Ubiquitin-specific peptidase 5 facilitates cancer stem cell-like properties in lung cancer by deubiquitinating β-catenin
**Background**: Lung cancer has the highest mortality rate globally, and growing evidence links cancer stem cells (CSCs) with poor prognosis, recurrence, and metastasis. Identifying new biomarkers and therapeutic targets for lung CSCs is critical.
**Methods**: We conducted single-sample gene set enrichment analysis (ssGSEA) on 1554 Reactome gene sets to uncover pathways associated with the mRNA expression-based stemness index (mRNAsi). This analysis was based on genome-wide RNA sequencing data from 509 lung adenocarcinoma (LUAD) patients in The Cancer Genome Atlas (TCGA). We evaluated the effects of ubiquitin-specific peptidase 5 (USP5) on CSC-like properties and metastasis through in vitro assays (sphere formation, migration, and invasion) and in vivo xenografted animal models. To verify USP5’s impact on β-catenin deubiquitination, we performed cycloheximide chase, co-immunoprecipitation, and deubiquitination assays.
**Results**: USP5 expression was positively associated with stemness signatures and poor clinical outcomes in lung cancer samples. Knocking down USP5 diminished CSC-like traits, epithelial-mesenchymal transition (EMT), and metastasis both in vitro and in vivo. USP5 was found to interact with β-catenin, leading to its deubiquitination, stabilization, and subsequent activation of the Wnt/β-catenin pathway. USP5 expression also correlated with increased Wnt/TCF pathway activity in human lung cancer. Suppressing β-catenin expression reduced USP5-induced sphere formation. Inhibition of USP5 using the small molecule WP1130 promoted β-catenin degradation and significantly inhibited sphere formation, migration, and invasion. Additionally, we identified a subgroup of tumors with poor prognosis characterized by high USP5 levels, Wnt signaling scores, and Stemness scores in both TCGA-LUAD and Rousseaux_2013 datasets.
**Conclusions**: Our findings highlight USP5’s role in enhancing Wnt/β-catenin signaling, which promotes lung cancer stemness and metastasis. Targeting USP5 could be a promising therapeutic strategy for improving lung cancer treatment outcomes.