Apoptosis is involved in many biologic processes and occurs in tumor cells especially during chemotherapy, radiation and hormonal therapy. The same conditions are also associated with an increased risk for thrombosis. Thus, the relationship between apoptosis and thrombogenicity was studied in various human tumor cells and benign cells, including primary human umbilical endothelial cells, acute myelogenous leukemia cells HL-60, acute promyelocytic leukemia cells NB4, benign breast epithelial cells MCF-10A, breast carcinoma cells MCF-7 and MDA-MB-231, lung squamous carcinoma cells CALU-1. Methods for apoptosis induction include serum deprivation, Fas ligation with anti-Fas antibody and addition of camptothecin. After the cells were stained with fluorescein isothiocyanate-conjugated Annexin V and propidium iodide, the percentage apoptosis was calculated by cell counting to derive the apoptosis index. Using the Russel's viper venom-defibrinated plasma as substrate, the thrombin generated by the cells was assayed with chromogenic substrate S-2238. The regression analysis showed a statistical correlation between apoptosis index and thrombin generation (P<0.001). Analysis of the coagulant activity leading to thrombin generation revealed that tissue factor (TF) was activated. The thrombin generation was neutralized by either anti-TF antibody or by tissue factor pathway inhibitor in a dose-responsive manner. The activation of TF was also significantly correlated with apoptosis index (P<0.005). The TF activation was achieved by phosphatidylserine (PS) exteriorized on the cell membrane during apoptosis. It was inhibited by the addition of Annexin V, which blocks PS on the membrane of apoptotic cells. These results indicate that apoptotic cells are thrombogenic and that there is a direct correlation between apoptosis and the thrombogenecity of these cells.
|Original language||English (US)|
|Issue number||11 PART I|
|Publication status||Published - Dec 1 2000|
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