Inhibition of ATM Increases Interferon Signaling and Sensitizes Pancreatic Cancer to Immune Checkpoint Blockade Therapy

Combinatorial strategies are needed to overcome the resistance of pancreatic cancer to immune checkpoint blockade (ICB). DNA damage activates the innate immune response and improves ICB efficacy. Because ATM is an apical kinase in the radiation-induced DNA damage response, we investigated the effects of ATM inhibition and radiation on pancreatic tumor immunogenicity. ATM was inhibited through pharmacologic and genetic strategies in human and murine pancreatic cancer models both in vitro and in vivo. Tumor immunogenicity was evaluated after ATM inhibition alone and in combination with radiation by assessing TBK1 and Type I interferon (T1IFN) signaling as well as tumor growth following PD-L1/PD-1 checkpoint inhibition. Inhibition of ATM increased tumoral T1IFN expression in a cGAS/STING-independent, but TBK1- and SRC-dependent, manner. The combination of ATM inhibition with radiation further enhanced TBK1 activity, T1IFN production, and antigen presentation. Furthermore, ATM silencing increased PD-L1 expression and increased the sensitivity of pancreatic tumors to PD-L1-blocking antibody in association with increased tumoral CD8+ T cells and established immune memory. In patient pancreatic tumors, low ATM expression inversely correlated with PD-L1 expression. Taken together, these results demonstrate that the efficacy of ICB in pancreatic cancer is enhanced by ATM inhibition and further potentiated by radiation as a function of increased tumoral immunogenicity, underscoring the potential of ATM inhibition in combination with ICB and radiation as an efficacious treatment strategy for pancreatic cancer. SIGNIFICANCE: This study demonstrates that ATM inhibition induces a T1IFN-mediated innate immune response in pancreatic cancer that is further enhanced by radiation and leads to increased sensitivity to anti-PD-L1 therapy.See related commentary by Gutiontov and Weichselbaum, p. 3815.

CD8+ T cells regulate tumor ferroptosis by targeting the system xc− during cancer immunotherapy

Cytotoxic T cells recognize specific antigens expressed on tumor cells and mediate tumor cell apoptosis mainly through perforin–granzyme-mediated and FAS-mediated pathways. Ferroptosis is a recently discovered form of cell death that differs from apoptosis and results from iron-dependent lipid peroxide accumulation. The potential contribution of CD8+ T cell-mediated cytotoxic activity and immunotherapy to tumor ferroptosis remains unknown. Here, we find that immunotherapy-activated CD8+ T cells sensitize tumor cell ferroptosis. Mechanistically, IFNγ released from CD8+ T cells downregulates expression of SLC3A2 and SLC7A11, two subunits of glutamate-cystine antiporter system xc−, restrains tumor cell cystine uptake, and as a consequence, promotes tumor cell lipid peroxidation and ferroptosis. In preclinical models, depletion of cyst(e)ine by cyst(e)inase in combination with checkpoint blockade synergistically enhances T cell-mediated anti-tumor immunity and induces tumor cell ferroptosis. Expression of glutamate-cystine antiporter system xc− is negatively associated with CD8+ T cell signature, IFNγ expression, and cancer patient outcome. Transcriptome analyses before and during nivolumab therapy reveal that clinical benefits correlate with reduced expression of SLC3A2 and increased IFNγ and CD8. Thus, T cell-promoted tumor ferroptosis is a novel anti-tumor mechanism. Targeting tumor ferroptosis pathway constitutes a therapeutic approach in combination with checkpoint blockade.

Spatial and phenotypic immune profiling of metastatic colon cancer

Paramount to the efficacy of immune checkpoint inhibitors is proper selection of patients with adequate tumor immunogenicity and a robust but suppressed immune infiltrate. In colon cancer, immune-based therapies are approved for patients with DNA mismatch repair (MMR) deficiencies, in whom accumulation of genetic mutations results in increased neoantigen expression, triggering an immune response that is suppressed by the PD-L1/PD-1 pathway. Here, we report that characterization of the microenvironment of MMR-deficient metastatic colorectal cancer using multiplex fluorescent immunohistochemistry (mfIHC) identified increased infiltration of cytotoxic T lymphocytes (CTLs), which were more often engaged with epithelial cells (ECs) and improved overall survival. A subset of patients with intact MMR but a similar immune microenvironment to MMR-deficient patients was identified and found to universally express high levels of PD-L1, suggesting that they may represent a currently untreated, checkpoint inhibitor-responsive population. Further, PD-L1 expression on antigen-presenting cells (APCs) in the tumor microenvironment (TME) resulted in impaired CTL/EC engagement and enhanced infiltration and engagement of Tregs. Characterization of the TME by mfIHC highlights the interconnection between immunity and immunosuppression in metastatic colon cancer and may better stratify patients for receipt of immunotherapies.

Human Naive T Cells Express Functional CXCL8 and Promote Tumorigenesis

Naive T cells are thought to be functionally quiescent. In this study, we studied and compared the phenotype, cytokine profile, and potential function of human naive CD4+ T cells in umbilical cord and peripheral blood. We found that naive CD4+ T cells, but not memory T cells, expressed high levels of chemokine CXCL8. CXCL8+ naive T cells were preferentially enriched CD31+ T cells and did not express T cell activation markers or typical Th effector cytokines, including IFN-γ, IL-4, IL-17, and IL-22. In addition, upon activation, naive T cells retained high levels of CXCL8 expression. Furthermore, we showed that naive T cell-derived CXCL8 mediated neutrophil migration in the in vitro migration assay, supported tumor sphere formation, and promoted tumor growth in an in vivo human xenograft model. Thus, human naive T cells are phenotypically and functionally heterogeneous and can carry out active functions in immune responses.

Aerobic Glycolysis Controls Myeloid-Derived Suppressor Cells and Tumor Immunity via a Specific CEBPB Isoform in Triple-Negative Breast Cancer

Myeloid-derived suppressor cells (MDSCs) inhibit anti-tumor immunity. Aerobic glycolysis is a hallmark of cancer. However, the link between MDSCs and glycolysis is unknown in patients with triple-negative breast cancer (TNBC). Here, we detect abundant glycolytic activities in human TNBC. In two TNBC mouse models, 4T1 and Py8119, glycolysis restriction inhibits tumor granulocyte colony-stimulating factor (G-CSF) and granulocyte macrophage colony-stimulating factor (GM-CSF) expression and reduces MDSCs. These are accompanied with enhanced T cell immunity, reduced tumor growth and metastasis, and prolonged mouse survival. Mechanistically, glycolysis restriction represses the expression of a specific CCAAT/enhancer-binding protein beta (CEBPB) isoform, liver-enriched activator protein (LAP), via the AMP-activated protein kinase (AMPK)-ULK1 and autophagy pathways, whereas LAP controls G-CSF and GM-CSF expression to support MDSC development. Glycolytic signatures that include lactate dehydrogenase A correlate with high MDSCs and low T cells, and are associated with poor human TNBC outcome. Collectively, tumor glycolysis orchestrates a molecular network of the AMPK-ULK1, autophagy, and CEBPB pathways to affect MDSCs and maintain tumor immunosuppression.

Suppression of FIP200 and autophagy by tumor-derived lactate promotes naïve T cell apoptosis and affects tumor immunity

Naïve T cells are poorly studied in cancer patients. We report that naïve T cells are prone to undergo apoptosis due to a selective loss of FAK family-interacting protein of 200 kDa (FIP200) in ovarian cancer patients and tumor-bearing mice. This results in poor antitumor immunity via autophagy deficiency, mitochondria overactivation, and high reactive oxygen species production in T cells. Mechanistically, loss of FIP200 disables the balance between proapoptotic and antiapoptotic Bcl-2 family members via enhanced argonaute 2 (Ago2) degradation, reduced Ago2 and microRNA1198-5p complex formation, less microRNA1198-5p maturation, and consequently abolished microRNA1198-5p-mediated repression on apoptotic gene Bak1 Bcl-2 overexpression and mitochondria complex I inhibition rescue T cell apoptosis and promoted tumor immunity. Tumor-derived lactate translationally inhibits FIP200 expression by down-regulating the nicotinamide adenine dinucleotide level while potentially up-regulating the inhibitory effect of adenylate-uridylate-rich elements within the 3' untranslated region of Fip200 mRNA. Thus, tumors metabolically target naïve T cells to evade immunity.

Relevance of host and tumor PD-L1 in PD-L1 pathway blockade

PD-L1 and PD-1 pathway blockade is a promising therapy against cancer. However, the mechanistic contribution of host and tumor PD-L1 and PD-1 signaling to therapeutic efficacy of PD-L1 and PD-1 blockade remains elusive. Using three tumor bearing mouse models that differ in their sensitivity to PD-L1 blockade, MC38, ID8, and B16-F10, we found a loss of therapeutic efficacy of PD-L1 blockade in immunodeficient mice and in PD-L1 and PD-1 deficient mice. In contrast, knockout or overexpression of PD-L1 in tumor cells had no effect on PD-L1 blockade. Human and murine studies show high levels of functional PD-L1 expression in dendritic cells and macrophages in the tumor microenvironments and draining lymph nodes. Further, expression of PD-L1 on dendritic cells and macrophages in ovarian cancer and melanoma patients correlates with the efficacy of anti-PD-1 and anti-PD-1 plus anti-CTLA-4 therapy. Thus, PD-L1+ dendritic cells and macrophages may mechanistically shape and therapeutically predict clinical efficacy of PD-L1/PD-1 blockade.

Host expression of PD-L1 determines efficacy of PD-L1 pathway blockade-mediated tumor regression

Programmed death-1 receptor (PD-L1, B7-H1) and programmed cell death protein 1 (PD-1) pathway blockade is a promising therapy for treating cancer. However, the mechanistic contribution of host and tumor PD-L1 and PD-1 signaling to the therapeutic efficacy of PD-L1 and PD-1 blockade remains elusive. Here, we evaluated 3 tumor-bearing mouse models that differ in their sensitivity to PD-L1 blockade and demonstrated a loss of therapeutic efficacy of PD-L1 blockade in immunodeficient mice and in PD-L1- and PD-1-deficient mice. In contrast, neither knockout nor overexpression of PD-L1 in tumor cells had an effect on PD-L1 blockade efficacy. Human and murine studies showed high levels of functional PD-L1 expression in dendritic cells and macrophages in the tumor microenvironments and draining lymph nodes. Additionally, expression of PD-L1 on dendritic cells and macrophages in ovarian cancer and melanoma patients correlated with the efficacy of treatment with either anti-PD-1 alone or in combination with anti-CTLA-4. Thus, PD-L1-expressing dendritic cells and macrophages may mechanistically shape and therapeutically predict clinical efficacy of PD-L1/PD-1 blockade.

miR-508 Defines the Stem-like/Mesenchymal Subtype in Colorectal Cancer

Colorectal cancer includes an invasive stem-like/mesenchymal subtype, but its genetic drivers, functional, and clinical relevance are uncharacterized. Here we report the definition of an altered miRNA signature defining this subtype that includes a major genomic loss of miR-508. Mechanistic investigations showed that this miRNA affected the expression of cadherin CDH1 and the transcription factors ZEB1, SALL4, and BMI1. Loss of miR-508 in colorectal cancer was associated with upregulation of the novel hypoxia-induced long noncoding RNA AK000053. Ectopic expression of miR-508 in colorectal cancer cells blunted epithelial-to-mesenchymal transition (EMT), stemness, migration, and invasive capacity in vitro and in vivo In clinical colorectal cancer specimens, expression of miR-508 negatively correlated with stemness and EMT-associated gene expression and positively correlated with patient survival. Overall, our results showed that miR-508 is a key functional determinant of the stem-like/mesenchymal colorectal cancer subtype and a candidate therapeutic target for its treatment.Significance: These results define a key functional determinant of a stem-like/mesenchymal subtype of colorectal cancers and a candidate therapeutic target for its treatment. Cancer Res; 78(7); 1751-65. ©2018 AACR.

Host expression of PD-L1 determines efficacy of PD-L1 pathway blockade-mediated tumor regression

Programmed death-1 receptor (PD-L1, B7-H1) and programmed cell death protein 1 (PD-1) pathway blockade is a promising therapy for treating cancer. However, the mechanistic contribution of host and tumor PD-L1 and PD-1 signaling to the therapeutic efficacy of PD-L1 and PD-1 blockade remains elusive. Here, we evaluated 3 tumor-bearing mouse models that differ in their sensitivity to PD-L1 blockade and demonstrated a loss of therapeutic efficacy of PD-L1 blockade in immunodeficient mice and in PD-L1- and PD-1-deficient mice. In contrast, neither knockout nor overexpression of PD-L1 in tumor cells had an effect on PD-L1 blockade efficacy. Human and murine studies showed high levels of functional PD-L1 expression in dendritic cells and macrophages in the tumor microenvironments and draining lymph nodes. Additionally, expression of PD-L1 on dendritic cells and macrophages in ovarian cancer and melanoma patients correlated with the efficacy of treatment with either anti-PD-1 alone or in combination with anti-CTLA-4. Thus, PD-L1-expressing dendritic cells and macrophages may mechanistically shape and therapeutically predict clinical efficacy of PD-L1/PD-1 blockade.

High expression of CC chemokine receptor 5 (CCR5) promotes disease progression in patients with B-cell non-Hodgkin lymphomas

Chemokines are small proteins, that regulate cell migration in many physiological and pathologic processes in human body. They are also responsible for cancer progression. CC chemokine receptor 5 (CCR5) is responsible for cell recruitment in inflammation and may be involved in antitumor immune response controlling. Aberrant CCR5 can be found in different kind of cancers, not only hematological, but also solid tumors. Non-Hodgkin lymphomas consist of many lymphoma subtypes. They predominantly derive from B cells and can have very heterogenous clinical course. That is why new prognostic factors are still needed to predict and select high-risk patients. We evaluated CCR5 expression in lymph nodes derived from B-cell lymphomas in comparison to reactive lymphatic tissue (reactive lymph nodes): samples of lymphoma lymph nodes, peripheral blood, and bone marrow aspirates of patients with B-cell non-Hodgkin lymphoma were taken at diagnosis and after completed chemotherapy. Gene expression was determined by the reverse transcription-polymerase chain reaction method. Expression was estimated from 0AU (no amplificate signal) to 3AU (maximal amplificate signal). We found low CCR5 expression in lymphomas and reactive lymph nodes. Higher CCR5 gene expression in lymphoma patients was correlated with advanced stage of the disease, high proliferation index (Ki-67), and international prognostic index. Patients with higher CCR5 expression had shorter survival. CCR5 high expression may have a role in non-Hodgkin's lymphomas progression and can influence patients' survival. CCR5 also can become an immunotherapeutic target for novel treatment options in the future as well as new prognostic factor.

Phenotype and tissue distribution of CD28H+ immune cell subsets

CD28H is a newly discovered co-receptor of the human B7 family. CD28H interacts with its ligand B7-H5 and regulates T cell response. Here we showed that CD28H was not expressed on granulocytes, monocytes, myeloid dendritic cells (MDCs), and B cells, but constitutively expressed with moderate levels on memory T cells and with high levels on naïve T cells, innate lymphoid cells (ILCs), natural killer (NK) cells, and plasmacytoid dendritic cells (PDCs) in human peripheral blood. Similar CD28H⁺ cell profile existed in secondary lymphoid organs and pathological tissues including multiple types of cancers. Further analysis demonstrated that CD28H⁺ naïve and CD28H⁺ memory T cells were characterized with increased naïve feature and less effector functional phenotype, respectively. High levels of constitutive CD28H expression on naïve T cells and innate immune cells suggest a potential role of CD28H in innate and adaptive immunity.

Fusobacterium nucleatum Promotes Chemoresistance to Colorectal Cancer by Modulating Autophagy

Gut microbiota are linked to chronic inflammation and carcinogenesis. Chemotherapy failure is the major cause of recurrence and poor prognosis in colorectal cancer patients. Here, we investigated the contribution of gut microbiota to chemoresistance in patients with colorectal cancer. We found that Fusobacterium (F.) nucleatum was abundant in colorectal cancer tissues in patients with recurrence post chemotherapy, and was associated with patient clinicopathological characterisitcs. Furthermore, our bioinformatic and functional studies demonstrated that F. nucleatum promoted colorectal cancer resistance to chemotherapy. Mechanistically, F. nucleatum targeted TLR4 and MYD88 innate immune signaling and specific microRNAs to activate the autophagy pathway and alter colorectal cancer chemotherapeutic response. Thus, F. nucleatum orchestrates a molecular network of the Toll-like receptor, microRNAs, and autophagy to clinically, biologically, and mechanistically control colorectal cancer chemoresistance. Measuring and targeting F. nucleatum and its associated pathway will yield valuable insight into clinical management and may ameliorate colorectal cancer patient outcomes.

Relevance of host and tumor PD-L1 expression in PD-L1 and PD-1 blockade

Therapeutic blockade of PD-1 or PD-L1 with monoclonal antibodies (mAb) leads to durable tumor regressions in patients across cancer types. Clinical responses to PD-L1 and PD-1 blockade may be associated with increased PD-L1 expression in the tumor tissues, tumor-infiltrating T cells, and tumor neoantigens. However, it is unclear which patient population(s) benefits from these treatments. Furthermore, why do some patients with PD-L1 negative tumor respond to PD-L1 and PD-1 blockade therapy? To dissect the molecular and cellular mechanisms that account for the clinical efficacy of PD-L1 and PD-1 blockade, we used Rag1tm1Mom(Rag1−/−), NOD.SCID gc-deficient (NSG), PD-L1 genetic deficient (PD-L1−/−), and PD-1 genetic deficient (PD-1−/−) mice, and studied PD-L1 blockade in MC38, ID8, B16-F10, and LLC models. We found a loss of therapeutic effect of anti-PD-L1 mAb treatment in Rag1−/−, NSG, PD-L1−/−, and PD-1−/−mice. We demonstrated the importance of PD-L1 expression on antigen presenting cells (APCs), particularly dendritic cells (DCs) in the tumor microenvironment and draining lymph nodes, in anti-PD-L1 treatment efficacy. Thus, the host immune system is indispensable for anti-PD-L1 therapy, and the host, rather than cancer cell-intrinsic PD-L1 may account for the therapeutic efficacy of PD-L1 signaling blockade.

IL-22 Promotes Pancreatic Cancer Tumorigenesis through Induction of Stemness and Epithelial to Mesenchymal Transition

Elevated levels of Interleukin 22 (IL-22) and its receptor (IL-22R) are associated with poor prognosis in pancreatic ductal adenocarcinoma (PDAC) and the underlying mechanism is currently unknown. Our aim is to investigate the role of the IL-22 axis in PDAC initiation and progression.

Impact of IL-22 on tumor initiation was assayed by subcutaneous and intravenous inoculation of PDAC cells into wild-type and IL-22−/− mice. The PKCY (Pdx1-Cre; KrasG12D; p53fl/+; RosaYFP) model of pancreas cancer was used to study the in-vivo presence and significance of IL-22 in spontaneous tumors. Results were confirmed in human specimens of surgically resected pancreas cancer.

IL-22R was present in all tested PDAC lines and IL-22 treatment led to STAT3 phosphorylation and subsequent increased expression of EMT (Epithelial to Mesenchymal Transition) transcription factors. Cells transitioned to a mesenchymal phenotype and robust tumor sphere formation was observed. While tumors readily formed in wild-type mice, initiation, establishment and growth were impaired in IL-22−/− mice and PKCY-IL-22−/− mice. Increased levels of IL-22 were found in both spontaneous murine tumors and surgical specimens compared to control tissue. IHC of tumors showed diffuse IL-22R staining with increasing intensity of pSTAT3 and EMT markers as tumors progressed to invasive cancer. FACS analysis identified type 3 innate lymphoid cells and TH22 cells as the source of IL-22 in both human and murine PDAC.

Our data suggests that IL-22 is integral in the initiation, progression and establishment of pancreatic cancer, positioning it as an attractive target for cancer therapy.

IL33 Promotes Colon Cancer Cell Stemness via JNK Activation and Macrophage Recruitment

The expression and biological role of IL33 in colon cancer is poorly understood. In this study, we show that IL33 is expressed by vascular endothelial cells and tumor cells in the human colon cancer microenvironment. Administration of human IL33 and overexpression of murine IL33 enhanced human and murine colon cancer cell growth in vivo, respectively. IL33 stimulated cell sphere formation and prevented chemotherapy-induced tumor apoptosis. Mechanistically, IL33 activated core stem cell genes NANOG, NOTCH3, and OCT3/4 via the ST2 signaling pathway, and induced phosphorylation of c-Jun N terminal kinase (JNK) activation and enhanced binding of c-Jun to the promoters of the core stem cell genes. Moreover, IL33 recruited macrophages into the cancer microenvironment and stimulated them to produce prostaglandin E₂, which supported colon cancer stemness and tumor growth. Clinically, tumor IL33 expression associated with poor survival in patients with metastatic colon cancer. Thus, IL33 dually targets tumor cells and macrophages and endows stem-like qualities to colon cancer cells to promote carcinogenesis. Collectively, our work reveals an immune-associated mechanism that extrinsically confers cancer cell stemness properties. Targeting the IL33 signaling pathway may offer an opportunity to treat patients with metastatic cancer. Cancer Res; 77(10); 2735-45. ©2017 AACR.

Synthetic RORγ agonists regulate multiple pathways to enhance antitumor immunity

RORγt is the key transcription factor controlling the development and function of CD4⁺ Th17 and CD8⁺ Tc17 cells. Across a range of human tumors, about 15% of the CD4⁺ T cell fraction in tumor-infiltrating lymphocytes are RORγ+ cells. To evaluate the role of RORγ in antitumor immunity, we have identified synthetic, small molecule agonists that selectively activate RORγ to a greater extent than the endogenous agonist desmosterol. These RORγ agonists enhance effector function of Type 17 cells by increasing the production of cytokines/chemokines such as IL-17A and GM-CSF, augmenting expression of co-stimulatory receptors like CD137, CD226, and improving survival and cytotoxic activity. RORγ agonists also attenuate immunosuppressive mechanisms by curtailing Treg formation, diminishing CD39 and CD73 expression, and decreasing levels of co-inhibitory receptors including PD-1 and TIGIT on tumor-reactive lymphocytes. The effects of RORγ agonists were not observed in RORγ−/− T cells, underscoring the selective on-target activity of the compounds. In vitro treatment of tumor-specific T cells with RORγ agonists, followed by adoptive transfer to tumor-bearing mice is highly effective at controlling tumor growth while improving T cell survival and maintaining enhanced IL-17A and reduced PD-1 in vivo. The in vitro effects of RORγ agonists translate into single agent, immune system-dependent, antitumor efficacy when compounds are administered orally in syngeneic tumor models. RORγ agonists integrate multiple antitumor mechanisms into a single therapeutic that both increases immune activation and decreases immune suppression resulting in robust inhibition of tumor growth. Thus, RORγ agonists represent a novel immunotherapy approach for cancer.

Inflammatory regulatory T cells in the microenvironments of ulcerative colitis and colon carcinoma

Foxp3(+)CD4(+) regulatory T (Treg) cells are thought to express negligible levels of effector cytokines, and inhibit immune responses and inflammation. Here, we have identified a population of IL-8(+)Foxp3(+)CD4(+) T cells in human peripheral blood, which is selectively increased in the microenvironments of ulcerative colitis and colon carcinoma. Phenotypically, this population is minimally overlapping with IL-17(+)Foxp3(+)CD4(+) T cells, and is different from IL-8(-)Foxp3(+)CD4(+) T cells in the same microenvironment. 40-60% of IL-8(+)Foxp3(+)CD4(+) T cells exhibit naive phenotype and express CD127, whereas IL-8(-)Foxp3(+)CD4(+) cells are basically memory T cells and express minimal CD127. The levels of CXCR5 expression are higher in IL-8(+)Foxp3(+) cells than in IL-8(-)Foxp3(+) cells. IL-2 and TGFβ induce IL-8(+)Foxp3(+) T cells. Exogenous Foxp3 expression promotes IL-8(+)Foxp3(+) T cells and inhibits effector cytokine IFNγ and IL-2 expression. Furthermore, Foxp3 binds to IL-8 proximal promoter and increases its activity. Functionally, IL-8(+)Foxp3(+) T cells inhibit T cell proliferation and effector cytokine production, but stimulate inflammatory cytokine production in the colon tissues, and promote neutrophil trafficking through IL-8. Thus, IL-8(+)Foxp3(+) cells may be an "inflammatory" Treg subset, and possess inflammatory and immunosuppressive dual biological activities. Given their dual roles and localization, these cells may be in a unique position to support tumor initiation and development in human chronic inflammatory environment.

Early TNFα signaling results in pulmonary DC1 polarization and programing of murine myeloid precursor cells in the bone marrow towards DC1 polarization throughout Cryptococcus neoformans infection

TNFα is required for protective Th1/Th17 immunity to Cryptococcus neoformans (CN), an opportunistic pulmonary fungal pathogen. The effects of TNFα are linked to the stable, early classical activation of dendritic cells (DC1), preventing alternative (DC2) activation. We hypothesized that TNFα signaling facilitates epigenetic modification of key DC genes during CN infection. We tested this hypothesis using CBA/J mice infected intratracheally with CN and injected once on day 0 intraperitoneally with control or a TNFα-depleting antibody (αTNFα). αTNFα mice had no difference in pulmonary CFU at 7 days post-infection (dpi), but had significantly higher fungal burden and extrapulmonary dissemination at 14 and 28 dpi. DCs from the lungs of control mice at 7 dpi had increased association of iNOS and IL-12b promoters with the activating modification histone 3 lysine 4 trimethylation (H3K4me3), while DCs from αTNFα mice did not. Because DCs have a relatively short half-life during infection, we assessed the bone marrow (BM) myeloid precursor cells (MPCs) from infected animals with and without TNFα. Intranuclear flow cytometry for H3K4me3 showed distinct patterns of global trimethylation between infected control and αTNFα mice as early as 7 dpi. We next tested whether BM-derived DCs (BMDCs) matured ex vivo from infected animals would yield DC1 or DC2 cells. BMDCs from control animals became DC1, and resisted changes to polarization when challenged with the DC2-skewing IL-4, while BMDCs matured from TNFα-depleted mice maintained DC2 polarization when challenged with IFNγ. We conclude that TNFα epigenetically modifies key DC1 genes in MPCs, thereby sustaining lasting DC1 programing of DCs required for clearance of CN from the infected lungs.

FIP200 targets Ago2 and mitochondria in naive T cells to control tumor immunity

Naive T cells are poorly studied in cancer patients. Here, we report that naïve T cells are susceptible to apoptosis and lost in human and mouse cancer. Accompanied with this feature is a selective loss of autophagy component, FIP200 in naïve T cells in tumor bearing hosts. FIP200-deficient T cells functionally resemble their counterparts in tumor bearing hosts and mediate poor anti-tumor immunity in vivo. Mechanistically, loss of FIP200 disables the balance between pro- and anti-apoptotic Bcl-2 family members via elevating argonaute (Ago) 2 ubiquitination and subsequently eliminating microRNA1198-5p expression and consequently lifting microRNA1198-5p-mediated repression on pro-apoptotic gene Bak1 expression. In vivo rebalance of the Bcl-2 family genes via enforcing Bcl-2 expression partially rescues FIP200-deficient T cell apoptosis. In parallel, specific FIP200 deficiency causes potent mitochondria activation and reactive oxygen species (ROS) release in T cells. In vivo ROS blockade prevents FIP200-deficient T cell apoptosis. Thus, tumor may trigger naïve T cell apoptosis via targeting its FIP200 to escape anti-tumor immunity.

The epigenetic cross-talk between tumor cells and immune microenvironment in colorectal cancer

Disruption of epigenetic processes can lead to altered gene function and malignant cellular transformation and influence the local anti-tumor immune response. In this study, we examined the relationship between the H3K27me3 and effector T-cell trafficking. We showed that H3K27me3 repress the tumor production of T helper 1 (TH1)-type chemokines CXCL9 and CXCL10, and subsequently determine effector T-cell trafficking to the tumor microenvironment. On the other hand, local trafficking in response to CCR6/CCL20 ligation is associated with increased Th22 phenotype. Th22 derived IL-22 activates DOT1L complex which turned on stem cell gene expression, increased cancer stemness, and promoted tumorigenic potential. The knowledge about the alterations in the epigenetic landscape of colorectal cancer may lead to understand colon cancer immunology and design effective treatments.

Epigenetic silencing of TH1-type chemokines shapes tumour immunity and immunotherapy

Epigenetic silencing including histone modifications and DNA methylation is an important tumorigenic mechanism. However, its role in cancer immunopathology and immunotherapy is poorly understood. Using human ovarian cancers as our model, here we show that enhancer of zeste homologue 2 (EZH2)-mediated histone H3 lysine 27 trimethylation (H3K27me3) and DNA methyltransferase 1 (DNMT1)-mediated DNA methylation repress the tumour production of T helper 1 (TH1)-type chemokines CXCL9 and CXCL10, and subsequently determine effector T-cell trafficking to the tumour microenvironment. Treatment with epigenetic modulators removes the repression and increases effector T-cell tumour infiltration, slows down tumour progression, and improves the therapeutic efficacy of programmed death-ligand 1 (PD-L1; also known as B7-H1) checkpoint blockade and adoptive T-cell transfusion in tumour-bearing mice. Moreover, tumour EZH2 and DNMT1 are negatively associated with tumour-infiltrating CD8(+) T cells and patient outcome. Thus, epigenetic silencing of TH1-type chemokines is a novel immune-evasion mechanism of tumours. Selective epigenetic reprogramming alters the T-cell landscape in cancer and may enhance the clinical efficacy of cancer therapy

Glycolysis promotes MDSCs and cancer stemness through the interaction between Sirt1 and C/EBPb

Glycolysis is considered a hallmark of cancer. However, its involvement in tumor immune regulation and breast cancer stem cell biology is poorly understood. Here we investigated how glycolysis affected the development of myeloid derived suppressor cells (MDSCs) and in turn controlled breast cancer stemness in breast cancer. G-CSF promotes MDSC development in 4T1 breast cancer model. We found that knock down of LDH-A in 4T1 cells resulted in decreased G-CSF production and reduced MDSC numbers. Accompanied with these findings was the inhibited tumor glycolysis, reduced breast cancer stemness potential, and increased mouse survival. Molecular mechanistic studies demonstrated that glycolysis regulated G-CSF expression, MDSCs and cancer stemness by controlling the interaction between Sirt1 and C/EBPb via NAD+-dependent manner. Moreover LDH-A expression is positively associated with breast cancer patient outcome. Collectively, our study has revealed that glycolytic metabolism is associated MDSCs and linked to breast cancer stemness.

Oxidative phosphorylation controls regulatory T cell suppressor activity of in the tumor microenvironment

Regulatory T cells (Tregs) are important elements of the tumor-associated immunosuppresive network. Here we show that Tregs in the tumor microenvironment are highly apoptotic. Although apoptotic Tregs express classical immunosuppressive proteins including PD-L1, CTLA-4, TGF-β and IL-35, blockade of these mediators does not abolish their suppressive effect. Apoptotic Tregs release a large amount of ATP and suppress T cell responses via adenosine A2A receptor. Furthermore, Tregs have higher mitochondrial load and their survival is associated with OxPhos and fatty acid β-oxidation. Apoptosis of Tregs leads to pannexin-1-dependent ATP release and provide a substrate for immunosuppression. The data support a novel notion that Tregs amplify their suppressor capacity via apoptosis and OxPhos may be a central metabolic pathway controlling Treg functionality in tumor.