Attenuation of androgenic regulation by brefeldin A in androgen-responsive prostate cancer cells.

OBJECTIVES: To investigate the effects of an antibiotic brefeldin A (BFA) on androgen-regulated cellular events in androgen-responsive prostate cancer cells, focusing on PSA (prostate-specific antigen) status, cell growth, and bioactivity of androgen receptor (AR).

MATERIALS AND METHODS: Androgen-responsive human prostate cancer LNCaP cells were employed and 5α-dihydrotestosterone (DHT) was used as an androgenic mediator to induce androgen-modulated cellular events. Effects of BFA on synthesis and secretion of PSA, cell growth, and AR activity were assessed using Tandem PSA assay, trypan blue exclusion method, and AR binding assay, respectively.

RESULTS: BFA (30 ng/ml) dramatically (90%) blocked secretion of PSA and also reduced cell growth by >75% under non-androgen-regulated condition. Under androgen-stimulated condition using DHT (1 nM), both the cellular and secreted PSA levels as well as cell growth was significantly elevated or stimulated by DHT (compared with controls); however, BFA was capable of completely inhibiting such DHT-stimulated cellular events. In addition, AR binding assay revealed that AR activity has been drastically (~90%) diminished by BFA, likely resulting in interruption of DHT-mediated events.

CONCLUSIONS: BFA is capable of attenuating androgenic regulation in LNCaP cells such as androgen-stimulated PSA synthesis/secretion and cell growth. This BFA-blocked androgen action appears to be primarily attributed to severe inactivation of AR with BFA because AR is a crucial factor for relaying androgenic messages (to DNA). Therefore, BFA could be considered a promising agent for a more effective treatment of hormone-dependent prostate cancer.