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Muscle inactivation of mTOR causes metabolic and dystrophin defects leading to severe myopathy.

Mammalian target of rapamycin (mTOR) is a key regulator of cell growth that associates with raptor and rictor to form the mTOR complex 1 (mTORC1) and mTORC2, respectively. Raptor is required for oxidative muscle integrity, whereas rictor is dispensable. In this study, we show that muscle-specific inactivation of mTOR leads to severe myopathy, resulting in premature death. mTOR-deficient muscles display metabolic changes similar to those observed in muscles lacking raptor, including impaired oxidative metabolism, altered mitochondrial regulation, and glycogen accumulation associated with protei

Loss of the tuberous sclerosis complex tumor suppressors triggers the unfolded protein response to regulate insulin signaling and apoptosis.

Mammalian target of rapamycin, mTOR, is a major sensor of nutrient and energy availability in the cell and regulates a variety of cellular processes, including growth, proliferation, and metabolism. Loss of the tuberous sclerosis complex genes (TSC1 or TSC2) leads to constitutive activation of mTOR and downstream signaling elements, resulting in the development of tumors, neurological disorders, and at the cellular level, severe insulin/IGF-1 resistance. Here, we show that loss of TSC1 or TSC2 in cell lines and mouse or human tumors causes endoplasmic reticulum (ER) stress and activates the un

Longitudinal inhibition of PI3K/Akt/mTOR signaling by LY294002 and rapamycin induces growth arrest of adult T-cell leukemia cells.

This study found that phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling was activated in human T-cell lymphotropic virus type I (HTLV-1)-infected leukemia cells. Rapamycin (1-100 nM, 48h), the inhibitor of mTOR and its analog RAD001 (1-100 nM, 48 h)-induced growth inhibition and G0/G1 cell cycle arrest of these cells in association with de-phosphorylation of p70S6K and 4E-BP-1, although IC50 was not achieved. Paradoxically, rapamycin-stimulated phosphorylation of Akt at Ser473. Blockade of Akt signaling by the PI3K inhibitor LY294002 (1-20 microM, 48 h) al

Rapamycin attenuates BAFF-extended proliferation and survival via disruption of mTORC1/2 signaling in normal and neoplastic B-lymphoid cells.

B cell activating factor from the TNF family (BAFF) stimulates B-cell proliferation and survival, but excessive BAFF promotes the development of aggressive B cells leading to malignant and autoimmune diseases. Recently, we have reported that rapamycin, a macrocyclic lactone, attenuates human soluble BAFF (hsBAFF)-stimulated B-cell proliferation/survival by suppressing mTOR-mediated PP2A-Erk1/2 signaling pathway. Here, we show that the inhibitory effect of rapamycin on hsBAFF-promoted B cell proliferation/survival is also related to blocking hsBAFF-stimulated phosphorylation of Akt, S6K1, and 4

PTEN regulates BCRP/ABCG2 and the side population through the PI3K/Akt pathway in chronic myeloid leukemia.

A small population of cancer stem cells named the "side population" (SP) has been demonstrated to be responsible for the persistence of many solid tumors. However, the role of the SP in leukemic pathogenesis remains controversial. The resistance of leukemic stem cells to targeted therapies, such as tyrosine kinase inhibitors (TKIs), results in therapeutic failure or refractory/relapsed disease in chronic myeloid leukemia (CML). The drug pump, ATP-binding cassette sub-family G member 2 (ABCG2), is well known as a specific marker of the SP and could be controlled by several pathways, including t

Grb10 promotes lipolysis and thermogenesis by phosphorylation-dependent feedback inhibition of mTORC1.

Identification of key regulators of lipid metabolism and thermogenic functions has important therapeutic implications for the current obesity and diabetes epidemic. Here, we show that Grb10, a direct substrate of mechanistic/mammalian target of rapamycin (mTOR), is expressed highly in brown adipose tissue, and its expression in white adipose tissue is markedly induced by cold exposure. In adipocytes, mTOR-mediated phosphorylation at Ser501/503 switches the binding preference of Grb10 from the insulin receptor to raptor, leading to the dissociation of raptor from mTOR and downregulation of mTOR

Activation of the mTOR pathway in primary medullary thyroid carcinoma and lymph node metastases.

PURPOSE: Understanding the molecular pathogenesis of medullary thyroid carcinoma (MTC) is prerequisite to the design of targeted therapies for patients with advanced disease. EXPERIMENTAL DESIGN: We studied by immunohistochemistry the phosphorylation status of proteins of the RAS/MEK/ERK and PI3K/AKT/mTOR pathways in 53 MTC tissues (18 hereditary, 35 sporadic), including 51 primary MTCs and 2 cases with only lymph node metastases (LNM). We also studied 21 autologous LNMs, matched to 21 primary MTCs. Staining was graded on a 0 to 4 scale (S score) based on the percentage of positive cells. We

Critical role of arachidonic acid-activated mTOR signaling in breast carcinogenesis and angiogenesis.

The mammalian target of rapamycin (mTOR) signaling pathway is upregulated in the pathogenesis of many cancers. Arachidonic acid (AA) and its metabolites play critical role in the development of breast cancer, but the mechanisms through which AA promotes mammary tumorigenesis and progression are poorly understood. We found that the levels of AA and cytosolic phospholipase A2 (cPLA2) strongly correlated with the signaling activity of mTORC1 and mTORC2 as well as the expression levels of vascular epithelial growth factor (VEGF) in human breast tumor tissues. In cultured breast cancer cells, AA ef

Hepatitis C virus NS5A binds to the mRNA cap-binding eukaryotic translation initiation 4F (eIF4F) complex and up-regulates host translation initiation machinery through eIF4E-binding protein 1 inactivation.

Initiation, a major rate-limiting step of host protein translation, is a critical target in many viral infections. Chronic hepatitis C virus (HCV) infection results in hepatocellular carcinoma. Translation initiation, up-regulated in many cancers, plays a critical role in tumorigenesis. mTOR is a major regulator of host protein translation. Even though activation of PI3K-AKT-mTOR by HCV non-structural protein 5A (NS5A) is known, not much is understood about the regulation of host translation initiation by this virus. Here for the first time we show that HCV up-regulates host cap-dependent tran

Regulation of TFEB and V-ATPases by mTORC1.

Mammalian target of rapamycin (mTOR) complex 1 (mTORC1) is an important, highly conserved, regulator of cell growth. Ancient among the signals that regulate mTORC1 are nutrients. Amino acids direct mTORC1 to the surface of the late endosome/lysosome, where mTORC1 becomes receptive to other inputs. However, the interplay between endosomes and mTORC1 is poorly understood. Here, we report the discovery of a network that links mTORC1 to a critical component of the late endosome/lysosome, the V-ATPase. In an unbiased screen, we found that mTORC1 regulated the expression of, among other lysosomal ge

Human chorionic gonadotropin stimulates theca-interstitial cell proliferation and cell cycle regulatory proteins by a cAMP-dependent activation of AKT/mTORC1 signaling pathway.

In addition to playing a cardinal role in androgen production, LH also regulates growth and proliferation of theca-interstitial (T-I) cells. Here, we show for the first time that LH/human chorionic gonadotropin (hCG) regulates T-I cell proliferation via the mammalian target of rapamycin complex 1 (mTORC1) signaling network. LH/hCG treatment showed a time-dependent stimulation of T-I cell proliferation and phosphorylation of protein kinase B (AKT), ERK1/2, and ribosomal protein (rp)S6 kinase 1 (S6K1), and its downstream effector, rpS6. Pharmacological inhibition of ERK1/2 signaling did not bloc

Differences in phosphorylation of the IL-2R associated JAK/STAT proteins between HTLV-I(+), IL-2-independent and IL-2-dependent cell lines and uncultured leukemic cells from patients with adult T-cell lymphoma/leukemia.

To determine activation status of the IL-2R-associated (Jak/STAT) pathway in the HTLV-I infected cells, we examined tyrosine phosphorylation of Jak3, STAT3, and STAT5 in several HTLV-I(+) T-cell lines and in uncultured leukemic T cells isolated from patients with adult T-cell lymphoma/leukemia (ATLL). Constitutive basal phosphorylation of Jak3 and, usually, STAT3 and STAT5 was detected in all four IL-2-independent cell lines tested, but in none of the three IL-2-dependent cell lines. Similarly, there was no detectable basal phosphorylation of Jak3 and STAT5 in the leukemic cells from ATLL pati

Oral Graft-Versus-Host Disease: A Pictorial Review and a Guide for Dental Practitioners.

IntroductionGraft-versus-host disease (GVHD) is a complication of haematopoietic stem cell transplantation (HSCT). GVHD may also develop following solid transplants or blood transfusions if white blood cells are transferred. GVHD affects multiple organs, including the oral tissues.ObjectiveThis pictorial review provides a background of GVHD to dental practitioners, describes the most common oral manifestations of GVHD and highlights the main treatment modifications needed to deliver dental care to patients with GVHD.MethodsA narrative review enhanced with clinical photographs.ResultsAcute GVHD

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… Currently, sirolimus, rituximab, imatinib, ibrutinib and ruxolitinib are more commonly used for treating cGVHD. Non-pharmacological modalities include extracorporeal photopheresis and phototherapy. … Sirolimus was reported to induce oral ulcerations ( Figure 13 ). 16 The elliptical lesions usually have a central yellowish fibrinous membrane and an erythematous periphery; larger lesions have a more irregular shape. …

Polyclonal and monoclonal antibodies for treating acute rejection episodes in kidney transplant recipients.

BACKGROUND: Registry data shows that the incidence of acute rejection has been steadily falling. Approximately 10% to 35% of kidney recipien … treated with more contemporary immunosuppressive regimens which include tacrolimus/mycophenolate or sirolimus. However, many kidney transplant centres around the world continue to use older immunosuppressive regimes and the findings of this review remain strongly relevant to their clinical practice.Larger studies with standardised reproducible outcome crite …

Epithelioid Hemangioendothelioma With a Novel Chromosomal Deletion and an Aggressive Clinical Course: A Case Report and Literature Review.

Epithelioid hemangioendothelioma (EHE) is a rare neoplastic process arising from the endothelial lining of virtually any blood vessel, with varying degrees of metastatic spread. In the following case report, the clinical course and treatment stratification are detailed for a 59-year-old female who originally presented with cervical radiculopathy and was found to have aggressive-type EHE refractory to multiple lines of therapy. In doing so, a novel deletion of the long arm of Chromosome 16 at Position 24, in all cells analyzed, ISCN Karyotype: 46,XX,del(16)(q24)[10] is also identified and may c

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… Other treatment options include antiangiogenic agents such as VEGFR tyrosine kinase inhibitors and cytotoxic chemotherapy [ 18 , 19 ], while immunomodulatory agents such as lenalidomide and sirolimus have demonstrated modest benefit in small series [ 20 , 21 ]. … G., Activity of Sirolimus in Patients With Progressive Epithelioid Hemangioendothelioma: A Case-Series Analysis Within the Italian Rare Cancer Network, Cancer. (2021) 127, no. 4, 569–576, 10.1002/cncr.33247. 22. Stacchiotti S., Tap W., Leonard H., Zaffaroni N., and Baldi G. …

Advances in drug therapy for systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is an autoimmune disorder that afflicts 500,000 people in the United States. There has not been a new SLE drug approved in the United States since 1958. However, a guidance document issued by the Food and Drug Administration in 2005 provided a roadmap for investigators which spawned numerous ongoing clinical trials. Among these, Belimumab, a monoclonal antibody to soluble B lymphocyte stimulator, met its primary endpoints in two large trials and will probably obtain FDA approval soon. Other promising agents targeting a variety of mechanisms of action are curr

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… | Proteosome/plasma cells Cytokines | Inhibition of IL-6, IL-10; TNF inhibitors Innate immune system | Inhibition of IFN-α and IFN-γ, blockade of TLR-7 and/or TLR-9, C5a inhibition Toleragens | Peptides derived from nucleosomes, splicosomes Cell surface receptor activation inhibition | Syk kinase, sirolimus … Sirolimus (rapamycin) binds the regulatory kinase mTOR and is used for renal transplant rejection prevention. Many SLE patients with transplants currently take this agent, and a phase II trial is in progress. …

Molecular Inhibitors of Growth Signals

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… Derivatives of rapamycin (sirolimus, temsirolimus, everolimus, ridaforolimus) are allosteric mTOR inhibitors, and are sometimes referred to as rapalogs. Sirolimus inhibits only TORC1. … Sirolimus derivatives are substrates for CYP3A4. As the mTOR pathway is important for glucose metabolism mTOR inhibitors increase blood glucose. Non-infectious pneumonitis is a class effect of sirolimus derivatives. Allergic reactions to sirolimus derivatives may be serious." …

Ceramide inhibits insulin-stimulated Akt phosphorylation through activation of Rheb/mTORC1/S6K signaling in skeletal muscle.

Ceramide is a negative regulator of insulin activity. At the molecular level, it causes a decrease in insulin-stimulated Akt Ser473 phosphorylation in C2C12 myotubes. Interestingly, we found that the phosphorylation of S6K at Thr389 was increased under the same conditions. Utilizing both rapamycin to inhibit mTORC1 activity and shRNA to knock down Rheb, we demonstrated that the decrease in Akt Ser473 phosphorylation stimulated by insulin after C2-ceramide incubation can be prevented. The mechanism by which C2-ceramide impairs signaling would seem to involve a negative feedback of activated S6K

[Significance of mTOR (mammalian target of rapamycin) activity in human lymphomas].

Neoplastic processes, tumor growth, and tumor cell proliferation and survival are often due to the altered activation of different signaling pathways. The increased activity of PI3K/AKT/mTOR signaling has been shown to be an important regulator of tumor growth in several solid tumors and in mantle cell lymphomas. The active form of mTOR kinase (mammalian target of rapamycin) is a key signaling molecule, and it exists in two different complexes, mTORC1 and mTORC2. In the present work, mTOR activity was investigated in different lymphoma types, in parallel with clinical data. We also examined in

Concurrent inhibition of PI3K and mTORC1/mTORC2 overcomes resistance to rapamycin induced apoptosis by down-regulation of Mcl-1 in mantle cell lymphoma.

Mantle cell lymphoma (MCL) is an aggressive form of Non-Hodgkin-lymphoma (NHL) with an ongoing need for novel treatments. Apart from the translocation t(11:14), which facilitates constitutive transcription of cyclin D1, additional aberrations are frequently observed in MCL, including a recurrent dysregulation of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway. mTOR, a key component of this pathway, is pivotal for the assembly of mTOR complex (mTORC) 1 and 2. Temsirolimus, an analog of the mTOR inhibitor rapamycin, is approv…