ZINC, COPPER, AND SUPEROXIDE-DISMUTASE IN HEPATOCELLULAR-CARCINOMA

Superoxide dismutase (Cu/Zn), a metalloenzyme, activity was found to b e significantly lower in the human hepatocellular carcinoma (hepatoma tissue) (0.78 +/- 0.33 U/mu g protein) compared with that seen in the surrounding ''normal'' or cirrhotic tissue (1.40 +/- 0.48 U/mu g; 1.27 +/- 0.64 U/mu g). The SOD activity of ''normal'' appearing liver cell s adjacent to the tumor or cirrhotic tissue is still lower than that l evel observed in the normal liver from the subjects without known live r disease (1.40 +/- 0.48 U/mu g vs 2.94 +/- 1.53 U/mu g). We have also observed that the trace elements of zinc and copper, which are essent ial in expressing the enzyme activity are also significantly lower in the hepatoma (22.54 +/- 6.73 mu g and 2.83 +/- 1.16 mu g per gram of t issue) compared with those in the surrounding ''normal'' hepatic tissu e (Zn2+, 64.36 +/- 9.17 mu g/g; Cu2+, 11.43 +/- 4.74 mu g/g). The diff erence in the zinc content between the ''normal'' and the cirrhotic ti ssue is also significant (64.36 +/- 9.17 mu g/g vs 42.37 +/- 10.97 mu g/g). However, the copper content in the cirrhotic tissue is higher bu t not statistically different from that level in the ''normal'' tissue (15.53 +/- 5.90 mu g/g vs 11.43 +/- 4.74 mu g/g). Furthermore, the pl asma zinc level is significantly lower among the patients who have suf fered fi-om hepatoma compared with those subjects without known liver disease (631.73 +/- 52.43 mu g/L vs 845.53 +/- 68.13 mu g/L). Our data suggest that the superoxide dismutase activity is impaired in the hep atoma tissue, The lower concentration of trace elements (Zn2+ and Cu2) found in the hepatoma tissue may contribute to cause the difference in the observed enzymic activities.