Vascular endothelial growth factor D (VEGF-D) is a member of the VEGF/platelet-derived growth factor (PDGF) family of proteins. VEGF-D is a potent angiogenic factor and promotes lymphangiogenesis, endothelial cell growth and survival, and can affect blood vessel permeability. VEGF-D is expressed in the lung, heart, small intestine, fetal lung, and at lower levels in the pancreas, colon, and skeletal muscle (Otrock et al.; Roy et al.; Stacker et al.; Yamada et al.). VEGF-D is a ligand for VEGF receptors 2 (Flk1) and 3 (Flt4) (Baldwin et al.). VEFGR-3 is highly expressed in lymphatic endothelial cells and is essential for their growth and differentiation (Otrock et al.; Roy et al.). Binding of VEGF-D to neuropilins contributes to VEGFR-3 signaling during lymphangiogenesis, whereas binding to integrin α9β1 promotes endothelial cell adhesion and migration (Roy et al.; Otrock et al.). During embryogenesis, VEGF-D also plays a role in the formation of the venous and lymphatic systems.