Butein reduced the viabilities of different breast cancer cells, while not affecting resistant cells HER2 positive HCC-1419 (human cell line isolated from primary ductal carcinoma), SKBR-3 (human breast cancer cell line that overexpresses the Her2 gene product) and HCC-2218 cells (epithelial fibroblast cell isolated from the mammary gland ductal carcinoma). Here, ERBB2 is linked to breast cancer.