Table of Contents Author Guidelines Submit a Manuscript
Contrast Media & Molecular Imaging
Volume 2019, Article ID 5635269, 10 pages
https://doi.org/10.1155/2019/5635269
Research Article

Synthesis and Evaluation of 18F-Labeled Peptide for Gonadotropin-Releasing Hormone Receptor Imaging

Nanfang PET Center, Nanfang Hospital, Southern Medical University, 1838 Guangzhou Avenue North, Guangzhou, Guangdong 510515, China

Correspondence should be addressed to Kongzhen Hu; moc.361@ssalgnots

Received 28 November 2018; Revised 23 January 2019; Accepted 29 January 2019; Published 7 March 2019

Academic Editor: Reza Vali

Copyright © 2019 Shun Huang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The gonadotropin-releasing hormone (GnRH) receptor is overexpressed in the majority of tumors of the human reproductive system. The purpose of this study was to develop an 18F-labeled peptide for tumor GnRH receptor imaging. In this study, the GnRH (pGlu1-His2-Trp3-Ser4-Tyr5-Gly6-Leu7-Arg8-Pro9-Gly10-NH2) peptide analogues FP-D-Lys6-GnRH (FP = 2-fluoropropanoyl) and NOTA-P-D-Lys6-GnRH (P = ethylene glycol) were designed and synthesized. The IC50 values of FP-D-Lys6-GnRH and NOTA-P-D-Lys6-GnRH were 2.0 nM and 56.2 nM, respectively. 4-Nitrophenyl-2-[18F]fluoropropionate was conjugated to the ε-amino group of the D-lysine side chain of D-Lys6-GnRH to yield the new tracer [18F]FP-D-Lys6-GnRH with a decay-corrected yield of 8 ± 3% and a specific activity of 20−100 GBq/µmol (). Cell uptake studies of [18F]FP-D-Lys6-GnRH in GnRH receptor-positive PC-3 cells and GnRH receptor-negative CHO-K1 cells indicated receptor-specific accumulation. Biodistribution and PET studies in nude mice bearing PC-3 xenografted tumors showed that [18F]FP-D-Lys6-GnRH was localized in tumors with a higher uptake than in surrounding muscle and heart tissues. Furthermore, the metabolic stability of [18F]FP-D-Lys6-GnRH was determined in mouse blood and PC-3 tumor homogenates at 1 h after tracer injection. The presented results indicated a potential of the novel tracer [18F]FP-D-Lys6-GnRH for tumor GnRH receptor imaging.