Current knowledge pertaining to the molecular mechanisms underlying the anti-cancer activity of metformin is focused on two pathways that inhibit mTOR: (1) the AMPK-dependent pathway, in which metformin activates LKB1-AMPK to inhibit mTOR; (2) the AMPK-independent pathway, in which metformin inhibits mTOR via the PI3K/Akt/mTOR cascade (Sosnicki et al., 2016; Zhang and Guo, 2016). The gene discussed is MTOR; the disease is cancer.