Tumor cell-intrinsic EPHA2 suppresses antitumor immunity by regulating PTGS2 (COX-2)

Abstract

Resistance to immunotherapy is one of the biggest problems of current oncotherapeutics. While T cell abundance is essential for tumor responsiveness to immunotherapy, factors that define the T cell-inflamed tumor microenvironment are not fully understood. We used an unbiased approach to identify tumor-intrinsic mechanisms shaping the immune tumor microenvironment (TME), focusing on pancreatic adenocarcinoma because it is refractory to immunotherapy and excludes T cells from the TME. From human tumors, we identified ephrin-A receptor 2 (EPHA2) as a candidate tumor-intrinsic driver of immunosuppression. Epha2 deletion reversed T cell exclusion and sensitized tumors to immunotherapy. We found that prostaglandin endoperoxide synthase 2 (PTGS2), the gene encoding cyclooxygenase-2, lies downstream of EPHA2 signaling through TGF-β and is associated with poor patient survival. Ptgs2 deletion reversed T cell exclusion and sensitized tumors to immunotherapy; pharmacological inhibition of PTGS2 was similarly effective. Thus, EPHA2/PTGS2 signaling in tumor cells regulates tumor immune phenotypes; blockade may represent a therapeutic avenue for immunotherapy-refractory cancers. Our findings warrant clinical trials testing the effectiveness of therapies combining EPHA2/TGF-β/PTGS2 pathway inhibitors with antitumor immunotherapy and may change the treatment of notoriously therapy-resistant pancreatic adenocarcinoma.