USP9X and melanoma: Ubiquitin‐specific peptidase 9X (USP9X) is a highly conserved DUB belonging to the ubiquitin‐specific protease (USP) family.21 Accumulating evidence shows that USP9X is frequently upregulated and promotes tumorigenesis and chemoresistance in some types of human cancer, such as breast22, 23, 24 and lung cancer,25, 26 melanoma,27 lymphoma,28, 29 and glioblastoma.30 Strikingly, a tumor suppressor role of USP9X has been documented in pancreatic,31, 32, 33 colorectal,34 and renal cancer.35 The complex role of USP9X in human cancers is determined by its various substrates.