synthesis and evaluation of a new radiolabeled bombesin analogue for diagnosis of grp receptor expressing tumors

introduction: bombesin (bn), a 14-amino acid neuropeptide, shows high affinity for the human grp (gastrin releasing peptide) receptors, which are overexpressed by a variety of cancers, including prostate, breast, pancreas, gastrointestinal, and small cell lung cancer. aim was to prepare [6-hydrazinopyridine-3-carboxylic acid (hynic0), d-tyr6, d-trp8] - bn [6-14] nh2 that could be easily labeled with 99mtc and evaluation of its potential as an imaging agent. methods: synthesis of the peptide amide was carried out onto rink amide mbha (4-methylbenzhydrylamine) resin. a bifunctional chelating agent (bfca) was attached to the n terminal peptide in solid-phase. 99mtc labeling was performed by addition of sodium pertechnetate to solution that include [hynic0, d-tyr6, d-trp8] bombesin [6-14] nh2, tricine, ethylenediamine-n,n′-diacetic acid (edda) and sncl2. radiochemical evaluation was carried out by reverse phase high-performance liquid chromatography (hplc) and instant thin layer chromatography (itlc). in-vitro internalization was tested using human prostate cancer cells (pc-3) with blocked and non-blocked receptors. biodistribution was determined in rats. results:[99mtc/tricine/edda-hynic0, d-tyr6, d-trp8] bombesin [6-14] nh2 was obtained with radiochemical purities >98%. results of in-vitro studies demonstrated a high stability in serum and suitable internalization. biodistribution data showed a rapid blood clearance, with renal excretion and specific binding towards grp receptor-positive tissues such as pancreas. conclusion: in this study, labeling of this novel conjugate with 99mtc easily was performed using coligand. the prepared 99mtc-hynic-bn conjugate has promising characteristics for the diagnosis of malignant tumors.