MTOR and cancer: Multitargeted receptor tyrosine kinase inhibitors pazopanib and sunitinib have been developed as first-line therapies for metastatic ccRCC via inhibiting the activity of vascular endothelial growth factor and mechanistic target of rapamycin (mTOR), also referred to as the mammalian target of rapamycin and belonging to a member of the phosphatidylinositol 3-kinase (PI3K)-related protein kinases, but the treatment response is varied, and most cancers eventually progress [4].