Correlation of the Production of Plasminogen Activator with Tumor Metastasis in B16 Mouse Melanoma Cell Lines¹

The correlation between the production of plasminogen activator (PA) of tumors and their metastatic potential was studied. B16 melanoma cells and “B16 mets” cells (harvested from the pulmonary metastatic nodules of C57BL/6J mice bearing B16 isografts) were examined with respect to their fibrinolytic activity (FA) in tissue culture. B16 mets cells had a significantly higher FA than did B16 cells. F1 (a B16 subline with a lower incidence of metastasis) and F10 (a highly metastatic B16 subline) were also studied. F10 cells produced more FA than did F1 cells. The difference between the FA's of these tumors was due to differences in their PA production. Significant differences in PA production between F1 and F10 could be consistently observed when 10⁵ or more cells were cultured for at least 24 hr. The cell-free supernatants harvested from 72-hr cultures of F10 cells had a higher FA than those harvested from F1 cultures. Results suggest that a quantitative difference in PA production between these 2 melanoma sublines does exist and that it may contribute to their different metastatic potential.