ERBB2 and breast cancer: Humanized anti-HER2 antibody rhuMAB 2C4 or pertuzumab (IMGT/mAb-DB, http://www.imgt.org) is an monoclonal antibody that blocks HER2 dimerization with other ERBB family members in HER2 overexpressing cancer cells [7], and the antibody has been reported to have no efficacy in cancer cells expressing low levels of HER2, such as MCF7 breast cancer cells [8, 9].