Evaluation of a new bombesin analogue labeled with 99mTc as potential targeted tumor scintigraphic agent

Background: Bombesin shows high affinity for Gastrin-releasing peptide (GRP) receptors which over expressed on the cell surfaces of several human tumors particularly in prostate and breast cancers. The aim of this study was labeling of designed analogue with99mTc via HYNIC and Tricine /EDDA and evaluation as potential targeted tumor scintigraphic agent. Materials and Methods: HYNIC-Bombesin was prepared by solid phase synthesis using Fmoc strategy and radiolabeled with 99mTc at 100 °C for 10 min by exchange method and radiochemical analysis involved ITLC and HPLC methods. The stability of radiopeptide was checked in the presence of human serum at 37 °C up to 24 h. Internalization was studied with the human GRP receptor cell line PC-3. Biodistribution study was performed in mice. Results: Radiochemical purities of >98% was obtained. Radiopeptide showed high stability in serum. Radioligand internalization into PC-3 cells was high and specific. Biodistribution study demonstrated that 99mTc-HYNIC peptide cleared fast from blood and most non-targeted tissues and was excreted mainly by renal pathway and was uptake significantly in GRPr positive tissues such as pancreas. Conclusion: Easy radiolabeling of peptide conjugate together with favorable in vitro and in vivo characteristics might be a useful peptide radiopharmaceutical in diagnosis of GRPr positive tumors.