Abstract
The angiopoietin-Tie2 system in endothelial cells is an important regulator of vasculogenesis and vascular integrity. High levels of angiopoietin-2 (Ang2) mRNA are observed in vascular activation during tumorigenesis. Although Ang2 is known to be a naturally occurring antagonist of angiopoietin-1 (Ang1) in vivo, the exact function of Ang2 itself is not known. Here, we found that a high concentration of Ang2 (800 ng/ml) acts as an apoptosis survival factor for endothelial cells during serum deprivation apoptosis. The survival effect of high concentration Ang2 was blocked by pre-treatment with soluble Tie2 receptor and the PI 3'-kinase-specific inhibitors, wortmannin and LY294002. Accordingly, 800 ng/ml of Ang2 induced phosphorylation of Tie2, the p85 subunit of phosphatidylinositol 3'-kinase (PI 3'-kinase), and serine-threonine kinase Akt at Ser473 in the human umbilical vein endothelial cells; lower concentrations of Ang2 (50 - 400 ng/ml) did not produce notable effects. These findings indicate that at high concentrations, Ang2, like Ang1, can be an apoptosis survival factor for endothelial cells through the activation of the Tie2 receptor, PI 3'-kinase and Akt, and thus may be a positive regulator of tumor angiogenesis. Oncogene (2000) 19, 4549 - 4552.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Androstadienes / pharmacology
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Angiopoietin-2
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Apoptosis / drug effects
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Cell Line
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Cell Survival / drug effects
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Chromones / pharmacology
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Culture Media, Serum-Free / pharmacology
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Dose-Response Relationship, Drug
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Endothelium, Vascular / cytology*
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Endothelium, Vascular / drug effects
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Endothelium, Vascular / metabolism*
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Enzyme Inhibitors / pharmacology
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Humans
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Morpholines / pharmacology
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Neoplasm Proteins / metabolism
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Neoplasm Proteins / pharmacology
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Phosphatidylinositol 3-Kinases / drug effects
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Phosphatidylinositol 3-Kinases / metabolism*
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Phosphoinositide-3 Kinase Inhibitors
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Phosphorylation
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Protein Serine-Threonine Kinases*
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Proteins / pharmacology*
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Proto-Oncogene Proteins / drug effects
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Proto-Oncogene Proteins / metabolism*
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Proto-Oncogene Proteins c-akt
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Receptor, TIE-2
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Signal Transduction
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Umbilical Veins / cytology
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Wortmannin
Substances
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Androstadienes
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Angiopoietin-2
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Chromones
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Culture Media, Serum-Free
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Enzyme Inhibitors
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MEN1 protein, human
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Morpholines
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Neoplasm Proteins
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Phosphoinositide-3 Kinase Inhibitors
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Proteins
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Proto-Oncogene Proteins
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2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
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Receptor, TIE-2
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AKT1 protein, human
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-akt
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Wortmannin