Tumor NLRP3 amplification promotes immunotherapy resistance by inhibiting STAT1 signaling and MHC class I expression

Immunotherapy resistance remains a challenge in immuno-oncology, and predictive biomarkers are needed to guide combination immunotherapy selection for the individual patient. We showed that elevated tumor-intrinsic NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) signaling activity correlates with checkpoint inhibitor resistance in several independent cohorts of stage III/IV melanoma and gastroesophageal (GE) adenocarcinoma. In situ hybridization demonstrated tumor NLRP3 copy number gain in immunotherapy-resistant melanomas and GE adenocarcinomas harboring enhanced NLRP3 signaling activity. Nlrp3 amplification suppressed NOD-, LRR-, and CARD-containing 5-mediated (NLRC5-mediated) MHC class I upregulation, while spatial transcriptomic analysis of patient-derived GE adenocarcinomas confirmed that NLRP3 signaling activity inversely correlated with NLRC5 and MHC class I-associated gene expression. Mechanistically, NLRP3 binds to and inhibits signal transducer and activator of transcription 1 (STAT1) dimerization, nuclear translocation, and NLRC5 transcription. Consistent with these findings, pharmacologic inhibition of the NLRP3 inflammasome augmented tumor STAT1/NLRC5 signaling, enhanced MHC class I surface expression, and overcame anti-programmed cell death 1 resistance in an orthotopic model of gastric adenocarcinoma. This work reveals a fundamental link between cellular stress and tumor-mediated immune evasion and indicates that the tumor NLRP3 signaling pathway merits further clinical study as a therapeutic target and a source of companion biomarkers for overcoming checkpoint inhibitor resistance in patients with cancer.