ZUP1 and cancer: Ubiquitin specific peptidase 9, X-linked (Usp9x), also known as FAF; FAM; DFFRX and MRX99, is a high MW DUB that has been shown to be over-expressed in several cancers, but can have both positive and negative impact on tumorigenicity, depending on the cancer type and disease model studied11, 12, 13, 14, 15, 16.