Anti-thrombotics in thrombosis and cancer
Many cancer patients have a reportedly hypercoagulable state, with recurrent thrombosis due to the impact of cancer cells and chemotherapy or radiotherapy on the coagulation cascade. Studies have demonstrated that unfractionated heparin or its low-molecular-weight fractions interfere with various processes involved in tumor growth and metastasis. These include fibrin formation; binding of heparin to angiogenic growth factors, such as basic fibroblast growth factor and vascular endothelial growth factor; modulation of tissue factor; and perhaps other more important modulatory mechanisms, such as enhanced tissue factor pathway inhibitor (TFPI) release and inhibition of various matrix-degrading enzymes. Clinical trials have suggested a clinically relevant effect of low-molecular-weight heparin (LMWH), as compared with unfractionated heparin, on the survival of cancer patients with deep vein thrombosis. Similarly, the impact of warfarin on the survival of cancer patients with thromboembolic disorders was demonstrated. Studies from the author's laboratory demonstrated a significant role for LMWH, warfarin, anti-VIIa, and LMWH-releasable TFPI on the regulation of angiogenesis, tumor growth and tumor metastasis. Thus, modulation of tissue factor/VIIa noncoagulant activities by LMWH, warfarin, anti-VIIa, or TFPI may be a useful therapeutic method for the inhibition of angiogenesis associated with human tumor growth and metastasis. Additionally, antiplatelet drugs may have an impact on tumor metastasis, and the combination of antiplatelets and anticoagulants at adjusted doses may provide greater benefits to cancer patients.