A Novel Compound Targeting Protease Receptor 1 Activators for the Treatment of Glioblastoma.

Data from human biopsies, and models, strongly supports the role of thrombin, and its protease-activated receptor (PAR1) in the pathology and progression of glioblastoma (GBM), a high-grade glial tumor. Activation of PAR1 by thrombin stimulates vasogenic edema, tumor adhesion and tumor growth. We here present a novel six amino acid chloromethyl-ketone compound (SIXAC) which specifically inhibits PAR1 proteolytic activation and counteracts the over-activation of PAR1 by tumor generated thrombin. SIXAC effects were demonstrated utilizing 3 cell-lines, including the highly malignant CNS-1 cell-line which was also used as a model for GBM . The effects of SIXAC on proliferation rate, invasion and thrombin activity were measured by XTT, wound healing, colony formation and fluorescent assays, respectively. The effect of SIXAC on GBM was assessed by measuring tumor and edema size as quantified by MRI imaging, by survival follow-up and brain histopathology. SIXAC was found to inhibit thrombin-activity generated by CNS-1 cells (IC = 5 × 10M) and significantly decrease proliferation rate ( < 0.03) invasion ( = 0.02) and colony formation ( = 0.03) of these cells. In the CNS-1 GBM rat animal model SIXAC was found to reduce edema volume ratio (8.8 ± 1.9 vs. 4.9 ± 1, < 0.04) and increase median survival (16 vs. 18.5 days, < 0.02 by Log rank Mental-Cox test). These results strengthen the important role of thrombin/PAR1 pathway in glioblastoma progression and suggest SIXAC as a novel therapeutic tool for this fatal disease.