Effect of apigenin on the expression of p21/waf1 and bax in human prostate cancer cells. A, Increase in the protein expression of p21/waf1 and bax at 20 μM and 40 μM doses of apigenin and 20 ng/ml HDAC inhibitor TSA after 24 h treatment Panel 1, PC-3 cells and Panel 2, 22Rv1 cells. B, Increase in the mRNA levels of p21/waf1 and bax at 20 μM and 40 μM doses of apigenin and 20 ng/ml HDAC inhibitor TSA after 24 h exposure Panel 1, PC-3 cells and Panel 2, 22Rv1 cells C, Binding of acetylated H3 to the promoters of p21/waf1 in PC-3 cells. Chromatin immunoprecipitation (ChIP) assay was performed to determine the association of acetylated histone H3 with the promoters of p21/waf1. Apigenin treatment to PC-3 cells causes increased association of acetylated histone H3 to the promoters of p21/waf1. The details are provided in ‘materials and methods’.