Abstract
The purpose of this study was to evaluate the tumor targeting and imaging properties of novel (111)In-labeled gonadotropin-releasing hormone (GnRH) peptides for human prostate cancer. Three new 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-linker-d-Phe-(d-Lys(6)-GnRH) peptides with different hydrocarbon linkers were designed to evaluate their effects on GnRH receptor binding affinities. The Aoc (aminooctanoic acid) linker was better than βAla (3-aminopropanoic acid) and Aun (aminoundecanoic acid) linkers in retaining strong receptor binding affinity. DOTA-Aoc-d-Phe-(d-Lys(6)-GnRH) exhibited 6.6±0.1nM GnRH receptor binding affinity. (111)In-DOTA-Aoc-d-Phe-(d-Lys(6)-GnRH) exhibited fast tumor uptake and urinary clearance in DU145 human prostate cancer-xenografted nude mice. The DU145 tumor lesions could be clearly visualized by single photon emission computed tomography (SPECT)/CT using (111)In-DOTA-Aoc-d-Phe-(d-Lys(6)-GnRH) as an imaging probe, providing an insight into the design of new GnRH peptides for prostate cancer in the future.