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      Single and combined effects of αvβ3- and α5β1-integrins on capillary tube formation in a human fibrinous matrix

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          Abstract

          The fibrinous exudate of a wound or tumor stroma facilitates angiogenesis. We studied the involvement of RGD-binding integrins during tube formation in human plasma-derived fibrin clots and human purified fibrin matrices. Capillary-like tube formation by human microvascular endothelial cells in a 3D plasma-derived fibrinous matrix was induced by FGF-2 and TNF-α and depended largely on cell-bound u-PA and plasmin activities. While tube formation was minimally affected by the addition of either the αvβ3-integrin inhibiting mAb LM609 or the α5-integrin inhibiting mAb IIA1, the general RGD-antagonist echistatin completely inhibited this process. Remarkably, when αvβ3- and α5β1-integrins were inhibited simultaneously, tube formation was reduced by 78%. It was accompanied by a 44% reduction of u-PA antigen accumulation and 41% less production of fibrin degradation products. αvβ5-integrin-blocking antibodies further enhanced the inhibition by mAb LM609 and mAb IIA1 to 94%, but had no effect by themselves. αv-specific cRGD only inhibited angiogenesis when α5β1-integrin was simultaneously blocked. Endostatin mimicked the effect of α5β1-integrin and inhibited tube formation only in the presence of LM609 or cRGD (73 and 80%, respectively). Comparable results were obtained when purified fibrin matrices were used instead of the plasma-derived fibrinous matrices. These data show that blocking of tube formation in a fibrinous exudate requires the simultaneous inhibition of αvβ3- and α5β1-integrins. This may bear impact on attempts to influence angiogenesis in a fibrinous environment.

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          Most cited references59

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          Angiogenesis in cancer, vascular, rheumatoid and other disease.

          J Folkman (1995)
          Recent discoveries of endogenous negative regulators of angiogenesis, thrombospondin, angiostatin and glioma-derived angiogenesis inhibitory factor, all associated with neovascularized tumours, suggest a new paradigm of tumorigenesis. It is now helpful to think of the switch to the angiogenic phenotype as a net balance of positive and negative regulators of blood vessel growth. The extent to which the negative regulators are decreased during this switch may dictate whether a primary tumour grows rapidly or slowly and whether metastases grow at all.
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            RGD and other recognition sequences for integrins.

            Proteins that contain the Arg-Gly-Asp (RGD) attachment site, together with the integrins that serve as receptors for them, constitute a major recognition system for cell adhesion. The RGD sequence is the cell attachment site of a large number of adhesive extracellular matrix, blood, and cell surface proteins, and nearly half of the over 20 known integrins recognize this sequence in their adhesion protein ligands. Some other integrins bind to related sequences in their ligands. The integrin-binding activity of adhesion proteins can be reproduced by short synthetic peptides containing the RGD sequence. Such peptides promote cell adhesion when insolubilized onto a surface, and inhibit it when presented to cells in solution. Reagents that bind selectively to only one or a few of the RGD-directed integrins can be designed by cyclizing peptides with selected sequences around the RGD and by synthesizing RGD mimics. As the integrin-mediated cell attachment influences and regulates cell migration, growth, differentiation, and apoptosis, the RGD peptides and mimics can be used to probe integrin functions in various biological systems. Drug design based on the RGD structure may provide new treatments for diseases such as thrombosis, osteoporosis, and cancer.
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              Vascular permeability factor/vascular endothelial growth factor: a critical cytokine in tumor angiogenesis and a potential target for diagnosis and therapy.

              Vascular endothelial growth factor A (VEGF-A), the founding member of the vascular permeability factor (VPF)/VEGF family of proteins, is an important angiogenic cytokine with critical roles in tumor angiogenesis. This article reviews the literature with regard to VEGF-A's multiple functions, the mechanisms by which it induces angiogenesis, and its current and projected roles in clinical oncology. VEGF-A is a multifunctional cytokine that is widely expressed by tumor cells and that acts through receptors (VEGFR-1, VEGFR-2, and neuropilin) that are expressed on vascular endothelium and on some other cells. It increases microvascular permeability, induces endothelial cell migration and division, reprograms gene expression, promotes endothelial cell survival, prevents senescence, and induces angiogenesis. Recently, VEGF-A has also been shown to induce lymphangiogenesis. Measurements of circulating levels of VEGF-A may have value in estimating prognosis, and VEGF-A and its receptors are potential targets for therapy. Recognized as the single most important angiogenic cytokine, VEGF-A has a central role in tumor biology and will likely have an important role in future approaches designed to evaluate patient prognosis. It may also become an important target for cancer therapy.
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                Author and article information

                Contributors
                +31-20-4449927 , +31-20-4448255 , p.koolwijk@vumc.nl
                Journal
                Angiogenesis
                Angiogenesis
                Springer Netherlands (Dordrecht )
                0969-6970
                1573-7209
                16 May 2009
                September 2009
                : 12
                : 3
                : 275-285
                Affiliations
                [1 ]Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Centre Amsterdam, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
                [2 ]Department of Endocrinology, Leiden University, Leiden, The Netherlands
                Article
                9150
                10.1007/s10456-009-9150-8
                2752504
                19449108
                bd65ea8d-6b95-427a-b7da-f50a7d6bf890
                © The Author(s) 2009
                History
                : 12 December 2008
                : 30 April 2009
                Categories
                Original Paper
                Custom metadata
                © Springer Science+Business Media B.V. 2009

                Human biology
                angiogenesis,αvβ3-integrin,endostatin,lm609,α5β1-integrin
                Human biology
                angiogenesis, αvβ3-integrin, endostatin, lm609, α5β1-integrin

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