title: Niclosamide inhibits androgen receptor variants expression and overcomes enzalutamide resistance in castration-resistant prostate cancer.
abstract: OBJECTIVE
  Enzalutamide, a second-generation antiandrogen, was recently approved for the treatment of castration-resistant prostate cancer (CRPC) in patients who no longer respond to docetaxel. Despite these advances that provide temporary respite, resistance to enzalutamide occurs frequently. Androgen receptor (AR) splice variants such as AR-V7 have recently been shown to drive castration-resistant growth and resistance to enzalutamide. This study was designed to identify inhibitors of AR variants and test its ability to overcome resistance to enzalutamide.
  
  
  METHODS
  The drug screening was conducted using luciferase activity assay to determine the activity of AR-V7 after treatment with the compounds in the Prestwick Chemical Library, which contains about 1,120 FDA-approved drugs. The effects of the identified inhibitors on AR-V7 activity and enzalutamide sensitivity were characterized in CRPC and enzalutamide-resistant prostate cancer cells in vitro and in vivo.
  
  
  RESULTS
  Niclosamide, an FDA-approved antihelminthic drug, was identified as a potent AR-V7 inhibitor in prostate cancer cells. Niclosamide significantly downregulated AR-V7 protein expression by protein degradation through a proteasome-dependent pathway. Niclosamide also inhibited AR-V7 transcription activity and reduced the recruitment of AR-V7 to the PSA promoter. Niclosamide inhibited prostate cancer cell growth in vitro and tumor growth in vivo. Furthermore, the combination of niclosamide and enzalutamide resulted in significant inhibition of enzalutamide-resistant tumor growth, suggesting that niclosamide enhances enzalutamide therapy and overcomes enzalutamide resistance in CRPC cells.
  
  
  CONCLUSIONS
  Niclosamide was identified as a novel inhibitor of AR variants. Our findings offer preclinical validation of niclosamide as a promising inhibitor of AR variants to treat, either alone or in combination with current antiandrogen therapies, patients with advanced prostate cancer, especially those resistant to enzalutamide.
authors.affiliation: Department of Urology, University of California Davis, CA, USA.
authors.forename: Chengfei
authors.initials: C
authors.lastname: Liu
authors.affiliation: Department of Urology, University of California Davis, CA, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Lou
authors.affiliation: Department of Urology, University of California Davis, CA, USA.|Graduate Program in Pharmacology and Toxicology, University of California Davis, CA, USA.
authors.forename: Yezi
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Department of Urology, University of California Davis, CA, USA.
authors.forename: Nagalakshmi
authors.initials: N
authors.lastname: Nadiminty
authors.affiliation: Department of Urology, University of California Davis, CA, USA.
authors.forename: Chad T
authors.initials: CT
authors.lastname: Schwartz
authors.affiliation: Department of Urology, University of California Davis, CA, USA.|UC Davis Comprehensive Cancer Center, University of California Davis, CA, USA.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Evans
authors.affiliation: Department of Urology, University of California Davis, CA, USA.|Graduate Program in Pharmacology and Toxicology, University of California Davis, CA, USA.|UC Davis Comprehensive Cancer Center, University of California Davis, CA, USA.
authors.forename: Allen C
authors.initials: AC
authors.lastname: Gao
mesh_terms: D000726:Androgen Antagonists / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001549:Benzamides; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D047369:Chromatin Immunoprecipitation; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D051379:Mice; D016513:Mice, SCID; D009534:Niclosamide / Q000494:pharmacology*; D009570:Nitriles; D010669:Phenylthiohydantoin / Q000031:analogs & derivatives* / Q000494:pharmacology; D064129:Prostatic Neoplasms, Castration-Resistant / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D011944:Receptors, Androgen / Q000737:chemistry* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
chemical_list: C410798:AR protein, human; D000726:Androgen Antagonists; D001549:Benzamides; D009570:Nitriles; D012333:RNA, Messenger; D011944:Receptors, Androgen; D010669:Phenylthiohydantoin; D009534:Niclosamide; C540278:enzalutamide
references.citation: Clin Cancer Res. 2009 Aug 1;15(15):4815-22
references.pmid: 19638459
references.citation: Prostate. 2011 Nov;71(15):1656-67
references.pmid: 21446008
references.citation: Cancer Res. 2011 Mar 15;71(6):2108-17
references.pmid: 21248069
references.citation: Clin Cancer Res. 2014 Feb 15;20(4):791-8
references.pmid: 24305618
references.citation: PLoS One. 2013 Sep 03;8(9):e74670
references.pmid: 24019973
references.citation: Mol Cancer Ther. 2013 Oct;12(10):2200-12
references.pmid: 23894143
references.citation: Genes Cancer. 2011 Feb;2(2):151-9
references.pmid: 21779488
references.citation: PLoS One. 2011 Apr 28;6(4):e19059
references.pmid: 21552559
references.citation: Mol Endocrinol. 1991 Oct;5(10):1396-404
references.pmid: 1775129
references.citation: Cancer Discov. 2013 Sep;3(9):1020-9
references.pmid: 23779130
references.citation: Prostate. 1997 Jun 1;31(4):223-33
references.pmid: 9180932
references.citation: J Biol Chem. 2013 Dec 13;288(50):35769-80
references.pmid: 24174532
references.citation: Curr Treat Options Oncol. 2012 Jun;13(2):189-200
references.pmid: 22539224
references.citation: Clin Cancer Res. 2011 Sep 15;17(18):5913-25
references.pmid: 21807635
references.citation: J Biol Chem. 2012 May 18;287(21):17530-17545
references.pmid: 22474287
references.citation: Clin Cancer Res. 2014 Feb 15;20(4):951-61
references.pmid: 24352647
references.citation: PLoS One. 2011;6(11):e27970
references.pmid: 22114732
references.citation: PLoS One. 2009 Sep 22;4(9):e7124
references.pmid: 19771169
references.citation: Lancet. 2010 Apr 24;375(9724):1437-46
references.pmid: 20398925
references.citation: Proc Natl Acad Sci U S A. 2013 Oct 22;110(43):17492-7
references.pmid: 24101480
references.citation: Cancer Res. 2009 Jan 1;69(1):16-22
references.pmid: 19117982
references.citation: Mol Cancer Ther. 2013 Aug;12(8):1629-37
references.pmid: 23699654
references.citation: Cancer Res. 2002 Nov 15;62(22):6606-14
references.pmid: 12438256
references.citation: Int J Cancer. 2013 Nov;133(9):2225-33
references.pmid: 23575870
references.citation: Cancer Res. 2009 Mar 15;69(6):2305-13
references.pmid: 19244107
references.citation: Prostate. 2014 Feb;74(2):201-9
references.pmid: 24307657
references.citation: Mol Cancer Ther. 2012 Aug;11(8):1703-12
references.pmid: 22576131
references.citation: N Engl J Med. 2011 May 26;364(21):1995-2005
references.pmid: 21612468
references.citation: Exp Parasitol. 2008 May;119(1):24-9
references.pmid: 18262524
references.citation: Cancer Res. 2010 Mar 15;70(6):2516-27
references.pmid: 20215516
references.citation: Cancer Discov. 2013 Sep;3(9):1030-43
references.pmid: 23842682
references.citation: Cancer Res. 2012 Jul 15;72(14):3457-62
references.pmid: 22710436
references.citation: Cancer Res. 2008 Jul 1;68(13):5469-77
references.pmid: 18593950
references.citation: Eur Urol. 2013 Jul;64(1):169-70
references.pmid: 23746320
references.citation: Cell. 2013 Dec 5;155(6):1309-22
references.pmid: 24315100
references.citation: J Clin Invest. 2010 Aug;120(8):2715-30
references.pmid: 20644256
references.citation: N Engl J Med. 2012 Sep 27;367(13):1187-97
references.pmid: 22894553
references.citation: Proc Natl Acad Sci U S A. 2010 Sep 28;107(39):16759-65
references.pmid: 20823238
references.citation: Exp Parasitol. 2008 Apr;118(4):637-40
references.pmid: 18226810
references.citation: J Biol Chem. 2012 Jun 1;287(23):19736-49
references.pmid: 22532567
references.citation: Cancer Res. 2013 Jan 15;73(2):483-9
references.pmid: 23117885
references.citation: J Clin Invest. 2013 Jul;123(7):2948-60
references.pmid: 23722902
references.citation: J Natl Cancer Inst. 2011 Jul 6;103(13):1018-36
references.pmid: 21685359
references.citation: Oncogene. 2012 Nov 8;31(45):4759-67
references.pmid: 22266865
references.citation: Cancer Res. 2011 Jun 15;71(12):4172-82
references.pmid: 21531761
references.citation: Bioorg Med Chem Lett. 2013 Apr 1;23(7):2187-91
references.pmid: 23453073