Coagulants, including thrombin, have been found in many tissues, including tumor cells, but their significance is not fully understood. Recently, the expression of the receptor (uPAR) for urokinase-type plasminogen activator (uPA) and of uPA by many cells has been found to regulate pericellular proteolysis which is essential for cell migration. It is well correlated with tumor invasiveness. We studied the effect of thrombin on the expression of uPAR in the human prostate cancer cell line, DU-145. Human α-thrombin added to a confluent cultures caused a dose-dependent increase in [125I]-pro-uPA binding capacity of DU-145 cells. Incubation with 2 U/ml thrombin for 16 h resulted in an increase in the number of u PAR from 10.3 ± 1.6 x 104 to 25.4 ± 3.3 x 104/cell, and in an increase in Kd of 0.4 ± 0.17 nM to 1.0 ± 0.32 nM. Northern blot analysis showed an increase in the level of uPAR mRNA, which reached a maximum of 5-fold. Thrombin treated with phenylalanyl-prolyl-arginylchloromethylketone and hirudin did not produce the effect on uPAR expression, nor did Factor Xa. This thrombin effect can also be produced by a thrombin receptor activating peptide, indicating that DU-145 cells have specific thrombin receptors and thrombin acts through its activation. Thrombin had no detectable effect on the expression of uPA and plasminogen activator inhibitor type-1. An acceleration of the activation of plasminogen was observed in the presence of thrombin-stimulated DU-145 cells, indicating a functional consequence of thrombin stimulation. These findings suggest an important role of thrombin in the regulation of invasive ability of tumor cells through the induction of uPAR expression.
ASJC Scopus subject areas