MTOR and cancer: Phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway participates in a variety of cellular and biological processes such as maintenance of protein synthesis, cell proliferation, metastasis, apoptosis, metabolism, and cell cycle regulation, thus playing an important role in tumorigenesis and cancer development [1].