Effect of antioxidants on androgen-induced AP-1 and NF-κB DNA-binding activity in prostate carcinoma cells

Background: Previous studies have suggested that male hormones (androgens) and certain forms of oxygen (reactive oxygen species) are linked to the development of prostate cancer. We hypothesized that androgens contribute to prostate carcinogenesis by increasing oxidative stress. We further hypothesized that antioxidants reduce prostate cancer risk by modulating androgen effects on cellular processes. Methods: To test these hypotheses, we looked for 1) a change in the level of reactive oxygen species in the presence of androgens, 2) androgen-induced binding activity of transcriptional activators AP-1 and NF-κB, whose activities are known to be altered during cell proliferation, and 3) the effect of antioxidants on androgen-induced transcription factor binding. Results: Physiologic concentrations (1 nM) of 5α-dihydrotestosterone or 1-10 nM R1881, a synthetic androgen, produced sustained elevation of AP-1 and NF-κB DNA- binding activity in LNCaP cells, an androgen-responsive human prostate carcinoma cell line. Androgen-independent DU145 cells (another human prostate carcinoma cell line) were unaffected by R1881 treatment. AP-1-binding activity increased 5 hours after 1 nM R1881 treatment; NF-κB DNA-binding activity increased after 36 hours. Both activities remained elevated for at least 120 hours. Nuclear AP-1 and NFκB protein levels were not elevated. Antioxidant vitamins C plus E blocked both androgen-induced DNA-binding activity and production of reactive oxygen species. Conclusion: Physiologic concentrations of androgens induce production of reactive oxygen species and cause prolonged AP-1 and NF-κB DNA-binding activities, which are diminished by vitamins C and E.