USP9X and cancer: Recently, a high‐throughput quantitative proteomic analysis to identify the potential substrates of USP9X using wild‐type (WT) and USP9X‐depleted HeLa cells indicates that BRCA1 could be regulated by USP9X.36 Considering the functional importance of BRCA1 in human cancer development and therapeutic responsiveness, in this study we aimed to address the functional and mechanistic role of USP9X in the regulation of BRCA1 in human cancer cells.