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

Abstract 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.