PBRM1 and nonpapillary renal cell carcinoma: However, when they tried to compare the type of tumor-immune microenvironment in ccRCC tumors according to the mutational status of PBRM1, in three different cohorts (TCGA, an independent cohort of untreated ccRCC tumors and patient tumors of their study), tumors harboring PBRM1 mutations in all three cohorts showed a lower expression of immune inhibitory ligands than those with intact PBRM1.