To survive, tumors need blood supply to provide them with nutrients and oxygen. To get that supply, cancer cells stimulate new blood vessel growth -- a process called tumor angiogenesis.Many attempts have been made to inhibit this process as a means to choke off tumors. But tumor angiogenesis can be sloppy, resulting in immature and malformed blood vessels. Since anti-cancer drugs are carried to tumors by the bloodstream, abnormal blood vessel development also hampers delivery.
