Angiogenesis is controlled by certain bodily chemicals.
These chemicals stimulate cells to repair damaged blood vessels or to form new ones. Other chemicals, called angiogenesis inhibitors, signal the process to stop. Angiogenesis plays an important role in the growth and spread of cancer. This allows the cells to grow, invade nearby tissue, spread to other parts of the body and form new colonies of cancer cells. Because cancer cannot grow or spread without the formation of new blood vessels, scientists are trying to find ways to stop angiogenesis.