Abstract 632: Exploiting pyroptosis in melanoma brain metastasis

Abstract Melanoma is the deadliest form of skin cancer due to its frequent metastasis to the brain. Melanoma brain metastases (MBM) are a significant clinical challenge, and current model systems and therapeutic strategies are poor. Inhibitors targeting the most common oncogenic driver of melanoma, BRAFV600E (BRAFi), disrupt mitogenic signaling and promote caspase-3 associated cell death. Though caspase-3 is a well-known apoptotic driver, it can also cleave Gasdermin E (GSDME) to create pore-forming N-terminal fragments that oligomerize at plasma and mitochondrial membranes and trigger pyroptosis - a form of immunogenic cell death (ICD). Our recent work illustrates the importance of GSDME mediated pyroptosis and associated immunogenicity in providing a durable therapeutic response against melanoma. Since pyroptosis can be activated by GSDME cleavage via caspase-3, and is prominent in various neuropathologies, a better understanding of the interplay between central nervous system (CNS) immune cells and BRAFi-mediated ICD is critical for designing more effective therapies against MBM. Here, we engineered a panel of inducible pyroptotic melanoma cells to model BRAFi-mediated pyroptosis. Using ex vivo CNS slice co-cultures, we found that inducible N-GSDME expression in human and murine melanoma cells drives propidium iodide uptake and release of inflammatory activators like HMGB1 and IL-1 - hallmarks of pyroptosis. Importantly, conditioned media from these pyroptotic cells stimulates a more robust phagocytic response from resident macrophages of the CNS and pyroptotic melanoma elicit stronger cytotoxicity from syngeneic CD8+ T cells, further highlighting the benefits of BRAFi-mediated ICD. Our findings provide evidence that resident CNS immune cells and peripheral T cells respond to pyroptotic melanoma, suggesting that induction of ICD should be a consideration in the development of anti-MBM therapies. Citation Format: Maria R. Cavallo. Exploiting pyroptosis in melanoma brain metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 632.