Rictor-dependent AKT activation and inhibition of urothelial carcinoma by rapamycin

Abstract Objective We previously reported a very high cumulative incidence of urothelial carcinoma in Taiwanese kidney transplant recipients. Rapamycin, the inhibitor of mTOR Complex 1, provides alternative immunosuppressive therapy after kidney transplantation with less neoplastic potential. We examined the in vivo and in vitro effects of rapamycin on urothelial carcinoma. Materials and methods The rat model of urothelial carcinoma was induced by 0.05% N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) in Fischer F344 rats. The anti-tumor effect of rapamycin was assessed grossly, microscopically, and by Western blot analysis. The mechanism of rapamycin's attenuation of urothelial carcinoma was also evaluated by T24 cells. Results Rapamycin significantly reduced urinary bladder tumor growth in the rat model of 0.05% BBN-induced urothelial carcinoma ( P Conclusions This study provides in vitro and in vivo evidence that rapamycin may inhibit the development of urothelial carcinoma. The present findings also suggest rictor-dependent AKT activation as a consequence of mTORC1 inhibition.