Ubiquitin-Specific Protease 1 Promotes Bladder Cancer Progression by Stabilizing c-MYC

Ubiquitination is an important post-transcriptional modification crucial for maintaining cell homeostasis. As a deubiquitination enzyme, ubiquitin-specific protease 1 (USP1) is associated with tumor progression; however, its role in bladder cancer is unknown. This study aimed to analyze USP1 expression and study its roles in bladder cancer.

The web server GEPIA was used to analyze the USP1 expression. To explore USP1's function in bladder cancer, we constructed USP1-knockout cell lines in UMUC3 cells. A FLAG-USP1 (WT USP1) plasmid and a plasmid FLAG-USP1 C90S (catalytic-inactive mutant) were used to overexpress USP1 in T24 cells. CCK8, colony formation, and Transwell assays were used to assess cell viability, proliferation, and migration. RNA-sequencing (RNA-seq) and dual-luciferase reporter assays were performed to screen the pathway. Co-immunoprecipitation and immunofluorescence were used to explore the interaction between USP1 and c-MYC. A xenograft mouse model was used to study the role of USP1 in bladder cancer.

USP1 expression was upregulated in human bladder cancer cells and correlated with poor patient prognosis. USP1 overexpression promoted cell proliferation, clone formation, and migration, and this was attenuated by genetic ablation of USP1. Furthermore, we observed that USP1 deficiency inhibited tumor formation in vivo. Mechanistically, the c-MYC pathway was remarkably activated compared with the other pathways. Furthermore, USP1 could interact with c-MYC and increase c-MYC's stability depending on the catalytic activity of USP1.

Our results suggested that high expression of USP1 promotes bladder cancer progression by stabilizing c-MYC; hence, USP1 may serve as a novel therapeutic target for treating bladder cancer.