Radioactive125I seeds suppress epithelial–mesenchymal transition (EMT) in glioblastoma multiforme (GBM) cells via a reactive oxygen species (ROS)-mediated signaling pathway. (A) The levels of ROS in U251 (left panel) and U87 (right panel) cells were measured by DCF-DA staining 24 hours after 125I seed and X-ray treatment. The green fluorescence intensity indicates the degree of ROS. (B) The levels of ROS in 125I seed- and X-ray-treated GBM cells were measured by flow cytometric analysis. The mean fluorescence intensity and the cells of P2 measured by flow cytometric analysis are presented in. (C) Pretreatment of cells with GSH obviously decreased DNA damage and apoptosis in U251 cells, reflected by γH2AX, activated ATM, ATR, Chk1, and Cdc2. EMT was also recovered by GSH. (D) The number of cells measured by transwell (upper panel) and Boyden (lower panel) assay was counted to calculate the average number of migrated cells when GSH was used. Moreover, colony-formation ability of GBM cells (E) of U251 cells, and DNA distribution (F) of U251 cells inhibited by 125I seeds were blocked by recovery of the expression levels of ROS. Data are presented as mean ± SD (n =3). Bars with different characters are statistically different at the P < 0.05 level.