Breast Cancer Molecular Subtypes and Oxidative DNA Damage

Oxidative stress is thought to play a major role in etiology of many cancers, including breast cancer. 8-hydroxy- 2'deoxyguanosine (8- OHdG) is the most abundant marker of oxidative DNA damage. The aim of this study was to assess the extent of oxidative DNA damage in different breast cancer molecular surrogate subtypes to investigate the prognostic relevance and role of oxidative base lesion (8-OHdG) in the etiology of breast cancer. 8-OHdG expression was immunohistochemicaly studied on tissue microarrays constructed from 152 patients with invasive breast cancer. Expression was correlated with other prognostic factors, as well as different breast cancer molecular surrogate subtypes such as luminal A, luminal B [human epidermal growth factor receptor 2 (HER2) negative], luminal B (HER2 positive), HER2-enriched ad triple-negative tumors. Triple-negative breast carcinomas (TNBCs) were more frequently 8-OHdG negative compared with non-TNBCs (P=0.036). There was no statistically significant difference between 8-OHdG expression and other breast cancer molecular subtypes.In univariate analysis, there was no significant difference between 8-OHdG expression and breast cancer- specific death, although in multivariate analysis 8-OHdG overexpression was associated with better breast cancer-specific survival (BCSS) (odds ratio=0.04, 95% confidence interval, 0.002- 0.62). In Cox regression analysis, patients with moderate and strong 8- OHdG expression had 0.9 times smaller breast cancer death hazard ratio than patients with negative 8-OHdG expression. Oxidative stress may have less impact in the pathogenesis of TNBCs compared with other surrogate breast cancer molecular subtypes. 8- OHdG may be a promising biomarker in the prediction of prognosis for breast cancer patients.