To identify the role of Brachyury on the proliferation and migration capability of breast cancer cells in vitro, the triple-negative breast cancer cell line MDA-MB-231 and ER+/PR+/HER-2-luminal human breast cancer cell line MCF-7 as models for the triple-negative and the luminal A subtype of breast cancer were utilized for further study. The gene discussed is ERBB2; the disease is breast cancer.