Serial analysis of resected prostate cancer suggests up-regulation of type 1 IGF receptor with disease progression.
OBJECTIVE
• To compare immunostaining protocols using different antibodies for the type 1 insulin-like growth factor receptor (IGF-1R) in channel transurethal resection of the prostate (chTURP) chips, and to investigate how IGF-1R expression varies with time in serial prostate cancer specimens from individual patients.


METHODS
• We studied IGF-1R expression in 44 prostate cancer specimens from 18 patients who had undergone serial chTURP at least 3 months apart. • Retrospective analysis of the hospital notes was undertaken to obtain clinical information, including age, Gleason score, prostate-specific antigen (PSA) level, hormone treatment and metastatic disease status at the time of each operation. • After an optimization process using three commercially-available IGF-1R antibodies, we used two antibodies for semiquantititve immunostaining of serial chTURP chips.


RESULTS
• Santa Cruz antibody sc713 gave positive staining in IGF-1R null R- cells, and was not used further. Antibodies from Cell Signaling Technology (Beverly, MA, USA) (CS) and NeoMarkers Inc. (Fremont, CA, USA) (NM) did not stain R- cells and, in prostate tissue, showed staining of the glandular epithelium, with negligible stromal staining. All 44 chTURP samples contained identifiable malignant tissue and, of these, 73% and 64% scored moderately or strongly (score 3 or 4) with the CS and NM antibodies respectively. • There was significant correlation of IGF-1R scores of malignant tissue between the two antibodies (P < 0.001). By contrast, staining of benign glands showed poor correlation between antibodies: CS gave significantly weaker staining than malignant epithelium in the same sections (P < 0.001), whereas NM showed poor discrimination between malignant and benign glands. IGF-1R staining scores generated by the CS antibody were used to analyze the clinical data. • Most patients (six of seven) with falling IGF-1R staining scores were responding to androgen deprivation therapy (confirmed by PSA response) between operations. Conversely, in seven of eight patients who had progression to androgen-independence between procedures, IGF-1R levels increased or remained high. Finally, seven of 11 patients who developed radiologically confirmed metastases between procedures showed stable or increasing IGF-1R staining scores.


CONCLUSIONS
• The present study is the first to assess changes in IGF-1R expression in serial prostate cancer samples. The results obtained indicate that IGF-1R expression usually remains high throughout the course of histologically-proven disease progression in serial specimens, suggesting that the IGF-1R remains a valid treatment target for advanced prostate cancer.
Turney
Benjamin W
BW
Molecular Oncology Laboratories, Weatherall Institute of Molecular Medicine, Department of Urology, Cancer and Haematology Centre, The Churchill Hospital, Old Road, Headington, Oxford, UK.
Turner
Gareth D H
GD
Brewster
Simon F
SF
Macaulay
Valentine M
VM
D000368:Aged; D000369:Aged, 80 and over; D000726:Androgen Antagonists / Q000627:therapeutic use; D018450:Disease Progression; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D017430:Prostate-Specific Antigen / Q000378:metabolism; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000628:therapy; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D012189:Retrospective Studies; D015854:Up-Regulation
D000726:Androgen Antagonists; D017526:Receptor, IGF Type 1; D017430:Prostate-Specific Antigen