FIG. 9.

Inhibition of NF-κB by mutant IκB did not sensitize MCF+SOD cells to radiation. (A) The activity of the I2E luciferase reporter that contains the intronic enhancer element from the SOD2 gene was inhibited in irradiated MCF+SOD+mIκB cells. Five grays induced I2E (containing an NF-κB site) luciferase reporter activity at 8 and 24 h following IR, and this IR-induced activation was inhibited in MCF+SOD cells by mutant IκB transfection. I2E reporters were cotransfected with the β-galactosidase reporter into MCF+SOD+mIκB and vector control MCF+SOD+V cells, and luciferase activity was measured at 0 (without IR), 8, and 24 h after 5-Gy IR (data represent mean ± 1 standard deviation [SD] of five separate experiments). **, irradiated groups that are significantly different from their irradiated vector control (paired Student's t test, P < 0.05). (B) MCF+SOD+mIκB cells were not radiosensitized. MCF+SOD+mIκB and MCF+SOD+V cells were exposed to a range of IR doses, and clonogenic survival was obtained after IR treatments. Surviving fractions were normalized to nonirradiated cells (data represent mean ± 1 SD of three independently irradiated cultures, each plated into at least two cloning dishes that were counted; P > 0.05, paired t test).