Integrative multi-omics analysis identifies key ubiquitination regulators in prostate cancer

BACKGROUND: Ubiquitination plays a crucial role in tumor regulation, yet its specific functions in prostate cancer (PCa) remain incompletely understood. This study aimed to identify key genes associated with ubiquitination processes in PCa and validate their roles across multiple biological levels. METHODS: We integrated single-cell RNA sequencing (scRNA-seq) data from the GEO database with summary-level genome-wide association study (GWAS) data. Through differential expression analysis, summary data-based Mendelian randomization (SMR), and single-cell trajectory analysis, ubiquitination-related genes (URGs) associated with PCa were screened. Validation was performed at both tissue and cellular levels: immunohistochemistry (IHC) on 30 PCa tissue samples stratified by Gleason grade (low-grade: ≤ 3 + 4; high-grade: ≥ 4 + 3), and Western blot (WB) along with quantitative PCR (qPCR) on PCa cell lines (22Rv1, LNCaP, PC-3) versus a normal prostate epithelial cell line (RWPE-1). Functional experiments including Transwell migration, wound healing, CCK-8 proliferation assays, and a cell line-derived xenograft (CDX) mouse model were conducted to validate the biological function of TRIM8. RESULTS: T lymphocytes and epithelial cells were the predominant cell types in the PCa microenvironment. SMR and MR analyses identified POLI and TRIM8 as key causal genes with significant protective associations against PCa (POLI: OR = 0.9385, P = 0.0046; TRIM8: OR = 0.8648, P < 0.001). Colocalization analyses supported their genetic regulatory roles. Molecular docking indicated a high binding affinity between selegiline hydrochloride and POLI (ΔG = -11.3kcal/mol). Experimental validations confirmed these findings: IHC revealed elevated POLI expression in high-grade tumors and higher TRIM8 expression in low-grade tumors. Consistently, WB and qPCR analyses demonstrated that POLI was significantly upregulated, while TRIM8 was downregulated, in PCa cell lines compared to normal controls. Functional assays further demonstrated that TRIM8 overexpression suppressed PC-3 cell migration, proliferation, and in vivo tumor growth, whereas TRIM8 knockdown exerted opposite effects, confirming its tumor-suppressive role. CONCLUSIONS: POLI and TRIM8 are key ubiquitination regulators with causal links to PCa pathogenesis, exhibiting distinct expression patterns correlated with tumor aggressiveness. Functional validation confirms TRIM8 as a tumor suppressor in PCa. These genes represent promising therapeutic targets, and the predicted interaction with selegiline hydrochloride highlights a potential drug-repurposing strategy.