Anchorage independent growth and plasminogen activator production by bovine endothelial cells.

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Abstract
Endothelial cells obtained from the aortae of 1-2 day old calves were cloned at high efficiency using fibrin-coated dishes. Primary cultures and clones derived from them produced high fibrinolytic activity when grown on 125I-fibrin-coated dishes which was 90% dependent upon the presence of plasminogen. High plasminogen-dependent proteolytic activity was also demonstrated in endothelial cell lysates and in the culture medium of the cells. The production and secretion of the plasminogen activator(s) increased during the log phase of cell growth and reached a maximum level at confluence. These endothelial cells exhibited morphological phenotypes comparable to those of transformed cells when grown in the presence of acid-treated fetal calf, dog, or human serum. They demonstrated anchorage independent growth and large colonies were formed in semisolid media. Spontaneous neoplastic transformation of these cells was excluded by karyotypic analysis, lack of tumorigenicity in athymic nude mice and limited lifespan in culture. Cell clones isolated from colonies grown in agarose demonstrated the same growth characteristics and proteolytic activity as before plating in agarose. High fibrinolytic activity, morphological changes in the appropriate serum and growth in semisolid media may therefore be indicative of the migratory and/or invasive capacity of nontransformed endothelial cells as well as tumor cells. [The loss of anchorage dependence of growth has been considered as evidence for neoplastic transformation.].