JY-1-106 sensitized tumor cells to chemotherapy. (A and B) Synergistic inhibition of cancer cell growth in vitro using a combination of JY-1-106 and Taxol. A549 cells were treated with JY-1-106 and Taxol at various concentrations. The viabilities of the treated cells were subsequently determined using the XTT assay. The results were converted to percentages of viable cells, and the data shown are representative of three independent experiments. Synergy was determined by calculating combination index (CI) values with Calcusyn software. (C) Western blot analysis of BH3-only proteins after Taxol treatment. A549 cells were exposed to 5 nM Taxol for 12 or 24 hours. Cellular proteins were then analyzed by western blotting using appropriate monoclonal and polyclonal antibodies specific for PUMA and Bim proteins. (D) Measurement of apoptotic cells using an Annexin V binding assay. A549 cells were labeled with Annexin V-FITC and counterstained with PI after exposure to JY-1-106, Taxol or a combination of both for 12 hours. Cells were analyzed by flow cytometry. The final results were presented as the average of three independent experiments.