Fig. 2: BRD4 mediates radiation response in ET-resistant breast cancer cells.

a Western blot analysis was performed on whole-cell lysates derived from the indicated panel of ET-resistant cell lines using anti-BRD4 antibody. b MCF-7 Y537S cells were treated 20 Gy of radiation after pre-treatment with vehicle or OTX015 (1 μM). Cells were harvested at the indicated time points, subjected to chromatic fractionation, and analyzed by immunoblotting using the indicated antibodies. c, d Immunofluorescence microscopy was used to quantify γ-H2AX foci formation in MCF-7 Y537S cells at 30 and 120 minutes after exposure to 4 Gy of IR following treatment with vehicle or OTX015 (1 μM) in triplicate. Blue = DAPI. Green = γ-H2AX. 40 cells were counted per independent experiment. e, f Alkaline comet assay of MCF-7 Y537S cells after exposure to 4 Gy of IR and 30 minute recovery following treatment with vehicle or OTX015 (1 μM) in triplicate. 25 olive tail movements were measured per independent experiment. d, f The edges of the box, denote first and third quartiles, the line denotes median, and the whiskers denote minimum and maximum derived from three independent experiments (n = 3). Statistical significance was evaluated using an unpaired, two-tailed t test at the indicated time point. ***p < 0.0005.