Knockdown of Survivin results in DNA damage and p53-dependent induction of the cdk-inhibitor p21waf/cip. a-c: Indirect-immunofluorescence analysis of SBC-2 and SBC-2shp53 cells, transduced with shLuc and shSurv, respectively. a: Representative images of simultaneous p21waf/cip and ɣH2AX stainings showing ɣH2AX-foci only in polyploid nuclei of shSurv-SBC-2 cells. Magnification bar 50 μm. b: Quantification of ɣH2AX and p21waf/cip expression. Depicted are the mean values and SEM (n = 3; **p < 0.01). Knockdown of Survivin causes DNA-damage irrespective of p53 status whereas induction of p21waf/cip is p53-dependent. c: Quantification of ɣH2AX positive cells with simultaneous p21waf/cip expression. Note the increase in p21waf/cip expression linked to DNA damage in SBC-2 cells with functional p53 (p < 0.01). d: Representative FACS-analysis showing an increase in ɣH2AX staining in Survivin-depleted HCT116 cells compared to shLuc control, irrespective of p53-status. e: Distribution of ɣH2AX expression in wild type and HCT116p53−/− cells in dependence of DNA content. The increase in ɣH2AX-positive cell fractions is independent from p53 status and directly correlates to the gradual increase in polyploidy.