Association of low repair efficiency with high hormone receptors expression and SOD activity in breast cancer patients

Objectives: To evaluate the antioxidant status and repair capacity in breast cancer patients as well as the relationship between these parameters and expression of critical proteins in breast cancer tissue. Design and methods: Blood samples were obtained from 25 female breast cancer patients and 19 healthy women. The antioxidant status was determined by the concentration of thiobarbituric-reactive substances (TBARS) and activity of superoxide dismutase (SOD) and catalase (CAT). The basal DNA damage and repair capacity in lymphocytes were evaluated by comet assay. The expression of p53, c-erbB2, Ki-67, estrogen receptor (ER) and progesterone receptor (PR) in cancer tissue was detected by immunohistochemical staining. Results: The breast cancer patients presented significantly elevated endogenous DNA damage in lymphocytes and lower susceptibility to DNA damage induced by H2O2 when compared to the control group. There is a negative correlation between TBARS and sensitivity to peroxide induced DNA damage in patients. The percentage of residual damage after H2O2 treatment followed by 3h of post-incubation is significantly higher in patients and also correlates positively with SOD activity, ER and PR expression and negatively with the basal DNA damage. Conclusions: Our results demonstrate low repair capacity in lymphocytes of breast cancer patients and suggest that the regulation of DNA repair is sensitive to cellular redox state and can be modulated by ER/PR status.