Irradiated normal brain promotes invasion of glioblastoma through vascular endothelial growth and stromal cell-derived factor 1

The significance of irradiated normal brain volume in glioma recurrence is usually ignored by radiotherapists. The whole-brain irradiation (WBI) of 15 Gy in three fractions was delivered to C57BL/6 mice before implantation of GL261 glioma cells. The changes in vascular endothelial growth (VEGF) and stromal cell-derived factor 1 (SDF-1) after WBI were evaluated by real-time RT-PCR and immunohistochemistry. Cell invasion assays were performed to study the effects of VEGF and SDF-1. The levels of VEGF and SDF-1 in normal brain tissues increased after 15 Gy WBI. The WBI before tumor implantation significantly increased the invasive ability of GL261 cells. VEGF and SDF-1 could promote invasion of GL261 cells even after high-dose irradiation. The combination of irradiation and inhibitors such as AMD3100 may prevent irradiation-stimulated dissemination of glioma cells.