Endothelial cadherins and tumor angiogenesis.

Adherens junctions and more specifically cadherins play an important role in endothelial cell integrity and growth and, in general, in vascular morphogenesis. Besides their adhesive properties, cadherins may act by transferring intracellular signals through interaction with a complex network of cytoskeletal and signaling molecules. Cadherins may signal in different ways: through direct activation of signaling pathways, through interaction with cell-specific growth factor receptors or by controlling beta-catenin and/or other transcription factors' translocation to the nucleus. Endothelial cells present different cadherins which may transfer specific signals and exert distinct functional roles. VE-cadherin is endothelial-specific and the major constituent of adherens junctions. This protein is able to protect endothelial cells from apoptosis and contributes to contact inhibition of endothelial cell growth. N-cadherin is also abundantly expressed in the endothelium and may be important in modulating VE-cadherin expression. T cadherin, R-cadherin and VE-cadherin 2 were found in specific regions of the vascular tree but their role in vascular development or angiogenesis is still unclear.