Increased oxidative DNA damage and impaired antioxidant defense system in patients with gastrointestinal cancer.

Background: Highly active intermediates are formed in aerobic metabolism which in turn leads to cellular damage. It is increasingly proposed that free radicals play a key role in human cancer development. The aim of this study was to investigate changes in 8-hydroxy-deoxyguanosine, nitrite+nitrate, total glutathione, total antioxidant capacity levels and superoxide dismutase, catalase, glutathione peroxidase activities in operative patients with gastrointestinal cancer before and after surgery and compare with inoperative patients.

Methods: Oxidative stress parameters were measured in 59 gastrointestinal cancer patients and 20 controls. 8-hydroxy-deoxyguanosine was quantitated by Elisa method. Superoxide dismutase, catalase, glutathione peroxidase were assayed with colorimetric methods; Nitrite+nitrate, total glutathione and total antioxidant capacity were assayed with spectrophotometric methods.

Results: 8-hydroxy-deoxyguanosine levels in cancer patients were higher than those of control group (p<0.01). Similarly, glutathione levels were increased compared with controls (p<0.01). However, nitrite+nitrate, total antioxidant capacity levels and superoxide dismutase and catalase activities were decreased in cancer patients compared with controls (p<0.01, p<0.01, p<0.05, p<0.01, respectively). The patients were divided into two groups; operative (n = 30) and inoperative (n = 29). A significant difference was found in inoperative group compared with postoperative group according to glutathione peroxidase activity (p<0.05).

Discussion: Our results demonstrate that the oxidant/antioxidant balance was altered in favor of free radicals and DNA damage in gastrointestinal cancer patients. Significant increases in 8-hydroxy-deoxyguanosine, glutathione and decreases in nitrite+nitrate, SOD, CAT activities and antioxidant molecules suggest the possible involvement of oxidative stress in gastrointestinal cancer. Glutathione peroxidase activities in postoperative patients were higher compared to inoperative patients.