Long-time (24–48 h) exposure to PKC activators such as phorbol ester 12-myristate 13-acetate (PMA, 100 nM) reduced hOCT1 mRNA-expression and activity in human hepatoma HepaRG cells and primary human hepatocytes (Mayati et al., 2015). Here, SLC22A1 is linked to hepatocellular carcinoma.