ERBB2 and breast cancer: The cancer-associated alterations of HER2 are more frequently related to its amplification and overexpression2,37,38; thus, we decided to comparatively characterize the membrane dynamics of endogenous EGFR and HER2 in two human breast cancer cell lines with either very low or very high HER2 expression — SUM15939 or SK-BR-340, respectively (Supplementary Fig. S6a).