Anti-lipid phosphate phosphohydrolase-3 (LPP3) antibody inhibits bFGF- and VEGF-induced capillary morphogenesis of endothelial cells

We report that bFGF and VEGF up-regulate LPP3 protein expression in ECs. Immunoprecipitation analyses show that LPP3 is a cell surface protein and undergoes N-glycosylation. Fluorescent activated cell sorting (FACS) data suggest that anti-LPP3-RGD detects native neoepitope on the surface of activated ECs. Moreover, we demonstrate LPP3 protein expression in tumor endothelium alongside VEGF. The embedding of ECs into three-dimensional type I collagen in the presence of bFGF and VEGF induce capillary formation. Importantly, we show that the addition of an anti-LPP3 antibody specifically and significantly blocks bFGF- and VEGF-induced capillary morphogenesis of ECs.These data suggest that activated ECs as well as tumor endothelium express LPP3 protein. In an in vitro assay, the anti-LPP3-RGD specifically blocks bFGF and VEGF induced capillary morphogenesis of ECs. Our results, therefore, suggest a role for LPP3 in angiogenesis.Angiogenesis, the sprouting or remodeling of preexisting quiescent blood vessels, is critical for embryonic development, wound healing, and various pathological conditions such as tumor progression, complications associated with acquired immune deficiency syndrome (AIDS), rheumatoid arthritis, and diabetic retinopathy [1-4]. Angiogenesis can be initiated by hypoxic tumors, inflammation or an increased accumulation of pro-angiogenic factors. These factors, in turn, trigger secretion of matrix metalloproteinases (MMPs) that dissolve the basement membrane. This MMP-mediated membrane dissolution is an essential event for subsequent EC activation, migration, and capillary formation [1-6]. Angiogenesis is regulated through a dynamic balance between pro- and anti-angiogenic factors [1-4]. Angiogenic mediators include growth factors such as basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), collagen and fibronectin, and proteases such as MMPs [2,4,6-8]. VEGF signaling activates ECs through VEGF receptor-1 (VEGFR-1, also know