Thrombin enhances tumor cell adhesive and metastatic properties via increased alpha IIb beta 3 expression on the cell...

The association between blood coagulation and cancer growth and metastatic dissemination is not yet completely understood. In this study we demonstrate that thrombin is capable of enhancing tumor cell adhesive properties and thereby increases tumor cell metastatic potential. Following exposure to alpha-thrombin, Walker 256 carcinosarcoma cells and B16 amelanotic melanoma cells became more adherent to both endothelial cell monolayers and the subendothelial matrix component, fibronectin. Preincubation of W256 and B16a cells with doses of alpha-thrombin from 0.01 to 10.0 U/ml produced a bell shape dose-response curve with the maximal effect (a 2-5-fold increase in adhesion) observed at 0.1 U/ml (corresponding to 0.8 nM). Complexes of alpha-thrombin with its inhibitors, hirudin and antithrombin III-heparin, diminished its effect on tumor cell adhesion. The effect of thrombin on tumor cell adhesion may be mediated by the alpha IIb beta 3 integrin as thrombin increased cell surface expression of the alpha IIb beta 3 complex. The significance of the in vitro observations was further substantiated by results of in vivo studies. Pretreatment of B16a cells with alpha-thrombin resulted in a 2-fold increase in the number of metastatic lung colonies in an experimental metastasis model. The data indicate a new role for thrombin in the metastatic spread of cancer.