title: The aryl hydrocarbon receptor is constitutively active in advanced prostate cancer cells.
abstract: BACKGROUND
  Distant prostate cancers are commonly hormone refractory and exhibit increased growth no longer inhibited by androgen deprivation therapy. Understanding all molecular mechanisms contributing to uncontrolled growth is important to obtain effective treatment strategies for hormone refractory prostate cancers (HRPC). The aryl hydrocarbon receptor (AhR) affects a number of biological processes including cell growth and differentiation. Several studies have revealed that exogenous AhR ligands inhibit cellular proliferation but recent evidence suggests AhR may possess intrinsic functions that promote cellular proliferation in the absence of exogenous ligands.
  
  
  RESULTS
  qRT-PCR and western blot analysis was used to determine AhR mRNA and protein expression in hormone sensitive LNCaP cells as well as hormone refractory DU145, PC3 and PC3M prostate cancer cell lines. LNCaP cells express AhR mRNA and protein at a much lower level than the hormone refractory cell models. Cellular fractionation and immunocytochemistry revealed nuclear localization of AhR in the established hormone refractory cell lines while LNCaP cells are devoid of nuclear AhR protein. qRT-PCR analysis used to assess basal CYP1B1 levels and a xenobiotic responsive element binding assay confirmed ligand independent transcriptional activity of AhR in DU145, PC3 and PC3M cells. Basal CYP1B1 levels were decreased by treatment with specific AhR inhibitor, CH223191. An in vitro growth assay revealed that CH223191 inhibited growth of DU145, PC3 and PC3M cells in an androgen depleted environment. Immunohistochemical staining of prostate cancer tissues revealed increased nuclear localization of AhR in grade 2 and grade 3 cancers compared to the well differentiated grade 1 cancers.
  
  
  CONCLUSIONS
  Together, these results show that AhR is constitutively active in advanced prostate cancer cell lines that model hormone refractory prostate cancer. Chemical ablation of AhR signaling can reduce the growth of advanced prostate cancer cells, an effect not achieved with androgen receptor inhibitors or growth in androgen depleted media.
authors.affiliation: Clark Atlanta University Center for Cancer Research and Therapeutic Development (CCRTD), Atlanta, Georgia, United States of America.
authors.forename: Oliver
authors.initials: O
authors.lastname: Richmond
authors.affiliation: Clark Atlanta University Center for Cancer Research and Therapeutic Development (CCRTD), Atlanta, Georgia, United States of America.
authors.forename: Maryam
authors.initials: M
authors.lastname: Ghotbaddini
authors.affiliation: Clark Atlanta University Department of Biological Sciences, Atlanta, Georgia, United States of America.
authors.forename: Cidney
authors.initials: C
authors.lastname: Allen
authors.affiliation: Clark Atlanta University Center for Cancer Research and Therapeutic Development (CCRTD), Atlanta, Georgia, United States of America.
authors.forename: Alice
authors.initials: A
authors.lastname: Walker
authors.affiliation: Shahid Sadoughi University of Medical Sciences and Health Services, Yazd, Iran.
authors.forename: Shokouh
authors.initials: S
authors.lastname: Zahir
authors.affiliation: Clark Atlanta University Center for Cancer Research and Therapeutic Development (CCRTD), Atlanta, Georgia, United States of America; Clark Atlanta University Department of Biological Sciences, Atlanta, Georgia, United States of America.
authors.forename: Joann B
authors.initials: JB
authors.lastname: Powell
mesh_terms: D000728:Androgens / Q000494:pharmacology; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008024:Ligands; D008297:Male; D009367:Neoplasm Staging; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D021381:Protein Transport / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D000728:Androgens; D051792:Basic Helix-Loop-Helix Proteins; D008024:Ligands; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; C111235:AHR protein, human
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