Investigation of bombesin peptide as a targeting ligand for the gastrin releasing peptide (GRP) receptor.
Gastrin releasing peptide (GRP) receptor (GRPR), a bombesin family receptor, is overexpressed in many cancers including breast, prostate, pancreatic and lung. The targeting of therapeutics to GRPR can be achieved using the full-length (14 amino acid) GRP analogue Bombesin (BBN) or the truncated BBN(6-14) sequence, both of which bind GRPR with high affinity and specificity. In this study, we have investigated the level of GRPR expression in various cancerous (Caco-2, HeLa, LNCap, MDA-MB-231, and PC-3) and non-cancerous (WPMY-1) cell lines using a western blotting approach. Such information is currently lacking in the literature, and is therefore of importance for the in vitro assessment of GRPR targeted therapeutics. Of the cell lines assessed, the PC-3 (prostate cancer) and Caco-2 (colon cancer) cell lines demonstrated the highest and lowest levels of GRPR expression respectively. Using this information, we further investigated the cellular uptake of carboxyfluorescein-labelled BBN and BBN(6-14) peptides by flow cytometry and confocal microscopy using cell lines that express GRPR (Caco-2, HeLa, PC-3). The uptake of each of these peptides was similar, suggesting that the shorter BBN(6-14) peptide is sufficient for GRPR targeting. Further, the uptake of these peptides could be inhibited by competition with unlabelled BBN peptides, suggesting their cellular uptake is GRPR-mediated, while the level of BBN uptake (as measured by flow cytometry) was found to be directly proportional to the level of GRPR expression. Overall, the information obtained from these studies provides useful information for the in vitro assessment of GRPR targeted therapeutics.
School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia 4072, Australia; School of Pharmacy, The University of Queensland, Woolloongabba 4102, Australia.
Anjuman Ara
AA
Begum
School of Pharmacy, The University of Queensland, Woolloongabba 4102, Australia. Electronic address: p.moyle@uq.edu.au.
Peter M
PM
Moyle
School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia 4072, Australia; School of Pharmacy, The University of Queensland, Woolloongabba 4102, Australia; Institute of Molecular Bioscience, The University of Queensland, St Lucia, St Lucia 4072, Australia.
Istvan
I
Toth
D001839:Bombesin / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008024:Ligands; D015394:Molecular Structure; D018004:Receptors, Bombesin / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000378:metabolism; D013329:Structure-Activity Relationship
D008024:Ligands; D018004:Receptors, Bombesin; D001839:Bombesin
Bombesin; Cell uptake; Gastrin releasing peptide receptor; Solid phase peptide synthesis; Targeting