RESUMO
OBJECTIVE. Colon cancer is the most common malignancy found in the developed countries. Cancer initiation and progression is known to be associated with the formation of reactive oxygen species, formed in excess in the gastrointestinal tract. The aim of the study was to assess the levels of protein thiols and thiobarbituric acid reactive substances (TBARS) in patients with colon cancer. MATERIAL AND METHODS. Serum samples were obtained from 60 subjects (M and F, mean age 50ñ15 years), 30 of which were from colon cancer patients and 30 from healthy individuals. All the serum samples were analyzed for carcinoembryonic antigen (CEA), protein thiols and TBARS. RESULTS. The levels of protein thiols were significantly lower in colon cancer patients (p<0.001) than in the healthy controls. The TBARS levels in colon cancer patients were moderately high (p<0.05) in comparison with those of the controls. CONCLUSIONS. Low levels of protein thiols and elevated TBARS of colon cancer patients support the hypothesis that colon cancer is associated with reactive oxygen species. Therefore protein thiols and TBARS may serve as additive non-invasive biochemical markers of oxidative stress in colon cancer and this hypothesis needs to be further investigated.