Cytochrome P-450 and
glutathione S-transferase (GST) activities were investigated in stomach
tumor and
tumor-adjacent tissues of patients (n = 211) with gastric
adenocarcinoma, and in the stomach tissues of unaffected individuals (normal tissues, n = 113). A significant reduction in total
cytochrome P-450 activity was observed in
tumor and
tumor-adjacent tissues versus normal stomach. In all cases,
cytochrome P-450 activity was significantly higher in males than in females. In the case of smokers,
cytochrome P-450 activity was 1.8-fold higher in
tumor-adjacent than in corresponding
tumor tissues, but no difference was observed in nonsmokers. Patients had significantly lower GST activity in
tumor and
tumor-adjacent tissues compared to normal tissues. Smokers showed lower GST activity in both
tumor and
tumor-adjacent tissues compared to nonsmokers. In addition, GST activity was significantly lower in tissues positive for Helicobacter pylori
infection than in H. pylori-negative tissues. However, the frequency of H. pylori
infection was higher in
tumor-adjacent (69%) than in
tumor (45%) or normal tissues (44%). Our data suggest that diminished GST
enzymes activity and increased
cytochrome P-450 activity in normal and
tumor-adjacent tissues might be due to the direct effect of the H. pylori
infection and cigarette smoking, respectively. Data indicate that alterations in the activities of
cytochrome P450 and GST may in part be associated with an increased risk for
gastric cancer.