Pathways of Blood Clotting Initiation by Cancer Cells

Although available information indicates that cancer cells may activate blood coagulation, the precise mechanism remains still uncertain. A procoagulant with characteristics of tissue thromboplastin has been found in human benign and malignant tissues and in some experimental tumors. On the other hand it has been reported that extracts from malignant tissues directly activate coagulation factor X, due to the presence of a serine protease. We have investigated the procoagulscitic fluid. Cells from Lewis lung carcinoma (primary and metastasis), Ehrlich carcinoma ascites and JW sarcoma ascites were able to shorten markedly the recalcification time of normal, factor VIII and factor VII-deficient, not of factor X-deficient human plasma. The same cells did generate thrombin when mixed with a source of prothrombin and factor X, absorbed bovine serum (as a source of factor V), phospholipid and CaCl2.Cells from Sarcoma ISO ascites were completely inactive in both test systems. It was a included that cells from some experimental tumors, similarly to normal platelets, possess the capacity to directly activate coagulation factor X. This suggests the existence of an alternative “cellular” pathway in blood clotting initiation distinct from both the intrin sic and extrinsic mechanisms.(Supported by Italian CNR and NIH, NCI, USA).