MTOR and renal carcinoma: PA activates mTOR by binding to the FKBP12-rapamycin-binding domain (FRB)12, 13, 14 that facilitates allosteric mTOR activation and displacement of the endogenous inhibitor FKBP38.15 Rapamycin, a potent mTOR inhibitor,16 associates with the immunophilin FBPK12 to form a complex that prevents FRB/PA interaction.12 Although effective against renal cancer, rapamycin derivatives have only modest effects and limited success in clinical trials for other solid tumors.