Inhibition of androgen receptor transcriptional activity as a novel mechanism of action of arsenic.
Environmental sodium arsenite is a toxin that is associated with male infertility due to decreased and abnormal sperm production. Arsenic trioxide (ATO), another inorganic trivalent semimetal, is an effective therapy for acute promyelocytic leukemia, and there is investigation of its possible efficacy in prostate cancer. However, the mechanism of arsenic action in male urogenital tract tissues is not clear. Because the androgen receptor (AR) plays an important role in spermatogenesis and prostate cancer, we explored the possibility that trivalent arsenic regulates AR function. We found that arsenic inhibited AR transcriptional activity in prostate cancer and Sertoli cells using reporter gene assays testing several androgen response element-containing regions and by assessing native target gene expression. Arsenic inhibition of AR activity was not due to down-regulation of AR protein levels, decreased hormone binding to AR, disruption of AR nuclear translocation, or interference with AR-DNA binding in vitro. However, chromatin immunoprecipitation studies revealed that arsenic inhibited AR recruitment to an AR target gene enhancer in vivo. Consistent with a deficiency in AR-chromatin binding, arsenic disrupted AR amino and carboxyl termini interaction. Furthermore, ATO caused a significant decrease in prostate cancer cell proliferation that was more pronounced in cells expressing AR compared with cells depleted of AR. In addition, inhibition of AR activity by ATO and by the AR antagonist, bicalutamide, was additive. Thus, arsenic-induced male infertility may be due to inhibition of AR activity. Further, because AR is an important target in prostate cancer therapy, arsenic may serve as an effective therapeutic option.
Rosenblatt
Adena E
AE
1600 Northwest Tenth Avenue (R-189), Miami, Florida 33136, USA.
Burnstein
Kerry L
KL
D000726:Androgen Antagonists / Q000494:pharmacology; D059002:Androgen Receptor Antagonists; D000728:Androgens / Q000378:metabolism / Q000494:pharmacology; D000813:Anilides / Q000008:administration & dosage / Q000494:pharmacology; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000008:administration & dosage / Q000494:pharmacology*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D004353:Drug Evaluation, Preclinical; D004357:Drug Synergism; D006801:Humans; D008297:Male; D009570:Nitriles / Q000008:administration & dosage / Q000494:pharmacology; D051958:Nuclear Receptor Coactivator 2 / Q000378:metabolism; D010087:Oxides / Q000008:administration & dosage / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000473:pathology; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000187:drug effects; D011944:Receptors, Androgen / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D020218:Response Elements / Q000502:physiology; D014105:Tosyl Compounds / Q000008:administration & dosage / Q000494:pharmacology; D015533:Transcriptional Activation / Q000187:drug effects*; D014407:Tumor Cells, Cultured
D000726:Androgen Antagonists; D059002:Androgen Receptor Antagonists; D000728:Androgens; D000813:Anilides; D001152:Arsenicals; C498001:NCOA2 protein, human; D009570:Nitriles; D051958:Nuclear Receptor Coactivator 2; D010087:Oxides; D011944:Receptors, Androgen; D014105:Tosyl Compounds; C053541:bicalutamide; D000077237:Arsenic Trioxide