ANTIANDROGENS INHIBIT HUMAN ANDROGEN RECEPTOR-DEPENDENT GENE-TRANSCRIPTION ACTIVATION IN THE HUMAN PROSTATE-CANCER CELLS LNCAP

Human androgen receptor (hAR) is a ligand-dependent transcription fact or that mediates androgen-induced actions on target tissues. Transfect ion studies in the human prostate cancer cell line LNCaP examine the a bility of dihydrotestosterone (DHT), hydroxyflutamide (HO-FLU), cyprot erone acetate (Cypro.A), and RU 23908-10 to stimulate or to inhibit th e transcription activation of mouse mammary tumor virus-bacterial chlo ramphenicol acetyltransferase (MMTV-CAT). DHT stimulated transcription activation of MMTV-CAT gene in LNCaP cells in a dose-dependent manner . HO-FLU, Cypro.A, and RU 23908-10, though only partially, also stimul ated the transcription activation of MMTV-CAT. Despite this, 100- to 1 ,000-fold molar excess of all antiandrogens inhibited the agonistic ac tivity of 10 nM DHT in this system. Receptor binding assays confirmed that HO-FLU, Cypro.A, and RU 23908-10 competed with DHT for AR binding in LNCaP cells. Western blot analysis using AR antipeptide antibodies raised in rabbits revealed the presence of two AR protein bands in LN CaP cells, following treatment with antiandrogens. Increasing doses of HO-FLU stimulated the expression of the 114-kDa AR by 2.5-fold, but d id not affect the 108-kDa AR. Increasing doses of Cypro.A and RU 23908 -10 decreased the levels of both the 114-kDa and the 108-kDa AR. Altho ugh the exact nature of 108-kDa and 114-kDa AR in LNCaP cells is still unknown, these data suggest that the regulatory actions of each indiv idual antiandrogen on AR expression in LNCaP cells may be different. ( C) 1994 Wiley-Liss, Inc.