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

Background and Aim: 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 ca ncers. The aim of this study was labeling of designed analogue with 99m Tc via HYNIC and Tricine /EDDA and evaluation as potential targeted tumor scintigraphi c agent. Methods: HYNIC-Bombesin was prepared by solid phase synthesis using Fmoc strategy and radiolabeled with 99m Tc 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 s erum 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 internalizatio n into PC-3 cells was high and specific. Biodistribution study demonstrated that 99m Tc-HYNIC peptide cleared fast from blood and most non-targeted tissues and w as excreted mainly by renal pathway and was uptake significantly in GRPr positi ve tissues such as pancreas. Conclusion: Easy radiolabeling of peptide conjugate together w ith favorable in vitro and in vivo characteristics might be a useful peptide radiopharmaceutical in diagnosis of GRPr positive tumors.