Faculty Bibliography

A protein that stimulates the production of plasminogen activator and latent collagenase in cultured bovine capillary endothelial cells has been purified 10(6)-fold from term human placenta by using a combination of heparin affinity chromatography, ion-exchange chromatography, and gel chromatography. The purified molecule has a molecular weight of 18,700 as determined by NaDodSO4/PAGE under both reducing and nonreducing conditions. The purified molecule stimulates the production of plasminogen activator and latent collagenase in a dose-dependent manner between 0.1 and 10 ng of protein/ml. The purified protein also stimulates DNA synthesis and chemotaxis in capillary endothelial cells in the same concentration range. Thus, this molecule has all of the properties predicted for an angiogenic factor

Sheep pituitary glands contain a protein that stimulates plasminogen activator (PA) activity 3- to 20-fold in serum-free cultures of T47D, MTW9/PL, and SC115 breast tumor cells. This protein was found to be similar to basic fibroblast growth factor (bFGF) in size, cationic nature, and affinity for heparin. Purified human placental bFGF, a homologue of human and bovine pituitary bFGF, was effective in stimulating mammary tumor cell PA at a concentration of 1 ng/ml. Antibodies to placental bFGF blocked the PA stimulatory activity of sheep pituitary extracts. Because of these properties, the active protein in sheep pituitary glands was identified as bFGF. This represents another function of bFGF, indicating that its spectrum of target cells is wider than previously thought. Because of previously established correlations between PA production in vitro and tumor growth in vivo, we suggest that bFGF may contribute to the growth of breast carcinomas in vivo. Other types of carcinomas may also be affected by bFGF

To understand the role of proteinases in tumor invasion, the effects of inhibitors of metallo-, serine-, and cysteine-proteinases on this process were studied using 125I-iododeoxyuridine-labeled B16/BL6 cells grown on human amnion basement membrane. Cellular invasion was quantitated by measuring the radioactivity associated with the amniotic membrane after the B16/BL6 cells on the basement membrane were removed by lysis followed by scraping. The results obtained with proteinase inhibitors showed that inhibitors of collagenase and plasmin prevented invasion of the amnion. Tissue invasion was also blocked by antiurokinase antibodies. On the contrary, cysteine-proteinase inhibitors and anti-tissue plasminogen activator antiserum were ineffective. Mersalyl, a compound known to activate collagenase, stimulated invasion under conditions where plasmin formation or activity were inhibited. Evidence for the role of a plasminogen activator-plasmin-collagenase activation cascade in B16 invasion is provided