Effects of DOX on IC₅₀ values of DOX in each group.

<p>Cytotoxicity assays were performed as described in the “Materials and Methods”. The IC₅₀ is the drug concentration (µmol/L) that results in a 50% inhibition of cell growth. A, B) The survival curve in MCF-7 cells and MDA-MB-231 cells, respectively.C, D) The IC₅₀ value of each group. A21, cells treated with 0.2 µmol/L DOX for 24 h; An, cells transfected with Sp1 ODNs for 24 h; AnA, cells treated with 0.2 µmol/L DOX for 24 h after their transfection with Sp1 ODNs; Mu, cells transfected with mock Sp1 ODNs for 24 h; MuA, cells treated with 0.2 µmol/L DOX for 24 h after they were transfected with mock Sp1 ODNs. **<i>p</i><0.01 compared with MCF-7 cells. # <i>p</i><0.05 compared with MDA-MB-231 cells.