P21 knockdown abrogates the tetraploid G1 arrest induced by cisplatin and sensitizes cells to p53-dependent killing.

<p><b>A)</b> HCT116 clones were either untreated (NT) or treated with 15 µM cisplatin. At the 24 hr time point after cisplatin treatment, cells were either mock transfected (MT) or transfected with the indicated siRNAs, and cultured in the continued presence of cisplatin for an additional 48 hrs. Representative cell cycle profiles are shown. The number in the upper right corner is the percentage of sub-G1 cells. <b>B)</b> Plotted is the percentage of sub-G1 (apoptotic) cells from the experiments in A). The data represent the average of 3 experiments +/− s.e.m.