Microparticle-associated tissue factor activity, venous thromboembolism and mortality in pancreatic, gastric, colorectal and brain cancer patients.

BACKGROUND: Tissue factor (TF) expression by tumors contributes to tumor growth. Release of TF-positive microparticles (MPs) may contribute to venous thromboembolism (VTE). OBJECTIVES: To conduct a prospective cohort study to determine whether elevated MP-associated TF (MP-TF) activity is predictive of VTE and mortality in four cancer types. PATIENTS/METHODS: We determined MP-TF activity in pancreatic, gastric, colorectal and brain cancer patients. We used a chromogenic endpoint assay for all patients and also a chromogenic kinetic assay for patients with pancreatic and brain cancer. RESULTS: During follow-up, 12/60 (20%) pancreatic, 6/43 (14%) gastric, 12/126 (10%) colorectal and 19/119 (16%) brain cancer patients developed VTE; 46/60 (77%), 30/43 (70%), 47/126 (37%) and 67/119 (56%), respectively, died. MP-TF activity levels were highest in pancreatic cancer. We did not find a statistically significant association of MP-TF activity with the risk of VTE in any of the four cancer types by using two statistical methods. An association of MP-TF activity with the risk of mortality was detected in pancreatic cancer with the endpoint assay (hazard ratio [HR] 1.8 and 95% confidence interval [CI] 1.4-2.3 per doubling of activity, P < 0.001) and the kinetic assay (HR 1.2, 95% CI 1.1-1.4, P < 0.001); adjustment for type of treatment was not performed. In pancreatic cancer, MP-TF activity correlated with D-dimer level (endpoint assay, r = 0.51; chromogenic assay, r = 0.48), and a correlation between assays (r = 0.61) was found. CONCLUSION: MP-TF activity was not associated with future VTE in pancreatic, gastric, colorectal and brain cancer. However, we found a strong association of MP-TF activity with mortality in pancreatic cancer. MP-TF activity might be reflective of an aggressive pancreatic cancer phenotype.

Pre-analytical and analytical variables affecting the measurement of plasma-derived microparticle tissue factor activity.

INTRODUCTION: Elevated levels of tissue factor positive (TF(+)) microparticles (MPs) are observed in plasma from a variety of patients with an increased risk of thrombosis. We and others have described the measurement of TF activity in MPs isolated from plasma. The aim of this study was to investigate the effects of pre-analytical and analytical variables on TF activity of MPs isolated from blood of healthy volunteers either untreated or treated ex vivo with bacterial lipopolysaccharide. MATERIALS AND METHODS: We evaluated the following parameters: use of different centrifugation speeds to isolate the MPs; comparison of TF activity of MPs isolated from platelet poor plasma versus platelet free plasma; effect of freeze/thaw on MP TF activity; and comparison of the MP TF activity assay with the measurement of TF protein by ELISA or flow cytometry. RESULTS: MPs prepared from platelet poor plasma by centrifugation at 20,000×g or 100,000×g for 15 minutes had similar levels of TF activity. However, significantly less TF activity was found in MPs isolated from platelet free plasma compared with platelet poor plasma. Interestingly, freeze/thawing of the plasma showed donor to donor variation in MP TF activity, with a moderate increase in some individuals. CONCLUSION: TF(+) MPs can be quantitatively isolated from platelet poor or platelet free plasma by centrifugation at 20,000×g for 15 minutes. Measurement of MP TF activity in plasma may be used to detect a prothrombotic state in patients with various diseases.