The inability of AG 1478 to abolish HER2 phosphorylation was not due to EGF stimulation since treatment of AG 1478 alone without EGF stimulation also failed to abolish HER2 phosphorylation in A431 cells and two other breast cancer lines, MDAMB-453 and SKBR3 (Figure S1D, upper panels) despite the effect on PKB and ERK 1/2 phosphorylation (Figure S1D, lower panels). Here, ERBB2 is linked to breast cancer.