A Preclinical Evaluation of Antimycin A as a Potential Antilung Cancer Stem Cell Agent
Figure 4
Antimycin A overcomes gefitinib resistance in lung cancer cells. (a) Gefitinib-resistant PC-9 lung cancer cells (PC-9/GR) were treated with gefitinib (5 μM), AMA (5 μM), and the two agents combined. AMA or gefitinib alone could only suppress PC-9/GR proliferation by approximately 35% and 42%, respectively. Gefitinib and AMA combined synergistically suppressed PC-9/GR proliferation by approximately 80%. Scale bar, 100 μm. (b) Isobologram analysis showed that the combination of gefitinib and AMA suppressed PC-9/GR proliferation synergistically. Normalized isobolograms are shown where PC-9/GR were exposed for 48 h to different combinations of AMA (0.5, 2.5, and 5 μM) and gefitinib (2.5, 5, and 10 μM). Symbols designate the combination index value for each fraction affected. The curves were generated by Calcusyn software to fit the experimental points. The data are representative of three independent experiments. Values below the line are synergistic, whereas those close to the line are additive and those above the line antagonistic. (c) AMA dose dependently decreased the percentage of side-population cells in lung cancer cells. A representative flow cytometric analysis showed that AMA decreased the percentage of SP cells in the A549 cell line (upper panel); AMA also suppressed the SP cell populations in PC-9 and PC-9/GR cell lines (bottom panel). (d) Western blot analysis demonstrated that gefitinib (5 μM) and AMA (5 μM) combination treatment significantly inhibited β-catenin-associated signaling components in A549 SP cells. *denotes while **represents as compared to their respective controls.
