ERBB2 and breast cancer: We used cell lines representing normal mammary epithelium, immortalised mammary epithelium (IMM) and the breast cancer molecular subtypes luminal (LUM: ER+, PR+, HER2−), HER2-enriched (HER2-E: ER−, PR−, HER2+) and basal/triple negative (TN: ER−, PR−, HER2−).