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Regulation of endothelial cell differentiation and transformation by H-Ras
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Genetics and Pathology.
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2003 (English)In: Experimental Cell Research, ISSN 0014-4827, E-ISSN 1090-2422, Vol. 291, no 1, 189-200 p.Article in journal (Refereed) Published
Abstract [en]

Angiogenesis is regulated by growth factors which activate tyrosine kinase receptors leading to the activation of a number of intracellular signaling pathways. The specific function of H-Ras during FGF-2 stimulated endothelial cell differentiation, defined as invasive growth and formation of branching networks in fibrin gels, was investigated by using conditionally immortalized endothelial cell lines induced to express H-Ras mutants. Expression of inhibitory N17Ras did not impair differentiation in response to FGF-2 and TNF-alpha. The farnesyltransferase inhibitor FTI-277 inhibited farnesylation of Ras but did not inhibit differentiation of human microvascular endothelial cells or mouse brain endothelial cells. In contrast, activated V12Ras inhibited endothelial cell differentiation and cells displayed a transformed phenotype with an increased rate of proliferation and loss of contact inhibited growth. Furthermore, V12Ras expressing endothelial cells grew as solid tumors when injected subcutaneously into mice. Our data suggest that, in endothelial cells, H-Ras activity is not required for differentiation. However, this activity must be tightly regulated as aberrant activity can disturb the ability of endothelial cells to undergo differentiation.

Place, publisher, year, edition, pages
2003. Vol. 291, no 1, 189-200 p.
Keyword [en]
Endothelium, Differentiation, Transformation, Proliferation, Ras, FGF-2, Angiogenesis, Tumor, Angiosarcoma
National Category
Medical and Health Sciences
URN: urn:nbn:se:uu:diva-91472DOI: 10.1016/S0014-4827(03)00347-1PubMedID: 14597419OAI: oai:DiVA.org:uu-91472DiVA: diva2:164211
Available from: 2004-03-09 Created: 2004-03-09 Last updated: 2011-06-28Bibliographically approved
In thesis
1. Molecular Mechanisms in Endothelial Cell Differentiation
Open this publication in new window or tab >>Molecular Mechanisms in Endothelial Cell Differentiation
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Angiogenesis is the formation of new blood vessels from the pre-existing blood vessels. Blood vessels are composed of endothelial cells and supporting musculature. Angiogenesis is regulated by numerous soluble ligands and by cell-matrix interactions. We have studied the molecular mechanisms in fibroblast growth factor-2 (FGF-2) and vascular endothelial growth factor-A (VEGF-A)-induced angiogenesis using immortalized endothelial cell lines in different angiogenesis assays.

The role of the signaling protein H-Ras in FGF-2-induced in vitro angiogenesis was studied by expressing mutated versions of H-Ras in immortalized mouse brain endothelial cells using a tetracycline-regulated expression system. In vitro angiogenesis was analyzed as the ability of cells to invade a fibrin matrix and form branching structures in response to a combination of FGF-2 and tumor necrosis factor-α (TNF-α). Inhibition of H-Ras through the expression of dominant negative (S17N) H-Ras or pharmacological inactivation of H-Ras with a farnesyl transferase inhibitor, did not inhibit growth factor-induced invasion. In contrast, expression of constitutively active (G12V) H-Ras caused cells to adopt a transformed phenotype which inhibited invasive growth and cells formed solid tumors when injected in nude mice. These studies suggest that H-Ras activity is not required for differentiation but its activity must be tightly regulated as aberrant activity impairs endothelial cell differentiation.

In order to screen for both known and novel genes that regulate angiogenesis we used large scale microarray analysis. In VEGF-A-stimulated telomerase immortalized human microvascular endothelial cells undergoing invasive growth in fibrin gels, or forming cord-like structures on collagen, we identified several genes that were differentially expressed. Some of these are known to be important for endothelial cell functions and angiogenesis while others have no previous connection with endothelial cell function or were transcripts with no assigned function. Further analysis of these proteins will aid in elucidating the molecular mechanisms underlying endothelial cell differentiation.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2004. 34 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 0282-7476 ; 1328
Pathology, angiogenesis, FGF-2, VEGF-A, signal transduction, in vitro angiogenesis assay, immortalized brain endothelial cells, H-Ras, tetracycline-regulated gene expression, microarray, telomerase immortalized human microvascular endothelial cells, differentiation, Patologi
National Category
Cell and Molecular Biology
urn:nbn:se:uu:diva-4059 (URN)91-554-5900-5 (ISBN)
Public defence
2004-04-02, Rudbeckssalen, Rudbecklaboratoriet, Dag Hammarskjölds väg 20, Uppsala, 09:15
Available from: 2004-03-09 Created: 2004-03-09Bibliographically approved

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Gerwins, Pär
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Department of Genetics and PathologyDepartment of Oncology, Radiology and Clinical ImmunologyDepartment of Medical Biochemistry and Microbiology
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