Decreased activity of scavenger enzymes in human hepatocellular carcinoma, but not in liver metastases

To investigate the role of oxygen free radicals in hepatocellular carcinoma we assayed tissue scavenger enzymes (superoxide dismutase and selenium-dependent glutathione peroxidase) in liver homogenate, plasma concentrations of vitamins A and E and the serum selenium level from 19 control patients, 23 cases of hepatocellular carcinoma and 18 cases of metastases to liver from different carcinomas. In hepatocellular carcinoma tissue the enzyme activities were all significantly lower than in control liver and in metastases-bearing liver; the enzyme activities of the latter tissues were not different from control liver. In contrast, normal liver adjacent to the hepatocellular carcinoma had decreased activity of superoxide dismutase. Serum selenium concentrations were significantly decreased in patients with hepatocellular carcinoma and those with liver metastases, while vitamin A was significantly decreased only in the former. These findings suggest that hepatocellular carcinoma develops in liver with severe impairment of cellular antioxidant systems, since, in patients with liver metastases from different cancers, despite low selenium concentrations, cellular scavenger enzymes have normal activities.