Anti-tumor substances in cartilaginous tissue

Anti-tumor substances were extracted from fetal bovine costal cartilage with 1 M guanidine hydrochloride (GuHCI) and partially purified by ultrafiltration through Amicon XM-300, YM-100 and YM-30 membranes, yielding four different molecular weight fractions (30 kD >, 30-100 kD, 100-300 kD, 300 kD <). Their anti-tumor activity was then assessed mainly by in vivo assay with B16 melanoma cells inoculated into BDF1 mice. Inhibitory activity against tumor angiogenesis was determined by using chick embryo chorioallantoic membranes (CAMs) and inhibitory activity against production of plasminogen activators (PAs) by B16 melanoma cells was assayed by the microplate immunocapture assay in vitro. The 30 kD > fraction showed little inhibitory activity against either tumor growth or tumor metastasis, but displayed strong anti-angiogenic activity on CAMs. The 30 kD > fraction, however, did not exhibit any inhibitory activity against PA production. In contrast, the 30-100 kD fraction contained strong inhibitory activity against PA production as well, in particular urokinase-type PA (uPA) production and showed the strongest inhibitory activity against tumor growth and tumor metastasis of all fractions, but little anti-angiogenic activity on CAMs. The other fractions did not show any inhibitory activity against tumor growth, tumor metastasis, or PA production. These findings suggest that the 30-100 kD fraction contain a cartilage-derived plasminogen activator inhibitor (CD-PAI) that appears to be the main anti-tumor substance in cartilaginous tissue and to play an important role in the anti-tumor mechanism of cartilaginous tissue.