Overexpression of IRF5 in MDA-MB-231 cells sensitizes them to IR-induced apoptosis. A. MDA-MB-231 cells were exposed to 5 Gy IR or the same dose plus IFN-γ (IR/γ) for 24 h. Percent of cells undergoing apoptosis was measured by FACS analysis of Annexin V-FITC (x-axis) and PI (y-axis) double-staining. Percent of Annexin V-FITC stained positive cells is shown in the upper and lower right-hand quadrants. Representative histogram plots from three independent experiments performed in duplicate are shown. B. Same as in (A), except cells were treated with 1 μM Dox or the same dose plus IFN-γ (Dox/γ) for five hours. Percent of Annexin V-FITC-stained positive cells compared to control is plotted on y-axis. Data are expressed as mean ± SD of three independent experiments performed in duplicate. Statistical significance was determined by comparing the difference between pBabe and pBIRF5 cells lines after each treatment; ** denotes P < 0.001. C. Same as in (B), except MCF-7 cells were treated with Dox.