ERBB2 and cancer: The human epidermal growth factor receptor 2 (HER2) signaling pathway has a key role in several malignancies (predominantly in breast cancers, for which around a quarter of the cells overexpress HER2), and its blockade has been shown to significantly halt cancer progression.107 Trastuzumab (Herceptin®; Genentech, San Francisco, CA, USA), the most dominant member of the HER2-targeted therapy, is a monoclonal antibody that confers the ability to reduce the proliferative and metastatic potential of HER2-overexpressing cancer cells.