title: Suppression of heat shock protein 27 using OGX-427 induces endoplasmic reticulum stress and potentiates heat shock protein 90 inhibitors to delay castrate-resistant prostate cancer.
abstract: BACKGROUND
  Although prostate cancer responds initially to androgen ablation therapies, progression to castration-resistant prostate cancer (CRPC) frequently occurs. Heat shock protein (Hsp) 90 inhibition is a rational therapeutic strategy for CRPC that targets key proteins such as androgen receptor (AR) and protein kinase B (Akt); however, most Hsp90 inhibitors trigger elevation of stress proteins like Hsp27 that confer tumor cell survival and treatment resistance.
  
  
  OBJECTIVE
  We hypothesized that cotargeting the cytoprotective chaperone Hsp27 and Hsp90 would amplify endoplasmic reticulum (ER) stress and treatment-induced cell death in cancer.
  
  
  METHODS
  Inducible and constitutive Hsp27 and other HSPs were measured by real-time reverse transcription-polymerase chain reaction and immunoblot assays. The combinations of OGX-427 with Hsp90 inhibitors were evaluated in vitro for LNCaP cell growth and apoptosis and in vivo in CRPC LNCaP xenograft models.
  
  
  METHODS
  Tumor volumes were compared using the Kruskal-Wallis test. Overall survival was analyzed using Kaplan-Meier curves, and statistical significance was assessed with the log-rank test.
  
  
  CONCLUSIONS
  Hsp90 inhibitors induced expression of HSPs in tumor cells and tissues in a dose- and time-dependent manner; in particular, Hsp27 mRNA and protein levels increased threefold. In vitro, OGX-427 synergistically enhanced Hsp90 inhibitor-induced suppression of cell growth and induced apoptosis by 60% as measured by increased sub-G1 fraction and poly(ADP-ribose) polymerase cleavage. These biologic events were accompanied by decreased expression of HSPs, Akt, AR, and prostate-specific antigen, and induction of ER stress markers (cleaved activating transcription factor 6, glucose-regulated protein 78, and DNA-damage-inducible transcript 3). In vivo, OGX-427 potentiated the anticancer effects of Hsp90 inhibitor PF-04929113 (orally, 25mg/kg) to inhibit tumor growth and prolong survival in CRPC LNCaP xenografts.
  
  
  CONCLUSIONS
  HSP90 inhibitor-mediated induction of Hsp27 expression can be attenuated by OGX-427, resulting in increased ER stress and apoptosis, and synergistic inhibition of CRPC tumor growth.
  
  
  RESULTS
  This study supports the development of targeted strategies using OGX-427 in combination with Hsp90 inhibitors to improve patient outcome in CRPC.
authors.affiliation: The Vancouver Prostate Centre, University of British Columbia, Vancouver, BC, Canada.
authors.forename: François
authors.initials: F
authors.lastname: Lamoureux
authors.affiliation: The Vancouver Prostate Centre, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Christian
authors.initials: C
authors.lastname: Thomas
authors.affiliation: Oncology Research, Pfizer Worldwide Research & Development, San Diego, CA, USA.
authors.forename: Min-Jean
authors.initials: MJ
authors.lastname: Yin
authors.affiliation: The Vancouver Prostate Centre, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Ladan
authors.initials: L
authors.lastname: Fazli
authors.affiliation: The Vancouver Prostate Centre, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Amina
authors.initials: A
authors.lastname: Zoubeidi
authors.affiliation: The Vancouver Prostate Centre, University of British Columbia, Vancouver, BC, Canada. Electronic address: m.gleave@ubc.ca.
authors.forename: Martin E
authors.initials: ME
authors.lastname: Gleave
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D016227:Benzoquinones / Q000494:pharmacology* / Q000627:therapeutic use; D045744:Cell Line, Tumor; D004721:Endoplasmic Reticulum / Q000502:physiology*; D000091342:Endoplasmic Reticulum Chaperone BiP; D055551:HSP27 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D047029:Lactams, Macrocyclic / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D051379:Mice; D009841:Oligonucleotides / Q000494:pharmacology* / Q000627:therapeutic use; D017430:Prostate-Specific Antigen / Q000097:blood; D064129:Prostatic Neoplasms, Castration-Resistant / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D012313:RNA / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects*; D015996:Survival Rate; D051742:Transcription Factor CHOP / Q000378:metabolism; D056811:Unfolded Protein Response / Q000187:drug effects
chemical_list: D000970:Antineoplastic Agents; D016227:Benzoquinones; D000091342:Endoplasmic Reticulum Chaperone BiP; D055551:HSP27 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D006576:Heterocyclic Compounds, 4 or More Rings; D047029:Lactams, Macrocyclic; D009841:Oligonucleotides; C534922:SNX 2112; D051742:Transcription Factor CHOP; C112765:tanespimycin; D012313:RNA; D017430:Prostate-Specific Antigen; C000595177:apatorsen
keywords: Androgen receptor; Castration-resistant prostate cancer; Hsp27; Hsp90 inhibition; OGX-427