Figure 5. The downregulation of p21 facilitates S phase entry at high concentrations of MPA .

1. HCT116 cells were treated with either the vehicle alone (−), 1 μM MPA, or 10 μM MPA for 24 h, before p21 immunolabeling, propidium iodide staining, and FACS analysis. Cell‐cycle profiles of the total cell population (upper panel, left), the total intensity of p21, and propidium iodide were determined in 20,000 cells and plotted in a scatter diagram (lower panel, left). The specific cell‐cycle profiles are shown of p21^high (upper panel, right) and p21^low (lower panel, right) cell populations. Mean ± SD of the percentage of cells in each cell‐cycle phase of at least two independent experiments is shown in the right panels.
2. HCT116 p21^−/− isogenic cell lines were transfected for 24 h with an empty plasmid (EV) or a plasmid encoding a p21^wt cDNA (p21‐OE), and then, cells were serum‐deprived for 16 h before the re‐addition of serum for additional 24 h in the absence or presence of 10 μM MPA. Cells were subjected to p21 immunolabeling, propidium iodide staining, and FACS analysis. The results are representative of two independent experiments.