Interaction of human tumor cells with human platelets and the coagulation system

This paper reports studies on the interaction between human platelets, the plasma coagulation system, and two human tumor cell lines grown in tissue culture: Melanoma and breast adenocarcinoma. The interaction was monitored through the use of ¹²⁵I-labelled fibrinogen, which measures both thrombin activity generated by cell-plasma interaction and fibrin/fibrinogen binding to platelets and tumor cells. Each tumor cell line activates both the platelets and the coagulation system simultaneously resulting in the generation of thrombin or thrombin-like activity. The melanoma cells activate the coagulation system through 'the extrinsic pathway' with a tissue factor-like effect on factor VII, but the breast tumor seems to activate factor X directly. Both tumor cell lines activate platelets to 'make available' a platelet-derived procoagulant material necessary for the conversion of prothrombin to thrombin. The tumor-derived procoagulant activity and the pletelet aggregating potential of cells do not seem to be inter-related, and they are not specific to malignant cells.