Genetic determinants of cancer coagulopathy, angiogenesis and disease progression.

Progression of human malignancies is accompanied by vascular events, such as formation and remodeling of blood vessels and systemic coagulopathy. Though long appreciated as comorbidity of cancer (Trousseau syndrome), vascular involvement is increasingly recognized as a central pathogenetic mechanism of tumor growth, invasion and metastasis. The major outstanding question in relation to this role has been, whether vascular perturbations are simply a reaction to the conditions of the tumor microenvironment, or are linked to the known genetic lesions causal for the onset and progression of malignancy. In this regard, we have previously hypothesized, and recently demonstrated experimentally that deregulation of certain hemostatic mechanisms, namely upregulation of tissue factor (TF) and possibly other changes (e.g. expression of thrombin receptor - PAR-1) are controlled by cancer-associated oncogenic events, such as activation of K-ras, epidermal growth factor receptor (EGFR), or inactivation of the p53 tumor suppressor gene in various human cancer cells. It appears that these respective transforming alterations exert their impact on both, cell-associated and soluble/circulating (microvesicle- associated) TF, i.e. may cause a systemic hypercoagulable state. Other genes, which more recently emerged as regulators of cancer coagulopathy include: PML-RARalpha, PTEN, and MET. While the spectrum of procoagulant targets of these genes may vary somewhat it includes: TF, PAI-1, COX-2 and possibly other hemostatic proteins. It is noteworthy that these prothrombotic changes may impact the malignant process directly (e.g. stimulate angiogenesis, tumor growth or metastasis) as a consequence of both coagulation-dependent and -independent effects. The latter are mostly related to cellular signaling events and changes in gene expression which are now known to be induced by the TF/FVIIa/Xa complex, thrombin and PARs, expressed on the surface of cancer cells, as well as tumor-associated endothelium. Interestingly, certain anticoagulants possess antimetastatic and anticancer properties (e.g. LMWH), an observation that further suggests that hypercoagulability may act as an effector mechanism of genetically driven tumor progression. Conversely, we suggest that oncogene-directed (targeted) anticancer agents could, at least in some cases, ameliorate not only cellular transformation itself, but also some of the chronic components of the cancer-related coagulopathy, something that may be relevant to therapeutic efficacy of these drugs. We also postulate that since TF is the oncogene target, circulating TF (microparticles) could serve as surrogate marker of the biological activity oncogene-directed agents exert in vivo. Thus, both genetic and epigenetic factors appear to conspire to activate various components of the hemostatic system in cancer patients, both locally and systemically. These activities act as mediators of cancer coagulopathy, angiogenesis, metastasis and other events involved in disease progression and should be recognized in designing better anticancer therapies.