ERBB2 and breast cancer: The importance of ErbB2 signaling in cardiac physiology soon became evident by a discovery that some breast cancer patients treated with Trastuzumab (Herceptin, anti-ErbB2), an inhibitor of HER2 signaling, develop synergistic cardiac dysfunction, particularly when Trastuzumab is combined with doxorubicin [1], [2], [3].