Role of Protease-Activated Receptor-1 in Glioma Growth.

Activation of a thrombin receptor, protease-activated receptor-1 (PAR-1), induces angiogenesis, cell proliferation, and invasion in tumors. The present study examined the effect of host PAR-1 gene deletion on glioma growth in a mouse model. F98 glioma cells were implanted into the right caudate of either wild type (WT) or PAR-1 knockout (KO) mice. Mice underwent magnetic resonance imaging (MRI) and the brains were used for measurements of brain water content and tumor mass. Levels of hypoxia-inducible factor-1 alpha (HIF-1α) and vascular endothelial growth factor (VEGF) were also measured by ELISA (enzyme-linked immunosorbent assay). We found brain water content in the ipsilateral hemisphere and the tumor mass were significantly lower in PAR-1 KO than WT mice at day 12 after implantation of F98 cells (p < 0.05). HIF-1α protein levels in the ipsilateral hemisphere were higher in the WT mice (373 ± 25 pg/g brain tissue vs 333 ± 35 pg/g brain tissue in PAR-1 KO mice, p < 0.05) 7 days after F98 cell implantation. VEGF protein levels were also higher in the ipsilateral hemisphere of WT mice (219 ± 21 vs 166 ± 22 pg/g brain tissue in PAR-1 KO mice, p < 0.01). In conclusion, PAR-1 has a role in glioma growth and could be a new therapeutic target for gliomas.