Activating gasdermin pores to induce pyroptosis and stimulate anti-tumor immunity

Cancer immunotherapy using checkpoint blockade (CPB) has revolutionized cancer treatment, providing durable cures with acceptable toxicity in some cancer patients. However, only a few cancer types respond and even in responding tumor types, response is often limited to a minority of these cancers, which raises the question whether directly targeting T cells is sufficient and whether other aspects of immunity can be exploited to stimulate or boost antitumor immunity. Inflammatory, or immunogenic, cell death is emerging to be an important immune node that bridges innate and adaptive immunity to stimulate antitumor immunity as well as to potentiate CPB. While antineoplastic agents currently used in humans can also sometimes induce inflammatory cell death to help re-establish immune surveillance in the tumor microenvironment, these agents do not predictably induce immunogenic cell death, thus leading to variable outcomes. The hypothesis we propose in this project can fundamentally change this scenario by inducing predictable immunogenic cell death through targeting key molecules known as gasdermins (GSDMs) in particular GSDMD, which are widely expressed in cancers and can directly induce immunogenic cell death upon activation. GSDMD mediates pyroptosis and cytokine release downstream of inflammasomes, which are supramolecular complexes that activate inflammatory caspases (caspase-1/-4/-5 in humans, caspase-1/-11 in mice). Activated caspase-1 processes IL-1 family cytokines to their active forms and all inflammatory caspases cleave GSDMD to produce an N-terminal (NT) fragment that forms pores in the cell membrane to induce pyroptosis, and to release IL-1 family cytokines and other inflammatory mediators, including ATP and HMGB1. We specifically propose to identify small molecule agonists of GSDMD for direct induction of immunogenic pyroptosis in cancer cells, which may also synergize with other immune modulators as well as with CPB. GSDMD is widely expressed in cancers. While GSDMD is also expressed in some normal tissues, the need for only a small fraction of tumor cells to undergo pyroptosis to alert the immune system may make GSDMD agonism non-toxic even when administered systemically.