A Placental Growth Factor Variant Unable to Recognize Vascular Endothelial Growth Factor (VEGF) Receptor-1 Inhibits VEGF-Dependent Tumor Angiogenesis via Heterodimerization

Angiogenesis is one of the crucial events for cancer development and growth. Two members of the vascular endothelial growth factor (VEGF) family, VEGF-A and placental growth factor (PlGF), which are able to heterodimerize if coexpressed in the same cell, are both required for pathologic angiogenesis. We have generated a PIGF1 variant, named PIGF1-DE in which the residues Asp(72) and Glu(73) were substituted with Ala, which is unable to bind and activate VEGF receptor-1 but is still able to heterodimerize with VEGF. Here, we show that overexpression in tumor cells by adenoviral delivery or stable transfection of PIGF1-DE variant significantly reduces the production of VEGF homodimer via heterodimerization, determining a strong inhibition of xenograft tumor growth and neoangiogenesis, as well as significant reduction of vessel lumen and stabilization, and monocyte-macrophage infiltration. Conversely, the overexpression of PIGF1wt, also reducing the VEGF homodimer production comparably with PIGF1-DE variant through the generation of VEGF/PlGF heterodimer, does not inhibit tumor growth and vessel density compared with controls but induces increase of vessel lumen, vessel stabilization, and monocyte-macrophage infiltration. The property of PIGF and VEGF-A to generate heterodimer represents a successful strategy to inhibit VEGF-dependent angiogenesis. The PIGF1-DE variant, and not PIGF1wt as previously reported, acts as a "dominant negative" of VEGF and is a new candidate for antiangiogenic gene therapy in cancer treatment. Cancer Res; 70(5); 1804-13. (C)2010 AACR.