ERBB2 and breast cancer: This "HER2 super-expression", which has not been reported in earlier trastuzumab-resistant breast cancer models [58-60], decreased back and even below the baseline HER2 level found in trastuzumab-sensitive SKBR3 parental cells when SKBR3/Tzb100 cells were treated with oleuropein aglycone (up to 71% reduction; Figure 7A).