In cancers, metformin induces alterations in cellular proliferation, apoptosis, cell cycle progression, and inflammatory responses through signaling pathways including AMPK, mechanistic target of rapamycin (mTOR), mitogen-activated protein kinase (MAPK), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB), and signal transducer and activator of transcription 3 (STAT3) pathways [11,12,13,14]. Here, STAT3 is linked to cancer.