18F-labeled bombesin analogs for targeting GRP receptor-expressing prostate cancer

The gastrin-releasing peptide receptor (GRPR) is found to be overexpressed in a variety of human tumors. The aim of this study was to develop 18F-labeled bombesin analogs for PET of GRPR expression in prostate cancer xenograft models. Methods: [Lys3]Bombesin ([Lys3]BBN) and aminocaproic acid-bombesin(7–14) (Aca-BBN(7–14)) were labeled with 18F by cou-pling the Lys3 amino group and Aca amino group, respectively, withN-succinimidyl-4-18F-fluorobenzoate (18F-SFB) under slightly basic condition (pH 8.5). Receptor-binding affinity of FB-[Lys3]BBN and FB-Aca-BBN(7–14) was tested in PC-3 human prostate carcinoma cells. Internalization and efflux of both radio-tracers were also evaluated. Tumor-targeting efficacy and in vivo kinetics of both radiotracers were examined in male athymic nude mice bearing subcutaneous PC-3 tumors by means of biodistribution and dynamic microPET imaging studies. 18F-FB