Metabolic inhibition induces pyroptosis in uveal melanoma

Abstract Few treatment options are available for metastatic uveal melanoma (UM) patients. Although the bispecific tebentafusp is FDA-approved, immunotherapy has largely failed, likely given the poorly immunogenic nature of UM. Treatment options that improve the recognition of UM by the immune system may be key to reducing disease burden. We investigated whether UM has the ability to undergo pyroptosis, a form of immunogenic cell death. Publicly available patient data and cell line analysis showed that UM expressed the machinery needed for pyroptosis, including gasdermins D and E (GSDMD and E), caspases 1, 3, 4, and 8 (CASP1, 3, 4, and 8), and ninjurin1 (NINJ1). We induced cleavage of gasdermins in UM cell lines treated with metabolic inhibitors. In particular, the CPT1 inhibitor, etomoxir, induced propidium iodide uptake, caspase 3 cleavage and the release of HMGB1 and IL-1β, indicating that the observed cleavage of gasdermins led to pyroptosis. Importantly, a gene-signature reflecting CPT1A activity correlated with poor prognosis in UM patients and knockdown of CPT1A also induced pyroptosis. Etomoxir-induced pyroptosis was GSDME-dependent, but GSDMD-independent and a pyroptosis gene-signature correlated with immune infiltration and improved response to immune checkpoint blockade in a set of UM patients. Together, these data show that metabolic inhibitors can induce pyroptosis in UM cell lines, potentially offering an approach to enhance inflammation-mediated immune targeting in metastatic UM patients. Implications: Induction of pyroptosis by metabolic inhibition may alter the tumor immune microenvironment and improve the efficacy of immunotherapy in uveal melanoma.