Dual-action ligand targeting both integrin αvβ3 and VEGF receptors

In cancer, some specific cell surface receptors, such as integrins aVb3, aVb5 and a5b1 and the growth factor receptors (e.g. VEGFRs), play a key role in tumor angiogenesis, progression and metastasis. Tumor cell proliferation is regulated by the activity of these receptors, through the formation of specific protein-protein complexes. Physical interaction of integrins with growth factor receptors (“cross-talk”) gives rise to synergistic effects. In vivo evidence of VEGFR2/aVb3 association has been provided, revealing co-localization of these receptors on endothelial cells of proliferating blood vessels, although the exact nature of the complex containing aVb3 and the VEGFRs is still unclear. Moreover, a dual-specific engineered protein able to bind both VEGFR2 and integrin aVb3 inhibited angiogenic processes in vitro and in vivo. Our research group developed a potent aVb3 integrin ligand, which consists of a cyclic RGD peptidomimetic containing a diketopiperazine scaffold functionalized for further conjugation with other molecular devices. Recently, a short helical peptide (15 aminoacid residues) was reported that selectively binds to the extracellular domain of VEGFR1 receptor and exhibits anti-angiogenic activity in vivo. Starting from these two selective ligands, we synthesized a covalently-linked dual-specific agent, aiming at inhibiting both aVb3 and VEGFR1. This compound was prepared through microwaveassisted solid-phase peptide synthesis, with a final “click” reaction between the alkynebearing solid-supported VEGFR1 ligand and the azido-functionalized PEG8-RGD integrin ligand. We are currently in vitro testing the anti-angiogenic activity of the dual-action ligand in VEGF165 - induced capillary tube formation experiments (HUVEC cells), in comparison with the singularly administered and the co-administered ligands. The intertwined relationship between VEGFRs and aVb3 integrin suggests that a dualspecific agent capable of inhibiting both receptors would offer interesting therapeutic potential.