AQP9 and hepatocellular carcinoma: In HepG2 cells, a human hepatocellular carcinoma cell line, insulin increased while leptin decreased AQP9 expression through the activation of the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling cascade (Rodríguez et al., 2011) and AMP protein kinase (AMPK), via forkhead box a2 (Fox a2) (Yokoyama et al., 2011).