes M., Cawthorn W.P., et al. The Wnt antagonist Dickkopf-1 and its receptors are coordinately regulated during early human adipogenesis. J Cell Sci. 2006;119(Pt 12):2613–2620. doi: 10.1242/jcs.02975.
134. Cadigan K.M., Waterman M.L. TCF/LEFs and Wnt signaling in the nucleus. Cold Spring Harb Perspect Biol. 2012;4(11) doi: 10.1101/cshperspect.a007906.
135. Xie Y.Y., Mo C.L., Cai Y.H., et al. Pygo2 regulates adiposity and glucose homeostasis via β-catenin-Axin2-GSK3β signaling pathway. Diabetes. 2018;67(12):2569–2584. doi: 10.2337/db18-0311.
136. Song L., Liu M., Ono N., Bringhurst F.R., Kronenberg H.M., Guo J. Loss of Wnt/β-catenin signaling causes cell fate shift of preosteoblasts from osteoblasts to adipocytes. J Bone Miner Res. 2012;27(11):2344–2358. doi: 10.1002/jbmr.1694.
137. Ehrlund A., Mejhert N., Lorente-Cebrián S., et al. Characterization of the Wnt inhibitors secreted Frizzled-related proteins (SFRPs) in human adipose tissue. J Clin Endocrinol Metab. 2013;98(3):E503–E508. doi: 10.1210/jc.2012-3416.
138. Mori H., Prestwich T.C., Reid M.A., et al. Secreted Frizzled-related protein 5 suppresses adipocyte mitochondrial metabolism through WNT inhibition. J Clin Invest. 2012;122(7):2405–2416. doi: 10.1172/JCI63604.
139. Crowley R.K., O'Reilly M.W., Bujalska I.J., et al. SFRP2 is associated with increased adiposity and VEGF expression. PLoS One. 2016;11(9) doi: 10.1371/journal.pone.0163777.
140. Lagathu C., Christodoulides C., Tan C.Y., et al. Secreted Frizzled-related protein 1 regulates adipose tissue expansion and is dysregulated in severe obesity. Int J Obes (Lond) 2010;34(12):1695–1705. doi: 10.1038/ijo.2010.107.
141. Hu L., Yang G., Hägg D., et al. IGF1 promotes adipogenesis by a lineage bias of endogenous adipose stem/progenitor cells. Stem Cells. 2015;33(8):2483–2495. doi: 10.1002/stem.2052.
142. Peterson L.W., Artis D. Intestinal epithelial cells: regulators of barrier function and immune homeostasis. Nat Rev Immunol. 2014;14(3):141–153. doi: 10.1038/nri3608.
143. Okumura R., Takeda K. Roles of intestinal epithelial cells in the maintenance of gut homeostasis. Exp Mol Med. 2017;49(5):e338. doi: 10.1038/emm.2017.20.
144. Gehart H., Clevers H. Tales from the crypt: new insights into intestinal stem cells. Nat Rev Gastroenterol Hepatol. 2019;16(1):19–34. doi: 10.1038/s41575-018-0081-y.
145. Haegebarth A., Clevers H. Wnt signaling, Lgr5, and stem cells in the intestine and skin. Am J Pathol. 2009;174(3):715–721. doi: 10.2353/ajpath.2009.080758.
146. Takashima S., Gold D., Hartenstein V. Stem cells and lineages of the intestine: a developmental and evolutionary perspective. Dev Genes Evol. 2013;223(1):85–102. doi: 10.1007/s00427-012-0422-8.
147. Barker N., van Oudenaarden A., Clevers H. Identifying the stem cell of the intestinal crypt: strategies and pitfalls. Cell Stem Cell. 2012;11(4):452–460. doi: 10.1016/j.stem.2012.09.009.
148. Garabedian E.M., Roberts L.J., McNevin M.S., Gordon J.I. Examining the role of Paneth cells in the small intestine by lineage ablation in transgenic mice. J Biol Chem. 1997;272(38):23729–23740. doi: 10.1074/jbc.272.38.23729.
149. Buczacki S.J.A., Zecchini H.I., Nicholson A.M., et al. Intestinal label-retaining cells are secretory precursors expressing Lgr5. Nature. 2013;495(7439):65–69. doi: 10.1038/nature11965.
150. van de Wetering M., Sancho E., Verweij C., et al. The β-catenin/TCF-4 complex imposes a crypt progenitor phenotype on colorectal cancer cells. Cell. 2002;111(2):241–250. doi: 10.1016/s0092-8674(02)01014-0.
151. Korinek V., Barker N., Moerer P., et al. Depletion of epithelial stem-cell compartments in the small intestine of mice lacking Tcf-4. Nat Genet. 1998;19(4):379–383. doi: 10.1038/1270.
152. Pinto D., Gregorieff A., Begthel H., Clevers H. Canonical Wnt signals are essential for homeostasis of the intestinal epithelium. Genes Dev. 2003;17(14):1709–1713. doi: 10.1101/gad.267103.
153. Takahashi M., Tsunoda T., Seiki M., Nakamura Y., Furukawa Y. Identification of membrane-type matrix metalloproteinase-1 as a target of the beta-catenin/Tcf4 complex in human colorectal cancers. Oncogene. 2002;21(38):5861–5867. doi: 10.1038/sj.onc.1205755.
154. van Es J.H., Jay P., Gregorieff A., et al. Wnt signalling induces maturation of Paneth cells in intestinal crypts. Nat Cell Biol. 2005;7(4):381–386. doi: 10.1038/ncb1240.
155. Sato T., van Es J.H., Snippert H.J., et al. Paneth cells constitute the niche for Lgr5 stem cells in intestinal crypts. Nature. 2011;469(7330):415–418. doi: 10.1038/nature09637.
156. Farin H.F., Van Es J.H., Clevers H. Redundant sources of Wnt regulate intestinal stem cells and promote formation of Paneth cells. Gastroenterology. 2012;143(6):1518–1529.e7. doi: 10.1053/j.gastro.2012.08.031.
157. Aoki R., Shoshkes-Carmel M., Gao N., et al. Foxl1-expressing mesenchymal cells constitute the intestinal stem cell niche. Cell Mol Gastroenterol Hepatol. 2016;2(2):175–188. doi: 10.1016/j.jcmgh.2015.12.004.
158. Schmitt M., Metzger M., Gradl D., Davidson G., Orian-Rousseau V. CD44 functions in Wnt signaling by regulating LRP6 localization and activation. Cell Death Differ. 2015;22(4):677–689. doi: 10.1038/cdd.2014.156.
159. Walter R.J., Sonnentag S.J., Munoz-Sagredo L., et al. Wnt signaling is boosted during intestinal regeneration by a CD44-positive feedback loop. Cell Death Dis. 2022;13(2):168. doi: 10.1038/s41419-022-04607-0.
160. Kalliolias G.D., Ivashkiv L.B. TNF biology, pathogenic mechanisms and emerging therapeutic strategies. Nat Rev Rheumatol. 2016;12(1):49–62. doi: 10.1038/nrrheum.2015.169.
161. Bradford E.M., Ryu S.H., Singh A.P., et al. Epithelial TNF receptor signaling promotes mucosal repair in inflammatory bowel disease. J Immunol. 2017;199(5):1886–1897. doi: 10.4049/jimmunol.1601066.
162. Zou W.Y., Blutt S.E., Zeng X.L., et al. Epithelial WNT ligands are essential drivers of intestinal stem cell activation. Cell Rep. 2018;22(4):1003–1015. doi: 10.1016/j.celrep.2017.12.093.
163. Dratwa M., Wysoczańska B., Łacina P., Kubik T., Bogunia-Kubik K. TERT-regulation and roles in cancer formation. Front Immunol. 2020;11 doi: 10.3389/fimmu.2020.589929.
164. Montgomery R.K., Carlone D.L., Richmond C.A., et al. Mouse telomerase reverse transcriptase (mTert) expression marks slowly cycling intestinal stem cells. Proc Natl Acad Sci U S A. 2011;108(1):179–184. doi: 10.1073/pnas.1013004108.
165. Suh H.N., Kim M.J., Jung Y.S., Lien E.M., Jun S., Park J.I. Quiescence exit of tert+ stem cells by Wnt/β-catenin is indispensable for intestinal regeneration. Cell Rep. 2017;21(9):2571–2584. doi: 10.1016/j.celrep.2017.10.118.
166. Martínez-Cerdeño V., Noctor S.C. Neural progenitor cell terminology. Front Neuroanat. 2018;12:104. doi: 10.3389/fnana.2018.00104.
167. Ma D.K., Bonaguidi M.A., Ming G.L., Song H. Adult neural stem cells in the mammalian central nervous system. Cell Res. 2009;19(6):672–682. doi: 10.1038/cr.2009.56.
168. Jin K., Galvan V. Endogenous neural stem cells in the adult brain. J Neuroimmune Pharmacol. 2007;2(3):236–242. doi: 10.1007/s11481-007-9076-0.
169. Ming G.L., Song H. Adult neurogenesis in the mammalian brain: significant answers and significant questions. Neuron. 2011;70(4):687–702. doi: 10.1016/j.neuron.2011.05.001.
170. Bowman A.N., van Amerongen R., Palmer T.D., Nusse R. Lineage tracing with Axin2 reveals distinct developmental and adult populations of Wnt/β-catenin-responsive neural stem cells. Proc Natl Acad Sci U S A. 2013;110(18):7324–7329. doi: 10.1073/pnas.1305411110.
171. Kalani M.Y., Cheshier S.H., Cord B.J., et al. Wnt-mediated self-renewal of neural stem/progenitor cells. Proc Natl Acad Sci U S A. 2008;105(44):16970–16975. doi: 10.1073/pnas.0808616105.
172. Islam M.M., Zhang C.L.T.L.X. A master regulator for neural stem cell maintenance and neurogenesis. Biochim Biophys Acta. 2015;1849(2):210–216. doi: 10.1016/j.bbagrm.2014.06.001.
173. Qu Q., Sun G., Li W., et al. Orphan nuclear receptor TLX activates Wnt/beta-catenin signalling to stimulate neural stem cell proliferation and self-renewal. Nat Cell Biol. 2010;12(1):31–39. doi: 10.1038/ncb2001.
174. Wexler E.M., Paucer A., Kornblum H.I., Palmer T.D., Geschwind D.H. Endogenous Wnt signaling maintains neural progenitor cell potency. Stem Cells. 2009;27(5):1130–1141. doi: 10.1002/stem.36.
175. Varela-Nallar L., Alfaro I.E., Serrano F.G., Parodi J., Inestrosa N.C. Wingless-type family member 5A (Wnt-5a) stimulates synaptic differentiation and function of glutamatergic synapses. Proc Natl Acad Sci U S A. 2010;107(49):21164–21169. doi: 10.1073/pnas.1010011107.
176. Arredondo S.B., Guerrero F.G., Herrera-Soto A., et al. Wnt5a promotes differentiation and development of adult-born neurons in the hippocampus by noncanonical Wnt signaling. Stem Cells. 2020;38(3):422–436. doi: 10.1002/stem.3121.
177. Lie D.C., Colamarino S.A., Song H.J., et al. Wnt signalling regulates adult hippocampal neurogenesis. Nature. 2005;437(7063):1370–1375. doi: 10.1038/nature04108.
178. Lee S.M., Tole S., Grove E., McMahon A.P. A local Wnt-3a signal is required for development of the mammalian hippocampus. Development. 2000;127(3):457–467. doi: 10.1242/dev.127.3.457.
179. Okamoto M., Inoue K., Iwamura H., et al. Reduction in paracrine Wnt3 factors during aging causes impaired adult neurogenesis. FASEB J. 2011;25(10):3570–3582. doi: 10.1096/fj.11-184697.
180. Agarwal S., Krishnamurthy K. StatPearls. StatPearls Publishing; Treasure Island (FL): May 8, 2022. Histology, Skin.
181. Li K.N., Tumbar T. Hair follicle stem cells as a skin-organizing signaling center during adult homeostasis. EMBO J. 2021;40(11) doi: 10.15252/embj.2020107135.
182. Stern C.D. Neural induction: 10 years on since the ‘default model’. Curr Opin Cell Biol. 2006;18(6):692–697. doi: 10.1016/j.ceb.2006.09.002.
183. Wilson S., Rydström A., Trimborn T., et al. The status of Wnt signalling regulates neural and epidermal fates in the chick embryo. Nature. 2001;411(6835):325–330. doi: 10.1038/35077115.
184. Das S., Yu S., Sakamori R., Stypulkowski E., Gao N. Wntless in Wnt secretion: molecular, cellular and genetic aspects. Front Biol. 2012;7(6):587–593. doi: 10.1007/s11515-012-1200-8.
185. Zhu X.J., Liu Y., Dai Z.M., et al. BMP-FGF signaling axis mediates Wnt-induced epidermal stratification in developing mammalian skin. PLoS Genet. 2014;10(10) doi: 10.1371/journal.pgen.1004687.
186. Schneider M.R., Schmidt-Ullrich R., Paus R. The hair follicle as a dynamic miniorgan. Curr Biol. 2009;19(3):R132–R142. doi: 10.1016/j.cub.2008.12.005.
187. Grubbs H., Nassereddin A., Morrison M. StatPearls. StatPearls Publishing; Treasure Island (FL): May 8, 2022. Embryology, Hair.
188. Rishikaysh P., Dev K., Diaz D., Qureshi W.M., Filip S., Mokry J. Signaling involved in hair follicle morphogenesis and development. Int J Mol Sci. 2014;15(1):1647–1670. doi: 10.3390/ijms15011647.
189. Andl T., Reddy S.T., Gaddapara T., Millar S.E. WNT signals are required for the initiation of hair follicle development. Dev Cell. 2002;2(5):643–653. doi: 10.1016/s1534-5807(02)00167-3.
190. Atit R., Sgaier S.K., Mohamed O.A., et al. β-catenin activation is necessary and sufficient to specify the dorsal dermal fate in the mouse. Dev Biol. 2006;296(1):164–176. doi: 10.1016/j.ydbio.2006.04.449.
191. Krause K., Foitzik K. Biology of the hair follicle: the basics. Semin Cutan Med Surg. 2006;25(1):2–10. doi: 10.1016/j.sder.2006.01.002.
192. Tumbar T., Guasch G., Greco V., et al. Defining the epithelial stem cell niche in skin. Science. 2004;303(5656):359–363. doi: 10.1126/science.1092436.
193. Huelsken J., Vogel R., Erdmann B., Cotsarelis G., Birchmeier W. β-catenin controls hair follicle morphogenesis and stem cell differentiation in the skin. Cell. 2001;105(4):533–545. doi: 10.1016/s0092-8674(01)00336-1.
194. Zhou P., Byrne C., Jacobs J., Fuchs E. Lymphoid enhancer factor 1 directs hair follicle patterning and epithelial cell fate. Genes Dev. 1995;9(6):700–713. doi: 10.1101/gad.9.6.700.
195. Zhang Y., Yu J., Shi C., et al. Lef1 contributes to the differentiation of bulge stem cells by nuclear translocation and cross-talk with the Notch signaling pathway. Int J Med Sci. 2013;10(6):738–746. doi: 10.7150/ijms.5693.
196. Lowry W.E., Blanpain C., Nowak J.A., Guasch G., Lewis L., Fuchs E. Defining the impact of beta-catenin/Tcf transactivation on epithelial stem cells. Genes Dev. 2005;19(13):1596–1611. doi: 10.1101/gad.1324905.
197. Van Mater D., Kolligs F.T., Dlugosz A.A., Fearon E.R. Transient activation of beta-catenin signaling in cutaneous keratinocytes is sufficient to trigger the active growth phase of the hair cycle in mice. Genes Dev. 2003;17(10):1219–1224. doi: 10.1101/gad.1076103.
198. Bao B., Ahmad A., Azmi A.S., Ali S., Sarkar F.H. Overview of cancer stem cells (CSCs) and mechanisms of their regulation: implications for cancer therapy. Curr Protoc Pharmacol. 2013;61(1) doi: 10.1002/0471141755.ph1425s61. 14.25.1-14.25.14.
199. Lathia J.D., Liu H. Overview of cancer stem cells and stemness for community oncologists. Target Oncol. 2017;12(4):387–399. doi: 10.1007/s11523-017-0508-3.
200. Shackleton M., Quintana E., Fearon E.R., Morrison S.J. Heterogeneity in cancer: cancer stem cells versus clonal evolution. Cell. 2009;138(5):822–829. doi: 10.1016/j.cell.2009.08.017.
201. Li Y., Wang Z., Ajani J.A., Song S. Drug resistance and cancer stem cells. Cell Commun Signal. 2021;19(1):19. doi: 10.1186/s12964-020-00627-5.
202. Zhao J. Cancer stem cells and chemoresistance: the smartest survives the raid. Pharmacol Ther. 2016;160:145–158. doi: 10.1016/j.pharmthera.2016.02.008.
203. Hanahan D., Coussens L.M. Accessories to the crime: functions of cells recruited to the tumor microenvironment. Cancer Cell. 2012;21(3):309–322. doi: 10.1016/j.ccr.2012.02.022.
204. Plaks V., Kong N., Werb Z. The cancer stem cell niche: how essential is the niche in regulating stemness of tumor cells? Cell Stem Cell. 2015;16(3):225–238. doi: 10.1016/j.stem.2015.02.015.
205. Zhao Y., Dong Q., Li J., et al. Targeting cancer stem cells and their niche: perspectives for future therapeutic targets and strategies. Semin Cancer Biol. 2018;53:139–155. doi: 10.1016/j.semcancer.2018.08.002.
206. Bajaj J., Diaz E., Reya T. Stem cells in cancer initiation and progression. J Cell Biol. 2020;219(1) doi: 10.1083/jcb.201911053.
207. Katoh M. Canonical and non-canonical WNT signaling in cancer stem cells and their niches: cellular heterogeneity, omics reprogramming, targeted therapy and tumor plasticity. Int J Oncol. 2017;51(5):1357–1369. doi: 10.3892/ijo.2017.4129. (Review)
208. Zhong Z., Virshup D.M. Wnt signaling and drug resistance in cancer. Mol Pharmacol. 2020;97(2):72–89. doi: 10.1124/mol.119.117978.
209. Cui J., Jiang W., Wang S., Wang L., Xie K. Role of Wnt/β-catenin signaling in drug resistance of pancreatic cancer. Curr Pharm Des. 2012;18(17):2464–2471. doi: 10.2174/13816128112092464.
210. Carmon K.S., Lin Q., Gong X., Thomas A., Liu Q. LGR5 interacts and cointernalizes with Wnt receptors to modulate Wnt/β-catenin signaling. Mol Cell Biol. 2012;32(11):2054–2064. doi: 10.1128/MCB.00272-12.
211. Xu L., Lin W., Wen L., Li G. Lgr5 in cancer biology: functional identification of Lgr5 in cancer progression and potential opportunities for novel therapy. Stem Cell Res Ther. 2019;10(1):219. doi: 10.1186/s13287-019-1288-8.
212. Yang L., Tang H., Kong Y., et al. LGR5 promotes breast cancer progression and maintains stem-like cells through activation of Wnt/β-catenin signaling. Stem Cells. 2015;33(10):2913–2924. doi: 10.1002/stem.2083.
213. Fatehullah A., Terakado Y., Sagiraju S., et al. A tumour-resident Lgr5+ stem-cell-like pool drives the establishment and progression of advanced gastric cancers. Nat Cell Biol. 2021;23(12):1299–1313. doi: 10.1038/s41556-021-00793-9.
214. Cao H.Z., Liu X.F., Yang W.T., Chen Q., Zheng P.S. LGR5 promotes cancer stem cell traits and chemoresistance in cervical cancer. Cell Death Dis. 2017;8(9) doi: 10.1038/cddis.2017.393.
215. Takahashi H., Ishii H., Nishida N., et al. Significance of Lgr5+ve cancer stem cells in the colon and rectum. Ann Surg Oncol. 2011;18(4):1166–1174. doi: 10.1245/s10434-010-1373-9.
216. Hoffmeyer K., Raggioli A., Rudloff S., et al. Wnt/β-catenin signaling regulates telomerase in stem cells and cancer cells. Science. 2012;336(6088):1549–1554. doi: 10.1126/science.1218370.
217. Zhang Y., Toh L., Lau P., Wang X. Human telomerase reverse transcriptase (hTERT) is a novel target of the Wnt/β-catenin pathway in human cancer. J Biol Chem. 2012;287(39):32494–32511. doi: 10.1074/jbc.M112.368282.
218. Zhang K., Guo Y., Wang X., et al. WNT/β-catenin directs self-renewal symmetric cell division of hTERThigh prostate cancer stem cells. Cancer Res. 2017;77(9):2534–2547. doi: 10.1158/0008-5472.CAN-16-1887.
219. Kawaguchi-Ihara N., Murohashi I., Nara N., Tohda S. Promotion of the self-renewal capacity of human acute leukemia cells by Wnt3A. Anticancer Res. 2008;28(5a):2701–2704.
220. Cai C., Zhu X. The Wnt/β-catenin pathway regulates self-renewal of cancer stem-like cells in human gastric cancer. Mol Med Rep. 2012;5(5):1191–1196. doi: 10.3892/mmr.2012.802.
221. Yamashita T., Ji J., Budhu A., et al. EpCAM-positive hepatocellular carcinoma cells are tumor-initiating cells with stem/progenitor cell features. Gastroenterology. 2009;136(3):1012–1024. doi: 10.1053/j.gastro.2008.12.004.
222. Yuzugullu H., Benhaj K., Ozturk N., et al. Canonical Wnt signaling is antagonized by noncanonical Wnt5a in hepatocellular carcinoma cells. Mol Cancer. 2009;8:90. doi: 10.1186/1476-4598-8-90.
223. Zheng M., Jiang Y.P., Chen W., et al. Snail and Slug collaborate on EMT and tumor metastasis through miR-101-mediated EZH2 axis in oral tongue squamous cell carcinoma. Oncotarget. 2015;6(9):6797–6810. doi: 10.18632/oncotarget.3180.
224. Wu Z.Q., Li X.Y., Hu C.Y., Ford M., Kleer C.G., Weiss S.J. Canonical Wnt signaling regulates Slug activity and links epithelial-mesenchymal transition with epigenetic Breast Cancer 1, Early Onset (BRCA1) repression. Proc Natl Acad Sci U S A. 2012;109(41):16654–16659. doi: 10.1073/pnas.1205822109.
225. Wang Y., Liu J., Ying X., Lin P.C., Zhou B.P. Twist-mediated epithelial-mesenchymal transition promotes breast tumor cell invasion via inhibition of hippo pathway. Sci Rep. 2016;6 doi: 10.1038/srep24606.
226. Howe L.R., Watanabe O., Leonard J., Brown A.M. Twist is up-regulated in response to Wnt1 and inhibits mouse mammary cell differentiation. Cancer Res. 2003;63(8):1906–1913.
227. Gujral T.S., Chan M., Peshkin L., Sorger P.K., Kirschner M.W., MacBeath G. A noncanonical Frizzled2 pathway regulates epithelial-mesenchymal transition and metastasis. Cell. 2014;159(4):844–856. doi: 10.1016/j.cell.2014.10.032.
228. Henry C., Llamosas E., Knipprath-Meszaros A., et al. Targeting the ROR1 and ROR2 receptors in epithelial ovarian cancer inhibits cell migration and invasion. Oncotarget. 2015;6(37):40310–40326. doi: 10.18632/oncotarget.5643.
229. Qin L., Yin Y.T., Zheng F.J., et al. WNT5A promotes stemness characteristics in nasopharyngeal carcinoma cells leading to metastasis and tumorigenesis. Oncotarget. 2015;6(12):10239–10252. doi: 10.18632/oncotarget.3518.
230. Cheng R., Sun B., Liu Z., et al. Wnt5a suppresses colon cancer by inhibiting cell proliferation and epithelial-mesenchymal transition. J Cell Physiol. 2014;229(12):1908–1917. doi: 10.1002/jcp.24566.
231. Jiang C., Yu M., Xie X., et al. miR-217 targeting DKK1 promotes cancer stem cell properties via activation of the Wnt signaling pathway in hepatocellular carcinoma. Oncol Rep. 2017;38(4):2351–2359. doi: 10.3892/or.2017.5924.
232. Wu G., Liu A., Zhu J., et al. miR-1207 overexpression promotes cancer stem cell-like traits in ovarian cancer by activating the Wnt/β-catenin signaling pathway. Oncotarget. 2015;6(30):28882–28894. doi: 10.18632/oncotarget.4921.
233. Yu Y., Kanwar S.S., Patel B.B., et al. microRNA-21 induces stemness by downregulating transforming growth factor beta receptor 2 (TGFβR2) in colon cancer cells. Carcinogenesis. 2012;33(1):68–76. doi: 10.1093/carcin/bgr246.
234. Mohammed M.K., Shao C., Wang J., et al. Wnt/β-catenin signaling plays an ever-expanding role in stem cell self-renewal, tumorigenesis and cancer chemoresistance. Genes Dis. 2016;3(1):11–40. doi: 10.1016/j.gendis.2015.12.004.
235. Luu H.H., Zhang R., Haydon R.C., et al. Wnt/beta-catenin signaling pathway as a novel cancer drug target. Curr Cancer Drug Targets. 2004;4(8):653–671. doi: 10.2174/1568009043332709.
236. Yang L., Wu X., Wang Y., et al. FZD7 has a critical role in cell proliferation in triple negative breast cancer. Oncogene. 2011;30(43):4437–4446. doi: 10.1038/onc.2011.145.
237. Griffiths C.L., Olin J.L. Triple negative breast cancer: a brief review of its characteristics and treatment options. J Pharm Pract. 2012;25(3):319–323. doi: 10.1177/0897190012442062.
238. King T.D., Suto M.J., Li Y. The Wnt/β-catenin signaling pathway: a potential therapeutic target in the treatment of triple negative breast cancer. J Cell Biochem. 2012;113(1):13–18. doi: 10.1002/jcb.23350.
239. Half E., Bercovich D., Rozen P. Familial adenomatous polyposis. Orphanet J Rare Dis. 2009;4:22. doi: 10.1186/1750-1172-4-22.
240. Mori Y., Nagse H., Ando H., et al. Somatic mutations of the APC gene in colorectal tumors: mutation cluster region in the APC gene. Hum Mol Genet. 1992;1(4):229–233. doi: 10.1093/hmg/1.4.229.
241. Kinzler K.W., Vogelstein B. Lessons from hereditary colorectal cancer. Cell. 1996;87(2):159–170. doi: 10.1016/s0092-8674(00)81333-1.
242. Korinek V., Barker N., Morin P.J., et al. Constitutive transcriptional activation by a beta-catenin-Tcf complex in APC-/- colon carcinoma. Science. 1997;275(5307):1784–1787. doi: 10.1126/science.275.5307.1784.
243. Liu W., Dong X., Mai M., et al. Mutations in AXIN2 cause colorectal cancer with defective mismatch repair by activating β-catenin/TCF signalling. Nat Genet. 2000;26(2):146–147. doi: 10.1038/79859.
244. Lammi L., Arte S., Somer M., et al. Mutations in AXIN2 cause familial tooth agenesis and predispose to colorectal cancer. Am J Hum Genet. 2004;74(5):1043–1050. doi: 10.1086/386293.
245. Wu Z.Q., Brabletz T., Fearon E., et al. Canonical Wnt suppressor, Axin2, promotes colon carcinoma oncogenic activity. Proc Natl Acad Sci U S A. 2012;109(28):11312–11317. doi: 10.1073/pnas.1203015109.
246. Satoh S., Daigo Y., Furukawa Y., et al. AXIN1 mutations in hepatocellular carcinomas, and growth suppression in cancer cells by virus-mediated transfer of AXIN1. Nat Genet. 2000;24(3):245–250. doi: 10.1038/73448.
247. Yardy G.W., Bicknell D.C., Wilding J.L., et al. Mutations in the AXIN1 gene in advanced prostate cancer. Eur Urol. 2009;56(3):486–494. doi: 10.1016/j.eururo.2008.05.029.
248. Morin P.J., Sparks A.B., Korinek V., et al. Activation of beta-catenin-Tcf signaling in colon cancer by mutations in beta-catenin or APC. Science. 1997;275(5307):1787–1790. doi: 10.1126/science.275.5307.1787.
249. Rubinfeld B., Robbins P., El-Gamil M., Albert I., Porfiri E., Polakis P. Stabilization of beta-catenin by genetic defects in melanoma cell lines. Science. 1997;275(5307):1790–1792. doi: 10.1126/science.275.5307.1790.
250. Arozarena I., Bischof H., Gilby D., Belloni B., Dummer R., Wellbrock C. In melanoma, beta-catenin is a suppressor of invasion. Oncogene. 2011;30(45):4531–4543. doi: 10.1038/onc.2011.162.
251. Chien A.J., Moore E.C., Lonsdorf A.S., et al. Activated Wnt/beta-catenin signaling in melanoma is associated with decreased proliferation in patient tumors and a murine melanoma model. Proc Natl Acad Sci U S A. 2009;106(4):1193–1198. doi: 10.1073/pnas.0811902106.
252. Lu D., Zhao Y., Tawatao R., et al. Activation of the Wnt signaling pathway in chronic lymphocytic leukemia. Proc Natl Acad Sci U S A. 2004;101(9):3118–3123. doi: 10.1073/pnas.0308648100.
253. Ng O.H., Erbilgin Y., Firtina S., et al. Deregulated WNT signaling in childhood T-cell acute lymphoblastic leukemia. Blood Cancer J. 2014;4(3) doi: 10.1038/bcj.2014.12.
254. Simon M., Grandage V.L., Linch D.C., Khwaja A. Constitutive activation of the Wnt/beta-catenin signalling pathway in acute myeloid leukaemia. Oncogene. 2005;24(14):2410–2420. doi: 10.1038/sj.onc.1208431.
255. Petropoulos K., Arseni N., Schessl C., et al. A novel role for Lef-1, a central transcription mediator of Wnt signaling, in leukemogenesis. J Exp Med. 2008;205(3):515–522. doi: 10.1084/jem.20071875.
256. Lane S.W., Gilliland D.G. Leukemia stem cells. Semin Cancer Biol. 2010;20(2):71–76. doi: 10.1016/j.semcancer.2009.12.001.
257. Wang Y., Krivtsov A.V., Sinha A.U., et al. The Wnt/beta-catenin pathway is required for the development of leukemia stem cells in AML. Science. 2010;327(5973):1650–1653. doi: 10.1126/science.1186624.
258. Valencia A., Román-Gómez J., Cervera J., et al. Wnt signaling pathway is epigenetically regulated by methylation of Wnt antagonists in acute myeloid leukemia. Leukemia. 2009;23(9):1658–1666. doi: 10.1038/leu.2009.86.
259. Takeda H., Lyle S., Lazar A.J.F., Zouboulis C.C., Smyth I., Watt F.M. Human sebaceous tumors harbor inactivating mutations in LEF1. Nat Med. 2006;12(4):395–397. doi: 10.1038/nm1386.
260. Duchartre Y., Kim Y.M., Kahn M. The Wnt signaling pathway in cancer. Crit Rev Oncol Hematol. 2016;99:141–149. doi: 10.1016/j.critrevonc.2015.12.005.
261. Gala M.K., Mizukami Y., Le L.P., et al. Germline mutations in oncogene-induced senescence pathways are associated with multiple sessile serrated adenomas. Gastroenterology. 2014;146(2):520–529.e6. doi: 10.1053/j.gastro.2013.10.045.
262. Giannakis M., Hodis E., Jasmine Mu X., et al. RNF43 is frequently mutated in colorectal and endometrial cancers. Nat Genet. 2014;46(12):1264–1266. doi: 10.1038/ng.3127.
263. Enomoto M., Hayakawa S., Itsukushima S., et al. Autonomous regulation of osteosarcoma cell invasiveness by Wnt5a/Ror2 signaling. Oncogene. 2009;28(36):3197–3208. doi: 10.1038/onc.2009.175.
264. Toyama T., Lee H.C., Koga H., Wands J.R., Kim M. Noncanonical Wnt11 inhibits hepatocellular carcinoma cell proliferation and migration. Mol Cancer Res. 2010;8(2):254–265. doi: 10.1158/1541-7786.MCR-09-0238.
265. Wagner E.R., Zhu G., Zhang B.Q., et al. The therapeutic potential of the Wnt signaling pathway in bone disorders. Curr Mol Pharmacol. 2011;4(1):14–25.
266. Zhang F., Song J., Zhang H., et al. Wnt and BMP signaling crosstalk in regulating dental stem cells: implications in dental tissue engineering. Genes Dis. 2016;3(4):263–276. doi: 10.1016/j.gendis.2016.09.004.
267. Paszty C., Turner C.H., Robinson M.K. Sclerostin: a gem from the genome leads to bone-building antibodies. J Bone Miner Res. 2010;25(9):1897–1904. doi: 10.1002/jbmr.161.
268. Baron R., Kneissel M. WNT signaling in bone homeostasis and disease: from human mutations to treatments. Nat Med. 2013;19(2):179–192. doi: 10.1038/nm.3074.
269. Sebastian A., Loots G.G. Genetics of Sost/SOST in sclerosteosis and van Buchem disease animal models. Metabolism. 2018;80:38–47. doi: 10.1016/j.metabol.2017.10.005.
270. Pouresmaeili F., Kamalidehghan B., Kamarehei M., Goh Y.M. A comprehensive overview on osteoporosis and its risk factors. Ther Clin Risk Manag. 2018;14:2029–2049. doi: 10.2147/TCRM.S138000.
271. Marini J.C., Forlino A., Bächinger H.P., et al. Osteogenesis imperfecta. Nat Rev Dis Primers. 2017;3 doi: 10.1038/nrdp.2017.52.
272. Fahiminiya S., Majewski J., Mort J., Moffatt P., Glorieux F.H., Rauch F. Mutations in WNT1 are a cause of osteogenesis imperfecta. J Med Genet. 2013;50(5):345–348. doi: 10.1136/jmedgenet-2013-101567.
273. Keupp K., Beleggia F., Kayserili H., et al. Mutations in WNT1 cause different forms of bone fragility. Am J Hum Genet. 2013;92(4):565–574. doi: 10.1016/j.ajhg.2013.02.010.
274. Pyott S.M., Tran T.T., Leistritz D.F., et al. WNT1 mutations in families affected by moderately severe and progressive recessive osteogenesis imperfecta. Am J Hum Genet. 2013;92(4):590–597. doi: 10.1016/j.ajhg.2013.02.009.
275. Laine C.M., Joeng K.S., Campeau P.M., et al. WNT1 mutations in early-onset osteoporosis and osteogenesis imperfecta. N Engl J Med. 2013;368(19):1809–1816. doi: 10.1056/NEJMoa1215458.
276. Korvala J., Jüppner H., Mäkitie O., et al. Mutations in LRP5 cause primary osteoporosis without features of OI by reducing Wnt signaling activity. BMC Med Genet. 2012;13:26. doi: 10.1186/1471-2350-13-26.
277. Yu P., Yang W., Han D., et al. Mutations in WNT10B are identified in individuals with oligodontia. Am J Hum Genet. 2016;99(1):195–201. doi: 10.1016/j.ajhg.2016.05.012.
278. Woods C.G., Stricker S., Seemann P., et al. Mutations in WNT7A cause a range of limb malformations, including Fuhrmann syndrome and Al-Awadi/Raas-Rothschild/Schinzel phocomelia syndrome. Am J Hum Genet. 2006;79(2):402–408. doi: 10.1086/506332.
279. Foo R., Guo Y., McDonald-McGinn D.M., Zackai E.H., Whitaker L.A., Bartlett S.P. The natural history of patients treated for TWIST1-confirmed Saethre-Chotzen syndrome. Plast Reconstr Surg. 2009;124(6):2085–2095. doi: 10.1097/PRS.0b013e3181bf83ce.
280. Behr B., Longaker M.T., Quarto N. Differential activation of canonical Wnt signaling determines cranial sutures fate: a novel mechanism for sagittal suture craniosynostosis. Dev Biol. 2010;344(2):922–940. doi: 10.1016/j.ydbio.2010.06.009.
281. Gilmour D.F. Familial exudative vitreoretinopathy and related retinopathies. Eye. 2015;29(1):1–14. doi: 10.1038/eye.2014.70.
282. Ye X., Wang Y., Nathans J. The Norrin/Frizzled4 signaling pathway in retinal vascular development and disease. Trends Mol Med. 2010;16(9):417–425. doi: 10.1016/j.molmed.2010.07.003.
283. Wang Z., Liu C.H., Huang S., Chen J. Wnt Signaling in vascular eye diseases. Prog Retin Eye Res. 2019;70:110–133. doi: 10.1016/j.preteyeres.2018.11.008.
284. Vallée A., Lecarpentier Y., Guillevin R., Vallée J.N. Aerobic glycolysis hypothesis through WNT/beta-catenin pathway in exudative age-related macular degeneration. J Mol Neurosci. 2017;62(3):368–379. doi: 10.1007/s12031-017-0947-4.
285. Tuo J., Wang Y., Cheng R., et al. Wnt signaling in age-related macular degeneration: human macular tissue and mouse model. J Transl Med. 2015;13:330. doi: 10.1186/s12967-015-0683-x.
286. Gong Y., Slee R.B., Fukai N., et al. LDL receptor-related protein 5 (LRP5) affects bone accrual and eye development. Cell. 2001;107(4):513–523. doi: 10.1016/s0092-8674(01)00571-2.
287. Wang W., Lo A.C.Y. Diabetic retinopathy: pathophysiology and treatments. Int J Mol Sci. 2018;19(6):E1816. doi: 10.3390/ijms19061816.
288. Chen Y., Hu Y., Zhou T., et al. Activation of the Wnt pathway plays a pathogenic role in diabetic retinopathy in humans and animal models. Am J Pathol. 2009;175(6):2676–2685. doi: 10.2353/ajpath.2009.080945.
289. Gao X., Ma K., Lu N., Xu Y., Hong T., Peng X. Elevated LRP6 levels correlate with vascular endothelial growth factor in the vitreous of proliferative diabetic retinopathy. Mol Vis. 2015;21:665–672.
290. Qiu F., He J., Zhou Y., et al. Plasma and vitreous fluid levels of Dickkopf-1 in patients with diabetic retinopathy. Eye. 2014;28(4):402–409. doi: 10.1038/eye.2013.229.
291. Eghrari A.O., Riazuddin S.A., Gottsch J.D. Overview of the Cornea: structure, function, and development. Prog Mol Biol Transl Sci. 2015;134:7–23. doi: 10.1016/bs.pmbts.2015.04.001.
292. Hsu C.C., Chang H.M., Lin T.C., et al. Corneal neovascularization and contemporary antiangiogenic therapeutics. J Chin Med Assoc. 2015;78(6):323–330. doi: 10.1016/j.jcma.2014.10.002.
293. Zhang Y.K., Li J.M., Qin L. Suppression of corneal neovascularization by curcumin via inhibition of Wnt/β-catenin pathway activation. Int J Ophthalmol. 2017;10(12):1791–1797. doi: 10.18240/ijo.2017.12.01.
294. Wang Z., Cheng R., Lee K., et al. Nanoparticle-mediated expression of a Wnt pathway inhibitor ameliorates ocular neovascularization. Arterioscler Thromb Vasc Biol. 2015;35(4):855–864. doi: 10.1161/ATVBAHA.114.304627.
295. Lusis A.J. Atherosclerosis. Nature. 2000;407(6801):233–241. doi: 10.1038/35025203.
296. Mani A., Radhakrishnan J., Wang H., et al. LRP6 mutation in a family with early coronary disease and metabolic risk factors. Science. 2007;315(5816):1278–1282. doi: 10.1126/science.1136370.
297. Singh R., Smith E., Fathzadeh M., et al. Rare nonconservative LRP6 mutations are associated with metabolic syndrome. Hum Mutat. 2013;34(9):1221–1225. doi: 10.1002/humu.22360.
298. Tomaszewski M., Charchar F.J., Barnes T., et al. A common variant in low-density lipoprotein receptor-related protein 6 gene (LRP6) is associated with LDL-cholesterol. Arterioscler Thromb Vasc Biol. 2009;29(9):1316–1321. doi: 10.1161/ATVBAHA.109.185355.
299. Christman M.A., 2nd, Goetz D.J., Dickerson E., et al. Wnt5a is expressed in murine and human atherosclerotic lesions. Am J Physiol Heart Circ Physiol. 2008;294(6):H2864–H2870. doi: 10.1152/ajpheart.00982.2007.
300. Kim J., Kim J., Kim D.W., et al. Wnt5a induces endothelial inflammation via beta-catenin-independent signaling. J Immunol. 2010;185(2):1274–1282. doi: 10.4049/jimmunol.1000181.
301. Ueland T., Otterdal K., Lekva T., et al. Dickkopf-1 enhances inflammatory interaction between platelets and endothelial cells and shows increased expression in atherosclerosis. Arterioscler Thromb Vasc Biol. 2009;29(8):1228–1234. doi: 10.1161/ATVBAHA.109.189761.
302. Yu B., Kiechl S., Qi D., et al. A cytokine-like protein Dickkopf-related protein 3 is atheroprotective. Circulation. 2017;136(11):1022–1036. doi: 10.1161/CIRCULATIONAHA.117.027690.
303. Quasnichka H., Slater S.C., Beeching C.A., Boehm M., Sala-Newby G.B., George S.J. Regulation of smooth muscle cell proliferation by β-catenin/T-cell factor signaling involves modulation of cyclin D1 and p21 expression. Circ Res. 2006;99(12):1329–1337. doi: 10.1161/01.RES.0000253533.65446.33.
304. Tsaousi A., Mill C., George S.J. The Wnt pathways in vascular disease: lessons from vascular development. Curr Opin Lipidol. 2011;22(5):350–357. doi: 10.1097/MOL.0b013e32834aa701.
305. Oerlemans M.I.F.J., Goumans M.J., van Middelaar B., Clevers H., Doevendans P.A., Sluijter J.P.G. Active Wnt signaling in response to cardiac injury. Basic Res Cardiol. 2010;105(5):631–641. doi: 10.1007/s00395-010-0100-9.
306. Meyer I.S., Jungmann A., Dieterich C., et al. The cardiac microenvironment uses non-canonical WNT signaling to activate monocytes after myocardial infarction. EMBO Mol Med. 2017;9(9):1279–1293. doi: 10.15252/emmm.201707565.
307. Barandon L., Casassus F., Leroux L., et al. Secreted Frizzled-related protein-1 improves postinfarction scar formation through a modulation of inflammatory response. Arterioscler Thromb Vasc Biol. 2011;31(11):e80–e87. doi: 10.1161/ATVBAHA.111.232280.
308. Nakamura K., Sano S., Fuster J.J., et al. Secreted Frizzled-related protein 5 diminishes cardiac inflammation and protects the heart from ischemia/reperfusion injury. J Biol Chem. 2016;291(6):2566–2575. doi: 10.1074/jbc.M115.693937.
309. Caira F.C., Stock S.R., Gleason T.G., et al. Human degenerative valve disease is associated with up-regulation of low-density lipoprotein receptor-related protein 5 receptor-mediated bone formation. J Am Coll Cardiol. 2006;47(8):1707–1712. doi: 10.1016/j.jacc.2006.02.040.
310. Pilichou K., Thiene G., Bauce B., et al. Arrhythmogenic cardiomyopathy. Orphanet J Rare Dis. 2016;11:33. doi: 10.1186/s13023-016-0407-1.
311. Chelko S.P., Asimaki A., Andersen P., et al. Central role for GSK3β in the pathogenesis of arrhythmogenic cardiomyopathy. JCI Insight. 2016;1(5) doi: 10.1172/jci.insight.85923.
312. Sklepkiewicz P., Shiomi T., Kaur R., et al. Loss of secreted Frizzled-related protein-1 leads to deterioration of cardiac function in mice and plays a role in human cardiomyopathy. Circ Heart Fail. 2015;8(2):362–372. doi: 10.1161/CIRCHEARTFAILURE.114.001274.
313. Hou N., Ye B., Li X., et al. Transcription factor 7-like 2 mediates canonical Wnt/β-catenin signaling and c-myc upregulation in heart failure. Circ Heart Fail. 2016;9(6) doi: 10.1161/CIRCHEARTFAILURE.116.003010.
314. Galicia-Garcia U., Benito-Vicente A., Jebari S., et al. Pathophysiology of type 2 diabetes mellitus. Int J Mol Sci. 2020;21(17):6275. doi: 10.3390/ijms21176275.
315. Grant S.F.A., Thorleifsson G., Reynisdottir I., et al. Variant of transcription factor 7-like 2 (TCF7L2) gene confers risk of type 2 diabetes. Nat Genet. 2006;38(3):320–323. doi: 10.1038/ng1732.
316. Tong Y., Lin Y., Zhang Y., et al. Association between TCF7L2 gene polymorphisms and susceptibility to type 2 diabetes mellitus: a large Human Genome Epidemiology (HuGE) review and meta-analysis. BMC Med Genet. 2009;10:15. doi: 10.1186/1471-2350-10-15.
317. Zhou Y., Park S.Y., Su J., et al. TCF7L2 is a master regulator of insulin production and processing. Hum Mol Genet. 2014;23(24):6419–6431. doi: 10.1093/hmg/ddu359.
318. Sakhneny L., Rachi E., Epshtein A., et al. Pancreatic pericytes support β-cell function in a Tcf7l2-dependent manner. Diabetes. 2018;67(3):437–447. doi: 10.2337/db17-0697.
319. da Silva Xavier G., Loder M.K., McDonald A., et al. TCF7L2 regulates late events in insulin secretion from pancreatic islet beta-cells. Diabetes. 2009;58(4):894–905. doi: 10.2337/db08-1187.
320. Mitchell R.K., Mondragon A., Chen L., et al. Selective disruption of Tcf7l2 in the pancreatic β cell impairs secretory function and lowers β cell mass. Hum Mol Genet. 2015;24(5):1390–1399. doi: 10.1093/hmg/ddu553.
321. Montanari T., Pošćić N., Colitti M. Factors involved in white-to-brown adipose tissue conversion and in thermogenesis: a review. Obes Rev. 2017;18(5):495–513. doi: 10.1111/obr.12520.
322. Saely C.H., Geiger K., Drexel H. Brown versus white adipose tissue: a mini-review. Gerontology. 2012;58(1):15–23. doi: 10.1159/000321319.
323. Christodoulides C., Scarda A., Granzotto M., et al. WNT10B mutations in human obesity. Diabetologia. 2006;49(4):678–684. doi: 10.1007/s00125-006-0144-4.
324. Wang J., Liu R., Wang F., et al. Ablation of LGR4 promotes energy expenditure by driving white-to-brown fat switch. Nat Cell Biol. 2013;15(12):1455–1463. doi: 10.1038/ncb2867.
325. Shi S.Q., Li S.S., Zhang X.Y., et al. LGR4 gene polymorphisms are associated with bone and obesity phenotypes in Chinese female nuclear families. Front Endocrinol. 2021;12 doi: 10.3389/fendo.2021.656077.
326. Ouchi N., Higuchi A., Ohashi K., et al. Sfrp5 is an anti-inflammatory adipokine that modulates metabolic dysfunction in obesity. Science. 2010;329(5990):454–457. doi: 10.1126/science.1188280.
327. Schulte D.M., Müller N., Neumann K., et al. Pro-inflammatory wnt5a and anti-inflammatory sFRP5 are differentially regulated by nutritional factors in obese human subjects. PLoS One. 2012;7(2) doi: 10.1371/journal.pone.0032437.
328. Carstensen-Kirberg M., Kannenberg J.M., Huth C., et al. Inverse associations between serum levels of secreted Frizzled-related protein-5 (SFRP5) and multiple cardiometabolic risk factors: KORA F4 study. Cardiovasc Diabetol. 2017;16(1):109. doi: 10.1186/s12933-017-0591-x.
329. Relling I., Akcay G., Fangmann D., et al. Role of wnt5a in metabolic inflammation in humans. J Clin Endocrinol Metab. 2018;103(11):4253–4264. doi: 10.1210/jc.2018-01007.
330. Inestrosa N.C., Arenas E. Emerging roles of Wnts in the adult nervous system. Nat Rev Neurosci. 2010;11(2):77–86. doi: 10.1038/nrn2755.
331. Knopman D.S., Amieva H., Petersen R.C., et al. Alzheimer disease. Nat Rev Dis Primers. 2021;7(1):33. doi: 10.1038/s41572-021-00269-y.
332. De Ferrari G.V., Papassotiropoulos A., Biechele T., et al. Common genetic variation within the low-density lipoprotein receptor-related protein 6 and late-onset Alzheimer's disease. Proc Natl Acad Sci U S A. 2007;104(22):9434–9439. doi: 10.1073/pnas.0603523104.
333. Folke J., Pakkenberg B., Brudek T. Impaired Wnt signaling in the prefrontal cortex of Alzheimer's disease. Mol Neurobiol. 2019;56(2):873–891. doi: 10.1007/s12035-018-1103-z.
334. Brion J.P., Anderton B.H., Authelet M., et al. Neurofibrillary tangles and tau phosphorylation. Biochem Soc Symp. 2001;67:81–88. doi: 10.1042/bss0670081.
335. Lovestone S., Reynolds C.H., Latimer D., et al. Alzheimer's disease-like phosphorylation of the microtubule-associated protein tau by glycogen synthase kinase-3 in transfected mammalian cells. Curr Biol. 1994;4(12):1077–1086. doi: 10.1016/s0960-9822(00)00246-3.
336. Hanger D.P., Hughes K., Woodgett J.R., Brion J.P., Anderton B.H. Glycogen synthase kinase-3 induces Alzheimer's disease-like phosphorylation of tau: generation of paired helical filament epitopes and neuronal localisation of the kinase. Neurosci Lett. 1992;147(1):58–62. doi: 10.1016/0304-3940(92)90774-2.
337. Ishiguro K., Omori A., Takamatsu M., et al. Phosphorylation sites on tau by tau protein kinase I, a bovine derived kinase generating an epitope of paired helical filaments. Neurosci Lett. 1992;148(1–2):202–206. doi: 10.1016/0304-3940(92)90839-y.
338. Takashima A., Murayama M., Murayama O., et al. Presenilin 1 associates with glycogen synthase kinase-3beta and its substrate tau. Proc Natl Acad Sci U S A. 1998;95(16):9637–9641. doi: 10.1073/pnas.95.16.9637.
339. Purro S.A., Dickins E.M., Salinas P.C. The secreted Wnt antagonist Dickkopf-1 is required for amyloid β-mediated synaptic loss. J Neurosci. 2012;32(10):3492–3498. doi: 10.1523/JNEUROSCI.4562-11.2012.
340. Marzo A., Galli S., Lopes D., et al. Reversal of synapse degeneration by restoring Wnt signaling in the adult hippocampus. Curr Biol. 2016;26(19):2551–2561. doi: 10.1016/j.cub.2016.07.024.
341. Toledo E.M., Inestrosa N.C. Activation of Wnt signaling by lithium and rosiglitazone reduced spatial memory impairment and neurodegeneration in brains of an APPswe/PSEN1ΔE9 mouse model of Alzheimer's disease. Mol Psychiatry. 2010;15(3):272–285. doi: 10.1038/mp.2009.72.
342. Balestrino R., Schapira A.H.V. Parkinson disease. Eur J Neurol. 2020;27(1):27–42. doi: 10.1111/ene.14108.
343. Jeong G.R., Lee B.D. Pathological functions of LRRK2 in Parkinson's disease. Cells. 2020;9(12):E2565. doi: 10.3390/cells9122565.
344. Berwick D.C., Javaheri B., Wetzel A., et al. Pathogenic LRRK2 variants are gain-of-function mutations that enhance LRRK2-mediated repression of β-catenin signaling. Mol Neurodegener. 2017;12(1):9. doi: 10.1186/s13024-017-0153-4.
345. Prakash N., Wurst W. A Wnt signal regulates stem cell fate and differentiation in vivo. Neurodegener Dis. 2007;4(4):333–338. doi: 10.1159/000101891.
346. McMahon A.P., Bradley A. The Wnt-1 (int-1) proto-oncogene is required for development of a large region of the mouse brain. Cell. 1990;62(6):1073–1085. doi: 10.1016/0092-8674(90)90385-r.
347. Panhuysen M., Vogt Weisenhorn D.M., Blanquet V., et al. Effects of Wnt1 signaling on proliferation in the developing mid-/hindbrain region. Mol Cell Neurosci. 2004;26(1):101–111. doi: 10.1016/j.mcn.2004.01.011.
348. Schulte G., Bryja V., Rawal N., Castelo-Branco G., Sousa K.M., Arenas E. Purified Wnt-5a increases differentiation of midbrain dopaminergic cells and dishevelled phosphorylation. J Neurochem. 2005;92(6):1550–1553. doi: 10.1111/j.1471-4159.2004.03022.x.
349. Meredith G.E., Rademacher D.J. MPTP mouse models of Parkinson's disease: an update. J Parkinsons Dis. 2011;1(1):19–33. doi: 10.3233/JPD-2011-11023.
350. L'Episcopo F., Tirolo C., Testa N., et al. Reactive astrocytes and Wnt/β-catenin signaling link nigrostriatal injury to repair in 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine model of Parkinson's disease. Neurobiol Dis. 2011;41(2):508–527. doi: 10.1016/j.nbd.2010.10.023.
351. Marchetti B. Wnt/β-catenin signaling pathway governs a full program for dopaminergic neuron survival, neurorescue and regeneration in the MPTP mouse model of Parkinson's disease. Int J Mol Sci. 2018;19(12):3743. doi: 10.3390/ijms19123743.
352. Harris-Johnson K.S., Domyan E.T., Vezina C.M., Sun X. Beta-Catenin promotes respiratory progenitor identity in mouse foregut. Proc Natl Acad Sci U S A. 2009;106(38):16287–16292. doi: 10.1073/pnas.0902274106.
353. Dasgupta C., Sakurai R., Wang Y., et al. Hyperoxia-induced neonatal rat lung injury involves activation of TGF-{beta}and Wnt signaling and is protected by rosiglitazone. Am J Physiol Lung Cell Mol Physiol. 2009;296(6):L1031–L1041. doi: 10.1152/ajplung.90392.2008.
354. Halt K., Vainio S. Coordination of kidney organogenesis by Wnt signaling. Pediatr Nephrol. 2014;29(4):737–744. doi: 10.1007/s00467-013-2733-z.
355. Grouls S., Iglesias D.M., Wentzensen N., et al. Lineage specification of parietal epithelial cells requires β-catenin/Wnt signaling. J Am Soc Nephrol. 2012;23(1):63–72. doi: 10.1681/ASN.2010121257.
356. Wang Y., Stokes A., Duan Z., et al. LDL receptor-related protein 6 modulates ret proto-oncogene signaling in renal development and cystic dysplasia. J Am Soc Nephrol. 2016;27(2):417–427. doi: 10.1681/ASN.2014100998.
357. Mandel H., Shemer R., Borochowitz Z.U., et al. SERKAL syndrome: an autosomal-recessive disorder caused by a loss-of-function mutation in WNT4. Am J Hum Genet. 2008;82(1):39–47. doi: 10.1016/j.ajhg.2007.08.005.
358. Yu H., Smallwood P.M., Wang Y., Vidaltamayo R., Reed R., Nathans J. Frizzled 1 and Frizzled 2 genes function in palate, ventricular septum and neural tube closure: general implications for tissue fusion processes. Development. 2010;137(21):3707–3717. doi: 10.1242/dev.052001.
359. Niemann S., Zhao C., Pascu F., et al. Homozygous WNT3 mutation causes Tetra-amelia in a large consanguineous family. Am J Hum Genet. 2004;74(3):558–563. doi: 10.1086/382196.
360. White J., Mazzeu J.F., Hoischen A., et al. DVL1 frameshift mutations clustering in the penultimate exon cause autosomal-dominant Robinow syndrome. Am J Hum Genet. 2015;96(4):612–622. doi: 10.1016/j.ajhg.2015.02.015.
361. Person A.D., Beiraghi S., Sieben C.M., et al. WNT5A mutations in patients with autosomal dominant Robinow syndrome. Dev Dyn. 2010;239(1):327–337. doi: 10.1002/dvdy.22156.
362. Trojian T.H., Chu S.M. Dupuytren's disease: diagnosis and treatment. Am Fam Physician. 2007;76(1):86–89.
363. Degreef I., De Smet L., Sciot R., Cassiman J.J., Tejpar S. Beta-catenin overexpression in Dupuytren's disease is unrelated to disease recurrence. Clin Orthop Relat Res. 2009;467(3):838–845. doi: 10.1007/s11999-008-0590-z.
364. Varallo V.M., Gan B.S., Seney S., et al. Beta-catenin expression in Dupuytren's disease: potential role for cell-matrix interactions in modulating beta-catenin levels in vivo and in vitro. Oncogene. 2003;22(24):3680–3684. doi: 10.1038/sj.onc.1206415.
365. Dolmans G.H., Werker P.M., Hennies H.C., et al. Wnt signaling and Dupuytren's disease. N Engl J Med. 2011;365(4):307–317. doi: 10.1056/NEJMoa1101029.
366. Ten Dam E.J.P.M., van Beuge M.M., Bank R.A., Werker P.M.N. Further evidence of the involvement of the Wnt signaling pathway in Dupuytren's disease. J Cell Commun Signal. 2016;10(1):33–40. doi: 10.1007/s12079-015-0312-8.
367. Wang X., Reid Sutton V., Omar Peraza-Llanes J., et al. Mutations in X-linked PORCN, a putative regulator of Wnt signaling, cause focal dermal hypoplasia. Nat Genet. 2007;39(7):836–838. doi: 10.1038/ng2057.
368. Bostwick B., Van den Veyver I.B., Sutton V.R. In: GeneReviews®. Adam M.P., Mirzaa G.M., Pagon R.A., et al., editors. University of Washington, Seattle; Seattle (WA): May 15, 2008. Focal dermal hypoplasia.
369. Rendon A., Schäkel K. Psoriasis pathogenesis and treatment. Int J Mol Sci. 2019;20(6):1475. doi: 10.3390/ijms20061475.
370. Reischl J., Schwenke S., Beekman J.M., Mrowietz U., Stürzebecher S., Heubach J.F. Increased expression of Wnt5a in psoriatic plaques. J Invest Dermatol. 2007;127(1):163–169. doi: 10.1038/sj.jid.5700488.
371. Gudjonsson J.E., Johnston A., Stoll S.W., et al. Evidence for altered Wnt signaling in psoriatic skin. J Invest Dermatol. 2010;130(7):1849–1859. doi: 10.1038/jid.2010.67.
372. Aros C.J., Pantoja C.J., Gomperts B.N. Wnt signaling in lung development, regeneration, and disease progression. Commun Biol. 2021;4(1):601. doi: 10.1038/s42003-021-02118-w.
373. Tanjore H., Degryse A.L., Crossno P.F., et al. β-catenin in the alveolar epithelium protects from lung fibrosis after intratracheal bleomycin. Am J Respir Crit Care Med. 2013;187(6):630–639. doi: 10.1164/rccm.201205-0972OC.
374. Qian C.N., Knol J., Igarashi P., et al. Cystic renal neoplasia following conditional inactivation of apc in mouse renal tubular epithelium. J Biol Chem. 2005;280(5):3938–3945. doi: 10.1074/jbc.M410697200.
375. Hernlund E., Svedbom A., Ivergård M., et al. Osteoporosis in the European Union: medical management, epidemiology and economic burden. A report prepared in collaboration with the International Osteoporosis Foundation (IOF) and the European Federation of Pharmaceutical Industry Associations (EFPIA) Arch Osteoporos. 2013;8(1):136. doi: 10.1007/s11657-013-0136-1.
376. Anagnostis P., Bosdou J.K., Vaitsi K., Goulis D.G., Lambrinoudaki I. Estrogen and bones after menopause: a reappraisal of data and future perspectives. Hormones (Athens) 2021;20(1):13–21. doi: 10.1007/s42000-020-00218-6.
377. Manolagas S.C., O'Brien C.A., Almeida M. The role of estrogen and androgen receptors in bone health and disease. Nat Rev Endocrinol. 2013;9(12):699–712. doi: 10.1038/nrendo.2013.179.
378. Varacallo M.A., Fox E.J. Osteoporosis and its complications. Med Clin North Am. 2014;98(4):817–831. doi: 10.1016/j.mcna.2014.03.007. xii-xiii.
379. Guzon-Illescas O., Perez Fernandez E., Crespí Villarias N., et al. Mortality after osteoporotic hip fracture: incidence, trends, and associated factors. J Orthop Surg Res. 2019;14(1):203. doi: 10.1186/s13018-019-1226-6.
380. Cefalu C.A. Is bone mineral density predictive of fracture risk reduction? Curr Med Res Opin. 2004;20(3):341–349. doi: 10.1185/030079903125003062.
381. Li H., Xiao Z., Quarles L.D., Li W. Osteoporosis: mechanism, molecular target and current status on drug development. Curr Med Chem. 2021;28(8):1489–1507. doi: 10.2174/0929867327666200330142432.
382. Rauner M., Taipaleenmäki H., Tsourdi E., Winter E.M. Osteoporosis treatment with anti-sclerostin antibodies-mechanisms of action and clinical application. J Clin Med. 2021;10(4):787. doi: 10.3390/jcm10040787.
383. Miller S.A., St Onge E.L., Whalen K.L. Romosozumab: a novel agent in the treatment for postmenopausal osteoporosis. J Pharm Technol. 2021;37(1):45–52. doi: 10.1177/8755122520967632.
384. Cosman F., Crittenden D.B., Adachi J.D., et al. Romosozumab treatment in postmenopausal women with osteoporosis. N Engl J Med. 2016;375(16):1532–1543. doi: 10.1056/NEJMoa1607948.
385. Saag K.G., Petersen J., Brandi M.L., et al. Romosozumab or alendronate for fracture prevention in women with osteoporosis. N Engl J Med. 2017;377(15):1417–1427. doi: 10.1056/NEJMoa1708322.
386. McClung M.R., Brown J.P., Diez-Perez A., et al. Effects of 24 months of treatment with romosozumab followed by 12 months of denosumab or placebo in postmenopausal women with low bone mineral density: a randomized, double-blind, phase 2, parallel group study. J Bone Miner Res. 2018;33(8):1397–1406. doi: 10.1002/jbmr.3452.
387. McColm J., Hu L., Womack T., Tang C.C., Chiang A.Y. Single- and multiple-dose randomized studies of blosozumab, a monoclonal antibody against sclerostin, in healthy postmenopausal women. J Bone Miner Res. 2014;29(4):935–943. doi: 10.1002/jbmr.2092.
388. Recker R.R., Benson C.T., Matsumoto T., et al. A randomized, double-blind phase 2 clinical trial of blosozumab, a sclerostin antibody, in postmenopausal women with low bone mineral density. J Bone Miner Res. 2015;30(2):216–224. doi: 10.1002/jbmr.2351.
389. Recknor C.P., Recker R.R., Benson C.T., et al. The effect of discontinuing treatment with blosozumab: follow-up results of a phase 2 randomized clinical trial in postmenopausal women with low bone mineral density. J Bone Miner Res. 2015;30(9):1717–1725. doi: 10.1002/jbmr.2489.
390. Glorieux F.H., Devogelaer J.P., Durigova M., et al. BPS804 anti-sclerostin antibody in adults with moderate osteogenesis imperfecta: results of a randomized phase 2a trial. J Bone Miner Res. 2017;32(7):1496–1504. doi: 10.1002/jbmr.3143.
391. Shah K., Panchal S., Patel B. Porcupine inhibitors: novel and emerging anti-cancer therapeutics targeting the Wnt signaling pathway. Pharmacol Res. 2021;167 doi: 10.1016/j.phrs.2021.105532.
392. Bordonaro M., Lazarova D.L. Determination of the role of CBP- and p300-mediated Wnt signaling on colonic cells. JMIR Res Protoc. 2016;5(2):e66. doi: 10.2196/resprot.5495.
393. Shin S.H., Lim D.Y., Reddy K., et al. A small molecule inhibitor of the β-catenin-TCF4 interaction suppresses colorectal cancer growth in vitro and in vivo. EBioMedicine. 2017;25:22–31. doi: 10.1016/j.ebiom.2017.09.029.
394. Fang L., Zhu Q., Neuenschwander M., et al. A small-molecule antagonist of the β-catenin/TCF4 interaction blocks the self-renewal of cancer stem cells and suppresses tumorigenesis. Cancer Res. 2016;76(4):891–901. doi: 10.1158/0008-5472.CAN-15-1519.
395. Menck K., Heinrichs S., Baden C., Bleckmann A. The WNT/ROR pathway in cancer: from signaling to therapeutic intervention. Cells. 2021;10(1):142. doi: 10.3390/cells10010142.
396. Thorvaldsen T.E. Targeting tankyrase to fight WNT-dependent tumours. Basic Clin Pharmacol Toxicol. 2017;121(2):81–88. doi: 10.1111/bcpt.12786.
397. Mizutani A., Yashiroda Y., Muramatsu Y., et al. RK-287107, a potent and specific tankyrase inhibitor, blocks colorectal cancer cell growth in a preclinical model. Cancer Sci. 2018;109(12):4003–4014. doi: 10.1111/cas.13805.
398. Shirai F., Mizutani A., Yashiroda Y., et al. Design and discovery of an orally efficacious spiroindolinone-based tankyrase inhibitor for the treatment of colon cancer. J Med Chem. 2020;63(8):4183–4204. doi: 10.1021/acs.jmedchem.0c00045.
399. Osman J., Bellamkonda K., Liu Q., Andersson T., Sjölander A. The WNT5A agonist Foxy5 reduces the number of colonic cancer stem cells in a xenograft mouse model of human colonic cancer. Anticancer Res. 2019;39(4):1719–1728. doi: 10.21873/anticanres.13278.
400. Canesin G., Evans-Axelsson S., Hellsten R., et al. Treatment with the WNT5A-mimicking peptide Foxy-5 effectively reduces the metastatic spread of WNT5A-low prostate cancer cells in an orthotopic mouse model. PLoS One. 2017;12(9) doi: 10.1371/journal.pone.0184418.
401. Atkinson J.M., Rank K.B., Zeng Y., et al. Activating the Wnt/β-catenin pathway for the treatment of melanoma: application of LY2090314, a novel selective inhibitor of glycogen synthase kinase-3. PLoS One. 2015;10(4) doi: 10.1371/journal.pone.0125028.
402. Kunnimalaiyaan S., Schwartz V.K., Jackson I.A., Clark Gamblin T., Kunnimalaiyaan M. Antiproliferative and apoptotic effect of LY2090314, a GSK-3 inhibitor, in neuroblastoma in vitro. BMC Cancer. 2018;18(1):560. doi: 10.1186/s12885-018-4474-7.
403. Wall J.A., Klempner S.J., Arend R.C. The anti-DKK1 antibody DKN-01 as an immunomodulatory combination partner for the treatment of cancer. Expert Opin Investig Drugs. 2020;29(7):639–644. doi: 10.1080/13543784.2020.1769065.
404. Gurney A., Axelrod F., Bond C.J., et al. Wnt pathway inhibition via the targeting of Frizzled receptors results in decreased growth and tumorigenicity of human tumors. Proc Natl Acad Sci U S A. 2012;109(29):11717–11722. doi: 10.1073/pnas.1120068109.
405. Le P.N., McDermott J.D., Jimeno A. Targeting the Wnt pathway in human cancers: therapeutic targeting with a focus on OMP-54F28. Pharmacol Ther. 2015;146:1–11. doi: 10.1016/j.pharmthera.2014.08.005.
406. Chen H.J., Hsu L.S., Shia Y.T., Lin M.W., Lin C.M. The β-catenin/TCF complex as a novel target of resveratrol in the Wnt/β-catenin signaling pathway. Biochem Pharmacol. 2012;84(9):1143–1153. doi: 10.1016/j.bcp.2012.08.011.
407. Chen M., Wang J., Lu J., et al. The anti-helminthic niclosamide inhibits Wnt/Frizzled1 signaling. Biochemistry. 2009;48(43):10267–10274. doi: 10.1021/bi9009677.
408. Liao Z., Nan G., Yan Z., et al. The anthelmintic drug niclosamide inhibits the proliferative activity of human osteosarcoma cells by targeting multiple signal pathways. Curr Cancer Drug Targets. 2015;15(8):726–738. doi: 10.2174/1568009615666150629132157.
409. Deng Y., Wang Z., Zhang F., et al. A blockade of IGF signaling sensitizes human ovarian cancer cells to the anthelmintic niclosamide-induced anti-proliferative and anticancer activities. Cell Physiol Biochem. 2016;39(3):871–888. doi: 10.1159/000447797.
410. Yu X., Liu F., Zeng L., et al. Niclosamide exhibits potent anticancer activity and synergizes with sorafenib in human renal cell cancer cells. Cell Physiol Biochem. 2018;47(3):957–971. doi: 10.1159/000490140.
411. Saraswati S., Alfaro M.P., Thorne C.A., Atkinson J., Lee E., Young P.P. Pyrvinium, a potent small molecule Wnt inhibitor, promotes wound repair and post-MI cardiac remodeling. PLoS One. 2010;5(11) doi: 10.1371/journal.pone.0015521.
412. He B.C., Gao J.L., Luo X., et al. Ginsenoside Rg3 inhibits colorectal tumor growth through the down-regulation of Wnt/ß-catenin signaling. Int J Oncol. 2011;38(2):437–445. doi: 10.3892/ijo.2010.858.
413. He B.C., Gao J.L., Zhang B.Q., et al. Tetrandrine inhibits Wnt/β-catenin signaling and suppresses tumor growth of human colorectal cancer. Mol Pharmacol. 2011;79(2):211–219. doi: 10.1124/mol.110.068668.