Detection of apoptosis in DN-treated A549 cells by Annexin V-FITC 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 stained with PI and AnnexinV-FITC, and measured by flow cytometry. (A) Representative dot plots from one of at least three independent experiments with the percentages of early apoptotic cells are shown. (B) Bar graphs with percentages of cells in the respective quadrants are indicated. LL: Viable cells, LR: Early apoptotic cells, UR: Late apoptotic cells, UL: Dead cells. *Statistical significance (p <0.05) versus control at equal incubation periods.