Cell cycle distributions of DN-treated A549 cells by flow cytometric analysis. A549 cells were either untreated or treated with 15 μM DN or 30 μM DN for 24, 48 and 72 h, then fixed, stained with PI, and analyzed by flow cytometry. Representative histograms from one of at least three independent experiments are shown. The percentages of cells in sub-G1, G0/G1, S and G2/M phases were analyzed using ModFit LT 3.2 program and indicated. *Statistical significance (p <0.05) versus control at equal incubation periods.