Fig. 1

Unique structure of tumor vasculature. The tumor vasculature is identified by several irregular characteristics: they are leaky, fragile with many holes and tears, and have chaotic blood flow. These structural differences in the tumor endothelial cells reflect a fundamental change in endothelial cell phenotype when in the presence of tumor secreted factors such as: VEGF, TGF-B, IL-4, IL-10, FGF, and many other cytokines/growth factors. This change in phenotype can be characterized by the upregulated expression of several related angiogenesis markers that have relatively low expression on healthy endothelium in vivo