The mTOR (also known as the mechanistic target of rapamycin and FK506-binding protein 12-rapamycin complex-associated protein 1) is a 289-kDa serine/threonine protein kinase, ubiquitously expressed throughout the body, which modulates metabolism, cellular survival, gene transcription, and cytoskeletal components. mTOR is activated through phosphorylation of its specific residues in response to growth factors, nutrients, mitogens, and hormones, whereas the deficiency of growth factors, amino acids, cellular nutrients, and oxygen can down-regulate mTOR activity.