Tumor blood vessels, a difficult hurdle for infiltrating leukocytes.

In spite of a gradual improvement of its therapy, cancer is still a deadly disease for millions of patients. Immunotherapy is one of promising treatment strategies, but several mechanisms counteract the development of a proper anti-tumor immune response and the formation of an effective inflammatory infiltrate. One of the difficult hurdles is the hampered recruitment of leukocytes from the blood into the tumor site. It has been demonstrated that tumor cells evolved mechanisms to escape immunity, based on down regulation of endothelial adhesion molecules. This paper reviews the endothelial cell adhesion molecules that mediate leukocyte recruitment and the regulation of them during tumor development. In addition, an overview will be given of the translational development and clinical application of the specific composition of adhesion molecules on tumor endothelium, in diagnosis and therapy.