Sameer Alshehri
University of Nebraska Medical Center, USA
Title: Investigation of BBN-HPMA conjugates for targeting Gastrin Releasing-Peptide (GRPR) Receptor
Biography
Biography: Sameer Alshehri
Abstract
Background: Compared to small radiolabeled bombesin (BBN) peptide conjugates, targeting efficacy of macromolecular conjugates modified with BBN analogues in tumors expressing gastrin releasing-peptide receptor (GRPR) is largely unexplored. Our goal was to investigate the targeting efficacy of BBN-conjugated polymeric system in vitro and in vivo.
Methods: Four concentrations, 2, 5, 10 and 15 mol% of L-BBN peptide, were conjugated to HPMA copolymer. As a control, 10 mol% D-BBN-HPMA was synthesized. Using PC-3 human prostate cancer cell line, 1 hr cellular internalization studies for all conjugates and 4 hr cellular internalization studies as well as confocal imaging studies for the 10% L-BBN-HPMA and 10% D-BBN-HPMA were performed. Results: After 1 hr, cellular internalization studies showed high uptake of 10% L-BBN-HPMA by around 13.76% internalized activity compared to 0.61%, 3.58%, 6.00% and 9.35% for 2% L-BBN-HPMA, 5% L-BBN-HPMA, 10% D-BBN-HPMA and 15% L-BBN-HPMA, respectively. Similarly, after 4 hr, 10% L-BBN-HPMA showed higher internalized radioactivity (16.96%) compared to 10% D-BBN-HPMA (9.59%).The confocal imaging study showed higher fluorescent signal for 10% L-BBN-HPMA compared to 10% D-BBN-HPMA by two folds. Surprisingly, biodistribution studies showed higher retention in liver and spleen for all conjugates except 2% L-BBN-HPMA. Interestingly, the retention in spleen was found to be directly proportional to the concentration of peptide/polymer.
Conclusion: The results indicate that incorporating of BBN peptides in the HPMA copolymer construct enhances the internalization into PC-3 cells, with 10% molar concentration being the optimum concentration. However, due to high retention in liver and spleen, further modifications to the construct are needed.