USP9X participates in a variety of normal biological functions of mammals.14 In addition, USP9X is involved in regulating tumor cell apoptosis, proliferation, adhesion, and other biological processes.15 USP9X is expressed abnormally in nonsmall cell lung cancer, breast cancer, melanoma, head and neck SCC, and other human malignancies.16, 17, 18, 19 USP9X regulates the ubiquitination of its target protein by ubiquitin‐specific protease activity, thereby affecting the expression level.20 Therefore, USP9X has become a potential target for tumor therapy. Here, USP9X is linked to breast cancer.