USP9X and neoplasm: The complement factor H-related (CFHR) protein family induces the ubiquitination of polo-like kinase 1 (PLK1) at lysine 209 (Zhu et al., 2021a), BRCA1-associated protein 1 (BAP1) enhances genomic stability (Perkail et al., 2020), and USP9X is found to restrain tumor growth in the patient-derived tumor xenograft (PDX) model (Pal et al., 2018).