Figure 3.

Senescence is the fate of cells undergoing mitotic catastrophe in PAB-treated A549 cells. (A) The cells were incubated with 20 μmol/L PAB or combined with different concentrations of Z-VAD for 3 d. Cell proliferation was measured by an MTT assay. (B, C) The cells treated with 20 μmol/L PAB or 0.1 μmol/L taxol at the indicated time points. Taxol (Tax) was used as a positive control. (B) The induction of apoptosis was determined by a flow cytometric analysis with Annexin V-FITC and PI-staining. The cells in the lower right (LR) quadrant indicate Annexin-positive/PI negative, early apoptotic cells. The cells in the upper right (UR) quadrant indicate Annexin-positive/PI-positive, late apoptotic or necrotic cells. The LR or UR ratio is indicated in the right panel. (C) The protein expression of caspase-3 was determined by a Western blot analysis after PAB or Tax treatment. (D, E) The cells were treated with 20 μmol/L PAB for 1, 2, 3 and 4 d. (D) The senescent cells were examined by SA-β-Gal staining (×200 magnification). The ratio of the SA-β-Gal positive cells is shown in the right panel. Black arrows: typical SA-β-Gal positive cells. (E) The protein levels of p53, p-p53 (Ser 15), and p21 were examined by Western blot analysis. The data are presented as the mean±SD of three independent experiments. ^*P<0.05, ^**P<0.01 vs control group.