Thrombomodulin is a determinant of metastasis through a mechanism linked to the thrombin binding domain but not the lectin-like domain

Abstract

and 5 BloodCenter of Wisconsin, Milwaukee, WI Thrombomodulin (TM) is a predominantly endothelial transmembrane glycoprotein that modulates hemostatic function through a domain that controls thrombinmediated proteolysis and an N-terminal lectin-like domain that controls inflammatory processes. To test the hypothesis that TM is a determinant of malignancy and dissect the importance of these functional domains in cancer biology, metastatic potential was evaluated in TM Pro mice expressing a mutant form of TM with reduced thrombin affinity and TM LeD mice lacking the N-terminal lectin-like domain. Studies of TM Pro mice revealed that TM is a powerful determinant of hematogenous metastasis. TM Pro mice exhibited a strongly prometastatic phenotype relative to control mice that was found to result from increased survival of tumor cells newly localized to the lung rather than any alteration in tumor growth. The impact of the TM Pro mutation on metastasis was dependent on both tumor cell-associated tissue factor and thrombin procoagulant function. In contrast, expression of a mutant form of TM lacking the lectin-like domain had no significant impact on metastasis. These studies directly demonstrate for the first time that TM-mediated regulation of tumor cell-driven procoagulant function strongly influences metastatic potential and suggest that endothelial cellassociated modulators of hemostasis may represent novel therapeutic targets in limiting tumor dissemination. (Blood. 2011; 118(10):2889-2895) IntroductionDetailed studies of the role of hemostatic factors in cancer biology have established that metastasis is strongly dependent on a cooperative interplay between tumor cell-associated procoagulant function and circulating hemostatic system components. 1,2 However, the significance of endothelial cell-associated regulators of coagulation to cancer progression remains largely unexplored. Thrombomodulin (TM) is a predominantly endothelial cellassociated transmembrane glycoprotein that serves as a high affinity receptor for thrombin as well as other ligands through distinct extracellular domains. [3][4][5][6] TM engagement of thrombin results in a profound restriction in thrombin-mediated cleavage of prothrombotic substrates, including fibrinogen, factor V, factor VIII, factor XI, factor XIII, and platelet-associated protease activated receptors (PARs), while enhancing the proteolytic activation of the anticoagulant/anti-inflammatory protease zymogen, protein C, and the carboxypeptidase zymogen, thrombin-activatable fibrinolysis inhibitor (TAFI). 5,6 TM also controls multiple biologic processes through thrombin-independent mechanisms that are, at least in part, mediated by the N-terminal lectin-like domain, including complement activation, sequestration of inflammatory mediators, apoptosis, inflammatory cell migration, cytokine production and cell signaling events. 3,[7][8][9][10][11] The broad biologic significance of TM is underscored by studies establishing the early developmental failure of TM-deficient embryos and pr...

Cancer Cells Induced to Express Mesenchymal Phenotype Release Exosome-like Extracellular Vesicles Carrying Tissue Factor

“…This is illustrated by studies demonstrating endothelial cell expression of TF in invasive breast cancer (42) or the impact of their genetic status on their anticoagulant potential (43). It remains to be studied whether TF trafficking from mesenchymal cancer cells to endothelium could produce similar effects and contribute to thrombosis or metastasis.…”

Thrombin induces osteosarcoma growth, a function inhibited by low molecular weight heparin in vitro and in vivo

“…For example, mice partially deficient in prothrombin have significantly diminished in vivo metastasis of Lewis lung carcinoma. 29 Many studies have demonstrated, through PAR-1 and other thrombin effector mechanisms, that thrombin directly promotes tumor cell proliferation, adhesion to platelets, production of endothelial cells, matrix proteins, and vascular endothelial growth factor A (VEGF-A) to support angiogenesis. 3 Fibrin appears to be important in this process, as fibrinogen-deficient mice also have diminished in vivo metastasis.…”

The relationship between tissue factor and cancer progression: insights from bench and bedside

“…50 This concept recently found even more support in a report on the pro-metastatic phenotype of mice with a thrombomodulin mutant with decreased affinity for thrombin. 51 Further evidence for a prominent role of downstream coagulation activation in metastasis comes from experiments in genetically modified mice that lack platelets, PAR4, or fibrinogen. Mice with either of these genetic modifications were protected from metastasis, which provides evidence that metastasis is facilitated by thrombinactivated platelets via PAR4.…”