Effect of apigenin on histone H3 and H4 acetylation in human prostate cancer cells. A, Increase in acetylation of histone H3 Panel 1, PC-3 cells and Panel 2, 22Rv1 cells with 20 μM and 40μM doses of apigenin and 20 ng/ml HDAC inhibitor TSA exposed for 24 h. B, Increase in acetylation of histone H4 Panel 1, PC-3 cells and Panel 2, 22Rv1 cells with 20 μM and 40 μM doses of apigenin and 20 ng/ml HDAC inhibitor TSA after 24 h treatment. The details are provided in ‘materials and methods’.