MTOR and cancer: Multiple signal transduction pathways are related to its anti-cancer effects, such as mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), phosphatidylinositol 3′-kinase (PI3K), protein kinase B (PKB, AKT), mechanistic target of rapamycin (mTOR), transforming growth factor beta 1 (TGF-beta 1), and small mothers against decapentaplegic (SMAD) [3,4].