Abstract
122 Background: The peptide bombesin (BN) and derivates thereof show high binding affinity for the gastrin-releasing peptide receptor (GRPR), which is highly expressed in primary and metastasized prostate cancer. We have synthesized a new BN-based radiopharmaceutical 99mTechnetium-HYNIC(tricine/TPPTS)-Aca-BN(7–14) (99mTc-HABN) and evaluated its GRPR targeting properties in vitro and in a xenograft tumor model for human prostate cancer in athymic mice. Methods: 99mTc- HABN was synthesized and its lipophilicity and stability were investigated. The IC50, internalization and efflux properties were determined in vitro using the GRPR expressing human prostate cancer cell line PC-3. 99mTc-HABN biodistribution and microSPECT imaging were performed in PC-3 tumor-bearing athymic mice. Results: 99mTc-HABN was prepared with high labeling yield (>90%), high radiochemical purity (>95%) and a specific activity of ∼19.8 MBq/nmol. The partition coefficient log P value was −1.60±0.06. 99mTc-HABN proved to be stable in human serum for 6 hours. The IC50 of HABN was 12.81±0.14 nM. Incubation of PC-3 cells with 99mTc-HABN demonstrated rapid cellular internalization and a long intracellular retention time. When mice were injected with 99mTc-HABN the activity was predominantly cleared via the kidneys. Uptake in the tumor was 2.24±0.64 %ID/g after 30 minutes, with a steady decrease during the 4 hours study period. In vivo experiments with a blocking agent showed GRPR mediated uptake. 99mTc-HABN microSPECT imaging resulted in clear delineation of the tumor. Conclusions: 99mTc-HABN is a novel BN-based radiopharmaceutical that appears to be suitable for targeted imaging of prostate cancer. No significant financial relationships to disclose.
Published Version
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