Flow cytometric analysis of cell division by dilution of CFSE. (A) CFSE histograms of control A549 cells (top) and DN-treated A549 cells (bottom) for 24, 48 and 72-h incubation period. A profile of sequential halving of CFSE fluorescence intensity with each generation was monitored, and numbers of cell division were analyzed using ModFit LT 3.2 program. (B) Proliferation index (left) and precursor frequency (right) of untreated and DN-treated A549 cells. Each bar graph represents the mean ± SD of at least three independent experiments. *Statistical significance (p <0.05) versus control.