Adhesion molecules in the vascular cell cross-talk

In the context of the vascular system, cell-cell adhesion is of paramount importance, as demonstrated by the fact that the inhibition of this process during embryogenesis is usually incompatible with normal development and often leads to death. Indeed, interendothelial contacts not only contribute to preserving the structure of the whole vascular tree, they also play a key role in regulating the exchanges of fluids, solutes and cells between the circulation and the peripheral tissues. This implies that the vascular cell-cell junctions are by no means static structures that simply link adjacent cells to each other; instead, they are highly dynamic in order to ensure a rapid response of the vascular system to microenvironmental stimuli. This chapter will provide an overview of the structural organization and of the molecules involved in the assembly and function of the cell-cell junctions in the vascular network. Based on the essential role of intercellular adhesion in various steps of the angiogenic process, it is conceivable that similar mechanisms are involved in tumor-associated neovascularization. Nevertheless, a clear definition of the molecular mechanisms that link interendothelial junctions to the formation of tumor vessels is still elusive. Progress in this field will have a profound impact on the design of innovative therapeutic strategies aimed at interfering with tumor angiogenesis and metastasis.