Fig. 5

HDAC inhibitor Valproic acid causes retention of γH2AX in both acquired and inherently radioresistant cells. a Western blotting depicts changes in levels of site-specific histone PTMs in MCF7-RR at different time points after treatment with 2.5 mM of HDAC inhibitor VPA and 4Gy radiation exposure. b Clonogenic assay of MCF7-RR cells to assess radio-sensitization potential of valproic acid. The graph depicts the number of colonies. Cells were treated with 4 Gy radiation and 2.5 mM VPA. c Representative z-stack projection images for comparison of retention of γH2AX levels by immunofluorescence in the U87 cell line. Cells were treated with 2.5 mM VPA and exposed to 4 Gy radiation. Scale bar—5 μm. d Western blotting for site-specific histone PTMs post irradiation in the U87 cell line. Scale bar—20 μm. Images were processed using LSM browser software. Hrs.—hours, IR—ionizing Radiation, VPA—valproic acid. Statistical analysis is done by Student’s t test. ^*p < 0.05, ^**p < 0.01. Error bars represent ± S.D. of 3 experiments