Figure 4. HER4 silencing reverses trastuzumab resistance and decreases cell counts in trastuzumab-resistant cells.

(A & B) Trastuzumab-resistant SKBR3 and BT474 cells were transfected with HER4 siRNA₁₀ and siRNA₁₁ in the presence (C) or withdrawal (W) of trastuzumab before western blot analysis for the indicated proteins. The middle and right panels show a relative quantification of HER4 and pHER4 levels from 3 independent experiments using Image J software. A 1-way ANOVA test with Bonferroni's multiple comparison was applied to determine significant differences between the groups (n.s=not significant, *p<0.05, ***p<0.001) (C & D) Cell count experiments were performed at 72 hr post transfection after siRNA experiments as in (A) and (B). The graphs show relative cell count relative to the scramble resistant cells. The mean ratios of cell counts ± SD from three independent experiments are shown (**p<0.01, ***p<0.001).