Clusterin expression is significantly enhanced in prostate cancer cells following androgen withdrawal therapy.
OBJECTIVE
Progression of prostate cancer to androgen independence (AI) results in part from the upregulation of anti-apoptotic genes following androgen withdrawal, and androgen-independent disease remains the primary obstacle to improved survival. Testosterone-repressed prostate message-2 (TRPM-2) encodes the anti-apoptotic protein clusterin, which is upregulated in response to cellular compromise as observed in normal and malignant tissues undergoing apoptosis. Systemic administration of antisense clusterin oligonucleotides in prostate cancer xenograft models delays progression to AI and enhances chemosensitivity. The objective of this study was to define changes in clusterin expression following neoadjuvant hormone therapy (NHT) in prostate cancer patients.


METHODS
Archival radical prostatectomy (RP) specimens were obtained for 128 patients who received either no NHT or treatment for 2-8 weeks, 3 months, or 8 months. Paired needle biopsy specimens were acquired for 30 patients and all tissues were subjected to clusterin immunohistochemistry. Western blot analysis was performed on frozen tissue from 5 untreated and 5 treated patients.


RESULTS
Clusterin expression in malignant prostatic tissue was significantly greater in patients who underwent preoperative NHT (P < 0.001). Needle biopsies obtained prior to NHT consistently demonstrated lower staining intensity than corresponding RP specimens (P < 0.001). Western blot analysis confirmed clusterin levels increased 17-fold beginning within 4 weeks after androgen withdrawal.


CONCLUSIONS
Upregulation of clusterin levels following androgen ablation therapy may represent an adaptive cell survival response following apoptotic signals like androgen withdrawal. These findings support clusterin as a valid therapeutic target in strategies employing novel multimodality therapy for advanced prostate cancer.
July
Laura V
LV
The Prostate Centre, Vancouver General Hospital, University of British Columbia, Vancouver, British Columbia, Canada.
Akbari
Majid
M
Zellweger
Tobias
T
Jones
Edward C
EC
Goldenberg
S Larry
SL
Gleave
Martin E
ME
D000328:Adult; D000368:Aged; D000726:Androgen Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D017209:Apoptosis; D001706:Biopsy; D015153:Blotting, Western; D002470:Cell Survival; D051152:Clusterin; D003169:Complement Inactivator Proteins / Q000096:biosynthesis*; D018450:Disease Progression; D006023:Glycoproteins / Q000096:biosynthesis*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D018832:Molecular Chaperones / Q000096:biosynthesis*; D020360:Neoadjuvant Therapy; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D015398:Signal Transduction; D013997:Time Factors; D015854:Up-Regulation
D000726:Androgen Antagonists; C495242:CLU protein, human; D051152:Clusterin; D003169:Complement Inactivator Proteins; D006023:Glycoproteins; D018832:Molecular Chaperones