Presence of receptors for bombesin/gastrin-releasing peptide and mRNA for three receptor subtypes in human prostate cancers

BACKGROUND. Bombesin-like peptides can function as autocrine or paracrine g rowth factors and stimulate the growth of some cancer cells, including huma n prostate cancer. Three bombesin receptor subtypes, termed gastrin-releasi ng peptide receptor (GRPR), neuromedin B receptor (NMBR), and bombesin rece ptor subtype 3 (BRS-3), have been identified in rodents and humans. METHODS. We investigated the presence and characteristics of the functional receptors for bombesin/GRP in human prostate adenocarcinoma specimens by r adio-receptor assay and the mRNA expression of the three bombesin receptor subtypes by RT-PCR. RESULTS. Of the 89 specimens of primary prostate cancer examined by recepto r binding assays, 50 (similar to 63%) showed high-affinity, low-capacity bi nding sites for bombesin/GRP, and 12 of these 50 receptor-positive specimen s also showed a second binding site. Of the 22 prostate cancer specimens an alyzed by RT-PCR, 20 (91%) expressed GRPR mRNA, 3 (14%) showed NMBR mRNA, a nd 2 (similar to 9%) revealed BRS-3 mRNA. No correlation was observed betwe en receptor expression and patients' age or pathological data. CONCLUSIONS. The detection of a wide distribution of bombesin/GRP receptors in human prostate carcinomas supports the view that they may be involved i n modulation of tumor progression and suggests that approaches based on bin ding of bombesin receptor antagonists or new targeted cytotoxic bombesin an alogs to prostate cancers could be considered for the therapy. Prostate 42: 295-303, 2000. (C) 2000 Wiley-Liss, Inc.