Figure 2: A) Expression of Sirt7 mRNA and B) Sirt7 protein in MCF7 cells transfected with Sirt7 hairpin RNAi. Results are normalized to GAPDH. Stably transfected MCF7 with plasmids expressing RNAi for Sirt7 resulted in C) doxorubicin and D) cisplatin resistance. Cells were incubated with doxorubicin or cisplatin for 48 hours. E) Microscopic brightfield images of MCF7 transfected with Sirt7 RNAi or mock. Knocking down Sirt7 in MCF7 cells caused the cells to exhibit smaller size with long extensions morphology. SA-β-Gal stain was weakly positive in most of MCF7 cells with Sirt7 knock down with 30% strong positive staining. Challenging these cells with different concentrations of doxorubicin (1 and 10 μM) for 48 hours did not induce apoptosis and caused the cells to exhibit very long extensions and increased the positively stained SA-β-Gal cells. Mock transfected MCF7 cells were negative for SA-β-Gal stain. Challenging these cells with doxorubicin increased the percentage of cells stained with SA-β-Gal and induced apoptosis. Results are presented as mean ± SE; *: P>0.05; n=4.