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.
Nune Markosyan, Jinyang Li, Yu H. Sun, Lee P. Richman, Jeffrey H. Lin, Fangxue Yan, Liz Quinones, Yogev Sela, Taiji Yamazoe, Naomi Gordon, John W. Tobias, Katelyn T. Byrne, Andrew J. Rech, Garret A. FitzGerald, Ben Z. Stanger, Robert H. Vonderheide