For example, a single effort to give sharks tumors in a laboratory failed. But Ostrander points out that several different efforts to give tumors in the lab to English sole also failed, even though that fish has high cancer rates in habitats such as Puget Sound. Shark cartilage advocates also seized upon scientists' efforts to suppress angiogenesis, a tumor's ability to encourage growth of new blood vessels. When researchers realized that angiogenesis allows tumors to obtain much of the raw material they need to fuel their own abnormal growth, they began to look for factors in the body that could stop angiogenesis. One of the first places they looked was cartilage, a tissue with relatively few blood vessels.
Sharks are animals with a great deal of cartilage.
All of those factors left sharks vulnerable to myth and misperception, Ostrander explains, but none of them changes the fact that sharks can get cancer or suggests that they must have a key to beating cancer. And chicken cartilage, human cartilage, and all other kinds of tissue have anti-angiogenic factors in them.