Figure 5. p21^waf1 protein half-life following SN38 treatment. Cells were incubated with 10 ng/ml SN38 for 24 h or for an additional 24 h in fresh medium. Cells were then incubated with the protein synthesis inhibitor cyclohexmide (10 µg/ml) for the indicated times. The half-lives are presented as the means ± SE for three independent experiments.