As matrine has therapeutic effects on various solid tumors, including liver, lung, stomach, esophageal, colorectal, cervical and ovarian cancer, as well as malignant lymphoma (11–13), the present study investigated whether matrine has antitumor effects on three breast cancer cell lines, ER-positive MCF7 cells, HER2-positive BT-474 cells and highly metastatic MDA-MB-231 cells. Here, ERBB2 is linked to breast cancer.