RBL1 and nonpapillary renal cell carcinoma: Notably, anti-FLAG immunoprecipitation of cyclin D1 from RB1−/− cells recovered p130 and the pRB paralog p107, suggesting that p107 can substitute for pRB to suppress cell proliferation in RB1−/− ccRCC cells deprived of CDK4/6 activity (Fig. 4E).