Blocking VEGFR-3 suppresses angiogenic sprouting and vascular network formation

Abstract

Angiogenesis, the growth of new blood vessels from pre-existing vasculature, is a key process in several pathological conditions, including tumour growth and age-related macular degeneration. Vascular endothelial growth factors (VEGFs) stimulate angiogenesis and lymphangiogenesis by activating VEGF receptor (VEGFR) tyrosine kinases in endothelial cells. VEGFR-3 (also known as FLT-4) is present in all endothelia during development, and in the adult it becomes restricted to the lymphatic endothelium. However, VEGFR-3 is upregulated in the microvasculature of tumours and wounds. Here we demonstrate that VEGFR-3 is highly expressed in angiogenic sprouts, and genetic targeting of VEGFR-3 or blocking of VEGFR-3 signalling with monoclonal antibodies results in decreased sprouting, vascular density, vessel branching and endothelial cell proliferation in mouse angiogenesis models. Stimulation of VEGFR-3 augmented VEGF-induced angiogenesis and sustained angiogenesis even in the presence of VEGFR-2 (also known as KDR or FLK-1) inhibitors, whereas antibodies against VEGFR-3 and VEGFR-2 in combination resulted in additive inhibition of angiogenesis and tumour growth. Furthermore, genetic or pharmacological disruption of the Notch signalling pathway led to widespread endothelial VEGFR-3 expression and excessive sprouting, which was inhibited by blocking VEGFR-3 signals. Our results implicate VEGFR-3 as a regulator of vascular network formation. Targeting VEGFR-3 may provide additional efficacy for anti-angiogenic therapies, especially towards vessels that are resistant to VEGF or VEGFR-2 inhibitors.

Cotargeting of VEGFR-1 and -3 and angiopoietin receptor Tie2 reduces the growth of solid human ovarian cancer in mice

“…VEGFR-3 is the main mediator of lymphangiogenesis and Tie2 is also involved in lymphatic vessel growth. 15 Thus, the increased amount of ascites might be due to simultaneous block of these pathways. The highest number of vessels without pericytes and a decrease in pericyte coverage was observed in group V (sVEGFR-1, -3 and sTie2) compared with controls.…”

“…12 VEGF-C and-D stimulate lymphangiogenesis through VEGFR-3 which is predominantly expressed not only in lymphatic endothelium 13,14 but also in angiogenic sprouts. 15 Angiopoietins (Ang1-4) are ligands for the tyrosine kinase receptor Tie2. [16][17][18] Ang1 activates Tie2 signaling pathways and promotes the recruitment of pericytes and smooth muscle cells to the developing vessels 16,19 and contributes to tumor dissemination and metastasis.…”

Interaction of tumor cells and lymphatic vessels in cancer progression

“…25 However, upon reactivation of angiogenesis, VEGFR-3 expression may be upregulated, most prominently in angiogenic vessel sprouts. 26,27 VEGFR-3 may function differentially on blood and lymphatic endothelial cells. VEGF ligand-induced activation of VEGFR-3 is indispensable for the development of the lymphatic vascular system, but not for blood vascular development.…”

Vascular-targeted agents for the treatment of angiosarcoma

“…VEGFR3 is chiefly expressed by lymphatic endothelial cells, and is the main receptor for VEGFC and D. VEGFR3 is not expressed on mature vascular endothelial cells, but is expressed by tip endothelial cells of angiogenic sprouts [13]. …”