MTOR and hepatocellular carcinoma: Fn may promote tumor metastasis by activating the autophagic pathway; it accomplishes this through its metabolite H2S which has been reported to promote autophagy in hepatocellular carcinoma cells by inhibiting the phosphoinositide 3-kinase/serine/threonine kinase/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway (13).