Immunohistochemical evaluation of bcl-2 gene family expression in liver of hepatitis C and cirrhotic patients: a novel mechanism to explain the high incidence of hepatocarcinoma in cirrhotics

Objective: The purpose of this study was to determine whether there is an increase in expression of bcl-2 and related bcl-2 gene family members bcl-X and bax in liver biopsy samples obtained from patients with either hepatitis C infection or cirrhosis. Bcl-2, bcl-X, and bax, as well as other bcl-2–related proteins, function coordinately through homo- and heterodimerization to regulate apoptosis. Bcl-2, which is characterized as an antiapoptotic, also functions as an antioxidant. We hypothesized that a mechanism that could account for increased hepatocellular carcinoma in patients with hepatitis C and cirrhosis is selection of bcl-2 expressing cells. This selection would be due to the capacity of individual cells to resist the toxic effects of inflammatory byproducts, specifically reactive oxygen species. Methods: Sections cut from archived liver biopsy samples embedded in paraffin were probed with antibody specific for bcl-2, bcl-X, or bax. Liver samples were from normal (N = 5), hepatitis C patients (N = 19), and cirrhotics (N = 10). Percent positive staining and intensity of staining were judged independently for hepatocytes, bile ducts, mononuclear cells, and Kupffer cells. Results: Bcl-2 expression was evident in bile ducts and mononuclear cells of hepatitis C patients, but was not commonly present in hepatocytes (two of 10). In the cirrhotic liver, bcl-2 expression was also detected in bile ducts and mononuclear cells, but in contrast to hepatitis patients was also expressed in hepatocytes (nine of 10). A similar pattern of expression was evident for bcl-X, but in general the level of expression was limited relative to that of bcl-2. Bax expression was infrequently present in sections from any of the three patient groups. Conclusions: The data indicate that bcl-2 expression is elevated in the liver of cirrhotics, but is not evident in the liver of hepatitis C patients. This increase in expression of bcl-2 in cirrhotic patients may correlate with development of hepatocellular carcinoma given the anti–apoptotic/oncogenic potential of bcl-2.