The major structural components of cartilage include several types of the protein collagen and several types of glycosaminoglycans, which are polysaccharides.[19,29,30,39,48,54,55]Chondroitin sulfate is the major glycosaminoglycan in cartilage.[39,54] Although there is no evidence that the collagens in cartilage, or their breakdown products, can inhibit angiogenesis, there is evidence that shark cartilage contains at least one angiogenesis inhibitor that has a glycosaminoglycan component (refer to the Laboratory/Animal/Preclinical Studies section of this summary for more information). Other data indicate that most of the antiangiogenic activity in cartilage is not associated with the major structural components.[26,30,48]
Some glycosaminoglycans in cartilage reportedly have anti-inflammatory and immune-system -stimulating properties,[1,2,14,16,56,57] and it has been suggested that either they or some of their breakdown products are toxic to tumor cells.[2,3,24] Thus, the antitumor potential of cartilage may involve more than one mechanism of action.
Cartilage products are sold commercially in the United States as dietary supplements. More than 40 different brand names of shark cartilage alone are available to consumers. In the United States, dietary supplements are regulated as foods, not drugs. Therefore, premarket evaluation and approval by the U.S. Food and Drug Administration (FDA) are not required unless specific disease prevention or treatment claims are made. Because manufacturers of cartilage products are not required to show evidence of anticancer or other biologic effects, it is unclear whether any of these products have therapeutic potential. In addition, individual products may vary considerably from lot to lot because standard manufacturing processes do not exist, and binding agents and fillers may be added during production. The FDA has not approved the use of cartilage as a treatment for people with cancer or any other medical condition. The FDA is notifying consumers of a refund program for purchasers of Lane Labs-USA, Inc.'s shark cartilage product, BeneFin. Consumers are eligible for a partial refund of the purchase price and any shipping and handling costs if this product was purchased between September 22, 1999 and July 12, 2004.