PBRM1 and renal cell carcinoma: However, through analysis of RCC cell lines with both native PBRM1 expression, and those with native loss of PBRM1, we could find no evidence of differential sensitivity to rapamycin therapy in standard and clonal growth assays at the standard dose of rapamycin 20nM, which is similar to serum trough levels of this compound achieved in patients with standard dosing, 10-15nM.