Androgen receptor activity at the prostate specific antigen locus: steroidal and non-steroidal mechanisms.
Ligand-activated androgen receptors (ARs) occupy target genes and recruit histone modifiers that influence transcriptional competency. In LNCaP prostate cancer cells, the natural ligand 5alpha-dihydrotestosterone (DHT) activates transiently transfected AR-responsive promoter constructs; concurrent treatment with the protein kinase A activator forskolin enhanced AR stimulation induced by DHT. Additional treatment with the cytokine IL-6, purportedly an AR activator, markedly inhibited receptor activity. To assess AR activity on natural chromatin-integrated promoters/enhancers, we determined AR occupancy of the endogenous prostate specific antigen (PSA) promoter/enhancer as well as PSA expression in LNCaP cells treated with DHT; AR occupancy of the PSA enhancer was rapid (within 1 h of stimulation), robust (10-fold over background), and sustained (8-16 h). In contrast, AR occupancy of the PSA promoter was only increased by 2-fold. Histone H3 acetylation at both the enhancer and promoter was evident 1-2 h after DHT treatment. Detectable pre- and mature PSA mRNA levels appeared after 1 and 6 h treatment, respectively. Substantial qualitative and quantitative differences in PSA expression and AR occupancy of the PSA enhancer were observed when DHT-induced and ligand-independent activations of the AR were compared; forskolin stimulated PSA mRNA and protein expression, whereas IL-6 inhibited both DHT- and forskolin-stimulated expression. IL-6 did not diminish DHT-dependent AR occupancy of the PSA enhancer but inhibited CBP/p300 recruitment, histone H3 acetylation, and cell proliferation. These findings provide a contextual framework for interpreting the contribution of non-steroidal activation of the AR to signaling in vivo, and have implications for prostate cancer cell growth.
Jia
Li
L
Department of Urology, Norris Cancer Center, University of Southern California Keck School of Medicine, Los Angeles, CA 90033, USA.
Kim
Joshua
J
Shen
Howard
H
Clark
Peter E
PE
Tilley
Wayne D
WD
Coetzee
Gerhard A
GA
D000107:Acetylation; D000262:Adenylyl Cyclases / Q000378:metabolism; D002455:Cell Division / Q000502:physiology; D005576:Colforsin / Q000494:pharmacology; D013196:Dihydrotestosterone / Q000378:metabolism / Q000494:pharmacology*; D017930:Genes, Reporter; D006657:Histones / Q000378:metabolism; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism / Q000494:pharmacology; D008024:Ligands; D008156:Luciferases / Q000235:genetics; D008297:Male; D011401:Promoter Regions, Genetic; D017430:Prostate-Specific Antigen / Q000235:genetics / Q000378:metabolism*; D011471:Prostatic Neoplasms; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D006657:Histones; D015850:Interleukin-6; D008024:Ligands; D011944:Receptors, Androgen; D013196:Dihydrotestosterone; D005576:Colforsin; D008156:Luciferases; D017430:Prostate-Specific Antigen; D000262:Adenylyl Cyclases