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Shark Cartilage ResearchResearch Abstract:
Shark Cartilage Contains Inhibitors of Tumor Angiogenesis
Inhibition of Tumor Angiogenesis Mediated by CartilageINHIBITION OF TUMOR ANGIOGENESIS MEDIATED
BY CARTILAGE*
By Henry Brem and Judah Folkman(From the Department of Surgery, Children's Hospital Medical Center, Harvard Medical School, Boston, Massachusetts 02115)
We have previously suggested that solid tumor growth is not continuous, but may be separated into two stages, avascular and vascular (1, 2). In the avascular phase, spheroidal tumors cannot generally exceed a diameter of 1-2 mm or a population of more than 101, cells (3, 4). Further growth occurs after new capillaries have been elicited from the host, and have penetrated the tumor.
Tumors elicit these new capillaries from the host by releasing a diffusible material, which we have termed tumor-angiogenesis-factor (TAP),' which is mitogenic to capillary endothelial cells (5-8).
Under the usual conditions of transplanting experimental tumors, the avascular phase is brief; i.e. 3-5 days (5). However, under special conditions, the avascular phase can be prolonged and tumors then become dormant. For example, when tumors are suspended in the anterior chamber of the rabbit eye, new vessels cannot reach them, and the tumors stop growing at about I mm diameter, although they remain viable (3).
We have suggested that if a means could be found to inhibit TAF, or block its stimulatory effect upon capillaries, tumors might be held in the avascular phase (9,10). We now show that cartilage from newborn rabbits strongly inhibits capillary proliferation induced by tumors. The data suggests that this inhibition may be mediated by a diffusible factor, thereby preventing these tumors from progressing to the vascular phase.
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