MTOR and neoplasm: Metformin, the first-line OHA for type 2 DM, is found to directly impacts on tumors by activating adenosine 5’-monophosphate-activated protein kinase (AMPK), leading to the suppression of mammalian Target of Rapamycin (mTOR) signaling pathway [25–27], thus inhibiting tumor growth, survival and proliferation [28] (Fig 3).