Targeted therapies of cancer: Angiogenesis inhibition seems not enough

The therapeutic potential of targeting tumor endothelium to induce tumor regression is now widely recognized. Tumors obtain their blood supply by the formation of new vasculature and the incorporation of pre-existent vessels. Since anti-angiogenic therapy prevents formation of neovasculature, vessels in more matured stages are not affected by such therapies. Therefore, additional vascular targeting therapy, which aim at regression of existent tumor vasculature, seems an attractive approach to effectively deprive tumors from blood supply. In this review we present an overview of different strategies to target tumor endothelium. In addition, we discuss the pitfalls of anti-angiogenic therapies in clinical settings.