title: Repression of activated aryl hydrocarbon receptor-induced transcriptional activation by 5alpha-dihydrotestosterone in human prostate cancer LNCaP and human breast cancer T47D cells.
abstract: Polycyclic aromatic hydrocarbons (PAHs) and dioxins are ubiquitous environmental pollutants and activate the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor. It has been reported that testosterone represses 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced transcription of the cytochrome P450 (CYP) 1A1 gene in LNCaP cells. In this study, we investigated the mechanism for the repression of 3-methylcholanthrene (3MC)-induced transcription of AhR-regulated genes, CYP1A1, CYP1A2, CYP1B1, and AhR repressor (AhRR), by 5alpha-dihydroteststerone (DHT) in LNCaP and T47D cells, which are androgen receptor (AR)- and AhR-positive. Real-time PCR analysis showed that DHT repressed 3MC-induced mRNA expression of the CYP1 family and AhRR genes. DHT repressed 3MC-induced luciferase activity in an AhR response element-driven luciferase reporter assay in LNCaP and T47D cells. The inhibitory effect of DHT was abolished by knockdown of AR protein with siRNA. The protein levels of AhR and AhR nuclear translocator (Arnt), the AhR-dimerizing partner, were not affected by DHT. Co-immunoprecipitation assay showed that DHT significantly facilitated the complex formation between AR and AhR in 3MC-treated cells. These results suggest that complex formation between activated AR and AhR plays an important role in the suppression of 3MC-induced transcription of CYP1 family genes by DHT.
authors.affiliation: Faculty of Pharmaceutical Sciences, Doshisha Women's College of Liberal Arts, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Sanada
authors.forename: Yuka
authors.initials: Y
authors.lastname: Gotoh
authors.forename: Rumiko
authors.initials: R
authors.lastname: Shimazawa
authors.forename: Carolyn M
authors.initials: CM
authors.lastname: Klinge
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Kizu
mesh_terms: D000728:Androgens / Q000494:pharmacology*; D001189:Aryl Hydrocarbon Hydroxylases / Q000187:drug effects / Q000235:genetics; D051792:Basic Helix-Loop-Helix Proteins; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D019363:Cytochrome P-450 CYP1A1 / Q000187:drug effects / Q000235:genetics; D019388:Cytochrome P-450 CYP1A2 / Q000187:drug effects / Q000235:genetics; D065633:Cytochrome P-450 CYP1B1; D013196:Dihydrotestosterone / Q000494:pharmacology*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D047468:Immunoprecipitation; D008156:Luciferases / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008748:Methylcholanthrene / Q000633:toxicity*; D016133:Polymerase Chain Reaction; D011471:Prostatic Neoplasms / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D012097:Repressor Proteins / Q000187:drug effects / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects*
chemical_list: D000728:Androgens; D001189:Aryl Hydrocarbon Hydroxylases; D051792:Basic Helix-Loop-Helix Proteins; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2; D065633:Cytochrome P-450 CYP1B1; D013196:Dihydrotestosterone; D008156:Luciferases; D008748:Methylcholanthrene; D012333:RNA, Messenger; D012097:Repressor Proteins; C492162:AHRR protein, human; C585496:CYP1B1 protein, human