Primary Role for Kinin B 1 and B 2 Receptors in Glioma Proliferation

This study investigated the role of kinins and their receptors in malignant brain tumors. As a first approach, GL-261 glioma cells were injected (2 × 10 5 cells in 2 μl/2 min) into the right striatum of adult C57/BL6 wild-type, kinin B 1 and B 2 receptor knockout (KOB 1 R and KOB 2 R) and B 1 and B 2 receptor double knockout mice (KOB 1 B 2 R). The animals received the selective B 1 R (SSR240612) and/or B 2 R (HOE-140) antagonists by intracerebroventricular (i.c.v.) route at 5, 10, and 15 days. The tumor size quantification, mitotic index, western blot analysis, quantitative autoradiography, immunofluorescence, and confocal microscopy were carried out in brain tumor samples, 20 days after tumor induction. Our results revealed an uncontrolled tumor growing in KOB 1 R or SSR240612-treated mice, which was blunted by B 2 R blockade with HOE-140, suggesting a crosstalk between B 1 R and B 2 R in tumor growing. Combined treatment with B 1 R and B 2 R antagonists normalized the upregulation of tumor B 1 R and decreased the tumor size and the mitotic index, as was seen in double KOB 1 B 2 R. The B 1 R was detected on astrocytes in the tumor, indicating a close relationship between this receptor and astroglial cells. Noteworthy, an immunohistochemistry analysis of tumor samples from 16 patients with glioma diagnosis revealed a marked B 1 R immunopositivity in low-grade gliomas or in older glioblastoma individuals. Furthermore, the clinical data revealed a significantly higher immunopositivity for B 1 R, when compared to a lower B 2 R immunolabeling. Taken together, our results show that blocking simultaneously both kinin receptors or alternatively stimulating B 1 R may be of therapeutic value in the treatment of brain glioblastoma growth and malignancy.