Enhanced radiation sensitivity in prostate cancer by inhibition of the cell survival protein clusterin.
OBJECTIVE
The purpose of this study is to evaluate the role of the cell survival gene clusterin in radiation-induced cell death in human LNCaP and PC-3 prostate cancer models.


METHODS
Radiation sensitivities were compared in parental and clusterin-overexpressing LNCaP cells and in PC-3 cells and tumors treated with antisense or mismatch clusterin oligonucleotides.


RESULTS
Clusterin-overexpressing LNCaP cells were less sensitive to irradiation with significantly lower cell death rates (23% after 8 Gy) compared with parental LNCaP cells (50% after 8 Gy) 3 days after irradiation. Clusterin expression in PC-3 cells after radiation was found to be up-regulated in a dose-dependent manner in vitro by 70% up to 12 Gy and in vivo by 84% up to 30 Gy. Inhibition of clusterin expression in PC-3 cells using antisense oligonucleotides (ASOs) occurred in a sequence- and dose-dependent manner and significantly enhanced radiation-induced apoptosis and decreased PC-3 cell growth rate and plating efficiency. Compared with mismatch control oligonucleotide treatment, clusterin ASO treatment enhanced radiation therapy and significantly reduced PC-3 tumor volume in vivo by 50% at 9 weeks. In addition, TUNEL staining revealed increased number of apoptotic cells in clusterin ASO-treated and irradiated PC-3 tumors, compared with treatment with mismatch control oligonucleotides plus radiation.


CONCLUSIONS
These findings support the hypothesis that clusterin acts as a cell survival protein that mediates radioresistance through the inhibition of apoptosis. In vivo results further suggest that inactivation of clusterin using ASO technology might offer a novel strategy to improve results of radiation therapy for prostate cancer patients.
Zellweger
Tobias
T
The Prostate Centre, Vancouver General Hospital, Vancouver, British Columbia V6H 3Z6, Canada.
Chi
Kim
K
Miyake
Hideaki
H
Adomat
Hans
H
Kiyama
Satoshi
S
Skov
Kirsten
K
Gleave
Martin E
ME
D000818:Animals; D017209:Apoptosis; D015152:Blotting, Northern; D002455:Cell Division; D051152:Clusterin; D003114:Colony-Forming Units Assay; D017931:DNA Primers / Q000737:chemistry; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D006023:Glycoproteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008819:Mice, Nude; D018832:Molecular Chaperones / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000532:radiotherapy*; D012333:RNA, Messenger / Q000378:metabolism; D011836:Radiation Tolerance; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured / Q000528:radiation effects
C495242:CLU protein, human; C495243:Clu protein, mouse; D051152:Clusterin; D017931:DNA Primers; D006023:Glycoproteins; D018832:Molecular Chaperones; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger