Targeting the chromatin structural changes of antitumor immunity

Epigenomic imbalance drives abnormal transcriptional processes,promoting the onset and progression of cancer.Although defective gene regulation generally affects carcinogenesis and tumor suppression networks,tumor immunogenicity and immune cells involved in antitumor responses may also be affected by epigenomic changes,which may have significant implications for the development and application of epigenetic therapy,cancer immunotherapy,and their combinations.Herein,we focus on the impact of epigenetic regulation on tumor immune cell function and the role of key abnormal epigenetic processes,DNA methylation,histone post-translational modification,and chromatin structure in tumor immunogenicity,and introduce these epigenetic research methods.We emphasize the value of small-molecule inhibitors of epigenetic modulators in enhancing antitumor immune responses and discuss the challenges of developing treatment plans that combine epigenetic therapy and immuno-therapy through the complex interaction between cancer epigenetics and cancer immunology.

Enhancing Antitumor by Immunization with Fusion of Dendritic Cells and Engineered Tumor Cells

A novel approach for a dentritic cells (DCs) based tumor vaccine was developed for the formation of hybrid engineered J558 after fusion with DCs. To make the hybrid tumor vaccine generate more efficient specific CTL cytotoxicity against wild type tumor cells, we genetically engineered tumor cells with mIL 12 gene prior to the cell fusion. mIL 12 was detected at 870±60 pg/(10 5 cells/ml) in the culture supernatants and the fusion ratio was about 30 % by the co focal microscopic analysis. Vaccination of mice with DCs fused with engineered J558 induced more efficient tumor specific CTL cytotoxicity against wild type tumor cells in vitro and with efficient antitumor immunity in vivo . These results suggest that this approach of using DCs fused with engineered tumor cells could be applied in clinical settings of DCs based cancer vaccines.

ANTITUMOR EFFECT OF GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR(GM-CSF)-GENE ENCODED VACCINIA MELANOMA ONCOLYSATE AND ITS IMMUNOLOGICAL MECHANISMS

Vaccinia melanoma oncolysate (VMO) prepared by infecting B16F10 melanoma cells with recombinant vaccinia virus encoding murine GMCSF gene was tested for its therapeutic effect on the preestablished melanoma. C57BL/6 mice were inoculated s.c. with 1×105 B16F10 melanoma cells and received s.c. administration with VMO prepared with GMCSF gene encoded vaccinia virus(GMCSFVMO), VMO prepared with thymidine kinase genedeficient vaccinia virus(TKVMO), B16F10 melanoma oncolysate(BMO), or PBS 3 days after tumor inoculation. The same treatment was bolstered one week later. The results demonstrated that GMCSFVMO treatment significantly inhibited the growth of subcutaneous tumor and prolonged the survival period of tumorbearing mice. Further study elucidated that cytotoxicity of PBL and splenocytes towards B16F10 increased obviously after treatment with GMCSFVMO, but NK activity remained unchanged. These results suggest that the tumor oncolysate vaccine prepared with GMCSF geneencoded vaccinia virus might exert potent therapeutic effect on the preestablished tumor through the efficient induction of specific antitumor immune response of the host.

Induction of Effective Antitumor Immune Response by Combined Administration of hIL-18 and NDV HN

To analyze the antitumor potential and mechanism of action of simultaneous Newcastle disease virus （NDV） hemagglutinin-neuraminidase（HN） and human interleukin 18（hIL-18） gene transfer in C57BL/6 mice with H22 hepatoma,the mouse model with H22 hepatoma was established in C57BL/6 mice, and the antitumor effects of the combined application of NDV HN and hIL-18 were evaluated in vivo. The results show that the growth of established tumors in mice immunized with adenovirus（Ad）-HN in conjunction with Ad-hIL-18 was significantly inhibited compared with that in mice immunized with Ad-HN, Ad-hIL-18 alone, or the empty vector（Ad-mock）. Furthermore, the immunization of mice with Ad-HN in conjunction with Ad-hIL-18 elicited strong natural killer activity and H22 tumor-specific cytotoxic T lymphocyte（CTL） responses in vivo. In addition, T cells from the lymph nodes of mice immunized with Ad-hIL-18 or Ad-HN＋Ad-hIL-18 secreted high levels of the Th1 cytokine IL-2 and interferon-γ （IFN-γ）, indicating that the regression of tumor cells is related to a Th1-type dominant immune response. These results demonstrate that vaccination with NDV HN together with hIL-18 may be a novel and powerful strategy for cancer immunotherapy.

Demethylzeylasteral induces PD-L1 ubiquitin-proteasome degradation and promotes antitumor immunity via targeting USP22

Programmed cell death ligand-1(PD-L1)is a T cell inhibitory immune checkpoint molecule that interacts with programmed cell death-1(PD-1)to promote immune escape of tumor cells.Compared with antibody therapies,small molecule drugs show better prospects due to their advantages such as higher bioavailability,better tissue penetration,and reduced risk of immunogenicity.Here,we found that the small molecule demethylzeylasteral(Dem)can significantly downregulate the expression of PD-L1 in colorectal cancer cells and enhance the killing effect of T cells on tumor cells.Mechanistically,Dem binds to the deubiquitinating enzyme USP22 and promotes its degradation,resulting in increased ubiquitination and degradation of PD-L1 through the proteasome pathway.In addition,Dem increased the activity of cytotoxic T cells and reduced the number of myeloid-derived suppressor cells(MDSCs)and regulatory T cells(Tregs)in tumor-infiltrating lymphocytes(TILs),thereby activating the tumor immune microenvironment and inhibiting the growth of subcutaneous MC38 tumors in C57BL/6 mice.Moreover,we also found that the combination of Dem and CTLA4 antibodies can further improve the efficacy of antitumor therapy.Our study reveals the mechanism by which Dem promotes PD-L1 degradation and suggests that the combination of Dem and CTLA4 antibodies may improve the efficacy of immunotherapy.

Combination of AAV-delivered tumor suppressor PTEN with anti-PD-1 loaded depot gel for enhanced antitumor immunity

Recent clinical studies have shown that mutation of phosphatase and tensin homolog deleted on chromosome 10(PTEN)gene in cancer cells may be associated with immunosuppressive tumor microenvironment(TME)and poor response to immune checkpoint blockade(ICB)therapy.Therefore,efficiently restoring PTEN gene expression in cancer cells is critical to improving the responding rate to ICB therapy.Here,we screened an adeno-associated virus(AAV)capsid for efficient PTEN gene delivery into B16F10 tumor cells.We demonstrated that intratumorally injected AAV6-PTEN successfully restored the tumor cell PTEN gene expression and effectively inhibited tumor progression by inducing tumor cell immunogenic cell death(ICD)and increasing immune cell infiltration.Moreover,we developed an anti-PD-1 loaded phospholipid-based phase separation gel(PPSG),which formed an in situ depot and sustainably release anti-PD-1 drugs within 42 days in vivo.In order to effectively inhibit the recurrence of melanoma,we further applied a triple therapy based on AAV6-PTEN,PPSG^(@anti-PD-1)and CpG,and showed that this triple therapy strategy enhanced the synergistic antitumor immune effect and also induced robust immune memory,which completely rejected tumor recurrence.We anticipate that this triple therapy could be used as a new tumor combination therapy with stronger immune activation capacity and tumor inhibition efficacy.

Dendritic Cell-Derived Exosomes Stimulate Stronger CD8^+ CTL Responses and Antitumor Immunity than TVimor Cell-Derived Exosomes

Exosomes （EXO） derived from dendritic cells （DC） and tumor cells have been used to stimulate antitumor immune responses in animal models and in clinical trials. However, there has been no side-by-side comparison of the stimulatory efficiency of the antitumor immune responses induced by these two commonly used EXO vaccines. In this study, we selected to study the phenotype characteristics of EXO derived from a transfected EG7 tumor cells expressing ovalbumin （OVA） and OVA-pulsed DC by flow cytometry. We compared the stimulatory effect in induction of OVA-specific immune responses between these two types of EXO. We found that OVA protein-pulsed DCOVA-derived EXO （EXODC） can more efficiently stimulate naive OVA-specific CD8^＋ T cell proliferation and differentiation into cytotoxic T lymphocytes in vivo, and induce more efficient antitumor immunity than EG7 tumor cell-derived EXO （EXOEG7）. In addition, we elucidated the important role of the host DC in EXO vaccines that the stimulatory effect of EXO is delivered to T cell responses by the host DC. Therefore, DC-derived EXO may represent a more effective EXO-based vaccine in induction of antitumor immunity. Cellular ＆ Molecular Immunology. 2006;3（3）：205-211.

Expression and significance of intratumoral interleukin-12 and interleukin-18 in human gastric carcinoma

AIM: To explore the effect of intratumoral expressions of interleukin-12 (IL-12) and interleukin-18 (IL-18) on clinical features, angiogenesis and prognosis of gastric carcinoma. METHODS: The expressions of IL-12 and IL-18 from 50 samples of gastric cancer tissue were analyzed by immunohistochemistry, and microvessel density (MVD) was determined with microscopic imaging analysis system. RESULTS: The positive expression rates of IL-12 and IL-18 were 44% (22/50) and 26% (13/50), respectively. IL-12 was significantly associated with pathologic differentiation, depth of invasion, lymph node metastasis, distant metastasis, and TNM stage, and IL-18 was closely related to distant metastasis. Intratumoral IL-12 and IL-18 expressions were not statistically related to MVD scoring. IL-12-positive patients survived significantly longer than those with IL-12-negative tumors, but there was no significant difference between IL-18-positive patients and IL-18-negative ones. The multivariate analysis with Cox proportional hazard model revealed IL-12, MVD and T stage were independent prognostic factors. CONCLUSION: The positive expressions of IL-12 and IL-18 can play an important role in progression and metastasis of gastric cancer, and IL-12 might be an independent factor of poor prognosis in gastric carcinoma.

Combinational adenovirus-mediated gene therapy and dendritic cell vaccine in combating well-established tumors

Recent developments in tumor immunology and biotechnology have made cancer gene therapy and immunotherapy feasible. The current efforts for cancer gene therapy mainly focus on using immunogenes, chemogenes and tumor suppressor genes. Central to all these therapies is the development of efficient vectors for gene therapy. By far, adenovirus （AdV）-mediated gene therapy is one of the most promising approaches, as has confirmed by studies relating to animal tumor models and clinical trials. Dendritic cells （DCs） are highly efficient, specialized antigen-presenting cells, and DC- based tumor vaccines are regarded as having much potential in cancer immunotherapy. Vaccination with DCs pulsed with tumor peptides, lysates, or RNA, or loaded with apoptotic/necrotic tumor cells, or engineered to express certain cytokines or chemokines could induce significant antitumor cytotoxic T lymphocyte （CTL） responses and antitumor immunity. Although both AdV-mediated gene therapy and DC vaccine can both stimulate antitumor immune responses, their therapeutic efficiency has been limited to generation of prophylactic antitumor immunity against re-challenge with the parental tumor cells or to growth inhibition of small tumors. However, this approach has been unsuccessful in combating well-established tumors in animal models. Therefore, a major strategic goal of current cancer immunotherapy has become the development of novel therapeutic strategies that can combat well-established tumors, thus resembling real clinical practice since a good proportion of cancer patients generally present with significant disease. In this paper, we review the recent progress in AdV-mediated cancer gene therapy and DC-based cancer vaccines, and discuss combined immunotherapy including gene therapy and DC vaccines. We underscore the fact that combined therapy may have some advantages in combating well-established tumors vis-a-vis either modality administered as a monotherapy.

CD4^(+) T cell-released exosomes inhibit CD8^(+) cytotoxic T-lymphocyte responses and antitumor immunity

T cells secrete bioactive exosomes(EXO),but the potential immunoregulatory effect of T-cell EXO is largely unknown.In this study,we generated activated ovalbumin(OVA)-specific CD4^(+) T cells in vitro via coculture of OVA-pulsed dendritic cells(DC_(OVA))with naive CD4^(+) T cells derived from OVA-specific T-cell receptor(TCR)transgenic OTII mice.CD4^(+) T-cell EXO were then purified from the CD4^(+) T-cell culture supernatants by differential ultracentrifugation.CD4^(+) T-cell EXO exhibited the‘saucer’shape that is characteristic of EXO with a diameter between 50 and 100 nm,as assessed by electron microscopy,and contained the EXO-associated proteins LAMP-1,TCR and lymphocyte function associated antigen-1(LFA-1),as determined by western blot.Flow cytometric analysis showed that CD4^(+) T-cell EXO expressed CD4^(+) T-cell markers(CD4,TCR,LFA-1,CD25 and Fas ligand),but to a lesser extent than CD4^(+) T cells.We demonstrated that DC_(OVA) took up CD4^(+) T-cell EXO via peptide/major histocompatibility complex(pMHC)II/TCR and CD54/LFA-1 interactions.OVA-specific CD4^(+) T-cell EXO from OTII mice,but not ConA-stimulated polyclonal CD4^(+) T-cell EXO from wild-type C57BL/6 mice inhibited DC_(OVA)-stimulated in vitro CD4^(+) T-cell proliferation and in vivo CD81 cytotoxic T lymphocyte(CTL)responses and antitumor immunity against OVA-expressing B16 melanoma BL6-10OVA cells.In addition,EXO derived from a T-cell hybridoma cell line,MF72.2D9,expressing an OVA-specific CD4^(+) TCR,had a similar inhibitory effect as OTII CD4^(+) T-cell EXO on CTL-mediated antitumor immunity.Taken together,our data indicate that antigen-specific T-cell EXO may serve as a new type of immunosuppressive reagent for use in transplant rejection and treatment of autoimmune diseases.

TGR5 deficiency activates antitumor immunity in non-small cell lung cancer via restraining M2 macrophage polarization

The bile acid-responsive G-protein-coupled receptor TGR5 is expressed in monocytes and macrophages,and plays a critical role in regulating inflammatory response.Our previous work has shown its role in promoting the progression of non-small cell lung cancer(NSCLC),yet the mechanism remains unclear.Here,using Tgr5-knockout mice,we show that TGR5 is required for M2 polarization of tumorassociated macrophages(TAMs)and suppresses antitumor immunity in NSCLC via involving TAMsmediated CD8+T cell suppression.Mechanistically,we demonstrate that TGR5 promotes TAMs into protumorigenic M2-like phenotypes via activating c AMP-STAT3/STAT6 signaling.Induction of c AMP production restores M2-like phenotypes in TGR5-deficient macrophages.In NSCLC tissues from human patients,the expression of TGR5 is associated with the infiltration of TAMs.The co-expression of TGR5 and high TAMs infiltration are associated with the prognosis and overall survival of NSCLC patients.Together,this study provides molecular mechanisms for the protumor function of TGR5 in NSCLC,highlighting its potential as a target for TAMs-centric immunotherapy in NSCLC.

OTUD5 promotes innate antiviral and antitumor immunity through deubiquitinating and stabilizing STING

Stimulator of interferon genes(STING)is an adaptor protein that is critical for effective innate antiviral and antitumor immunity.The activity of STING is heavily regulated by protein ubiquitination,which is fine-tuned by both E3 ubiquitin ligases and deubiquitinases.Here,we report that the deubiquitinase OTUD5 interacts with STING,cleaves its K48-linked polyubiquitin chains,and promotes its stability.Consistently,knockout of OTUD5 resulted in faster turnover of STING and subsequently impaired type I IFN signaling following cytosolic DNA stimulation.More importantly,Lyz2-Cre Otud5^(fl/Y) mice and CD11-Cre Otud5^(fl/Y) mice showed more susceptibility to herpes simplex virus type 1(HSV-1)infection and faster development of melanomas than their corresponding control littermates,indicating that OTUD5 is indispensable for STING-mediated antiviral and antitumor immunity.Our data suggest that OTUD5 is a novel checkpoint in the cGAS-STING cytosolic DNA sensing pathway.

Regulation of antitumor immunity by inflammation-induced epigenetic alterations

Chronic inflammation promotes tumor development,progression,and metastatic dissemination and causes treatment resistance.The accumulation of genetic alterations and loss of normal cellular regulatory processes are not only associated with cancer growth and progression but also result in the expression of tumor-specific and tumor-associated antigens that may activate antitumor immunity.This antagonism between inflammation and immunity and the ability of cancer cells to avoid immune detection affect the course of cancer development and treatment outcomes.While inflammation,particularly acute inflammation,supports T-cell priming,activation,and infiltration into infected tissues,chronic inflammation is mostly immunosuppressive.However,the main mechanisms that dictate the outcome of the inflammation-immunity interplay are not well understood.Recent data suggest that inflammation triggers epigenetic alterations in cancer cells and components of the tumor microenvironment.These alterations can affect and modulate numerous aspects of cancer development,including tumor growth,the metabolic state,metastatic spread,immune escape,and immunosuppressive or immunosupportive leukocyte generation.In this review,we discuss the role of inflammation in initiating epigenetic alterations in immune cells,cancer-associated fibroblasts,and cancer cells and suggest how and when epigenetic interventions can be combined with immunotherapies to improve therapeutic outcomes.

Inducing immunogenic cell death in immuno-oncological therapies

Immunotherapy has revolutionized cancer treatment and substantially improved patient outcomes with respect to multiple types of tumors.However,most patients cannot benefit from such therapies,mainly due to the intrinsic low immunogenicity of cancer cells(CCs)that allows them to escape recognition by immune cells of the body.Immunogenic cell death(ICD),which is a form of regulated cell death,engages in a complex dialogue between dying CCs and immune cells in the tumor microenvironment(TME),ultimately evoking the damage-associated molecular pattern(DAMP)signals to activate tumor-specific immunity.The ICD inducers mediate the death of CCs and improve both antigenicity and adjuvanticity.At the same time,they reprogram TME with a“cold-warmhot”immune status,ultimately amplifying and sustaining dendritic cell-and T cell-dependent innate sensing as well as the antitumor immune responses.In this review,we discuss how to stimulate ICD based upon the biological properties of CCs that have evolved under diverse stress conditions.Additionally,we highlight how this dynamic interaction contributes to priming tumor immunogenicity,thereby boosting anticancer immune responses.We believe that a deep understanding of these ICD processes will provide a framework for evaluating its vital role in cancer immunotherapy.

Interferon γ Stimulates Cellular Maturation of Dendritic Cell Line DC2.4 Leading to Induction of Efficient Cytotoxic T Cell Responses and Antitumor Immunity

Dendritic cells （DCs） are the most potent antigen-presenting cells （APCs） for the initiation of antigen （Ag）-specific immune responses. In most studies, mature DCs are generated from bone marrow cells or peripheral monocytes; in either case, the harvested cells are then cultured in medium containing recombinant GM-CSF, IL-4 and TNF-α for 7-10 days and stimulated with lipopolysaccharide （LPS）. However, this approach is time-consuming and expensive. There is another less cost approach of using immobilized DC cell lines, which can easily grow in the medium. A disadvantage with the immobilized DC cell lines, however, is that they are immature DCs and lack expression of MHC class Ⅱ and costimulatory CD40 and CD80 molecules. This, therefore, limits their capacity for inducing efficient antitumor immunity. In the current study, we investigated the possible efficacy of various stimuli （IL-1β, IFN-γ, TNF-α CpG and LPS） in converting the immature dendritic cell line DC2.4 to mature DCs. Our findings were quite interesting since we demonstrated for the first time that IFN-γ was able to stimulate the maturation of DC2.4 cells. The IFN-γ-activated ovalbumin （OVA）-pulsed DC2.4 cells have capacity to upregulate MHC class Ⅱ, CD40, CD80 and CCR7, and to more efficiently stimulate in vitro and in vivo OVA-specific CD8^＋ T cell responses and antitumor immunity. Therefore, IFN-γ-activated immortal DC2.4 ceils may prove to be useful in the study of DC biology and antitumor immunity.

Immune reaction and colorectal cancer:Friends or foes?

The potential clinical impact of enhancing antitumor immunity is increasingly recognized in oncology therapeutics for solid tumors.Colorectal cancer is one of the most studied neoplasms for the tumor-host immunity relationship.Although immune cell populations involved in such a relationship and their prognostic role in colorectal cancer development have clearly been identified,still no approved therapies based on host immunity intensification have so far been introduced in clinical practice.Moreover,a recognized risk in enhancing immune reaction for colitis-associated colorectal cancer development has limited the emphasis of this approach.The aim of the present review is to discuss immune components involved in the host immune reaction against colorectal cancer and analyze the fine balance between pro-tumoral and anti-tumoral effect of immunity in this model of disease.

Hyperthermia based individual in situ recombinant vaccine enhances lymph nodes drainage for de novo antitumor immunity

The continuing challenges that limit effectiveness of tumor therapeutic vaccines were high heterogeneity of tumor immunogenicity, low bioactivity of antigens, as well as insufficient lymph nodes(LNs) drainage of antigens and adjuvants. Transportation of in situ neoantigens and adjuvants to LNs may be an effective approach to solve the abovementioned problems. Therefore, an FA-TSL/AuNCs/SV nanoplatform was constructed by integrating simvastatin(SV) adjuvant loaded Au nanocages(AuNCs)as cores(AuNCs/SV) and folic acid modified thermal-sensitive liposomes(FA-TSL) as shells to enhance de novo antitumor immunity. After accumulation in tumor guided by FA, AuNCs mediated photothermal therapy(PTT) induced the release of tumor-derived protein antigens(TDPAs) and the shedding of FATSL. Exposed AuNCs/SV soon captured TDPAs to form in situ recombinant vaccine(AuNCs/SV/TDPAs). Subsequently, AuNCs/SV/TDPAs could efficiently transport to draining LNs owing to the hyperthermia induced vasodilation effect and small particle size, achieving co-delivery of antigens and adjuvant for initiation of specific T cell response. In melanoma bearing mice, FA-TSL/AuNCs/SV and laser irradiation effectively ablated primary tumor, against metastatic tumors and induced immunological memory. This approach served a hyperthermia enhanced platform drainage to enable robust personalized cancer vaccination.

Immune responses of dendritic cells combined with tumor-derived autophagosome vaccine on hepatocellular carcinoma

Background： To induce and collect tumor-derived autophagosomes （DRibbles） from tumor cells as an antitumor vaccine by inhibiting the functions of proteasomes and lysosomes. Methods： Dendritic cells （DCs） generated from peripheral blood mononuclear cell （PBMC） of hepatocellular carcinoma （HCC） patients were cocultured with DRibbles, and then surface molecules of DCs, as well as surface molecules on DCs, were determined by flow cytometry. Meanwhile, immune responses of the DCs-DRibbles were examined by mixed lymphocyte reactions. Results： DRibbles significantly induced the expression of CD80, CD83, CD86 and HLA-DR on DCs. The enzyme-linked immunosorbnent assay （ELISA） showed that IFN-γ, levels after vaccination increased than before in most patients, but CDS＋ proportion of PBMC increased only in nine patients. Higher levels of IFN-γ, were detected in the CD8＋ cells than CD4＋ T cells. These results suggested that DCs-DRibbles vaccine could induce antigen-specific cellular immune response on HCC and could prime strong CD8＋ T cell responses, supporting it as a tumor vaccine candidate. Conclusions： Our results demonstrate that HCC/DRibbles-pulsed DCs immunotherapy might be deployed as an effective antitumor vaccine for HCC immunotherapy in clinical trials.

CFTR is a negative regulator ofγδT cell IFN-γproduction and antitumor immunity

CFTR,a chloride channel and ion channel regulator studied mostly in epithelial cells,has been reported to participate in immune regulation and likely affect the risk of cancer development.However,little is known about the effects of CFTR on the differentiation and function ofγδT cells.In this study,we observed that CFTR was functionally expressed on the cell surface ofγδT cells.Genetic deletion and pharmacological inhibition of CFTR both increased IFN-γrelease by peripheralγδT cells and potentiated the cytolytic activity of these cells against tumor cells both in vitro and in vivo.Interestingly,the molecular mechanisms underlying the regulation ofγδT cell IFN-γproduction by CFTR were either TCR dependent or related to Ca^(2+)influx.CFTR was recruited to TCR immunological synapses and attenuated Lck-P38 MAPK-c-Jun signaling.In addition,CFTR was found to modulate TCR-induced Ca^(2+)influx and membrane potential(Vm)-induced Ca^(2+)influx and subsequently regulate the calcineurin-NFATc1 signaling pathway inγδT cells.Thus,CFTR serves as a negative regulator of IFN-γproduction inγδT cells and the function of these cells in antitumor immunity.Our investigation suggests that modification of the CFTR activity ofγδT cells may be a potential immunotherapeutic strategy for cancer.

Myc inhibition tips the immune balance to promote antitumor immunity

Aberrant expression of Myc is one of the most common oncogenic events in human cancers.Scores of Myc inhibitors are currently under development for treating Myc-driven cancers.In addition to directly targeting tumor cells,Myc inhibition has been shown to modulate the tumor microenvironment to promote tumor regression.However,the effect of Myc inhibition on immune cells in the tumor microenvironment remains poorly understood.Here,we show that the adaptive immune system plays a vital role in the antitumor effect of pharmacologic inhibition of Myc.Combining genetic and pharmacologic approaches,we found that Myc inhibition enhanced CD8 T cell function by suppressing the homeostasis of regulatory T(Treg)cells and the differentiation of resting Treg(rTreg)cells to activated Treg(aTreg)cells in tumors.Importantly,we demonstrated that different Myc expression levels confer differential sensitivity of T cell subsets to pharmacologic inhibition of Myc.Although ablation of the Myc gene has been shown to suppress CD8 T cell function,Treg cells,which express much less Myc protein than CD8 T cells,are more sensitive to Myc inhibitors.The differential sensitivity of CD8 T and Treg cells to Myc inhibitors resulted in enhanced CD8 T cell function upon Myc inhibition.Our findings revealed that Myc inhibitors can induce an antitumor immune response during tumor progression.