Induction of DNA Damage in Ovarian Cancer Induces Type I Interferon Signaling

Abstract

ObjectiveEpithelial ovarian cancer patients initially respond to cytotoxic chemotherapy, however the majority develop recurrent disease that is resistant to current treatments and 5‐year survival is less than 50%. Immunotherapies have shown promise in some solid tumors, yet response rates in ovarian cancer are only 10–15%. We therefore sought to identify new approaches to increase ovarian cancer tumor immunogenicity with the goal of improving immunotherapy response rates. We previously found that the DNA damage repair protein DEK is overexpressed in ovarian cancer cell lines and primary tumors, and that decreasing DEK levels induces DNA damage and apoptotic cell death. Cytoplasmic DNA from damaged cells can activate the DNA‐sensing protein STING, resulting in induction of the type I interferon (IFN‐I) signaling pathway that facilitates antigen‐presenting cell (APC) maturation and cross‐priming of T cells. Therefore, our objective was to determine if decreasing DEK levels induces IFN‐I signaling to enhance ovarian cancer immune signaling.MethodsWe developed a new machine learning tool, Fast and Robust Deconvolution of Expression Profiles (FARDEEP) to characterize the landscape of tumor‐infiltrating lymphocytes (TIL) in 299 high grade serous ovarian cancers from the Cancer Genome Atlas (TCGA). We then performed RNA‐Seq analysis on OVCAR8 and OVCAR3 ovarian cancer cell lines with stable expression of shRNA targeting DEK (shDEK) or control shRNA. Gene expression patterns were analyzed by Gene Set Enrichment Analysis and confirmed by RT‐PCR. In addition, IFN‐I signature transcripts were further validated by RT‐PCR after ovarian cancer cell lines were infected with lentivirus expressing shDEK or control. ID8 cells from an immunocompetent ovarian cancer mouse model were analyzed by RT‐PCR for IFN‐I signatures after being transfected with siRNA targeting Dek or control without or with Sting expression plasmid.ResultsFARDEEP analysis demonstrated that elevated levels of IFN‐I signature genes including CXC chemokines CXCL9 and CXCL10 are correlated with TIL subsets essential for anti‐tumor immunity, indicating IFN‐I signaling is important in preventing ovarian cancer immune escape. RNA‐Seq in ovarian cancer cell lines revealed that decreasing DEK levels resulted in an upregulation of interferon response signals. Further evaluation of IFN‐I signaling demonstrated that decreasing DEK levels enhanced transcription of IFN‐I signature genes, including interferon beta 1 (IFNB1), CXCL9 and CXCL10. In addition, Dek‐deficiency in ID8 cells enhanced Sting‐mediated induction of Ifnb1, Cxcl9 and Cxcl10.ConclusionOur TIL deconvolution findings support the hypothesis that IFN‐I signaling is pivotal for the immunogenicity of ovarian cancer. Decreasing DEK expression induces DNA damage and resultant IFN‐I signaling. Further studies are underway with the ID8 ovarian cancer mouse model system. Our results suggest a potential approach to increase immune signaling in the tumor microenvironment and thus improve response rates to immunomodulatory therapies in ovarian cancer.Support or Funding InformationMichigan Ovarian Cancer Alliance Geri Fournier Ovarian Cancer Research AwardsThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.