Jones P A, Laug W E, Benedict W F
Cell. 1975 Oct;6(2):245-52. doi: 10.1016/0092-8674(75)90015-x.
Seven clones were isolated from the HT1080 human fibrosarcoma cell line using a fibrinagarose overlay technique. Three of these clones induced lysis of the fibrin overlay, whereas four did not. The extracellular and intracellular levels of protease were then measured using 125I-fibrin plates incubated with acid-treated human serum. The extracellular protease can be directly assayed in the medium from cells incubated with 10% fetal calf serum. Although there were large differences in the amounts of protease secreted by these two sets of clones, the intracellular levels of protease were similar. No significant differences were found between the abilities of the cells to grow in soft agar or as tumors in immunosuppressed hamsters. However, cells grown from tumors derived from all the low secretors of protease showed an increase in the amount of protease secreted. It appeared, therefore, that the secretion of protease might be selected for or induced during tumor growth. Further detailed studies with one of the low secreting clones (clone E) suggested an inductive rather than a selective mechanism for this increase in extracellular plasminogen activator.
使用纤维蛋白琼脂糖覆盖技术从HT1080人纤维肉瘤细胞系中分离出七个克隆。其中三个克隆诱导纤维蛋白覆盖物溶解，而四个则不能。然后使用与酸处理的人血清一起孵育的125I-纤维蛋白平板测量蛋白酶的细胞外和细胞内水平。细胞外蛋白酶可直接在与10%胎牛血清一起孵育的细胞培养基中测定。尽管这两组克隆分泌的蛋白酶量存在很大差异，但蛋白酶的细胞内水平相似。在软琼脂中生长或在免疫抑制仓鼠中形成肿瘤的细胞能力之间未发现显著差异。然而，从所有低蛋白酶分泌者衍生的肿瘤中生长的细胞显示出分泌的蛋白酶量增加。因此，似乎蛋白酶的分泌可能在肿瘤生长过程中被选择或诱导。对其中一个低分泌克隆（克隆E）的进一步详细研究表明，细胞外纤溶酶原激活剂增加的机制是诱导性的而非选择性的。
