International Journal of Molecular Sciences Review Role of VEGFs/VEGFR-1 Signaling and Its Inhibition in Modulating Tumor Invasion: Experimental Evidence in Different Metastatic Cancer Models 1 1 2, 1, , Claudia Ceci , Maria Grazia Atzori , Pedro Miguel Lacal y and Grazia Graziani * y 1 Department of Systems Medicine, University of Rome Tor Vergata, Via Montpellier 1, 00133 Rome, Italy;
[email protected] (C.C.);
[email protected] (M.G.A.) 2 Laboratory of Molecular Oncology, “Istituto Dermopatico dell’Immacolata-Istituto di Ricovero e Cura a Carattere Scientifico”, IDI-IRCCS, Via dei Monti di Creta 104, 00167 Rome, Italy;
[email protected] * Correspondence:
[email protected]; Tel.: +30-0672596338 Equally contributing co-last authors. y Received: 21 January 2020; Accepted: 14 February 2020; Published: 18 February 2020 Abstract: The vascular endothelial growth factor (VEGF) family members, VEGF-A, placenta growth factor (PlGF), and to a lesser extent VEGF-B, play an essential role in tumor-associated angiogenesis, tissue infiltration, and metastasis formation. Although VEGF-A can activate both VEGFR-1 and VEGFR-2 membrane receptors, PlGF and VEGF-B exclusively interact with VEGFR-1. Differently from VEGFR-2, which is involved both in physiological and pathological angiogenesis, in the adult VEGFR-1 is required only for pathological angiogenesis. Besides this role in tumor endothelium, ligand-mediated stimulation of VEGFR-1 expressed in tumor cells may directly induce cell chemotaxis and extracellular matrix invasion. Furthermore, VEGFR-1 activation in myeloid progenitors and tumor-associated macrophages favors cancer immune escape through the release of immunosuppressive cytokines. These properties have prompted a number of preclinical and clinical studies to analyze VEGFR-1 involvement in the metastatic process.