Cartilage-derived anti-tumor factor (CATF) - Partial purification and correlation of inhibitory activity against tumor growth with anti-angiogenic activity

Cartilage-derived anti-tumor factor (CATF) inhibits the proliferation and DNA synthesis of bovine pulmonary artery endothelial (BPAE) cells in culture (Takigawa, M. et al. Cell. Biol. Inn. Rep., 9, 619-625, 1985). In the present study, we partially purified CATF by monitoring inhibition of DNA synthesis in BPAE cells and tested the effects of the purified materials on the growth of solid tumors and tumor-induced angiogenesis. Crude CATF (CATF_20-300k), the fraction of 20 k to 300 k daltons, separated by ultrafiltration was further separated into three fractions by ultrafiltration. The fraction of 100 k to 300 k daltons (CATF_100-300k) caused slightly more inhibition than CATF_20-300k of DNA synthesis in BPAE cells. On the other hand, the fraction of 20 k to 50 k daltons had only a slight effect, and the fraction of 50 k to 100 k had even less effect on DNA synthesis in BPAE cells. CATF_100-300k caused slightly more inhibition than CATF_20-300k of the growth of solid tumors of B16 melanoma, while the fraction of 20 k to 100 k daltons did not inhibit the growth of tumors at all. CATF_100-300k also inhibited B16 melanoma-induced angiogenesis in chick embryo chorioallantoic membranes (CAM), whereas the fraction of 20 k to 100 k daltons had little effect on the angiogenesis. CATF_100-300k was further purified by DEAE-Sepharose CL-6B chromatography. The main peak with activity on DNA synthesis in BPAE cells was eluted with 0.3 to 0.35 M NaCl at pH 8.0. The activity of this peak on DNA synthesis in BPAE cells was about 70 fold that of CATF_100-300k. The purified CATF also inhibited the growth of B16 melanoma and B16 melanoma-induced angiogenesis in CAM. On the other hand, the inactive fraction on DNA synthesis in BPAE cells obtained by DEAE-Sepharose chromatography was also inactive in inhibiting the growth of B16 melanoma and B16 melanoma-induced angiogenesis in CAM. These findings strongly suggest that CATF is an anionic macromolecule(s) and has anti-angiogenic activity, thereby inhibiting the growth of solid tumors.