MTOR and medullary thyroid gland carcinoma: Another study used metformin, which is an antidiabetic agent that decreases the proliferation of cancer cells through the 5′-AMP-activated protein kinase-dependent inhibition of mTOR, in MTC cell lines to show that the growth-inhibitory effects on the cells were associated with the downregulation of both the mTOR/6SK and pERK signaling pathways [49].