FIGURE 8: Silencing COX4-1 increases O₂^•− production in GBM cells with acquired radioresistance. (A) Quantification of mitochondrial O₂^•− production in U251-RR (top) and D456-RR (bottom) cells transfected with shRNA targeting COX4-1 or scramble shRNA and treated with or without AA (10 μM for 15 min), assessed by MitoSOX assay. Data are presented as the mean ± SEM (n=3). (B) Clonogenic survival curves for U251-RR (top) and D456-RR (bottom) cells transfected with shRNA targeting COX4-1 or scramble shRNA. Cells were irradiated (0–8 Gy) and immediately plated. Clonogenic survival was estimated on day 14 after irradiation. ***p<0.001, calculated using one-way ANOVA followed by Tukey's multiple comparison test. p < 0.0001 (****), calculated by Student t-test. a.u., arbitrary units; AA, antimycin A; ns, not significant.