SummaryEpigenetic silencing including histone modifications and DNA methylation is an important tumorigenic mechanism1 However, its role in cancer immunopathology and immunotherapy is poorly understood. Using ovarian cancers as our model, we found that enhancer of zeste homolog 2 (EZH2)-mediated histone H3 lysine 27 trimethylation (H3K27me3) and DNA methyltransferase (DNMT) 1-mediated DNA methylation repress the tumor production of Th1-type chemokines CXCL9 and CXCL10, and subsequently determine effector T cell trafficking to the tumor microenvironment. Treatment with epigenetic modulators removes the repression and increases effector T cell tumor infiltration, slows down tumor progression, and improves therapeutic efficacy of PD-L1 (B7-H1) checkpoint blockade2–4 and adoptive T cell transfusion5 in tumor bearing mice. Moreover, tumor EZH2 and DNMT1 are negatively associated with tumor infiltrating CD8+ T cells and patient outcome. Thus, epigenetic silencing of Th1-type chemokine is a novel tumor immune evasion mechanism. Selective epigenetic reprogramming alters T cell landscape6 in cancer and may enhance clinical efficacy of cancer therapy.

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SUMMARY Myeloid derived suppressor cells (MDSCs) and cancer stem cells (CSCs) are important cellular components in the cancer microenvironment, and may affect cancer phenotype and patient outcome. The nature of MDSCs and their interaction with CSCs in ovarian carcinoma are unclear. We examined the interaction between MDSCs and CSCs in patients with ovarian carcinoma and showed MDSCs inhibited T cell activation, enhanced CSC gene expression, sphere formation and cancer metastasis. MDSCs triggered miRNA101 expression in cancer cells. miRNA101 subsequently repressesed the co-repressor gene C-terminal binding protein-2 (CtBP2), and CtBP2 directly targeted stem cell core genes resulting in increased cancer cell stemness, and increasing metastatic and tumorigenic potential. Increased MDSC density and tumor microRNA101 expression, and decreased tumor CtBP2 expression independently predict poor survival. Collectively, the work identifies an immune associated cellular, molecular and clinical network involving MDSCs-microRNA101-CtBP2-stem cell core genes, which extrinsically controls cancer stemness and impacts patient outcome.

Aerobic glycolysis regulates T cell function. However, if and how primary cancer alters T cell glycolytic metabolism and affects tumor immunity remains a question in cancer patients. Here we report that ovarian cancers imposed glucose restriction on T cells and dampened their function via maintaining high expression of microRNA101 and microRNA26a, which constrained expression of the methyltransferase EZH2. EZH2 activated the Notch pathway by suppressing Notch repressors, Numb and Fbxw7, via H3K27me3, and consequently stimulated T cell polyfunctional cytokine expression and promoted their survival via Bcl-2 signaling. Moreover, human shRNA-knockdown-EZH2-deficient T cells elicited poor anti-tumor immunity. EZH2+CD8+ T cells were associated with improved cancer patient survival. Together, the data unveil a novel metabolic target and mechanism of cancer immune evasion.

SUMMARY Effector T cells and fibroblasts are major components in the tumor microenvironment. The means through which these cellular interactions affect chemoresistance is unclear. Here, we show that fibroblasts diminish nuclear accumulation of platinum in ovarian cancer cells, resulting in resistance to platinum-based chemotherapy. We demonstrate that glutathione and cysteine released by fibroblasts contribute to this resistance. CD8+ T cells abolish the resistance by altering glutathione and cystine metabolism in fibroblasts. CD8+ T-cell-derived interferon (IFN)γ controls fibroblast glutathione and cysteine through upregulation of glutamyltransferases and transcriptional repression of system xc− cystine and glutamate antiporter via the JAK/STAT1 pathway. The presence of stromal fibroblasts and CD8+ T cells is negatively and positively associated with ovarian cancer patient survival, respectively. Thus, our work uncovers a mode of action for effector T cells: they abrogate stromal-mediated chemoresistance. Capitalizing upon the interplay between chemotherapy and immunotherapy holds high potential for cancer treatment.