Factor IXi-antithrombin (IXiAT) and thrombin-antithrombin (TAT) complexes in lung cancer patients.

Coagulation activation frequently occurs in cancer patients, resulting in thromboembolic complications and/or intravascular coagulation activation. The mechanisms leading to these alterations still are poorly understood. One explanation for the coagulation activation in malignant diseases is the presence of a direct factor X-activating cancer procoagulant. Coagulation activation in lung cancer patients develops at earlier stages than factor X activation; we demonstrated increased factor IXiAT complexes in addition to elevated TAT complexes. The increases of factor IXiAT complexes were not dependent upon the stage of the disease. In contrast, TAT complexes were higher in patients suffering from advanced pulmonary non-small cell carcinoma than in patients with limited disease. In conclusion, coagulation activation in pulmonary cancer patients occurs at earlier steps in the coagulation cascade than factor X activation. While this activation is not dependent upon the stage of the disease, the observation that TAT complexes showed higher elevations in patients with advanced than in those with limited pulmonary non-small cell carcinoma could be an indication of a cancer procoagulant that directly activates factor X.