In an attempt to optimize anti-HER2 therapies, the initial monotherapy with humanized anti-HER2 mAb trastuzumab (Herceptin®, Genentech, South San Francisco, CA, USA) against metastatic gastric or breast cancer was gradually replaced by combination therapies with cytostatic agents (e.g., docetaxel, capecitabine, paclitaxel) and/or other anti-HER2 mAb (e.g., pertuzumab), and/or tyrosine kinase inhibitors (e.g., lapatinib) (2, 3, 6–12). Here, ERBB2 is linked to breast cancer.