USP54 is a ubiquitin-specific peptidase that functions as an active deubiquitinase with high specificity for Lys-63-linked polyubiquitin chains 1. Unlike previously annotated pseudoenzymes, USP54 cleaves within K63-linked ubiquitin chains and requires polyubiquitin chains of at least 3 ubiquitins, recognizing ubiquitin at the S2 position within the chain 1. USP54 mediates deubiquitination of multiple substrates including p53, EGFR, PLK4, and ULK1, thereby regulating their stability and downstream signaling 234. In cancer biology, USP54 exhibits context-dependent roles. USP54 suppression inhibits lung adenocarcinoma progression by reducing p53 ubiquitination and subsequent GLUT1-mediated aerobic glycolysis 2. Similarly, USP54 knockdown enhances gefitinib sensitivity in resistant NSCLC by increasing EGFR ubiquitination and degradation 3. Conversely, USP54 is overexpressed in colorectal cancer stem cells and nasopharyngeal carcinoma, promoting tumorigenesis and malignancy through ULK1 stabilization and autophagy activation 54. USP54 elevation correlates with castration-resistant prostate cancer progression via androgen receptor signaling 6. Additionally, USP54 expression increases with skeletal muscle aging and may influence sarcopenia-associated pathways 7.