Cartilage

General Information about Shark CartilageBovine (cow) cartilage and shark cartilage have been investigated as treatments for people with cancer, psoriasis,  arthritis, and a number of other medical conditions for more than 30 years.[1-13] Reviewed in [14-20] At least some of the interest in cartilage as a treatment for people with cancer arose from the mistaken belief that sharks, whose skeletons are made primarily of cartilage, are not affected by this disease. Reviewed in [16,21,22] Although reports of malignant tumors in sharks are rare, a variety of cancers have been detected in these animals. Reviewed in [21-24]
Nonetheless, several substances that have antitumor activity have been identified in cartilage.[25-47] Reviewed in [2-4,7,15-20,46,48-50] More than half a dozen clinical studies of cartilage as a treatment for people with cancer have already been conducted.[2-4,7-9,50,51] Reviewed in [6,15-19] Additional clinical studies, MDA-ID-99303 and AETERNA-AE-MM-00-02 have been completed. Reviewed in [6,15,51]

The absence of blood vessels in cartilage led to the hypothesis that cartilage cells (also known as chondrocytes) produce one or more substances that inhibit blood vessel formation. Reviewed in [28-31,36,37,49] The formation of new blood vessels or angiogenesis is necessary for tumors to grow larger than a few millimeters in diameter (i.e., larger than approximately 100,000 to 1,000,000 cells) because tumors, like normal tissues, must obtain most of their oxygen and nutrients from blood. Reviewed in [34,35,42,52-55] A developing tumor, therefore, cannot continue to grow unless it establishes connections to the circulatory system of its host. It has been reported that tumors can
initiate the process of angiogenesis when they contain as few as 100 cells.[54] Inhibition of angiogenesis at this early stage may, in some instances, lead to complete tumor regression.[54] The possibility that cartilage could be a source of one or more types of angiogenesis inhibitors for the treatment of cancer has prompted much research.

The major structural components of cartilage include several types of the protein collagen and several types of glycosaminoglycans, which are polysaccharides. Reviewed in [20,30,31,40,49,55,56] Chondroitin sulfate is the major glycosaminoglycan in cartilage. Reviewed in [40,55] 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).[47] Other data indicate that most of the antiangiogenic activity in cartilage is not associated with the major structural components. Reviewed in [27,31,49]

Some glycosaminoglycans in cartilage reportedly have anti-inflammatory and immune-system -stimulating properties,[57,58] Reviewed in [1,2,14,16] and it has been suggested that either they or some of their breakdown products are toxic to tumor cells.[25] Reviewed in [2,3] Thus, the antitumor potential of cartilage may involve more than one mechanism of action.