mTOR(mammalian target of rapamycin),a serine/threonine kinase,plays a central role in cell growth,proliferation,metabolism and survival[1].Dysregulation of mTOR signal pathway is closely related with tumor initiation and progress,making this kinase protein an attractive target for cancer therapy.mTOR inhibitors can block abnormal signal transduction and their effect on prolonging the survival of patients have been demonstrated in clinical trials[2].