Improved detection of hepatocyte proliferation using antibody to the pre‐replication complex: an association with hepatic fibrosis and viral replication in chronic hepatitis C virus infection

Summary. To test the hypothesis that hepatitis C virus (HCV) might induce hepatocyte proliferation directly, thereby predisposing HCV carriers to cirrhosis and hepatocellular carcinoma, we have used a new method to identify proliferating hepatocytes, employing a novel monoclonal antibody to minichromosome maintenance (Mcm) proteins, essential components of the pre‐replication complex. Antibody to Ki‐67, a conventional marker of cell division, was also studied. Eighty‐seven patients with chronic HCV infection and a broad spectrum of histological change were studied. Proliferation was observed rarely in hepatocytes from normal liver from healthy controls (always less than 0.01%). However, proliferating hepatocytes were detected in all HCV‐infected patients and the proportion of hepatocytes expressing Mcm‐2 (3–40%) always exceeded that expressing Ki‐67 (1–14%) and correlated positively with increasing stage of fibrosis (P = 0.0001) and viral replication (P = 0.0004). There were weaker but significant associations between the proportion of hepatocytes expressing Mcm‐2 and inflammatory indices including interface hepatitis, portal tract inflammation, lobular inflammation and steatosis. There was no association between the proportion of hepatocytes expressing Mcm‐2 and age, gender or past alcohol consumption, but there was a weak association with current consumption of alcohol (P = 0.0067). The proportion of Ki‐67 hepatocytes did not correlate with any clinical, laboratory or histological parameter. Mcm‐2 was also detected in bile duct cells, sinusoidal lining cells and infiltrating lymphocytes, but at low frequency. These data indicate first, that Mcm‐2 is a more sensitive marker of hepatocyte proliferation than Ki‐67, second that many hepatocytes in chronic HCV infection have entered the cell cycle and third, suggest that interference with the hepatocyte cell cycle might be an alternative approach to therapy.