Melatonin elicits nuclear exclusion of the human androgen receptor and attenuates its activity

BACKGROUND. The androgen receptor (AR) promotes growth and functionality of androgen sensitive benign and cancer tissues. The pineal hormone melatonin is an androgen protagonist in vivo and in vitro. The interference of melatonin in the AR cascade was explored. METHODS. The effects of melatonin on AR expression, level, agonist and androgen-response element (ARE) binding, reporter gene activity and intracellular localization were explored in prostate cancer LNCaP cell line. RESULTS. Melatonin increased immunoreactive AR cells in the absence and presence of dihydrotestosterone. Despite this increase and maintenance of AR agonist binding capacity, the androgen-induced reporter gene activity and suppression of AR-mRNA were attenuated. Immunocytochemical analysis and subcellular fractionation studies revealed nuclear exclusion of AR by melatonin. CONCLUSIONS. The melatonin-mediated nuclear exclusion of the AR may explain the attenuation of AR activity in the prostate cancer cells. This is the first demonstration of a hormone-induced mislocalization of the AR in prostate epithelial cells and may represent a novel route for regulating AR activity.