Synergistic activation of the androgen receptor by bombesin and low-dose androgen.
OBJECTIVE
Neuropeptide growth factors such as bombesinare implicated in progression to androgen-independent prostate cancer (PC). We examined the impact of bombesin on androgen receptor (AR)-mediated gene expression.


METHODS
The AR together with the AR-responsive probasin ARR(3)tk-luc or PSA-pPUE-ELB-luc promoter was cotransfected into Swiss 3T3 and PC-3 cells, both of which express high-affinity bombesin receptors; the cells were incubated with bombesin (0-50 nM) and dihydrotestosterone (DHT; 0-10 nM), and luciferase activities were measured. DHT increased transcription approximately 40-fold at doses of 1 and 10 nM but had no effect at 10 pM. Bombesin alone, or with 1 or 10 nM DHT, did not further increase transcription. However, 5 nM bombesin and 10 pM DHT, doses that by themselves had no effect, resulted in a approximately 20 fold increase in transcription (P < 0.005). This synergistic effect was blocked by bombesin receptor antagonists and recombinant neutral endopeptidase, which hydrolyzes bombesin. Bombesin and DHT together also increased binding of nuclear extracts from PC-3 cells transfected with AR to a consensus androgen response element in mobility shift assays and increased the level of secreted prostate-specific antigen in LNCaP cell supernatant compared with DHT or bombesin alone. Immunoprecipitation of AR from (32)P-labeled LNCaP cells revealed that 5 nM bombesin + 10 pM DHT induced AR phosphorylation comparable with 1 nM DHT, whereas bombesin or 10 pM DHT alone did not.


CONCLUSIONS
These data indicate that bombesin can synergize with low (castrate) levels of DHT to induce AR-mediated transcription and suggest that neuropeptides promote AR-mediated signaling in androgen-independent prostate cancer.
Urologic Oncology Research Laboratory, Department of Urology, Joan and Stanford I. Weill Medical College, Cornell University, New York, New York 10021, USA.
Jie
J
Dai
Ruoqian
R
Shen
Makoto
M
Sumitomo
Rosalyn
R
Stahl
Daniel
D
Navarro
Marvin C
MC
Gershengorn
David M
DM
Nanus
D001839:Bombesin / Q000494:pharmacology*; D013196:Dihydrotestosterone / Q000494:pharmacology*; D004357:Drug Synergism; D024202:Electrophoretic Mobility Shift Assay; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D008297:Male; D010766:Phosphorylation / Q000187:drug effects; D011233:Precipitin Tests; D017430:Prostate-Specific Antigen / Q000235:genetics / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism*; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism*; D018004:Receptors, Bombesin / Q000235:genetics / Q000378:metabolism; D020218:Response Elements; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects
D011944:Receptors, Androgen; D018004:Receptors, Bombesin; D013196:Dihydrotestosterone; D008156:Luciferases; D017430:Prostate-Specific Antigen; D001839:Bombesin