HNF4A and hepatocellular carcinoma: HNF4α deletion in hepatocytes is reported to cause hepatocyte differentiation defects and, in DEN‐treated mice, it induces accumulation of HPCs and formation of tumors showing HCC morphology.[27] The HNF4α‐mediated hepatocyte differentiation program results in bipotential progenitors, creating a persistent pre‐neoplastic state primed for transformation by additional oncogenic mutation.[28] Rap1GAP is a GTPase‐activating protein that inactivates Rap1‐GTP, which is the functional form of Rap1.