[Blood coagulation and metastasis]

To elucidate the correlation of platelet aggregating activity of tumor cells and their metastatic potentials, we established a highly and a low metastatic clone with a different platelet aggregating activity from murine fibrosarcoma (Meth A). The parental Meth A cell and its low metastatic clone (ML-01) showed a typical platelet aggregation pattern with a certain lag time, while a highly metastatic clone (MH-02) showed a biphasic aggregation with no lag time in which the first reversible aggregation was caused by ADP released from MH-02, since it was eliminated by apyrase treatment. The highly metastatic potential, however, was not solely due to the platelet aggregating activity because the administration of PGI2-analogue TEI-8153A did not completely inhibit their pulmonary metastasis. In fact, MH-02 attached more preferentially to type IV collagen or endothelial cell than ML-01 in vitro. These results suggest that MH-02 exerts its high metastatic property through the mechanisms involving multiple factors such as the increased platelet aggregating potential or enhanced adhesiveness.