Angiogenic and antiangiogenic chemokines.

Chemokines are a family of vertebrate-specific, small-secreted molecules that were originally identified as mediators of leukocyte migration and tissue positioning during the immune response. Subsequently, chemokines were discovered to control movement also of endothelial cells and other cell types in many different contexts. The human chemokine system comprises about 50 chemokines and more than 20 receptors belonging to the seven-transmembrane receptor family. In the present chapter, we review the literature supporting a role for chemokines in angiogenesis and lymphangiogenesis. We highlight that chemokines exert both pro- and antiangiogenic roles either by acting directly on endothelial cells or by recruiting leukocytes that, in turn, secrete angiogenic mediators. This latter mode of action is possibly the most relevant in tumor angiogenesis. Finally, we explore the angiogenic properties of nonchemokine chemoattractant molecules.