[Endothelium, angiogenesis and metastasis]

The turnover of endothelium in a normal adult male is very low. Angiogenesis, the formation of new blood vessels, involves a high turnover of endothelial cells. It takes place during embryogenesis, ovulation and many pathological conditions, e.g. tumor growth. Soluble polypeptide growth factors for endothelial cells have been biochemically characterized. They are able to induce angiogenesis in vivo. Inhibitors of angiogenesis can inhibit tumor vascularization and the growth of solid tumors in mice. Tumor metastasis involves the migration of malignant tumor cells through endothelial cells. The organ and tissue specificity of these and other invasive migrations through vascular endothelium may be related to the heterogeneity and organ specificity of endothelial cells.