Figure 3. Asclepiasterol sensitizes MDR cells to apoptosis.

MDR cells were treated with paclitaxel alone (1.0 μM), asclepiasterol alone (5.0 μM), VRP alone (10.0 μM), or their combination for 48h. The IC₅₀ values for paclitaxel had been previously determined for each cell line. Apoptosis was analyzed by flow cytometry as the percentage of cells labeled by Annexin V and PI. A representative set of data from three independent experiments is shown. MDR cells were resistant to paclitaxel, and asclepiasterol or VRP increased cell apoptosis induced by paclitaxel. All experiments were repeated three times and data are presented in histogram as means±SD. *P < 0.05, **P < 0.01, compared with doxorubicin treatment alone.