Effect of silymarin on HAT activity and acetylated histones H3 and H4 in A549 and H460 human NSCLC cells. (A and B) A549 and H460 cell lines were treated with various concentrations of silymarin for 24 h and HAT activity was measured using HAT Activity/Inhibition Assay Kit (Epigentek Group, Inc.). Treatment of NSCLC cells with silymarin enhanced the levels of HAT activity in both A549 (A) and H460 (B) cell lines in a dose-dependent manner. Data on HAT activity are presented in terms of percent of control as the mean ± SD, n=3. Significant difference versus vehicle-treated controls, ¶P<0.01, **P<0.001. (C and D) A549 and H460 cell lines were treated with various concentrations of silymarin for 24 h, and lysates were subjected to western blot analysis for acetylated forms of histones at various lysine residues. As shown, silymarin increased the expression levels of histone acetylation at various lysine residues in A549 and H460 cells. Equal loading of protein samples was verified using anti-histone H3 antibody.