A, Effects of Nutlin-3 (5 μmol/L, 48 h) on total cell numbers following introduction of Control (Ctrl), p16, p21, or p53 shRNA lentiviral constructs. Validation of genetic knockdown is shown in Figure 5E. B, Time-dependent effects of Nutlin-3 on cellular proliferation of SK-Mel-103 as described in A. C, Microphotographs depicting SA-β-Gal activity at day 7 following double infections with the indicated shRNA constructs in SK-Mel-103. D, Protein immunoblots illustrate differing effects on the cell cycle regulator E2F-1 following MDM2 inactivation by shRNA or Nutlin-3 (5 μmol/L) as compared to Doxorubicin (DOX; 0.5 μg/mL). E, Time-dependent effects on the p53-MDM2 pathway and S-phase cell cycle regulators comparing MDM2 inactivation by RNA interference (Control shRNA, C-sh; or MDM2 shRNA, MDM2 sh) to Nutlin-3 (5 μmol/L) treatment.