title: Thrombospondin-1 modulates vascular endothelial growth factor activity at the receptor level.
abstract: Vascular endothelial growth factor (VEGF) is a well-established stimulator of vascular permeability and angiogenesis, whereas thrombospondin-1 (TSP-1) is a potent angiogenic inhibitor. In this study, we have found that the TSP-1 receptors CD36 and beta1 integrin associate with the VEGF receptor 2 (VEGFR2). The coclustering of receptors that regulate angiogenesis may provide the endothelial cell with a platform for integration of positive and negative signals in the plane of the membrane. Thus, this complex may represent a molecular switch that regulates angiogenesis and determines endothelial cell behavior. In this context, physiological levels of TSP-1 appear to support VEGFR2 function on both the cellular and tissue level, because phosphorylation of VEGFR2 and vascular permeability in response to VEGF are decreased in TSP-1-null mice and isolated endothelial cells. A therapeutic agent based on the antiangiogenic domain of TSP-1, designated 3TSR (for three TSP-1 type 1 repeats), has significant antiangiogenic and antitumor efficacy. Systemic treatment of wild-type mice with 3TSR significantly decreased VEGF-induced permeability. Consistent with this result, VEGF-stimulated phosphorylation of VEGFR2 was also significantly decreased in lung extracts from 3TSR-treated mice. Moreover, 3TSR significantly decreased VEGF-stimulated VEGFR2 phosphorylation in human dermal microvascular endothelial cells in culture. Taken together, the results indicate that TSP-1 and 3TSR modulate the function of VEGFR2.
authors.affiliation: Division of Cancer Biology and Angiogenesis, Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, USA.
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Zhang
authors.forename: Shideh
authors.initials: S
authors.lastname: Kazerounian
authors.forename: Mark
authors.initials: M
authors.lastname: Duquette
authors.forename: Carole
authors.initials: C
authors.lastname: Perruzzi
authors.forename: Janice A
authors.initials: JA
authors.lastname: Nagy
authors.forename: Harold F
authors.initials: HF
authors.lastname: Dvorak
authors.forename: Sareh
authors.initials: S
authors.lastname: Parangi
authors.forename: Jack
authors.initials: J
authors.lastname: Lawler
mesh_terms: D000818:Animals; D002199:Capillary Permeability / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism*; D051379:Mice; D008817:Mice, Mutant Strains; D017463:Receptors, Complement 3b / Q000378:metabolism*; D019700:Thrombospondin 1 / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism*
chemical_list: D019012:Integrin beta1; D017463:Receptors, Complement 3b; D019700:Thrombospondin 1; D042461:Vascular Endothelial Growth Factor A; D040301:Vascular Endothelial Growth Factor Receptor-2