Modeling Renal Cell Carcinoma in mice: Bap1 and Pbrm1 Inactivation Drive Tumor Grade [Research Articles]

Clear cell renal cell carcinoma (ccRCC) is characterized by BAP1 and PBRM1 mutation, which are associated with tumors of different grade and prognosis. However, whether BAP1 and PBRM1 loss causes ccRCC and determines tumor grade is unclear. We conditionally targeted Bap1 and Pbrm1 (with Vhl) in the mouse using several Cre drivers. Sglt2 and Villin proximal convoluted tubule drivers failed to cause tumorigenesis, challenging the conventional notion of ccRCC origins. In contrast, targeting with Pax8, a developmental lineage-specific transcription factor, led to ccRCC of different grade. Bap1-deficient tumors were high grade and showed greater mTORC1 activation than Pbrm1-deficient tumors, which exhibited longer latency. Disrupting one allele of the mTORC1 negative regulator, Tsc1, in Pbrm1-deficient kidneys triggered higher grade ccRCC. This study establishes Bap1 and Pbrm1 as lineage-specific drivers of ccRCC and histological grade, implicates mTORC1 as a tumor grade rheostat, and suggests that ccRCC may arise from Bowman capsule cells.

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