Role of endogenous thrombin in tumor implantation, seeding, and spontaneous metastasis

Abstract

Tumor/host-generated thrombin (endogenous thrombin) was investigated with tumor growth and metastasis experiments in mice by the use of hirudin, a highly potent specific inhibitor of thrombin. Pretreatment with hirudin inhibited tumor implantation in nude or syngeneic mice, following subcutaneous injection of 2 human and 2 murine tumors. Hirudin induced a considerable lag period in the appearance of tumor growth, compared with phosphate-buffered saline (PBS) treatment, but had no effect on established tumor nodule growth in vivo or on tumor growth in vitro. Hirudin treatment induced central necrosis of the tumor nodule compared with no effect with PBS treatment. Greater protection was noted with longer duration of treatment. Tumor seeding into blood was examined with green fluorescent protein ( IntroductionThe association of thrombosis and cancer (platelet and fibrin deposition) is well established, 1-5 but the role that activation of the coagulation pathway plays in promoting neoplastic progression is not well defined. We and others have shown that exogenous thrombin (1 U/mL) acting through its PAR-1 receptor, is capable of enhancing tumor adhesion to platelets, 6-8 endothelial cells, 9 fibronectin, and von Willebrand factor 7 in vitro. Studies have also revealed that exogenous thrombin promotes tumor growth in vitro 10 and in vivo 6,7,11 as well as experimental (tail-vein injection) metastasis. [6][7][8]12 Exogenous thrombin is also capable of inducing angiogenesis in a chorioallantoic membrane model. 13 However, the pathophysiologic relevance of thrombin in the host, that is, the end result of endogenous generation of host thrombin during tumor growth and spontaneous metastasis, has not been examined. Indeed, the concentration of thrombin generated by a developing tumor in the plasma at the interface is unknown and uncertain. In addition, the effect of thrombin on tumor growth in vitro is biplasic (activation at Ͻ 0.5 U/mL and inhibition at higher concentration). 10 Most tumor cells have constitutively active tissue factor on their surface capable of generating thrombin in vitro. However, the host has antithrombin mechanisms capable of neutralizing this activity.An approach was therefore designed to explore the mechanism of endogenously generated thrombin with its possible effect on tumor growth, seeding, and spontaneous metastasis by employing the highly potent and specific inhibitor of thrombin, hirudin. Hirudin is twice as potent as heparin in animal thrombosis models. [14][15][16] Unlike heparin, it is capable of neutralizing thrombin bound to the tumor thrombus as well as in the plasma, 17,18 with a Ki (inhibitory constant) of 0.05 pM. 19 It has other antithrombotic properties. It is able to dissociate thrombin-platelet receptor complexes (greater affinity of hirudin for thrombin than for platelets). 20 It can displace reversibly bound Factor Xa from vascular endothelium, 20 which then becomes inactivated by plasma protease inhibitors, leading to reduced prothrombin activation. It has also been reported...

Thrombin is a therapeutic target for metastatic osteopontin-positive hepatocellular carcinoma

“…6 Previous studies have also indicated that thrombin expression is associated with a more malignant cancer phenotype. 15,16 In this study we demonstrated for the first time that the thrombin expression was significantly correlated with metastatic potential of HCC, postoperative tumor recurrence, and poor prognosis of HCC patients. This finding is supported by the fact that a high thrombin expression was significantly associated with the aggressive histopathological characteristics of HCC, such as large tumor size, vascular invasion, and high TNM staging.…”

“…[12][13][14] Thrombin has also been shown to contribute to tumor progression in manners both coagulation-dependent and coagulation-independent. 15,16 However, the possible mechanism for how thrombin and OPN are involved in HCC metastasis is not yet known. Furthermore, the prognostic value of thrombin and OPN for HCC has not yet been established.…”

Platelet glycoprotein Ibα supports experimental lung metastasis

“…Tumorigenesis has been linked to several molecules essential for blood coagulation and normal platelet function. These include thrombin, tissue factor, platelet P-selectin, fibrinogen, and lysophosphatidic acid (3,4,(7)(8)(9)(10)(11)(12)(13)(14)(15)(16). Together, these results suggest that platelets and their procoagulant activity support tumor metastasis, possibly by aiding tumor cells to lodge in the microvasculature and either extravasate to the surrounding tissue or grow as an intravascular tumor (17).…”

Differential effects of anticoagulants on tumor development of mouse cancer cell lines B16, K1735 and CT26 in lung

“…However, mechanisms of the effects of anticoagulants on cancer progression are still not exactly known. Animal studies showed that different components of the coagulation system, such as tissue factor (TF) [10], factor Xa [11], thrombin [12] and fibrinogen [13] can promote tumor progression, whereas the TF pathway inhibitor (TFPI) inhibits tumor growth in mice [14]. The congenital coagulation disorder FV Leiden (FVL) promotes melanoma tumor development in mouse lung, whereas FVIII-deficient (haemophilic) mice are protected against melanoma tumor growth in lungs indicating a role for the coagulation process [15].…”