ERBB2 and breast cancer: Besides, SWT reversed tamoxifen-induced antiproliferative effects in MCF-7 cells, both in vitro and in vivo; and SWT also reversed trastuzumab-induced antiproliferative activity in different properties of breast cancer HER2+ cell lines (SK-BR-3 and BT-474) through increased phosphorylation of the cell cycle regulatory protein p27(Kip1) and possibly of the antiapoptosis protein P38 [17, 19].