Her2 (human epidermal growth factor family receptor2, aka ERBB2) overexpressing breast cancers are typically treatedwith Her2 inhibitors such as trastuzumab, pertuzumab, and nivolumab.However, ∼15% of Her2-overexpressing cancers do not respondto these drugs at baseline,20 and mostpatients develop resistance within 1 year.21 Thus, understanding the biology of Her2 and its downstream signalingremains an urgent goal in cancer research. Here, ERBB2 is linked to breast cancer.