The reversal efficacy of the indole derivatives in combination with 2.5 μM of MX in NCI-H460/MX20 cells. The inhibition of proliferation indicates the inhibition of the proliferation of NCI-H460/MX20 cells after incubation with MX in the absence or presence of the indole derivatives, compared to the proliferation of cells in the control group. The results were obtained from three independent experiments performed in triplicate. *, P < 0.05, **, P < 0.01, ****, P < 0.0001 versus no indole derivatives group, two-way ANOVA.