Additionally, metformin (Met) has been reported to directly exert antitumor effects by activating adenosine monophosphate-activated protein kinase (AMPK) in the AMPK/mammalian target of rapamycin (mTOR) pathway, which is critical for cancer progression, and inhibiting mitochondrial respiratory-chain nicotinamide adenine dinucleotide (NADH) dehydrogenase (complex I) activity, thus suppressing the respiration of cancer cells [10–12]. This evidence concerns the gene MTOR and cancer.