Characterisation of rat tumour cell hybrids: procoagulant and fibrinolytic activities.

The formation of lung colonies after i.v. injection of highly metastatic rat mammary adenocarcinoma cells (MAT 13762) was greatly reduced by concurrent treatment of rats with heparin. The procoagulant activity (PCA) of these cells, and of a non-metastatic adenocarcinoma (DMBA-8) has therefore been measured. These have been compared with PCA expressed by MAT 13762 cell derivatives including a non-metastatic hybrid clone (MAT 13762 X DMBA-8), its metastatic revertant, and clones selected in vivo from lung metastases. Potent PCA was expressed on intact MAT 13762 cells and in their spent culture media, the latter being sedimentable and associated with shed membrane vesicles. Cell-derived PCA, unlike thromboplastin, was equally effective in factor VII-deficient and normal bovine plasma. There were, however, no major differences in the expression of PCA (either cell-associated or shed) between the metastatic and non-metastatic cell types studied. Plasminogen activator (PA) production by these cells has also been measured. The results are discussed in the context of the possible role of fibrin formation and fibrinolysis in the metastatic process.