title: Overexpression of the cytoprotective protein clusterin decreases radiosensitivity in the human LNCaP prostate tumour model.
abstract: OBJECTIVE
  To evaluate the effect of clusterin overexpression on radiation-induced tumour growth rates and apoptosis in human prostate LNCaP cells, as prostate cancer cells are relatively resistant to radiation-induced apoptosis and local recurrences are common, but overexpression of the anti-apoptotic protein clusterin can accelerate progression to androgen-independence and to confer a chemoresistant phenotype in various prostate cancer models.
  
  
  METHODS
  Western blot analysis and immunohistochemistry were used to compare clusterin expression levels in parental (P) and clusterin-transfected (T) LNCaP cells in vitro and in vivo. The effects of radiation on clusterin-expression in both parental LNCaP/P and clusterin-transfected LNCaP/T tumours were analysed by Northern blot analysis. The cellular response to radiation was determined up to 3 weeks after irradiation using tetrazolium and re-growth assays, and cell-cycle analysis by flow cytometry.
  
  
  RESULTS
  Clusterin mRNA expression increased from undetectable to low levels in LNCaP/P tumours after radiation and more than three-fold in LNCaP/T tumours. Clusterin overexpression decreased the radiosensitivity in a time-dependent manner, reducing the extent of growth arrest and apoptosis by up to 54%. Re-growth assays showed that the improved survival rates of LNCaP/T cells after radiation did not change after 3 days, remaining constant over 3 weeks.
  
  
  CONCLUSIONS
  These results identify clusterin as a promoter of cell survival that may help mediate resistance to radiation-induced apoptosis. Furthermore, clusterin overexpression seems to provide an extended protection against radiation-induced cell cycle arrest and apoptosis.
authors.affiliation: The Prostate Centre, Vancouver General Hospital, BC, Canada.
authors.forename: T
authors.initials: T
authors.lastname: Zellweger
authors.forename: S
authors.initials: S
authors.lastname: Kiyama
authors.forename: K
authors.initials: K
authors.lastname: Chi
authors.forename: H
authors.initials: H
authors.lastname: Miyake
authors.forename: H
authors.initials: H
authors.lastname: Adomat
authors.forename: K
authors.initials: K
authors.lastname: Skov
authors.forename: M E
authors.initials: ME
authors.lastname: Gleave
mesh_terms: D017209:Apoptosis / Q000528:radiation effects*; D015152:Blotting, Northern; D015153:Blotting, Western; D002455:Cell Division / Q000528:radiation effects; D051152:Clusterin; D005434:Flow Cytometry; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D018832:Molecular Chaperones / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000532:radiotherapy; D012333:RNA, Messenger / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: C495242:CLU protein, human; D051152:Clusterin; D006023:Glycoproteins; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D012333:RNA, Messenger