title: Inhibition of tumor growth by targeting tumor endothelium using a soluble vascular endothelial growth factor receptor.
abstract: Vascular endothelial growth factor (VEGF) is a leading candidate for an endogenous mediator of tumor angiogenesis. Recently, two endothelial cell surface receptors, flk-1 and flt-1, have been shown to mediate the angiogenic activities of VEGF. In this study, we have evaluated whether a soluble VEGF receptor could suppress tumor angiogenesis and thereby inhibit tumor growth. A soluble VEGF receptor was constructed by fusing the entire extracellular domain of murine flk-1 to a six-histidine tag at the COOH terminus (ExFlk.6His). In vitro, recombinant ExFlk.6His protein bound VEGF with high affinity (Kd, 16 nM) and blocked receptor activation in a dose-dependent manner and inhibited VEGF-induced endothelial cell proliferation and migration. ExFlk.6His bound to endothelial cells only in the presence of VEGF, and cell surface cross-linking yielded a high molecular weight complex consistent with the VEGF-mediated formation of a heterodimer between ExFlk.6His and the endogenous VEGF receptor. In vivo, ExFlk.6His potently inhibited corneal neovascularization induced by conditioned media from a rat mammary carcinoma cell line (R3230AC). Moreover, when ExFlk.6His protein was administered into a cutaneous tumor window chamber concomitantly with R3230AC carcinoma transplants, tumor growth was inhibited by 75% (P < 0.005) and vascular density was reduced by 50% (P < 0.002) compared with control-treated tumors. These results demonstrate the potential of ExFlk.6His to inhibit VEGF action by a potent "dominant-negative" mechanism and suggest that targeting VEGF action using a soluble receptor may be an effective antiangiogenic therapy for cancer and other "angiogenic" diseases.
authors.affiliation: Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: P
authors.initials: P
authors.lastname: Lin
authors.forename: S
authors.initials: S
authors.lastname: Sankar
authors.forename: S
authors.initials: S
authors.lastname: Shan
authors.forename: M W
authors.initials: MW
authors.lastname: Dewhirst
authors.forename: P J
authors.initials: PJ
authors.lastname: Polverini
authors.forename: T Q
authors.initials: TQ
authors.lastname: Quinn
authors.forename: K G
authors.initials: KG
authors.lastname: Peters
mesh_terms: D000818:Animals; D002455:Cell Division; D002465:Cell Movement; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000473:pathology*; D009374:Neoplasms, Experimental / Q000098:blood supply / Q000473:pathology*; D009389:Neovascularization, Pathologic / Q000517:prevention & control; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000502:physiology*; D017978:Receptors, Growth Factor / Q000502:physiology*; D040262:Receptors, Vascular Endothelial Growth Factor; D011994:Recombinant Proteins
chemical_list: D017978:Receptors, Growth Factor; D011994:Recombinant Proteins; D020794:Receptor Protein-Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor