Thrombin-induced cell proliferation and platelet-derived growth factor-AB release from A172 human glioblastoma cells

Background: In a previous study, we found that thrombin induced proliferation of TM-1 and T98G human glioma cells and that the mitogenic effect was abolished by hirudin. Objectives: We investigated thrombin's effects on the proliferation of A172 human glioblastoma cells and the induction of growth factors. Furthermore, we examined whether or not the expression of heparin cofactor II (HCII) in A172 cells using adenovirus vector could suppress thrombin's effects. Methods: The effect of thrombin on cell proliferation was assessed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The amount of growth factors in the conditioned medium was measured by enzyme-linked immunosorbent assay. The level of platelet-derived growth factor (PDGF)-B mRNA was assessed by reverse transcriptase-polymerase chain reaction analysis. Results: Thrombin-induced proliferation of A172 cells primarily depended on the enhanced secretion of PDGF-AB by thrombin. The action of thrombin depended on its proteolytic activity. However, thrombin-induced PDGF-AB secretion was not abolished by anti-protease-activated receptor (PAR) antibody. The PAR-1 agonist peptide had no effect on cell growth and PDGF-AB levels. Thrombin did not increase PDGF-B gene expression. Expression of HCII effectively suppressed thrombin-induced PDGF-AB release. Conclusions: These results indicate that thrombin may play an important role in the proliferation of A172 cells by inducing PDGF-AB secretion and that thrombin's action is mediated by its proteolytic activity. Inhibition of thrombin's proteolytic activity may be a new therapeutic method for gliomas.