Assessment of DNA damage responses and DNA repair. (a, b) Immunofluorescence staining for γH2AX. Tumor cells isolated from MMT mice were cultured with T-oligo or control-oligo at a concentration of 40 μM for 24 hours in chamber slides. After 3 Gy IR, cells were stained with FITC-anti-γH2AX mAb at indicated time. The number of γH2AX foci per cell was counted and calculated from at least 70 cells in each group after subtraction of γH2AX foci from the un-irradiated tumor cells and presented as means ± SD from repeated experiments. Statistical significance was determined by one-way ANOVA. (c, d) Comet assay. Tumor cells treated with T-oligo or control-oligo (40 μM) or medium with or without 3 Gy IR 24 hours later were assessed for DNA repair at three hours after IR using Trevigen's CometAssay® kit. Comet images were selected randomly from the microscope field of view using a defined sequence of searching to ensure the same image was only scored once. Statistical significance was determined by one-way ANOVA.