(A) CHO cells were transfected with expression plasmids encoding the indicated HER2 full length wild-type (WT) or oncogenic point mutants G600D or V664E. Forty hours post-transfection cells were treated for 1 h with 1 μM lapatinib or 30 μM AC3573 and HER2 phosphorylation status was assessed by Western blot with the indicated primary antibodies. (B) Quantification of pY1248HER2/Total HER2 ratio as percentage of DMSO treated conditions. Data are means ± SD from N = 3 independent experiments. (C) Quantification of pY877HER2/Total HER2 ratio as percentage of DMSO treated conditions. Data are means ± SD from N = 3 independent experiments. (D) Quantification of pY1221HER2/Total HER2 ratio as percentage of DMSO treated conditions. Data are means ± SD from N = 3 independent experiments.