Figure 5.

Up-regulation of p53 is a necessary but not sufficient condition for noscapine-mediated apoptosis. The p21 gene is a crucial player mediating the apoptotic effects downstream of the p53 gene. Reintroduction of p21 in p21-null cells significantly increased the sub-G₁ population and the extent of apoptosis as revealed by cell cycle experiments and Annexin V staining. A, cell cycle profiles of p21-transfected p21-null cells (T) along with their empty vector–transfected controls. B, graphical representation of the quantitation of the sub-G₁ population. C, graphical depiction of the percent Annexin-positive cells for p21-transfected cells and empty vector–transfected controls on noscapine treatment for 0, 12, 24, and 48 h. Columns, average of three independent experiments; bars, SD (P < 0.05). D, immunoblot analysis of cell lysates from p21-transfected p21-null cells and empty vector–transfected controls.