A unique factor X procoagulant, which initiates the formation of a protective fibrin coat around cells detached from the primary tumor and so increases their potential for survival and growth, exists in some malignant tumor types. Lewis lung carcinoma, a spontaneous tumor of C57BL/6 mice with a factor X procoagulant activity, grows locally in syngeneic hosts and metastasizes selectively to the lungs. Warfarin, an anticoagulant drug widely used in humans, diminishes factor X procoagulant activity in Lewis lung primary tumors and is effective in diminishing the size and number of lung metastases. Dietary-induced vitamin K deficiency also diminishes both factor X procoagulant activity in Lewis lung primary tumors and the frequency of lung metastases. The overall goal of the project is to determine if the interactions which exist between warfarin and vitamin K in liver also exist in Lewis lung tumor tissue.
The specific aims are to establish: (1) the pathways of vitamin K metabolism in Lewis lung tumor tissue and to determine if they differ significantly from those in C57BL/6 mouse liver; (2) the effects of warfarin and its metabolites on these pathways; (3) the roles of vitamin K and warfarin in regulating the activity of the factor X procoagulant; and (4) if the antimetastatic activity of warfarin is due solely to effects on the factor X procoagulant. Pathways of vitamin K metabolism in Lewis lung tumor and liver tissue will be determined in isolated subcellular fractions by scintillation counting or ultraviolet absorption of vitamin products separated by high performance liquid chromatography. Those pathways which are sensitive to warfarin and/or its metabolites will be determined by inhibition of product formation with vitamin K or its known metabolites as substrates. The factor X procoagulant will be isolated by affinity and conventional chromatographic techniques, and the existence of gamma carboxyglutamate residues in it determined by incorporation of tritiated water and amino acid analysis. The effects of administration of warfarin and its metabolites on Lewis lung tumor spread and growth will be determined from changes in the size and number of metastases in the lung. Results obtained from these investigations will enhance existing knowledge of the mechanisms involved in vitamin K and warfarin inhibition of tumor metastasis and will provide a sound theoretical basis for the use of warfarin as an antimetastatic agent in humans. Ultimately, they will aid in the design of drugs which are more effective than warfarin in controlling metastasis. (N)
