ERBB2 and breast cancer: We used several cell lines in our in vitro studies (Osipo et al, 2008); however, we chose to use BT474 ErbB-2-positive breast cancer cells as they are sensitive to trastuzumab and have been used numerous times in preclinical studies (Nagata et al, 2004; Rimawi et al, 2011) to represent the clinical setting.