Androgen manipulation alters oxidative DNA adduct levels in androgen-sensitive prostate cancer cells grown in vitro and in vivo

Intracellular reactive oxygen species (ROS) may cause oxidative DNA damage, resulting in the formation of adducts such as 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxo-dG) and the cyclic pyrimidopurinone N-1, N2 malondialdehyde-2′-deoxyguanosine (M1dG). These adducts have been associated with carcinogenesis, genomic instability and clonal evolution. We tested two hypotheses in human prostate cancer cells grown in vitro and in a xenograft model: (1) treatment of androgen-sensitive cells with DHT increases levels of oxidative DNA adduct levels; (2) flutamide, a competitive androgen receptor antagonist, prevents DHT-induced changes. Levels of M1dG and 8-oxo-dG adducts were determined by immunoslot blot and liquid chromatography–tandem mass spectrometry. M1dG and 8-oxo-dG levels were significantly higher than control levels in LNCaP cells exposed to supra-physiological concentrations (25–100 nM) of DHT (both P < 0.05 by ANOVA). Flutamide pre-treatment completely prevented this increase. In the xenograft model, tumour levels of M1dG were decreased by 46% (P = 0.001 by Mann–Whitney Test) in flutamide-treated animals compared to controls. The changes demonstrated suggest that oxidative DNA adducts may serve as biomarkers of the efficacy of androgen manipulation in chemoprevention trials.