Novel therapies are urgently needed for ovarian cancer, the deadliest gynecologic malignancy. Ovarian cancer has thus far been refractory to immunotherapies that stimulate the host immune system to recognize and kill cancer cells. This may be because of a suppressive tumor immune microenvironment and lack of recruitment and activation of immune cells that kill cancer cells. Our previous work showed that epigenetic drugs including DNA methyltransferase inhibitors and histone deacetylase 6 inhibitors (DNMTis and HDAC6is) individually increase immune signaling in cancer cells. We find that combining DNMTi and HDAC6i results in an amplified type I interferon response, leading to increased cytokine and chemokine expression and higher expression of the MHC I antigen presentation complex in human and mouse ovarian cancer cell lines. Treating mice bearing ID8 Trp53−/− ovarian cancer with HDAC6i/ DnMti led to an increase in tumor-killing cells such as ifng+ CD8, NK, and NKT cells and a reversal of the immunosuppressive tumor microenvironment with a decrease in MDSCs and PD-1 hi CD4 T cells, corresponding with an increase in survival. Thus combining the epigenetic modulators DNMTi and HDAC6i increases anti-tumor immune signaling from cancer cells and has beneficial effects on the ovarian tumor immune microenvironment. The five-year survival for ovarian cancer has remained unchanged for decades, and novel therapies are urgently needed 1. Ovarian cancer has the deadliest outcome among gynecologic cancers due to its late (typically Stage III or IV) presentation and aggressive phenotype. High-grade serous ovarian cancer, the most common subtype, is characterized by genomic instability with >95% of cases exhibiting mutations in the tumor suppressor P53 2. Treatment involves surgical staging and optimal debulking to reduce tumor burden, followed by chemotherapy with a platinum-based agent and a taxane, or vice versa (chemotherapy before surgery). Unfortunately most cancers recur within two years of chemotherapy. Significant advances in the pathobiology of the disease, including the identification of a subset of tumors with defects in homologous recombination (HR), have led to the use of PARP inhibitors, which can cause synthetic lethality in HR-deficient tumors. However, less than half of ovarian cancers are HR-deficient and there is no curative therapy for the majority of ovarian cancer patients 1,3. Cancer cells may be recognized as foreign by host immune cells that kill the cancer cells, but as they progress cancers exhibit mechanisms of immune evasion or immunoediting 4. The tumor microenvironment (TME) is composed of both pro-and anti-cancer immune cells. These include CD8 effector T cells that recognize specific antigens on tumor cells to kill them, natural killer (NK) cells, part of the innate immune system that can kill tumor cells, and immuno-suppressive cell types including macrophages, regulatory T cells, and myeloid-derived suppressor cells. Novel drugs that activate CD8 effector T cells to fight cancer cells, includ...