HNF4A and hepatocellular carcinoma: A previous study has showed that in human hepatoma cells, activation of MAPK signal down‐regulates HNF‐4 expression and completely inhibits C/EBPα expression with compromised recruitment of HNF‐3β and HNF‐1α to the HNF‐4 enhancer, and RNA polymerase II to the proximal HNF‐4 promoter,49 indicating MPAK signal is a negative regulator of these liver transcription factors.