Introduction
Conventional anticancer chemotherapy remains the main treatment modality for many types of cancer. Generally, chemotherapeutic agents exert their cytotoxic effects on cancer cells by interrupting metabolic processes, inhibiting DNA replication and interfering with protein biosynthesis or generating chemical species that damage cancer cells. [ 1 , 2 ] For example, cyclophosphamide inhibits DNA synthesis due to its metabolite phosphoramide mustard that induces DNA crosslinking, thus leading to cell death. [ 3 , 4 ] However, the potential contribution of chemotherapeutic agents in activating the immune system is often neglected, [ 5 , 6 ] and their supportive role in immunotherapy has thus far hardly been exploited. Notably, both in human and animal models, chemical antineoplastic drugs often induce immunosuppression, particularly at high concentration. [ 7 ] For example, temozolomide can cause lymphopenia [ 8 , 9 ] , methotrexate and cyclophosphamide are used as immunosuppressive agents in the treatment of autoimmune diseases. [ 10 – 12 ]
However, an increasing number of preclinical and clinical studies have also shown that chemotherapeutics can provoke cancer immunity. [ 13 ] Chemotherapeutics can stimulate the immune system via two main mechanisms. Firstly, certain chemotherapeutic agents directly trigger cancer cells to undergo immunogenic cell death (ICD) which can initiate anti-cancer immune reactions within the tumor microenvironment (TME). [ 14 ] During ICD, apoptotic cancer cells express danger-associated molecular patterns (DAMPs) and release cancer antigens which together induce adaptive immunity. [ 15 , 16 ] Moreover, chemotherapeutic agents can also directly activate the immune system, for example, by promoting macrophage polarization, dendritic cell (DC) maturation and T cell response against cancer. [ 17 – 20 ] When M2-like macrophages are polarized into M1-like macrophages by chemotherapeutic drugs, they become pro-inflammatory and produce pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β), and interleukin 6 (IL-6). [ 21 , 22 ] Chemotherapeutic drugs can also directly induce DC maturation by promoting the expression of histocompatibility complex (MHC) class molecules, and/or of co-stimulatory molecules such as CD80 and CD86 on the surface of DCs when used at low doses. The maturation of DCs is necessary for presenting antigens and priming T lymphocytes. [ 23 , 24 ] While there is growing evidence supporting the ability of chemotherapeutics to activate the immune system, different chemotherapeutics may induce the same type of immunoactivation via different mechanisms. Moreover, chemotherapeutics can directly contribute to cancer immunotherapy by depleting immunosuppressive cells, including CD4 + CD25 + regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs). [ 25 ] Tregs are known to suppress the immune system and prevent it from attacking cancer cells, while MDSCs also have immunosuppressive functions and inhibit the activation of T cells. [ 26 , 27 ] Studies have reported that certain chemotherapeutic agents, such as gemcitabine and cyclophosphamide, can induce apoptosis and dysfunction of Tregs and MDSCs, thereby enhancing antitumor immune response. [ 27 – 30 ] For example, low-dose gemcitabine has been shown to inhibit tumor growth by depleting master regulator (MR) genes expressing in tumor-infiltrating regulatory T cells (TI-Tregs) in vivo . [ 31 ]
In this review, we provide an overview of the immunoactivation effects of chemotherapeutic drugs ( Figure 1 ). We identify prerequisites for achieving optimal combinations of chemo- and immunotherapy, and discuss the molecular and cellular mechanisms through which conventional chemotherapeutics agents directly activate immune cells such as macrophages, DCs, NK cells, T cells and B cells. This information may guide clinicians and researchers to develop effective immunotherapeutic strategies that harness the synergistic effects of chemotherapy and immunotherapy.
Direct activation of innate immune system by chemotherapeutic agents
The innate immune system is the first line of defense against invading pathogens and is an essential part of the body's immune response. [ 32 ] The innate immune system is composed of physical, chemical and cellular barriers. [ 33 ] Skin and mucous membranes are part of the innate immune system which act as a physical barrier to prevent pathogens from entering the body. [ 34 , 35 ] Chemical barriers include enzymes and proteins, such as lysozyme and complement, which can break down and destroy foreign invaders. Cellular barriers include various types of immune cells, such as macrophages, neutrophils, and NK cells, which can recognize and eliminate pathogens through phagocytosis, releasing of toxic substances, or inducing apoptosis. [ 36 , 37 ] Unlike the adaptive immune system, which relies on the recognition of specific antigens, the innate immune system can recognize a wide range of pathogens with pattern recognition receptors (PRRs) that recognize conserved structures of microbial components, called pathogen-associated molecular patterns (PAMPs). The innate immune system provides rapid and non-specific defense against invading pathogens and plays a critical role in preventing infections and maintaining homeostasis within the body. [ 36 , 38 ] It is also essential in the initiation of anti-cancer immunity.
Chemotherapeutic agents polarizing macrophages
Macrophages play crucial roles in host defense against tumors and stimulate antitumor immune response. [ 39 ] Macrophages originate from monocytes and are further differentiated into subtypes, for example, conventionally defined type 1 pro-inflammatory (M1) and type 2 anti-inflammatory (M2) subsets. The M1 subset is classically activated macrophages contributing to anti-infection and antitumor effects, [ 40 ] while the M2 subset is alternatively activated and responsible for tissue repairment. [ 41 – 43 ] The presence of immunomodulatory factors such as interferon-γ (IFN-γ), IL-4, IL-10, and transforming growth factor-beta (TGF-β) can significantly impact macrophage function and phenotype. [ 44 ] Several studies have investigated that chemotherapeutic regimens were able to subvert the pro-tumorigenic activities of macrophages and increase the production of inflammatory cytokines by switching from an M2-like phenotype to an M1-like phenotype in vivo. [ 45 , 46 ] For example, paclitaxel, the active component of Taxol, is an important antineoplastic drug widely used against a variety of solid tumor types [ 47 ] by disrupting cellular microtubule networks. [ 48 ] Low-dose paclitaxel treatment induced the skewing of M2-like macrophages into M1-like macrophages, while it did not exert obvious cytotoxicity to macrophages. [ 49 , 50 ] Furthermore, emerging evidence indicates that paclitaxel's most significant immune activity is its capacity to reverse macrophage-mediated immune suppressor activities. [ 51 ]
Several reports have described that paclitaxel has lipopolysaccharide (LPS)-mimetic capabilities to reprogram M2-polarized macrophages to M1 through the Toll-like receptor-4 (TLR-4) without inducing their apoptosis. [ 52 – 54 ] TLR-4 is expressed on various immune cells as cell-surface receptors to recognize pathogens and mediate inflammatory response. [ 49 ] TLR-4 is the most important member of the TLR protein family for LPS recognition and its ligation leads to the activation of the TNF-α signaling pathway as well as the production of various inflammatory cytokines. [ 27 , 55 , 56 ] Cullis et al. have shown that the antitumor activity of nab-paclitaxel, an albumin-based nanoformulation of paclitaxel, may be TLR-4-dependent because TLR-4 inhibitors abrogated immunostimulatory cytokine expression by macrophages in vivo and vitro. [ 51 ] Therefore, the polarization of M2-like macrophages to an M1-like phenotype by paclitaxel may occur by the activation of TLR-4 signal pathway. Micropinocytosis of nab-paclitaxel promotes macrophage polarization may account for its elevated drug delivery ability over the conventional solvent-based formulation of paclitaxel. [ 57 ] Furthermore, Kashyap et al. reported that microtubule-targeting drug, plinabulin, can directly promote M1-Like macrophage polarization and proliferation of macrophages via the Jun N-terminal kinase pathway both in murine and human models.. [ 58 ]
Ding and colleagues sought to identify the underlying mechanism of Taxol immunoactivation. [ 59 ] The myeloid differentiation protein-88 (MyD88) is a crucial signal adaptor protein required for binding the cognate ligand to active TLR-4. MyD88 signaling activates downstream molecules such as mitogen-activated protein kinases (MAPKs) and nuclear factor-κB (NF-κB). [ 60 , 61 ] To determine whether TLR-4 and its downstream molecule MyD88 are required for the immunoactivation effects of paclitaxel and LPS, the authors used primary macrophages from TLR-4-deficient or MyD88-knockout mice. Macrophages from wild-type mice were shown to secrete tumor necrosis factor (TNF) and nitric oxide (NO) after treatment with paclitaxel, whereas macrophages from TLR4-deficient or MyD88-knockout mice produced significantly lower levels of these two soluble factors. Furthermore, paclitaxel did not induce MAPK and NF-κB activation in TLR4-deficient macrophages and delayed NF-κB activation in MyD88 knockout macrophages. These results suggest that paclitaxel and LPS may share TLR4/MyD88-dependent and TLR4-dependent/MyD88-independent pathways in the production of inflammatory mediators.
Recently, nanomedicines have been employed to deliver immunomodulatory chemotherapeutic drugs. [ 48 , 62 ] Nanomedicines can overcome certain physiological barriers and achieve enhanced tumor drug accumulation via the enhanced permeability and retention (EPR) effect, while at the same time attenuating adverse effects of drugs in healthy tissues. [ 63 – 65 ] We have previously demonstrated the ability ofdocetaxel-loaded Π electron-stabilized polymeric micelles to polarize macrophages to an M1-like phenotype. The micelle formulation exhibited high stability and effectively incorporated docetaxel via Π-Π stacking interactions ( Figure 2A ). [ 66 ] In vitro cytotoxicity studies showed that polymeric micelles loaded with docetaxel were equally efficient as free docetaxel in inhibiting gastrointestinal (GI) cancer cell growth in vitro ( Figure 2B ). Then, multiple mouse models included cell-line derived xenografts (CDX) and patient-derived xenografts (PDX) were established to investigate the effectiveness of polymeric micelles loaded docetaxel in advanced-stage GI cancer. The efficacy of the polymeric micelles loaded with docetaxel was evaluated using a subcutaneous CDX model of SGC7901 cells. Free docetaxel slightly inhibited tumor growth while the polymeric micelles loaded with docetaxel showed significantly higher efficacy at two dose levels (5 and 10 mg/kg). The better efficacy was achieved at a dose of 10 mg/kg, leading to nearly complete tumor regression after repeated injection, whereas free docetaxel at the same dose was less effective ( Figure 2C ). In addition to its antitumor effect, immunofluorescence staining was performed to identify M1-like and M2-like macrophages. Compared to the non-treated group, the ratio of M1-like to M2-like macrophages was significantly increased in mice treated with free docetaxel and polymeric micelles loaded with docetaxel. Importantly, the micelle formulation of docetaxel showed more effective macrophage polarization than free docetaxel ( Figure 2D ). Furthermore, in a PDX model, the polymeric micelles loaded with docetaxel showed a significantly increased ratio of M1-/M2-like macrophages ( Figure 2E ) and better therapeutic efficacy compared to free docetaxel ( Figure 2F ). This work demonstrated that Π electron-stabilized polymeric micelles improve the therapeutic efficacy and macrophage modulation effect of docetaxel.
Several clinical trials have provided evidence that doxorubicin can provoke cancer immunity by promoting macrophage polarization from an M2-like to M1-like phenotype through TLR-4 pathway. Notably, blocking TLR-4 signaling effectively decreased doxorubicin-induced macrophage polarization. [ 67 – 69 ] Similarly, low-dose cyclophosphamide induced re-polarization of M2-like macrophages to a more M1-like phenotype in vivo, upregulating the production of the pro-inflammatory cytokines IL-6 and IL-12, while down-regulating the anti-inflammatory cytokines IL-10 and TGF-β. [ 70 ] In another study, formyl peptide receptor (FPR1/2) modified cisplatin prodrug was reported to active macrophages by delivering cisplatin to FPR1/2-overexpressing immune cells including macrophages and triggered the production of proinflammatory cytokines such as TNF-α and IFN-γ. [ 71 ]
Direct activation of dendritic cells by chemotherapeutic agents
DCs are antigen-presenting cells (APCs) and crucial for the initiation of antitumor T-cell response. [ 25 , 26 ] Upon antigen capture, DCs undergo a maturation process in which they upregulate the expression of MHC molecules, costimulatory molecules (CD80/86), cytokines, chemokines, and the chemokine receptor CCR7. [ 27 , 28 ] Consequently, mature DCs migrate to regional lymphoid tissues via CCR7 and prime naive T cells to differentiate to various effector T cells, including T helper (Th) 1 cells, Th2 cells, Th17 cells, T follicular helper (TFH) cells, and CD8 + cytotoxic T-lymphocytes (CTLs) [ 19 , 27 , 28 ] . Activation of naive DCs is crucial to trigger antigen-specific immune response and elicit anti-cancer effects.
Maturation of DCs is a complex process, encompassing multiple functions, including antigen processing and presentation, migration to lymphoid tissues, and T cell priming. These functions bridge innate and adaptive immunity. [ 72 – 74 ] Recently, studies have suggested that several chemotherapeutic agents may directly affect DC maturation. [ 75 , 76 ] Shurin et al. reported that a variety of chemotherapeutic agents at low nontoxic concentrations can upregulate the antigen processing machinery and enhance CD80, CD40 and IL-12p70 expression in murine bone marrow-derived DCs, [ 77 ] these costimulatory molecules are crucial to T cell activation. [ 73 , 78 ] Furthermore, since MHC class complexes are important in T cell priming, [ 79 , 80 ] paclitaxel and methotrexate could increase percentages of CD11c + CD86 + and CD11c + MHC-II + DCs for more efficient T cell activation ( Figure 3A and B ). In addition, it was shown that chemotherapeutics drugs, especially paclitaxel, can increase IL-12 expression by DCs ( Figure 3C ). All tested chemotherapeutic drugs up-regulated antigen presentation in wild-type DCs, however, the ability of paclitaxel, methotrexate, doxorubicin, and vinblastine to upregulate antigen presentation was significantly abrogated in IL-12 knock-out mice ( Figure 3D ).
CD40 expression on DCs is critical for the induction of proliferation of allogeneic T lymphocytes and Th1 response. [ 81 , 82 ] Akira et al. revealed that chemotherapeutic agents, for example vinblastine, could increase the expression of CD40, CD80, CD86, and MHC II, and trigger IL-1?, IL-6, and IL-12 production by mouse bone marrow-derived DCs. [ 83 ] Notably, local injection of low concentrations of vinblastine could induce phenotypic and functional maturation of DCs by triggering in situ maturation of skin-resident DCs. [ 84 , 85 ] Gruijand colleagues found that short-time exposure to anthraquinone-derivatives such as mitoxantrone and doxorubicin promoted the differentiation of CD34 + DCs precursors into mature DCs, which then induced primary allogeneic T cell proliferation. [ 86 ]
The mechanisms of DC differentiation and maturation by chemotherapeutic drugs remain to be fully elucidated. The most extensively studied family of pattern-recognition receptors (PRRs) on DCs are the TLRs. [ 87 ] Similar to macrophage polarization, three major signaling pathways determine the function of TLR activation on DCs: NF-κB, MAPK and interferon regulatory factor (IRF). [ 88 , 89 ] TLRs stimulate different Toll/IL-1R homology (TIR) domain signaling molecules, such as MyD88, interferon-β (TRIF), TRIF-related adaptor molecule (TRAM) and TIRAP (MAL), and most TLR ligation activates TAK1 (TGF-β Activated Kinase 1; MAP3K7) by utilizing the MyD88 adaptor pathway. This activates downstream signals such as NF-κB and MAPK, and then induce pro-inflammatory cytokines secretion (TNF-α, IL-12 and IL-6). [ 90 – 92 ] It has been proposed that low dose paclitaxel can induce DC maturation by interacting with TLR-4. [ 93 , 94 ] Recent studies have shown that activation of TLR-4 on dendritic cells induced release of pro-inflammatory mediators, eventually contributing to antibody response. [ 95 , 96 ] Armstrong and colleagues found that low dose paclitaxel enhanced DC maturation and upregulates the expression of costimulatory molecules including CD80 and CD86 by signaling through TLR-4. Blocking of the TLR-4 signaling pathway inhibited the expression of co-stimulatory molecules by 50%. [ 97 ]
In addition to traditional chemotherapeutic drugs, dolastatin, a family of natural microtubule inhibitors isolated from Dolabella Auricularia, has also been shown to induce DC migration and maturation. [ 98 , 99 ] Dolastatin 15 is a seven-subunit depsipeptide and dolastatin 10 is a five-subunit peptide obtained from the same organism. [ 100 ] Müller et al. demonstrated that dolastatin upregulates the maturation markers CD80, CD86, CD40 and MHC-II expression by murine DCs ( Figure 4A ). [ 101 ] Consistent with the in vitro results, dolastatin 10 and 15 induced the expression of CD86 and MHC-II on skin-resident langerhans cells (LCs) in C57BL/6 mice ( Figure 4B ). Interestingly, dolastatin induced similar levels of CD86, CD40 and MHC-II expression by DCs from wild-type and MyD88 - / - mice while CpG provoked lower expression of these markers by DCs from MyD88 - / - mice than wild-type DCs. This result suggested that the DC activation effects of dolastatin were MyD88-independent ( Figure 4C ). Similar responses were observed in human monocyte-derived DCs ( Figure 4D ). These results suggested that dolastatin-based therapies can activate DCs, thus, contributing to anti-cancer immunity.
NK cell activation by chemotherapy
NK cells are a type of cytotoxic lymphocytes that are part of the innate immune system, displaying cytotoxic functions and producing several cytokines. [ 7 , 102 ] The cytotoxic and immunomodulatory activities of NK cells can be influenced by chemotherapeutic drug administration. In fact, chemotherapy regimens used to treat cancer patients mainly work by inhibiting NK cell-mediated killing of cancer cells and their production of cytokines. [ 103 , 104 ] However, several experiments analyzing the effects of chemotherapeutic drugs on NK cells have shown that changing the type and dose of the drug can have different effects. Recently, a low-dose metronomic cyclophosphamide regimen was reported to stimulate NK-dependent antitumor immunity and promote cytokine production, reducing tumor angiogenesis through Treg depletion. [ 25 ] Incubation of human NK cells with paclitaxel resulted in a dose-dependent reduction in cytotoxicity against tumor cell lines, as well as peripheral blood mononuclear cells (PBMCs), MHC-unrestricted T cells and CTLs. [ 25 ] There is much evidence about the ability of NK cells to reduce the progression of multiple myeloma. Santoni et al. reported that myeloma cells treated with low doses of doxorubicin, melphalan, and bortezomib up-regulate DNAX accessory molecule-1 (DNAM-1) and NKG2D ligands resulting in enhanced NK cell susceptibility. [ 105 ] Additionally, tumors treated with 5-fluorouracil and IFN-α increasingly expressed the MHC-I and presented with higher numbers of infiltrating NK cells. This indicates that NK cells can be activated by 5-fluorouracil and IFN-α treatment. [ 104 , 106 ]
Direct activation of adaptive immune system by chemotherapeutic agents
Adaptive immunity is crucial when innate immunity cannot effectively eliminate infection. [ 107 ] The main immune cells of the adaptive immune system are T and B lymphocytes. T cells are activated by T cell receptor interaction with MHC class I/II molecules, co-stimulation signals, and cytokines. This activation process stimulates T cell differentiation, primarily into CD8 + cells, Th CD4 + cells, and Tregs. [ 108 , 109 ] B cells are stimulated mainly by B cell receptors and CD40, and differentiate into antibody-producing cells, i.e., plasma cells. [ 81 , 110 ]
Chemotherapeutic agents activating cytotoxic and helper T cells
High-dose chemotherapeutics can exhibit cytotoxic effects on T lymphocytes, leading to prolonged immunosuppression. [ 111 , 112 ] In contrast, several recent studies demonstrated that chemotherapeutic agents displayed positive effects on T cells and improved T cell-mediated immune response. [ 113 ] For example, Tseng et al. found that tumor-bearing mice treated with cisplatin followed by CRT/E7 (calreticulin linked to human papillomavirus type 16 E7 antigen) DNA vaccine exhibited an increased E7-specific CD8 + T cell response, leading to effective antitumor response and long-term survival. [ 114 ] In another study, low-dose cisplatin and paclitaxel reduced immunosuppression and induced strong tumor-specific CD8 + T cell response in both murine and patients. [ 115 ] Kim, Daejin and colleagues demonstrated that doxorubicin enhanced proliferation of antigen-specific CD4 + and CD8 + T cells when co-administered with Ii-PADRE (invariant Pan MHC-II cell surface receptor reactive epitope) DNA vaccination. [ 116 ] Moreover, treatment with 5-fluorouracil also increased production of IFN-γ by tumor-specific CD8 + T cells within the tumor and promoted T cell-dependent antitumor response. [ 117 ] Additional studies demonstrated that docetaxel can elevate IFN-γ production by CD8 + T cells and potentiate antigen-specific T-cell response. [ 118 ]
Naive CD4 + T cells can be differentiated into Th cells, [ 119 ] including Th1, Th2, Th17 cells based on their cytokine profiles. [ 120 , 121 ] Additionally, Th cells exhibit high plasticity, meaning that cells from one lineage can convert into another lineage under specific conditions. Cyclophosphamide is an alkylating agent widely employed in chemotherapy. Apart from its direct cytotoxic effects on cancer cells, cyclophosphamide exerts direct immunomodulatory effects on T cells. [ 122 ] Various studies showed that treatment with cyclophosphamide followed by the adoptive transfer of tumor-reactive CD4 + T cells led to the eradication of pleural mesothelioma tumors. [ 123 ] These studies have demonstrated that the robust antitumor effects are associated with the development of Th1 antitumor immunity. Cyclophosphamide has been found to induce a shift from a Th2 to a Th1 cytokine profile in lymphoma-bearing mice, promoting the differentiation of CD4 + T cells into highly activated effector cells. [ 124 , 125 ] These effector cells have the ability to produce multiple Th1-type cytokines such as IL-2, IFN-γ, and TNF-α simultaneously.
Proietti and colleagues discovered that low-dose cyclophosphamide increased the number of CD44 high T cells in mice. [ 126 ] They also found a significant increase Ly-6C positive T cells in the spleen of mice on different days after treatment with a single injection of cyclophosphamide ( Figure 5A ). The percentages of CD44 high T cells in the spleen and lymph nodes of mice treated with cyclophosphamide and poly I:C (a TLR-3 agonist) were found to be higher compared to that of mice injected with saline. In poly I:C injected mice, a similar increase in the percentages of CD44 high T cells was observed as compared to that of the cyclophosphamide-treated group ( Figure 5B ). These results suggest that both the injection of cyclophosphamide and poly I:C led to T cell activation. Moreover, type I IFN in the serum, spleens and lymph nodes was also upregulated by cyclophosphamide treatment in mice. [ 126 , 127 ] These findings indicate that cyclophosphamide can promote the CD44 high phenotype in both CD4 + and CD8 + T cells. Besides, Xiong et al. demonstrated that paclitaxel can augment Th1 cytokine (IFN-γ and IL-2) production in patients with advanced non-small cell lung cancer. [ 128 ] Flow cytometry data showed a significantly increased number of CD4 + IL-2 + T cells and CD8 + IFN-γ + T cells among total lymphocytes after paclitaxel treatment ( Figure 5C ). High expression of CD44 on T cells indicates T cell actitation and the CD44 expression levels were elevated for both CD4 + T cells and CD8 + T cells in mice treated with paclitaxel ( Figure 5D ).
Recently, Vennin and colleagues reported that chemotherapeutics such as taxanes can trigger tumor cells eradicated by directly increase T cell cytotoxic activity without T cell receptors (TCR) activation both in murine and human models. [ 129 ] CD4 + and CD8 + T cells were isolated from mouse spleens and treated with docetaxel in vitro, subsequently, these treated T cells were co-cultured with organoids derived from tumor suppressor genes Brca1 and Trp53 (KB1P) models. These T cells induced noticeably higher cell death in the organoids compared to untreated T cells ( Figure 6A ). To investigate whether the T cell killing was mediated by TCR, a lymphocyte kinase inhibitor (LCKi) was used to block TCR-mediated killing. The LCKi didn't hinder docetaxel-induced T cell cytotoxicity in the KB1P organoids ( Figure 6B ). Interestingly, docetaxel-treated T cells contained a higher protein content compared to non-treated T cells. Notably, these proteins did not belong to known factors driving T cell-mediated killing. A gene ontology analysis revealed high quantities of proteins associated with extracellular vesicles (EVs) derived from docetaxel-treated T cells and the result was confirmed by a proteomics analysis ( Figure 6C ). Splenic T cells from healthy mice were treated with docetaxel and then intravenously injected into mice with KB1P or MMTV-PyMT (overexpression of the oncogene PyMT) tumors. The mice receiving docetaxel-treated T cells displayed significantly slower tumor growth compared to those receiving non-treated T cells ( Figure 6D ). These results suggest that docetaxel-treated T cells have a potent anti-cancer effect via a TCR-independent mechanism.
Chemotherapy-induced activation of B cells
B cells are increasingly considered as a crucial component in antitumor immunity, because of antigen presentation and cancer antibody production after differentiation into plasma cells. [ 130 , 131 ] Tumor-infiltrating B cells (TIL-B) have been found to be important for cancer immunotherapy, [ 132 – 134 ] contributing to the formation of CD4 + memory T cells and promoting the survival and proliferation of CD8 + T cells. Evidence for the positive impact of chemotherapeutic agents on antitumor immune response also arises from activating B cells. [ 135 ] Erik et al. found that administration of cyclophosphamide not only increased the percentage of CD3 + and CD4 + /CD8 + T cells but also improved the percentage of B cells in the spleen and tumor. [ 136 ] Additionally, several experiments indicated that incubation of B cells with low levels of doxorubicin led to increased proliferative B cell response, which was attributed to the upregulation of the co-stimulatory molecule CD86. [ 137 ] Winqvist et al. investigated the influence of cisplatin, doxorubicin and irinotecan on the antigen-presenting ability of B cells. [ 138 ] Pre-treatment of B cells with irinotecan and cisplatin showed moderate increase in CD4 + lymphoblast formation when co-cultured with untreated CD4 + T cells. Interestingly, when doxorubicin treated B cells were used as antigen-presenting cells, there was a significant increase in lymphoblast formation ( Figure 7A ). The expression of HLA-DR (MHC-II cell surface receptor) on CD19 + B cells remained unchanged when cultured with doxorubicin. However, doxorubicin treatment led to an increased expression of CD86, while CD80 expression remained unaltered ( Figure 7B ). These data suggest that doxorubicin-enhanced antigen presentation by B cells was achieved by amplifying the CD86 co-stimulatory signal. This hypothesis was confirmed by CD86 blocking which reduced blast transformation of CD4 + T cells ( Figure 7C ). In patients treated with chemotherapy, PBMCs were significantly increased when CD86 expression on CD19 + B cells was upregulated ( Figure 7D ). These findings suggest that chemotherapy may have positive immunomodulatory effects in anti-tumor immune response through B cell activation.
Conclusion
Numerous preclinical and clinical studies have demonstrated that, although high-dose chemotherapy generally results in immunosuppression, chemotherapeutic drugs can also directly stimulate immunity, especially when administered at noncytotoxic doses. Hence, understanding the direct impact of chemotherapeutics on immune cells is crucial for optimizing cancer treatment strategies and improving patient outcomes. One of the key effects of chemotherapeutic agents is the promotion of immune cell maturation. Such direct immunostimulation is different from the so-called immunogenic cell death which indirectly stimulates immunity by danger-associated molecular patterns released by apoptotic cancer cells. For example, several drugs can induce the maturation of DCs; these drugs include clinically well-used taxanes. This enables the effective presentation of cancer cell antigens to T cells, leading to a robust and specific antitumor immune response. Chemotherapeutic drugs also can directly contribute to lymphocyte activation. The immunostimulation role of chemotherapeutics opens new avenues for combination therapies that aim to synergize the cytotoxic effects of chemotherapy with its immunostimulatory potential, ultimately leading to more effective cancer treatment strategies. Further research efforts are warranted to unravel the underlying mechanisms governing these effects and to develop innovative approaches that enhance the anti-tumor response while minimizing immunosuppression. One promising approach lies in the formulation of chemotherapeutic drugs in nanomedicines to enable targeted delivery and controlled release, as well as decreased side effects and immunosuppression. By combining chemotherapy and immunotherapy, with a focus on harnessing chemotherapy-induced direct immune cell activation, we envision improved therapeutic outcomes and enhanced quality of life for cancer patients.
Acknowledgements
The authors acknowledge funding support from European Research Council (ERC: BeaT-IT: 101040996), the Deutsche Forschungsgemeinschaft (DFG: SH 1223/1-1; GRK/RTG 2375 (Tumor-targeted Drug Delivery, 331065168)), China Scholarship Council (CSC: 202108310135), and the German Federal Ministry of Research and Education (BMBF: 16GW0319K).
Conflict of interest
The authors declare no conflict of interest.
[1] Mollaei M Hassan ZM Khorshidi F Langroudi L Transl Oncol 2021 14 101056 33684837 10.1016/j.tranon.2021.101056 PMC7938256
[2] Anand U Dey A Chandel AKS Sanyal R Mishra A Pandey DK De Falco V Upadhyay A Kandimalla R Chaudhary A Dhanjal JK Genes Dis 2022 10.1016/j.gendis.2022.02.007 PMC10310991 37397557
[3] Alkhalaf MI Alansari WS Alshubaily FA Alnajeebi AM Eskandrani AA Tashkandi MA Babteen NA Sci Rep 2020 10 12599 32724173 10.1038/s41598-020-68608-9 PMC7387554
[4] Steinbrecht S Kiebist J König R Thiessen M Schmidtke K-U Kammerer S Küpper J-H Scheibner K AMB Express 2020 10 128 32683510 10.1186/s13568-020-01064-w PMC7368878
[5] Galluzzi L Humeau J Buqué A Zitvogel L Kroemer G Nat Rev Clin Oncol 2020 17 725 32760014 10.1038/s41571-020-0413-z
[6] Briukhovetska D Dörr J Endres S Libby P Dinarello CA Kobold S Nat Rev Cancer 2021 21 481 34083781 10.1038/s41568-021-00363-z PMC8173513
[7] Shurin MR Naiditch H Gutkin DW Umansky V Shurin GV Curr Med Chem 2012 19 1792 22414087 10.2174/092986712800099785
[8] Lamb LS Pereboeva L Youngblood S Gillespie GY Nabors LB Markert JM Dasgupta A Langford C Spencer HT Sci Rep 2021 11 21133 34702850 10.1038/s41598-021-00536-8 PMC8548550
[9] Daniel P Meehan B Sabri S Jamali F Sarkaria JN Choi D Garnier D Kitange G Glennon KI Paccard A Karamchandani J Neurooncol Adv 2022 4 vdac076 35795471 10.1093/noajnl/vdac076 PMC9252128
[10] Cronstein BN Aune TM Nat Rev Rheumatol 2020 16 145 32066940 10.1038/s41584-020-0373-9
[11] Nalwa HS Prasad P Ganguly NK Chaturvedi V Mittal SA Transl Med Commun 2023 8 10
[12] Xiang X Wang R Chen L Chen Y Zheng B Deng S Liu S Sun P Shen G NPJ Sci Food 2022 6 26 35478196 10.1038/s41538-022-00140-8 PMC9046246
[13] Lei L Dong Z Xu L Yang F Yin B Wang Y Yue R Guan G Xu J Song G Zhang XB Theranostics 2022 12 6207 36168615 10.7150/thno.75323 PMC9475458
[14] Kroemer G Galassi C Zitvogel L Galluzzi L Nature Immunology 2022 23 487 35145297 10.1038/s41590-022-01132-2
[15] Ahmed A Tait SWG Mol Oncol 2020 14 2994 33179413 10.1002/1878-0261.12851 PMC7718954
[16] Fucikova J Kepp O Kasikova L Petroni G Yamazaki T Liu P Zhao L Spisek R Kroemer G Galluzzi L Cell Death Dis 2020 11 1013 33243969 10.1038/s41419-020-03221-2 PMC7691519
[17] Tariq M Zhang J Liang G Ding L He Q Yang B J Cell Biochem 2017 118 2484 28106295 10.1002/jcb.25895
[18] Li F Zheng X Wang X Xu J Zhang Q Transl Oncol 2021 14 101202 34390893 10.1016/j.tranon.2021.101202 PMC8365514
[19] Hu J Kinn J Zirakzadeh AA Sherif A Norstedt G Wikström A-C Winqvist O Clin Exp Immunol 2013 172 490 23600838 10.1111/cei.12060 PMC3646449
[20] Wang X Waschke BC Woolaver RA Chen SMY Chen Z Wang JH Cell Mol Immunol 2021 18 723 32427883 10.1038/s41423-020-0463-2 PMC8027191
[21] Murray PJ Annu Rev Physiol 2017 79 541 27813830 10.1146/annurev-physiol-022516-034339
[22] Duan Z Luo Y Signal Transduct Tar 2021 6 127 10.1038/s41392-021-00506-6 PMC7994399 33767177
[23] Hu J Kinn J Zirakzadeh AA Sherif A Norstedt G Wikström AC Winqvist O Clin Exp Immunol 2013 172 490 23600838 10.1111/cei.12060 PMC3646449
[24] Wculek SK Cueto FJ Mujal AM Melero I Krummel MF Sancho D Nat Rev Immunol 2020 20 7 31467405 10.1038/s41577-019-0210-z
[25] Ghiringhelli F Menard C Puig PE Ladoire S Roux S Martin F Solary E Le Cesne A Zitvogel L Chauffert B Cancer Immunol Immunother 2007 56 641 16960692 10.1007/s00262-006-0225-8 PMC11030569
[26] Ohkura N Sakaguchi S Cell Res 2020 30 465 32367041 10.1038/s41422-020-0324-7 PMC7264322
[27] Veglia F Sanseviero E Gabrilovich DI Nat Rev Immunol 2021 21 485 33526920 10.1038/s41577-020-00490-y PMC7849958
[28] Li K Shi H Zhang B Ou X Ma Q Chen Y Shu P Li D Wang Y Signal Transduct Tar 2021 6 362 10.1038/s41392-021-00670-9 PMC8497485 34620838
[29] Mikyšková R Indrová M Polláková V Bieblová J Símová J Reiniš M J Immunol 2012 35 374 10.1097/CJI.0b013e318255585a 22576342
[30] Diaz-Montero CM Salem ML Nishimura MI Garrett-Mayer E Cole DJ Montero AJ Cancer Immunol Immunother 2009 58 49 18446337 10.1007/s00262-008-0523-4 PMC3401888
[31] Obradovic A Ager C Turunen M Nirschl T Khosravi-Maharlooei M Iuga A Jackson CM Yegnasubramanian S Tomassoni L Fernandez EC McCann P Cancer Cell 2023 41 933 37116491 10.1016/j.ccell.2023.04.003 PMC10193511
[32] Iwasaki A Medzhitov R Nat Immunol 2015 16 343 25789684 10.1038/ni.3123 PMC4507498
[33] Wu J Chen ZJ Annu Rev Microbiol 2014 32 461 10.1146/annurev-immunol-032713-120156 24655297
[34] Li X Dai H Wang H Han W Cell Mol Immunol 2021 18 1607 33854207 10.1038/s41423-021-00679-8 PMC8167086
[35] Paludan SR Pradeu T Masters SL Mogensen TH Nat Rev Immunol 2021 21 137 32782357 10.1038/s41577-020-0391-5 PMC7418297
[36] Vance RE Isberg RR Portnoy DA Cell Host Microbe 2009 6 10 19616762 10.1016/j.chom.2009.06.007 PMC2777727
[37] Stuart LM Paquette N Boyer L Nat Rev Immunol 2013 13 199 23411798 10.1038/nri3398 PMC4121468
[38] Ichinohe T Pang IK Iwasaki A Nat Immunol 2010 11 404 20383149 10.1038/ni.1861 PMC2857582
[39] Stout RD Jiang C Matta B Tietzel I Watkins SK Suttles J J Immunol 2005 175 342 15972667 10.4049/jimmunol.175.1.342
[40] Chen X Liu Y Gao Y Shou S Chai Y Int Immunopharmacol 2021 96 107791 34162154 10.1016/j.intimp.2021.107791
[41] Yunna C Mengru H Lei W Weidong C Eur J Pharmacol 2020 877 173090 32234529 10.1016/j.ejphar.2020.173090
[42] Chen S Saeed AFUH Liu Q Jiang Q Xu H Xiao GG Rao L Duo Y Signal Transduct Tar 2023 8 207 10.1038/s41392-023-01452-1 PMC10200802 37211559
[43] Orecchioni M Ghosheh Y Pramod AB Ley K Front Immunol 2019 10 1084 31178859 10.3389/fimmu.2019.01084 PMC6543837
[44] Lake RA Robinson BWS Nat Rev Cancer 2005 5 397 15864281 10.1038/nrc1613
[45] Maeda H J Controlled Release 2012 164 138 10.1016/j.jconrel.2012.04.038 22595146
[46] Atcha H Meli VS Davis CT Brumm KT Anis S Chin J Jiang K Pathak MM Liu WF Front Immunol 2021 12 10.3389/fimmu.2021.689397 PMC8493066 34630381
[47] Fitzpatrick FA Wheeler R Int J Immunopharmacol 2003 3 1699 10.1016/j.intimp.2003.08.007 14636822
[48] Shi Y Adv Ther 2020 3 1900215
[49] Gelman AE Zhang J Choi Y Turka LA J Immunol 2004 172 6065 15128790 10.4049/jimmunol.172.10.6065 PMC2833313
[50] Kawai T Akira S Int Immunol 2009 21 317 19246554 10.1093/intimm/dxp017 PMC2721684
[51] Cullis J Siolas D Avanzi A Barui S Maitra A Bar-Sagi D Cancer Immunol Res 2017 5 182 28108630 10.1158/2326-6066.CIR-16-0125 PMC5570452
[52] Rajput S Volk-Draper LD Ran S Mol Cancer Ther 2013 12 1676 23720768 10.1158/1535-7163.MCT-12-1019 PMC3742631
[53] Volk-Draper L Hall K Griggs C Rajput S Kohio P DeNardo D Ran S Cancer Res 2014 74 5421 25274031 10.1158/0008-5472.CAN-14-0067 PMC4185415
[54] Kawasaki K Akashi S Shimazu R Yoshida T Miyake K Nishijima M J Biol Chem 2000 275 2251 10644670 10.1074/jbc.275.4.2251
[55] Ciesielska A Matyjek M Kwiatkowska K Cell Mol Life Sci 2021 78 1233 33057840 10.1007/s00018-020-03656-y PMC7904555
[56] Vasudevan SO Russo AJ Kumari P Vanaja SK Rathinam VA Cell Rep 2022 39 110755 35508125 10.1016/j.celrep.2022.110755 PMC9376664
[57] Kundranda MN Niu J Drug Des Devel Ther 2015 9 3767 10.2147/DDDT.S88023 PMC4521678 26244011
[58] Natoli M Herzig P Pishali Bejestani E Buchi M Ritschard R Lloyd GK Mohanlal R Tonra JR Huang L Heinzelmann V Trüb M Front Oncol 2021 11 10.3389/fonc.2021.644608 PMC7966525 33747968
[59] Byrd-Leifer CA Block EF Takeda K Akira S Ding A Eur J Immunol 2001 31 2448 11500829 10.1002/1521-4141(200108)31:8<2448::aid-immu2448>3.0.co;2-n
[60] Li Y Zhang H Kosturakis AK Cassidy RM Zhang H Kennamer-Chapman RM Jawad AB Colomand CM Harrison DS Dougherty PM Brain Behav Immun 2015 49 255 26065826 10.1016/j.bbi.2015.06.003 PMC4567501
[61] Janssens S Beyaert R Trends Biochem Sci 2002 27 474 12217523 10.1016/s0968-0004(02)02145-x
[62] Saeed M Gao J Shi Y Lammers T Yu H Theranostics 2019 9 7981 31754376 10.7150/thno.37568 PMC6857062
[63] Irvine DJ Dane EL Nat Rev Immunol 2020 20 321 32005979 10.1038/s41577-019-0269-6 PMC7536618
[64] Huang J Yang B Peng Y Huang J Wong SHD Bian L Zhu K Shuai X Han S Adv Funct Mater 2021 31 2011171
[65] Tang W Yang J Yuan Y Zhao Z Lian Z Liang G Nanoscale 2017 9 6529 28466929 10.1039/c6nr09895a
[66] Liang C Bai X Qi C Sun Q Han X Lan T Zhang H Zheng X Liang R Jiao J Zheng Z Biomaterials 2021 266 120432 33069116 10.1016/j.biomaterials.2020.120432 PMC7611946
[67] Kaczmarek A Brinkman BM Heyndrickx L Vandenabeele P Krysko DV J Pathol 2012 226 598 21960132 10.1002/path.3009
[68] Leal AD Kadakia KC Looker S Hilger C Sorgatz K Anderson K Jacobson A Grendahl D Seisler D Hobday T Loprinzi CL Support Care Cancer 2014 22 1313 24402411 10.1007/s00520-013-2089-8 PMC3969765
[69] Wang L Chen Q Qi H Wang C Wang C Zhang J Dong L Cancer Res 2016 76 6631 27680684 10.1158/0008-5472.CAN-15-3034
[70] Bryniarski K Szczepanik M Ptak M Zemelka M Ptak W Pharmacol Rep 2009 61 550 19605955 10.1016/s1734-1140(09)70098-2
[71] Wong DYQ Yeo CHF Ang WH Angew Chem Int Ed 2014 53 6752 10.1002/anie.201402879 24844571
[72] Pfannenstiel LW Lam SSK Emens LA Jaffee EM Armstrong TD Cell Immunol 2010 263 79 20346445 10.1016/j.cellimm.2010.03.001 PMC2862830
[73] Hwang J-R Byeon Y Kim D Park S-G Exp Mol Med 2020 52 750 32439954 10.1038/s12276-020-0435-8 PMC7272404
[74] Shui J-W Boomer JS Han J Xu J Dement GA Zhou G Tan T-H Nat Immunol 2007 8 84 17115060 10.1038/ni1416
[75] Hirschhorn-Cymerman D Rizzuto GA Merghoub T Cohen AD Avogadri F Lesokhin AM Weinberg AD Wolchok JD Houghton AN J Exp Med 2009 206 1103 19414558 10.1084/jem.20082205 PMC2715041
[76] Everts B Amiel E Huang SC-C Smith AM Chang C-H Lam WY Redmann V Freitas TC Blagih J van der Windt GJW Artyomov MN Nat Immunol 2014 15 323 24562310 10.1038/ni.2833 PMC4358322
[77] Shurin GV Tourkova IL Kaneno R Shurin MR J Immunol 2009 183 137 19535620 10.4049/jimmunol.0900734 PMC4005417
[78] Shyer JA Flavell RA Bailis W Cell Res 2020 30 649 32709897 10.1038/s41422-020-0379-5 PMC7395146
[79] Tourkova IL Shurin GV Ferrone S Shurin MR Cancer Immunol Immunother 2009 58 567 18751977 10.1007/s00262-008-0579-1 PMC4006356
[80] Whiteside TL Stanson J Shurin MR Ferrone S J Immunol 2004 173 1526 15265880 10.4049/jimmunol.173.3.1526
[81] Bullock TNJ Cell Mol Immunol 2022 19 14 34282297 10.1038/s41423-021-00734-4 PMC8752810
[82] Lacy M Bürger C Shami A Ahmadsei M Winkels H Nitz K van Tiel CM Seijkens TTP Kusters PJH Karshovka E Prange KHM Nat Commun 2021 12 3754 34145241 10.1038/s41467-021-23909-z PMC8213756
[83] Shurin MR Yurkovetsky ZR Tourkova IL Balkir L Shurin GV Int J Cancer 2002 101 61 12209589 10.1002/ijc.10576
[84] Tanaka H Matsushima H Mizumoto N Takashima A Cancer Res 2009 69 6978 19706756 10.1158/0008-5472.CAN-09-1101 PMC2769260
[85] Cheong C Matos I Choi J-H Dandamudi DB Shrestha E Longhi MP Jeffrey KL Anthony RM Kluger C Nchinda G Koh H Cell 2010 143 416 21029863 10.1016/j.cell.2010.09.039 PMC3150728
[86] van de Ven R Reurs AW Wijnands PGJTB van Wetering S Kruisbeek AM Hooijberg E Scheffer GL Scheper RJ de Gruijl TD Cancer Immunol Immunother 2012 61 181 21874304 10.1007/s00262-011-1039-x PMC11028503
[87] Cheng CS Feldman KE Lee J Verma S Huang D-B Huynh K Chang M Ponomarenko JV Sun S-C Benedict CA Ghosh G Sci Signal 2011 4 ra11 21343618 10.1126/scisignal.2001501 PMC3096068
[88] Dalod M Salazar-Mather TP Malmgaard L Lewis C Asselin-Paturel C Briére F Trinehieri G Biron CA J Exp Med 2002 195 517 11854364 10.1084/jem.20011672 PMC2193614
[89] Cusson-Hermance N Khurana S Lee TH Fitzgerald KA Kelliher MA J Biol Chem 2005 280 36560 16115877 10.1074/jbc.M506831200
[90] Sartorius R Trovato M Maneo R D’Apiee L De Berardinis P npj Vaccines 2021 6 127 34711839 10.1038/s41541-021-00391-8 PMC8553822
[91] Fitzpatrick JM Minogue E Curham L Tyrrell H Gavigan P Hind W Downer EJ J Neuroimmunol 2020 343 577217 32244040 10.1016/j.jneuroim.2020.577217
[92] Sameer AS Nissar S Biomed Res Int 2021 2021 1157023 34552981 10.1155/2021/1157023 PMC8452412
[93] John J Ismail M Riley C Askham J Morgan R Melcher A Pandha H BMC Immunol 2010 11 14 20302610 10.1186/1471-2172-11-14 PMC2850888
[94] Chau J Moza D Hossain N Lee JK Bienenstock J Karimi K Eur J Pharmacol 2013 715 321 23701916 10.1016/j.ejphar.2013.04.050
[95] Watts C West MA Zaru R Curr Opin Immunol 2010 22 124 20083398 10.1016/j.coi.2009.12.005
[96] Pfannenstiel LW Lam SS Emens LA Jaffee EM Armstrong TD Cell Immunol 2010 263 79 20346445 10.1016/j.cellimm.2010.03.001 PMC2862830
[97] Armstrong DK Bundy B Wenzel L Huang HQ Baergen R Lele S Copeland LJ Walker JL Burger RA N Engl J Med 2006 354 34 16394300 10.1056/NEJMoa052985
[98] Pettit GR Hogan F Toms S J Nat Prod 2011 74 962 21534541 10.1021/np1007334 PMC3116808
[99] Caligiuri MA Blood 2008 112 461 18650461 10.1182/blood-2007-09-077438 PMC2481557
[100] Bai R Friedman SJ Pettit GR Hamel E Biochem Pharmacol 1992 43 2637 1632820 10.1016/0006-2952(92)90153-a
[101] Müller P Martin K Theurich S Schreiner J Savic S Terszowski G Lardinois D Heinzelmann-Schwarz VA Schlaak M Kvasnicka H-M Spagnoli G Cancer Immunol Res 2014 2 741 24916470 10.1158/2326-6066.CIR-13-0198
[102] Vivier E Tomasello E Baratin M Walzer T Ugolini S Nat Immunol 2008 9 503 18425107 10.1038/ni1582
[103] Fine JH Chen P Mesci A Allan DSJ Gasser S Raulet DH Carlyle JR Cancer Res 2010 70 7102 20823164 10.1158/0008-5472.CAN-10-1316 PMC3108335
[104] Niu C Jin H Li M Zhu S Zhou L Jin F Zhou Y Xu D Xu J Zhao L Hao S Oncotarget 2017 8 5954 27992381 10.18632/oncotarget.13979 PMC5351604
[105] Soriani A Zingoni A Cerboni C Iannitto ML Ricciardi MR Di Gialleonardo V Cippitelli M Fionda C Petrucci MT Guarini A Foà R Blood 2009 113 3503 19098271 10.1182/blood-2008-08-173914
[106] Khallouf H Märten A Serba S Teichgräber V Büchler MW Jäger D Schmidt J J Immunother 2012 35 245 22421942 10.1097/CJI.0b013e31824b3a76
[107] Metur SP Klionsky DJ Cell Mol Immunol 2021 18 1096 33785844 10.1038/s41423-021-00662-3 PMC8093269
[108] Blanchard N Salvioni A Robey EA Weiss LM Kim K Chapter 26 - Adaptive immunity Toxoplasma gondii (Third Edition) Academic Press 2020 1107
[109] Cebrian I Croce C Guerrero NA Blanchard N Mayorga LS EMBO Rep 2016 17 1753 27861124 10.15252/embr.201642358 PMC5283579
[110] Craig VJ Cogliatti SB Arnold I Gerke C Balandat JE Wündisch T Müller A Leukemia 2010 24 1186 20428202 10.1038/leu.2010.76
[111] Lu J Liu X Liao Y-P Salazar F Sun B Jiang W Chang CH Jiang J Wang X Wu AM Meng H Nat Commun 2017 8 1811 29180759 10.1038/s41467-017-01651-9 PMC5703845
[112] Setlai BP Hull R Bida M Durandt C Mulaudzi TV Chatziioannou A Dlamini Z Biomedicines 2022 10 682 35327484 10.3390/biomedicines10030682 PMC8945019
[113] Roselli M Cereda V di Bari MG Formica V Spila A Jochems C Farsaci B Donahue R Gulley JL Schlom J Guadagni F Oncoimmunology 2013 2 e27025 24353914 10.4161/onci.27025 PMC3862634
[114] Tseng C-W Hung C-F Alvarez RD Trimble C Huh WK Kim D Chuang C-M Lin C-T Tsai Y-C He L Monie A Clin Cancer Res 2008 14 3185 18483387 10.1158/1078-0432.CCR-08-0037 PMC3066100
[115] Chang C-L Hsu Y-T Wu C-C Lai Y-Z Wang C Yang Y-C Wu T-C Hung C-F Cancer Res 2013 73 119 23108141 10.1158/0008-5472.CAN-12-2225 PMC3537885
[116] Kim D Monie A Tsai YC He L Wang MC Hung CF Wu TC Gene Ther 2008 15 1176 18463686 10.1038/gt.2008.79 PMC3071604
[117] Vincent J Mignot G Chalmin F Ladoire S Bruchard M Chevriaux A Martin F Apetoh L Rébé C Ghiringhelli F Cancer Res 2010 70 3052 20388795 10.1158/0008-5472.CAN-09-3690
[118] Garnett CT Schlom J Hodge JW Clin Cancer Res 2008 14 3536 18519787 10.1158/1078-0432.CCR-07-4025 PMC2682419
[119] van den Broek T Borghans JAM van Wijk F Nat Rev Immunol 2018 18 363 29520044 10.1038/s41577-018-0001-y
[120] Papadopoulos AO Ndhlovu ZM Nat Methods 2022 19 36 34949808 10.1038/s41592-021-01332-y
[121] Hanna J Beke F O’Brien LM Kapeni C Chen H-C Carbonaro V Kim AB Kishore K Adolph TE Skjoedt M-O Skjoedt K Nat Commun 2022 13 4075 35835905 10.1038/s41467-022-31722-5 PMC9281293
[122] Madondo MT Quinn M Plebanski M Cancer Treat Rev 2016 42 3 26620820 10.1016/j.ctrv.2015.11.005
[123] Noordam L Kaijen MEH Bezemer K Cornelissen R Maat LAPWM Hoogsteden HC Aerts JGJV Hendriks RW Hegmans JPJJ Vroman H Oncoimmunology 2018 7 e1474318 30524884 10.1080/2162402X.2018.1474318 PMC6279421
[124] Sistigu A Viaud S Chaput N Bracci L Proietti E Zitvogel L Semin Immunopathol 2011 33 369 21611872 10.1007/s00281-011-0245-0
[125] Lee HL Jang JW Lee SW Yoo SH Kwon JH Nam SW Bae SH Choi JY Han NI Yoon SK Sci Rep 2019 9 3260 30824840 10.1038/s41598-019-40078-8 PMC6397294
[126] Schiavoni G Mattei F Di Pucchio T Santini SM Bracci L Belardelli F Proietti E Blood 2000 95 2024 10706870
[127] Bao L Hao C Wang J Wang D Zhao Y Li Y Yao W Front Pharmacol 2020 11 10.3389/fphar.2020.00775 PMC7261842 32523537
[128] Zhang L Dermawan K Jin M Liu R Zheng H Xu L Zhang Y Cai Y Chu Y Xiong S Clin Immunol 2008 129 219 18771959 10.1016/j.clim.2008.07.013
[129] Vennin C Cattaneo CM Bosch L Vegna S Ma X Damstra HGJ Martinovic M Tsouri E Ilic M Azarang L van Weering JRT Cancer Cell 2023 41 1170 37311414 10.1016/j.ccell.2023.05.009
[130] Shi Y J Control Release 2021 339 156 34563591 10.1016/j.jconrel.2021.09.028
[131] Yuseff M-I Pierobon P Reversat A Lennon-Duménil A-M Nat Rev Immunol 2013 13 475 23797063 10.1038/nri3469
[132] Rodríguez-Pinto D Cell Mol Immunol 2005 238 67 10.1016/j.cellimm.2006.02.005 16574086
[133] Liang B Mamula MJ * Cell Mol Life Sci 2000 57 561 11130456 10.1007/PL00000718 PMC11147036
[134] Whitmire JK Asano MS Kaech SM Sarkar S Hannum LG Shlomchik MJ Ahmed R J Immunol 2009 182 1868 19201839 10.4049/jimmunol.0802501 PMC2658628
[135] Ziebart A Huber U Jeske S Laban S Doescher J Hoffmann TK Brunner C Jackson EK Schuler PJ Oncotarget 2018 9 5834 29464038 10.18632/oncotarget.23533 PMC5814178
[136] Liu P Jaffar J Hellstrom I Hellstrom KE J Immunother 2010 33 53 19952956 10.1097/CJI.0b013e3181b56af4 PMC2811714
[137] Kinn JM Zirakzadeh A Hu J Winqvist O J Transl Med 2011 9 P17
[138] Zirakzadeh AA Kinn J Krantz D Rosenblatt R Winerdal ME Hu J Hartana CA Lundgren C Bergman EA Johansson M Holmström B Clin Immunol 2017 176 63 28025135 10.1016/j.clim.2016.12.003