Abstract B58: Gasdermin E suppresses tumor growth by activating antitumor immunity

Abstract

Abstract The gasdermins (GSDM) are a family of homologous pore-forming proteins that cause pyroptosis, an inflammatory death associated with loss of cell membrane integrity and release of inflammatory mediators. Gasdermin E (GSDME, also known as DFNA5) as the most ancient member of the GSDM family has been implicated as a tumor suppressor. GSDME is epigenetically inactivated by promoter DNA methylation in a number of cancers and mutated in some other cancers. Worse 5-year survival and an increase in lymph node metastases are associated with reduced GSDME in breast cancer. During classic apoptosis, caspase-3 activates GSDME by cleaving after Asp270. GSDME activation converts noninflammatory apoptotic death to an inflammatory pyroptotic death. This switch could have a profound effect on the ability of tumor cells to survive intrinsic cellular stresses and extrinsic challenges, such as ER stress, chemotherapy drugs, or immune attack by cytotoxic lymphocytes. Here we show reduced GSDME function of 7 of 8 tested cancer-associated mutations. By manipulating GSDME expression in diverse cancer cell lines, we show that Gsdme knockout in GSDME-expressing tumors enhances, while ectopic expression in Gsdme-repressed tumors inhibits, tumor growth. Our data demonstrate that GSDME tumor-suppressive effect is cell-extrinsic, mediated by cytotoxic lymphocyte killing and abrogated in perforin-deficient mice or mice lacking lymphocytes. Tumor suppression depended on GSDME’s ability to form cell membrane pores that cause inflammatory pyroptosis, since it was completely blocked by mutating the GSDME cleavage site for pore formation. Using different cancer models, we further show that GSDME expression enhances tumor-associated macrophage phagocytosis and the number and functions of tumor-infiltrating NK and CD8+ T lymphocytes. Importantly, we identify that immune killer cells could activate GSDME-mediated pyroptosis independently of caspase activation, when killer cell cytotoxic protease granzyme B directly cleaves and activates GSDME at the same site as caspase-3 (Asp270). Therefore, immune killer cells induce pyroptosis in target GSDME-expressing cancer cells, creating an inflammatory tumor microenvironment that further facilities immune cell tumor infiltration and forms a positive feedback loop. Thus, GSDME suppresses tumor growth by activating antitumor immunity. Citation Format: Zhibin Zhang, Ying Zhang, Shiyu Xia, Qing Kong, Shunying Li, Xing Liu, Caroline Junqueira, James Ansara, Satyaki Sengupta, Yandan Yao, Hao Wu, Judy Lieberman. Gasdermin E suppresses tumor growth by activating antitumor immunity [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr B58.