Tissue factor-dependent activation of platelets by cells and microvesicles of SK-OS-10 human osteogenic sarcoma cell line.

Cultured SK-OS-10 cells (human osteogenic sarcoma metastatic to lung) shed microvesicles (dia. 300-1000 nm) that contained procoagulant and proaggregatory activities inhibitable by hirudin, by anti-tissue factor antibody and by phospholipase A2. These results show that SK-OS-10 cells belong to a group including U87MG human glioblastoma and HL-60 promyelocytic leukemia in which these activities are due to a thrombin-dependent mechanism arising from the presence of tissue factor on the surface of the tumor cells and their shed microvesicles.