Figure 8
YD in combination with gefitinib achieves synergistic suppression of resistance by inhibiting compensatory mechanisms of AXL. (a) Characterization of the combination of YD and gefitinib in A549-PTXR-derived GPs upon AXL RNAi. Cells were treated with the indicated combination of drugs for 48 h. Cell viability was determined by SRB assay and the combination synergy was measured by calculating the combination index values. Values represent mean ± SD of three biological replicates. Python (seaborn; https://seaborn.pydata.org/) was used to generate the plot. (b) Combination effects description after combination treatment with YD and gefitinib. *P < 0.05, **P < 0.01, ***P < 0.005, Student’s t test. (c) Luminescence-based kinase assay for AKT, AXL, and EGFR in indicated cells, as in a, upon AXL RNAi. Cells were treated with indicated drugs alone or in combination (#1, 2.4 nM YD + 4 μM gefitinib; #2, 4.8 nM YD + 8 μM YD) for 48 h. Values are relative to untransfected control (UT). Values represent mean ± SD of two biological replicates. GraphPad Prism 7.01 was used to generate the plot. (d) Characterization of gefitinib resistance in indicated cells as in A upon AXL RNAi. Cells were treated with indicated drugs alone or in combination as in b. Cells were then treated with or without gefitinib for 72 h with a concentration dilution series and were assayed for SRB. Resistance was assessed based on drug IC50 values. Values represent mean ± SD of three biological replicates. GraphPad Prism 7.01 was used to generate the plot. All IC50s were calculated using TableCurve 2D v5.01.
