PR-SET7 inactivation causes hepatocyte necrosis and spontaneous development of hepatocellular carcinoma derived from ductal progenitor cells

PR-SET7-mediated histone-4 lysine-20 methylation has been implicated in mitotic condensation, DNA damage response and replication licencing. Here we show that PR-SET7 function in the liver is pivotal for maintaining genome integrity. Hepatocyte-specific deletion of PR-SET7 in mouse embryos resulted in G2 arrest followed by massive cell death and defect in liver organogenesis. Inactivation at postnatal stages caused cell duplication-dependent hepatocyte necrosis with unusual features of autophagy, termed "endonucleosis". Necrotic death was accompanied by inflammation, fibrosis and compensatory growth induction of neighboring hepatocytes and resident ductal progenitor cells. Prolonged necrotic-regenerative cycles coupled with oncogenic STAT3 activation replaced pre-existing hepatocytes with hepatocellular carcinoma derived entirely from ductal progenitor cells. Hepatocellular carcinoma in these mice displays a cancer stem cell gene signature specified by the co-expression of ductal progenitor markers and oncofetal genes.