348484 Physiological Levels of Blood Coagulation Factors IX and X Control Coagulation Kinetics in an in Vitro Model of Circulating Tissue Factor

Monday, November 4, 2013
Grand Ballroom B (Hilton)
Ayesha Khader1, Garth Tormoen2, Andras Gruber3 and Owen J T McCarty3, (1)College of Engineering, Oregon State University, Corvallis, OR, (2)Oregon Health and Science University, Portland, OR, (3)Oregon Health and Science University

Thrombosis significantly contributes to cancer morbidity and mortality. In vitro, cancer cell lines have the ability to activate blood coagulation through the tissue factor (TF) pathway of the coagulation cascade. The kinetics of coagulation activation correlate strongly with the linear separation of these cells suggesting that diffusion transport of coagulation factors to and from the cancer cells is rate-limiting. However, circulating TF antigen level alone has failed to predict thrombosis in patients with cancer. We hypothesize that coagulation factor levels regulate the kinetics of circulating TF-induced thrombosis. Coagulation kinetics were measured as a function of individual coagulation factor levels and TF particle concentration. Clotting times increased when pooled plasma was mixed at or above a ratio of 4:6 with PBS. Clotting times increased when pooled plasma was mixed at or above a ratio of 8:2 with factor VII-depleted plasma, 7:3 with factor IX- or factor X-depleted plasmas, or 2:8 with factor II-, V- or VIII-depleted plasmas. Addition of coagulation factors VII, X, IX, V and II to depleted plasmas shortened clotting and enzyme initiation times, and increased enzyme generation rates in a concentration-dependent manner. Only additions of factors IX and X from low-normal to high-normal levels shortened clotting times and increased enzyme generation rates. Our results demonstrate that coagulation kinetics for TF particles are controlled by factor IX and X levels within the normal physiological range. We hypothesize that individual patient factor IX and X levels may be prognostic for susceptibility to circulating TF-induced thrombosis.

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