SU11657 Enhances Radiosensitivity of Human Meningioma Cells

Purpose: To analyze the effect of the multireceptor tyrosine kinase inhibitor SU11657 (primarily vascular endothelial growth factor, platelet-derived growth factor) in combination with irradiation in freshly isolated primary human meningioma cells. Methods and Materials: Tumor specimens were obtained from meningioma patients undergoing surgery at the Department of Neurosurgery, University of Heidelberg, Germany. For the present study only cells up to passage 6 were used. Benign and atypical meningioma cells and human umbilical vein endothelial cells (HUVEC) were treated with SU11657 alone and in combination with 6-MV photons (0-10 Gy). Clonogenic survival and cell proliferation were determined alone and in coculture assays to determine direct and paracrine effects. Results: Radiation and SU11657 alone reduced cell proliferation in atypical and benign meningioma cells as well as in HUVEC in a dose-dependent manner. SU11657 alone also reduced clonogenic survival of benign and atypical meningioma cells. SU11657 increased radiosensitivity of human meningioma cells in clonogenic survival and cell number/proliferation assays. The anticlonogenic and antiproliferative effects alone and the radiosensitization effects of SU11657 were more pronounced in atypical meningioma cells compared with benign meningioma cells. Conclusion: Small-molecule tyrosine kinase inhibitors like SU11657 are capable of amplifying the growth inhibitory effects of irradiation in meningioma cells. These data provide a rationale for further clinical evaluation of this combination concept, especially in atypical and malignant meningioma patients