Figure 1. Chemoresistance of breast cancer MDA-MB-231 cells against PAX, cyclophosphamide or epirubicin. MDA-MB-231 cells were treated with different concentrations of epirubicin (A), cyclophosphamide (B), or PAX (C) for 24 hours, respectively. Chemoresistance was shown by cell viability. n=3 for each treatment. **p<0.01 compared to untreated cells. (D) The half maximal inhibitory concentration (IC50) of PAX in MDA-MB-231 cells was determined by using CCK8. (E) BEAS-2B, the immortalized normal cells, and MDA-MB-231 cells were treated with 0.01, 0.1, 1 or 5 μg/ml PAX respectively for 24 hours. n=3 for each treatment. **p<0.01 compared to the value of BEAS-2B cells at the corresponding time point.