Elevated tissue factor levels in leukemic cell homogenate

Hemostatic function in hyperfibrinolytic disseminated intravascular coagulation

BACKGROUND

Global hemostatic mechanism(s) in patients with disseminated intravascular coagulation (DIC) are poorly understood. There are few diagnostic criteria of DIC based on overall or global hemostatic mechanisms.

METHODS

We have assessed in detailed the dynamic global hemostatic changes using thrombin and plasmin generation assay (T/P-GA), clot fibrinolytic waveform analysis (CFWA) and not-activated rotational thromboelastometry (NATEM), in a young girl with DIC associated with acute myeloid leukemia (AML). The ratios of endogenous thrombin potential (T-EP) and plasmin lag time (P-LT) relative to normal plasma was sourced from pooled normal plasma from healthy volunteers on T/P-GA.

RESULTS

The inverse P-LT ratio prior to tranexamic acid (TXA) treatment was greater than the T-EP ratio (1.1-2.8 and 0.83-1.2, respectively). Significant reduction in inverse P-LT ratio (0.084-1.3) was observed after TXA treatment. The interval from clotting to the initiation of fibrinolysis (fibrinolysis lag time: FLT) in CFWA was significantly shorter than the control at onset (74.2-91.6 s vs 109 s), indicating enhanced fibrinolysis. Data from an adult with acute promyelocytic leukemia-associated DIC also supportively showed a high inverse P-LT ratio (2.1) and shortened FLT (83.7 s). The clotting time in patient whole blood using NATEM-mode during an episode of severe epistaxis markedly shortened beyond control, but returned to normal after the addition of an anti-tissue factor (TF) monoclonal antibody.

CONCLUSION

The release of intravascular TF contributed to sustained activation of coagulation and subsequent fibrinolytic activity in this patient with AML-associated DIC, and T/P-GA could provide better quantitative data than conventional assays in these circumstances.

Therapeutic Antibody-Like Immunoconjugates against Tissue Factor with the Potential to Treat Angiogenesis-Dependent as Well as Macrophage-Associated Human Diseases

Accumulating evidence suggests that tissue factor (TF) is selectively expressed in pathological angiogenesis-dependent as well as macrophage-associated human diseases. Pathological angiogenesis, the formation of neovasculature, is involved in many clinically significant human diseases, notably cancer, age-related macular degeneration (AMD), endometriosis and rheumatoid arthritis (RA). Macrophage is involved in the progression of a variety of human diseases, such as atherosclerosis and viral infections (human immunodeficiency virus, HIV and Ebola). It is well documented that TF is selectively expressed on angiogenic vascular endothelial cells (VECs) in these pathological angiogenesis-dependent human diseases and on disease-associated macrophages. Under physiology condition, TF is not expressed by quiescent VECs and monocytes but is solely restricted on some cells (such as pericytes) that are located outside of blood circulation and the inner layer of blood vessel walls. Here, we summarize TF expression on angiogenic VECs, macrophages and other diseased cell types in these human diseases. In cancer, for example, the cancer cells also overexpress TF in solid cancers and leukemia. Moreover, our group recently reported that TF is also expressed by cancer-initiating stem cells (CSCs) and can serve as a novel oncotarget for eradication of CSCs without drug resistance. Furthermore, we review and discuss two generations of TF-targeting therapeutic antibody-like immunoconjugates (ICON and L-ICON1) and antibody-drug conjugates that are currently being tested in preclinical and clinical studies for the treatment of some of these human diseases. If efficacy and safety are proven in current and future clinical trials, TF-targeting immunoconjugates may provide novel therapeutic approaches with potential to broadly impact the treatment regimen of these significant angiogenesis-dependent, as well as macrophage-associated, human diseases.

Alterations in Procoagulant, Anticoagulant, and Fibrinolytic Systems Before and After Start of Induction Chemotherapy in Children With Acute Lymphoblastic Leukemia

Induction chemotherapy is associated with increased thrombosis risk in children with acute lymphoblastic leukemia (ALL). In this prospective study, we explored the effects of ALL and induction chemotherapy on the procoagulant, anticoagulant, and fibrinolytic systems in 20 children with ALL. The levels of d-dimer, factor VIII, von Willebrand factor, protein C, antithrombin III, and thrombin-activated fibrinolysis inhibitor (TAFI) were elevated at diagnosis. These changes were not related with peripheral blast count. The levels of fibrinogen, d-dimer, coagulation inhibitors, and plasminogen decreased, whereas the levels of tissue factor pathway inhibitor and plasminogen activator inhibitor 1 increased progressively following prednisolone monotherapy, administration of vincristine plus daunorubicin, and l-asparaginase. The levels of factor VIII, d-dimer, and TAFI remained elevated during the study period. In conclusion, coagulation activation and impaired fibrinolysis already exist at diagnosis, whereas induction chemotherapy leads to reactivation of coagulation and progressive impairment in fibrinolytic and anticoagulant capacities in childhood ALL.

Tissue factor in tumour progression

The linkage between activation of the coagulation system and cancer is well established, as is deregulation of tissue factor (TF) by cancer cells, their vascular stroma and cancer-associated inflammatory cells. TF is no longer perceived as an 'alternative' coagulation factor, but rather as a central trigger of the coagulation cascade and an important cell-associated signalling receptor activated by factor VIIa, and interacting with several other regulatory entities, most notably protease-activated receptors (PAR-1 and PAR-2). Preclinical studies revealed the role of oncogenic transformation and tumour micro-environment as TF regulators in cancer, along with the impact of this receptor on gene expression, tumour growth, metastasis, angiogenesis and, possibly, formation of the cancer stem cell niche. Increasing interest surrounds the shedding of TF-containing microvesicles from cancer cells, their entry into the circulation and their role in the intercellular transfer of TF activity, cancer coagulopathy and other processes. Recent data also suggest differential roles of cell autonomous versus global effects of TF in various settings. Questions are raised regarding the consequences of TF expression by tumour cells themselves and by their associated host stroma. Progress in these areas may soon begin to impact on clinical practice and, as such, raises several important questions. Can TF be exploited as a therapeutic target in cancer? Where and when may this be safe and beneficial? Is expression of TF in various disease settings useful as a biomarker of cancer progression or the associated hypercoagulability? What clinical questions related to TF are especially worthy of further exploration, at present and in the near future? Some of these developments and questions will be discussed in this chapter.

Cancer and thrombosis revisited

Remarkable progress has been made since the first description of the association between cancer and thrombosis by Trousseau over 100 years ago. Now, it is clear that there is a two-way connection between coagulation and cancer as tumor results in alterations in hemostatic balance, and thrombosis may promote tumor cell growth. A variety of clinical thrombotic syndromes may present in cancer patients including local and systemic venous and arterial thromboses. More evidence is now being gathered on the potential of antithrombotic regimens to prolong survival of cancer patients. Whether the use of novel antithrombotic drugs may result in a better outcome remains to be determined.