A study of peripheral blood monocytes isolated from 20 HER2+ breast cancer patients, demonstrated increased antibody-dependent cell-mediated cytotoxicity (ADCC) in patients who received paclitaxel plus trastuzumab compared to patients who received trastuzumab as a monotherapy [19] and in vitro studies demonstrate that trastuzumab alone enhances class I-restricted presentation of endogenous HER-2 antigen, resulting in higher susceptibility of HER2-overexpressing tumors to lysis by the HER-2-specific cytotoxic T-lymphocytes [20, 21]. This evidence concerns the gene ERBB2 and breast cancer.