Angiogenesis: the physiological process through which new blood vessels form. Angiogenesis is a normal and vital process in growth and development. In adults, this process is important mainly for wound healing and pregnancy.
This process is also a vital part of tumor growth and survival. This process is an important step that allows tumor expansion and invasion. Without angiogenesis, tumors have no way of getting nutrient and removing waste. However by sending signals known as angiogenic factors, tumor cells can stimulate the growth of hundreds of new capillaries from nearby blood vessels to bring nutrients and oxygen. The more blood vessels the tumor cells connect to, the bigger it grows and the more places they can travel to. Thus, the once benign tumor becomes cancer.
In modern cancer treatment, there are drugs on the market that prevent the angiogenesis at various stages of the process. These drugs interfere with angiogenesis by blocking blood vessel growth factor, blocking signals within the cell or affecting the signals between cells. Some of these drugs block vascular endothelial growth factor (VEGF) from attaching to the receptors on the cells that line the blood vessels. This stops the blood vessels from growing. A drug that blocks VEGF is bevacizumab (Avastin). It is also a monoclonal antibody.
Other drugs stop the VEGF receptors from sending growth signals into the blood vessel cells. These treatments are also called cancer growth blockers or tyrosine kinase inhibitors (TKIs). The last kind of drugs act on the chemicals that cells use to signal to each other to grow. This can block the formation of blood vessels. Drugs that works in this way include thalidomide and lenalidomide (Revlimid).