PIK3CA and nonpapillary renal cell carcinoma: To investigate the dysregulated pathways upon knockdown of PB1, we firstly focused on the AKT–mTOR signalling pathway, because AKT–mTOR is one of the most disturbed signalling pathways and a large number of ccRCC samples harbouring PB1 mutations do not have mutations of other key genes of AKT–mTOR signalling pathway such as PTEN,PIK3CA,AKT2,TSC1,TSC2,RHEB and MTOR.