Figure 4: Expression of p53 and p21(cip-1/waf-1) in drug-resistant cells (MCF7 and A2780) and cells transfected with Sirt7 or mock measured by PCR primers amplifying exon 5; B) Western blot analysis of p53, p21 and caspase-3 in control and Sirt7 knockdown MCF7 cells in the absence or presence of doxorubicin. RNAi-mediated inhibition of Sirt7 expression resulted in increased procaspase-3 expression. Doxorubicin increased the protein expression levels of p53 and p21 in a dose-dependent manner in Sirt7 knockdown cells. The mRNA and protein expression levels of p53 and p21 were quantified, and the results are presented in graphical form below each panel in A and B, respectively. Results represent the means ± SE of least 4 experiments; *: P>0.05.