Angiogenesis and signal transduction in endothelial cells.

Endothelial cells receive multiple information from their environment that eventually leads them to progress along all the stages of the process of formation of new vessels. Angiogenic signals promote endothelial cell proliferation, increased resistance to apoptosis, changes in proteolytic balance, cytoskeletal reorganization, migration and, finally, differentiation and formation of a new vascular lumen. We aim to review herein the main signaling cascades that become activated in angiogenic endothelial cells as well as the opportunities of modulating angiogenesis through pharmacological interference with these signaling mechanisms. We will deal mainly with the mitogen-activated protein kinases pathway, which is very important in the transduction of proliferation signals; the phosphatidylinositol-3-kinase/protein kinase B signaling system, particularly essential for the survival of the angiogenic endothelium; the small GTPases involved in cytoskeletal reorganization and migration; and the kinases associated to focal adhesions which contribute to integrate the pathways from the two main sources of angiogenic signals, i.e. growth factors and the extracellular matrix.