Peptide-Based Targeting of the Platelet-Derived Growth Factor Receptor Beta

The aim of this work is to identify new ligands targeting the platelet-derived growth factor receptor beta (PDGFR beta). Biopanning was carried out with a 12-amino-acid phage display library against the recombinant extracellular domain of PDGFR beta. The identified peptide PDGFR-P1 was chemically synthesized and labeled with I-125 or I-131. In vitro studies were performed on the PDGFR beta-expressing cell lines BxPC3 and MCF7 and on PDGFR beta-transfected HEK cells in comparison to negative control wtHEK293 and CaIX-transfected HEK cells. Biodistribution experiments were performed in Balb/c nude mice, carrying subcutaneously BxPC3 tumors. In vitro studies demonstrated a higher binding to BxPC3, MCF7, and PDGFR beta-tr-HEK cells in comparison to negative control cell lines. Binding was inhibited up to 90% by the unlabeled PDGFR-P1 peptide. Organ distribution studies revealed a higher accumulation in BxPC3 tumors than in most organs. PDGFR-P1 is a promising candidate for targeting human PDGFR beta.