PBRM1 loss defines a nonimmunogenic tumor phenotype associated with checkpoint inhibitor resistance in renal carcinoma

A non-immunogenic tumor microenvironment (TME) is a significant barrier to immune checkpoint blockade (ICB) response. The impact of Polybromo-1 ( PBRM1 ) on TME and response to ICB in renal cell carcinoma (RCC) remains to be resolved. Here we show that PBRM1 / Pbrm1 deficiency reduces the binding of brahma-related gene 1 (BRG1) to the IFNγ receptor 2 ( Ifngr2 ) promoter, decreasing STAT1 phosphorylation and the subsequent expression of IFNγ target genes. An analysis of 3 independent patient cohorts and of murine pre-clinical models reveals that PBRM1 loss is associated with a less immunogenic TME and upregulated angiogenesis. Pbrm1 deficient Renca subcutaneous tumors in mice are more resistance to ICB, and a retrospective analysis of the IMmotion150 RCC study also suggests that PBRM1 mutation reduces benefit from ICB. Our study sheds light on the influence of PBRM1 mutations on IFNγ-STAT1 signaling and TME, and can inform additional preclinical and clinical studies in RCC. PBRM1, encoding for a subunit of the SWI/SNF complex, is the second most frequently mutated gene in clear cell renal cell carcinoma (ccRCC). Here, the authors show that PBRM1 loss reduces IFNγ-mediated signalling resulting in a less immunogenic tumor microenvironment and that PBRM1 mutations correlate with lack of response to checkpoint inhibitor therapy in ccRCC patients..