Angiogenesis is the process of developing new blood vessels. Angiogenesis is important in the normal development of the embryo and fetus. It also appears important to tumor formation. Certain proteins, including angiostatin and endostatin, secreted by tumors work (at least in mice) by interfering with the blood supply tumors need. Interfering with formation of blood supply to tumors is an area of cancer research and is the basis of the alternative treatment of cancer with shark and bovine cartilage. Development of new blood vessel channels in the adult is called neoangiogenesis.