A factor X procoagulant activity occurs in some malignant tumor types such as mouse Lewis lung(LL) carcinoma which initiates the formation of a protective fibrin coat around cells explanted from the primary tumor. Warfarin, an antivitamin K drug, and dietary induced vitamin K deficiency both dimisinh factors X procoagulant activity in LL primary tumors and are effective in diminishing lung metastases. Recent data have demonstrated the procoagulant of LL cells is not an endogenous single protease as in rabbit V2 carcinoma, but rather its activity is dependent upon a LL cellular component and a vitamin K-dependent protein in serum or plasma. The overall goals of the project are to better define the role of procoagulant activity in metastasis and the mechanism of factor X activation by neoplastic cells.
The specific aims are to: 1) establish whether other neoplastic cell lines whose metastasis is inhibited by warfarin possess a procoagulant system similar to that of LL cells; 2) probe and identify the vitamin K-dependent protein binding region of the cell receptor by treatment of LL cells with various modifiers; 3) characterize the components of the procoagulant system including the vitamin K-dependent protein receptor and isolate them in a purified state; and 4) define more precisely the role of procoagulant activity in cell adhesion and growth in remote tissues. Initially, the procoagulant systems of Walker 256 and prostatic PAIII tumor cells will be investigated using methods developed in this laboratory. Functional groups of the cell receptor will be assessed by treatment with a variety of chemical modifying reagents and enzymes. The identification of the receptor will be accomplished by SDS-PAGE of selectively radiolabeled membrane components. Isolation of the procoagulant components will be accomplished by affinity, immunoaffinity and conventional chromatographic techniques. The effects of procoagulant activity on tumor adhesion and growth will be determined by i.v. injection of LL cells containing various levels of the vitamin K-dependent protein and subsequent quantitation of lung colony formation. Results from these investigations will enhance existing knowledge of the mechanisms involved in vitamin K and warfarin inhibition of tumor metastasis and permit the rational design of more effective therapeutic approaches which will not suffer the bleeding complications presently associated with warfarin use.
