The activity of class I, III, and IV of alcohol dehydrogenase isoenzymes and aldehyde dehydrogenase in gastric cancer.

The metabolism of cancer is in many way different than in healthy cells. Increased metabolism of several carcinogenic substances may take place in cancer cells. The one of them was ethanol, that is oxidized by alcohol dehydrogenase (ADH) to high concentration of acetaldehyde, a toxic and carcinogenic compound. The enzyme responsible for oxidation of acetaldehyde is aldehyde dehydrogenase (ALDH). The aim of this study was to compare the capacity for ethanol metabolism measured by ADH isoenzymes and ALDH activity between gastric cancer and normal gastric mucosa. Total ADH activity was measured by photometric method with p-nitrosodimethylaniline (NDMA) as a substrate and ALDH activity by the fluorometric method with 6-methoxy-2-naphtaldehyde as a substrate. For the measurement of the activity of class I isoenzymes, we used fluorometric methods, with class-specific fluorogenic substrates. The activity of class III ADH was measured by the photometric method with n-octanol and class IV with m-nitrobenzaldehyde as a substrate. The samples were taken surgically during routine operations of gastric carcinomas from 55 patients. The activities of total ADH, and the most important in gastric mucosa, class IV ADH were significantly higher in cancer cells than in healthy tissues. The other tested classes of ADH and ALDH showed a tendency toward higher activity in cancer than in healthy mucosa. The activities of all tested enzymes and isoenzymes were not significantly higher in men than in women in wither gastric cancer tissues or normal mucosa. The increased ADH IV activity may be 1 of the factors intensifying carcinogenesis by the increased ability to acetaldehyde formation from ethanol.