Platelet-aggregating activities of metastasizing tumor cells. IV. Effects of cell surface modification on thrombin generation, platelet aggregation and subsequent lung colonization.

Platelet-aggregating and thrombin-generating activities of B16 and 3LL cells were inhibited by trypsin, phospholipase A2 and by heating, but not by neuraminidase. It was confirmed that the platelet aggregation effect of these cells is due to thrombin generation. The lung-colonizing ability of treated cells injected intravenously was directly proportional to the ability to generate thrombin and to aggregate platelets. These results suggest that B16 and 3LL cells aggregate platelets through thrombin generation probably via their heat-labile surface lipoprotein, and that emboli composed of platelets, fibrin, and tumor cells may aid further the metastatic process.