Objectives: Previous studies have suggested the importance of reactive oxygen species in all the steps of carcinogenesis. Antioxidant enzymes are considered as the most specific and efficient way to protect cells from reactive oxygen species. The purpose of the current study was to identify the role of oxidative stress and major antioxidant enzymes in ovarian carcinomas.

Methods: The material consisted of 68 invasive ovarian carcinomas which were studied by immunohistochemistry with antibodies to antioxidant enzymes peroxiredoxins (Prxs) I-VI and thioredoxin and oxidative stress markers nitrotyrosine and 8-hydroxydeoxyguanosine (8-OHdG). Both the intensity and the extent of the stainings were assessed, and the nuclear and cytoplasmic expressions were evaluated separately.

Results: The study revealed the hydroxyl radical-derived oxidative stress marker in DNA, 8-OHdG, to be a powerful prognostic factor in ovarian carcinoma (Kaplan-Meier survival log-rank-analysis P = 0.003; risk of death to ovarian carcinoma 2.69; 95% confidence interval 1.35-5.35. 8-OHdG was also associated with poor differentiation (P = 0.053), higher stage (P < 0.001), and non-optimal surgical outcome (P = 0.002). High cytoplasmic Prx IV immunostaining was associated with a better prognosis (P = 0.024), and elevated cytoplasmic expression rates of Prxs V (P = 0.043) and VI (P = 0.032) were associated with a higher stage.

Conclusions: To conclude, it appears that hydroxyl radical-derived oxidative stress, but not nitric oxide radical-derived oxidative stress, plays a significant role in ovarian carcinogenesis. Immunohistochemical assessment of 8-OHdG could provide a useful prognostic marker in ovarian cancer.