e14505 Background: The increased risk of thrombosis in patients with cancer has been well established. However, the triggers in these patients have yet to be fully defined. Under pathological conditions, the potent procoagulant protein Tissue Factor (TF) is found in the circulation and may trigger thrombosis. Methods: We evaluated the level of TF expression in 4 different human pancreatic cancer cell lines. We also measured TF microparticle (MP) release from these tumors in vivo by flow cytometry and TF activity assay. We then used these lines in a mouse model of pancreatic cancer to evaluate the sources of TF that activate coagulation and contribute to thrombosis using a saphenous vein model. Results: We found that mice bearing orthotopic pancreatic tumors which express higher levels of TF (HPAC and HPAF) show increased activation of coagulation (measured by thrombin-antithrombin complex) as compared to mice bearing TF negative tumors (MIA-PaCa-2 and PANC-1). This activation of coagulation could be reduced by treatment with a human TF antibody. Further, mice bearing tumors derived from TF high cell line HPAC demonstrated an activation of coagulation despite a lack of circulating TF-positive MPs. Mice bearing TF expressing pancreatic tumors also demonstrated increased thrombosis by a saphenous vein model. Treatment of tumor-free mice with TF MPs did not result in an activation of coagulation or increased thrombosis unless mice were given 40-100 fold higher levels of TF bearing MPs than are found in the circulation of tumor bearing mice. Conclusions: The data suggest that TF on the tumor itself is involved in the activation of coagulation whereas circulating TF-positive MPs is likely to contribute to thrombosis. Elevated levels of TF-positive MPs may be used as a biomarker to identify cancer patients at risk for thrombosis.
Resveratrol, a multitargeted agent, can enhance antitumor activity of gemcitabinein vitroand in orthotopic mouse model of human pancreatic cancer
