Before the 1960s, cancer researchers believed that the blood supply reached tumors simply because pre-existing blood vessels dilated. But experiments have shown that angiogenesis—the growth of the new blood vessels—is necessary for cancerous tumors to keep growing and spreading. Research by William Li, MD, has shown that tumor cells secrete growth factors (VEGF, bFGF) that bind to endothelial cell receptors in the lining of blood vessels, which activate the growth of new capillaries (angiogenesis) in order to bring nutrients to the tumor. In addition, the tumor cells stop producing the enzyme PKG, an anti-VEGF or inhibitor. Much as with tumors, fat tissue is highly angiogenetic. Estimates are that one pound of excess fat may contain from 7 to 100 miles of capillaries. Anti-angiogenesis factors may, therefore, have a potentially positive impact on obesity. More tomorrow.