ERBB2 and breast carcinoma: Pertuzumab binds to the dimerization domain (domain II) of HER2 (human epidermal growth factor receptor 2) and inhibits the dimerization of HER2 with other HER receptors, in turn inhibiting the down-stream transduction of tumor survival signals1; trastuzumab targeting at the fourth domain (domain IV) of HER22 inhibits HER2-positive breast cancer growth by down-regulating the HER2 expression, inhibiting the releasing of the HER2 ectodomain and inducing antibody-dependent cell-mediated cytotoxicity (ADCC).