Tumor Endothelial Cell Abnormalities

In the 1970’s, anti-angiogenic therapy was realized as a potential strategy to shrink solid tumors. Since that time, many aspects of vascular biology have been investigated in attempts at understanding the mechanisms that regulate how blood vessels develop in health and disease. In the tumor microenvironment, factors such as hypoxia and acidosis impinge on normal endothelial cell (EC) function. Accordingly, the vascular structure in tumors is highly disorganized, vessels are of variable diameter, and there is vessel leakiness. Although these morphological changes in the tumor vasculature have been known for some time, it was only recently shown that tumor-associated EC are indeed distinct from normal EC at the molecular level. This chapter will discuss the abnormalities observed in the tumor endothelium.