ESR1 and breast cancer: Our previous in vitro [17] and in vivo studies using MCF-7 breast cancer cells have shown that Si-Wu-Tang (SWT) is able to reverse the antiproliferative effects induced by tamoxifen, including tumor weight, tumor volume, increased ERα expression, and N-cadherin expression, when the tamoxifen + SWT-treated group is compared to the tamoxifen-treated group [19].