MCF-7 and MDA-MB-468 cells were treated with OC for 5 and 7 days, respectively; 2 µM rotenone (complex I inhibitor) was added during the last 24 h of culture. a Alizarin red S staining was performed in different treatment groups, and quantitative analysis of calcification was conducted using cetylpyridinium chloride. P value was calculated by one-way ANOVA with Bonferroni post-test. **P < 0.01, NS not significant. b Western blotting was performed to determine the expression of calcification-related markers in MDA-MB-468 and MCF-7 cells. c The corresponding expression of epithelial-to-mesenchymal transition (EMT)-related molecules was evaluated by immunoblotting in MDA-MB-468 and MCF-7 cells. d Cell extracts were subjected to western blotting with the antibodies against phospho-Smad2/3, phospho-JNK, phospho-ERK, phospho-P38, Smad2/3, JNK, ERK, P38 and β-actin. e, f MCF-7 and MDA-MB-468 cells were treated with OC for 5 and 7 days, respectively; 10 µM LY 3200882 (transforming growth factor (TGF)-β inhibitor, Selleck) was added during the last 24 h of culture. The corresponding expression of EMT-related molecules and OXPHOS complex subunits was evaluated by western blotting. Data are shown as mean ± SD, and they represent three independent experiments with similar results.