Detection of Superoxide Dismutase-1 in Nipple Aspirate Fluids: A Reactive Oxygen Species—Regulating Enzyme in the Breast Cancer Microenvironment

Abstract

Introduction Analysis of nipple aspirate fluid (NAF) allows the noninvasive identification of both cellular and biomolecular markers of human breast cancer, the most common female malignancy in developed countries. Cytosolic superoxide dismutase (SOD-1) represents a detoxifying enzyme able to regulate the balance between oncogenic and oncosuppressor reactive oxygen species. Patients and Methods We analyzed SOD-1 expression in 126 NAF samples collected from 67 women with and 59 without breast cancer, using enzyme-linked immunosorbent assay, immunoprecipitation, Western blotting, and immunocytochemistry. Results SOD-1 median values in plasma presented no difference between the no-cancer and cancer subgroups. No significant difference in the median level of SOD-1 between matched plasma and NAF from cancer patients was found, whereas SOD-1 median level in no-cancer NAF was significantly higher when compared with matched plasma. Finally, the SOD-1 median value in no-cancer NAF was significantly higher (about 2-fold) than in cancer NAF. Conclusion NAF measurement of SOD-1 is a useful tool to identify intracellular redox status of the breast microenvironment, mirroring the oxidative metabolic pathways occurring in breast tissue, both in physiologic and cancer conditions and in improving the identification of women at increased breast cancer risk. SOD-1 activity in the breast microenvironment may represent a functional "switch" between the detrimental/oncogenic properties and the oncosuppressor/proapoptotic role of this antioxidant enzyme.