Combination epigenetic therapy activates immune cells in a murine model of ovarian cancer

Abstract Ovarian cancer (OC) is the fifth leading cause of cancer death in women in the United States. Despite novel therapies and significant advances in our understanding of the disease, the five-year survival rate for OC has not changed in decades. The immunosuppressive microenvironment of OC leads to a low response rate to immunotherapies. We have previously shown that in a murine model of OC epigenetic therapies including DNA methyltransferase inhibitors (DNMTis) and histone deacetylase inhibitors (HDACis) activate type I interferon signaling in tumor cells to drive immune infiltration and sensitization to immunotherapy. This indicates a role for immune control of the tumor, but we did not directly investigate the effects of these epigenetic therapies on the immune cells. We hypothesized that T cells could be activated by epigenetic therapy in this model. We isolated T cells from the spleens of healthy C57/Bl6 mice and treated the cells with a DNMTi, 5-azacytidine (Aza) at 500 nmol/L, and an HDACi, ITF-2357 (ITF) at 100 nmol/L, singly and in combination. Cell pellets were isolated, RNA extracted, and analyzed via qRT-PCR. Cell supernatants were analyzed for cytokine and chemokine production using a Legendplex assay. The treated bulk T cells, CD8+ T cells, and CD4+ T cells showed anti-tumor cytokines, including CCL5, TNF-α and IFN-γ, were upregulated while the pro-tumor cytokine IL-10 was downregulated. These changes were evident at the transcript and secreted cytokine level, pointing to transcriptional upregulation of the target genes. This study demonstrates direct activation of T cells by DNMTis and HDACis and provides mechanistic insight into the role of epigenetic therapies in the murine model of OC.