A Prognostic Model for Prostate Cancer Screened from Stress Granule-Related Genes: An Integrated Bioinformatic Analysis and Experimental Verification of SPAG5 Function

Background: Stress granules (SGs) are associated with cancer development, but their role in prostate cancer remains unclear. This study aims to identify SG-associated prognostic genes and to discover the biological and clinical significance of these genes. Methods: We integrated PCa transcriptomic, clinical, and scRNA-seq data from GEO and TCGA and obtained SG-related genes from GeneCards. Then we applied differential expression analysis, univariate Cox regression, and LASSO regression to identify candidate genes. Subsequently, a risk model was established, encompassing nomogram analysis, functional enrichment, immune infiltration, and scRNA-seq validation. Clinical tissue samples were validated using RT-qPCR and IHC. We performed an shRNA-mediated knockdown of SPAG5 in PC-3 and 22Rv1 cells and then applied RT-qPCR, Western blot, CCK-8, colony formation, wound healing, and Transwell assays to assess its effects. Results: Six prognostic genes (SPAG5, FN1, CCK, EGF, SELE, PTGS2) were identified. The risk model classified patients into low-risk and high-risk groups. A nomogram combining risk score and T stage showed moderate discriminatory capacity (AUC > 0.60). High-risk patients exhibited differences in cell cycle pathway enrichment and immune infiltration, and FN1 was positively correlated with Tregs (r = 0.60). ScRNA-seq revealed the dynamic expression of CCK, FN1, and PTGS2 in epithelial cells from paired tumor and normal samples. RT-qPCR and IHC confirmed that EGF and SPAG5 are upregulated in PCa tissue, while CCK, FN1, SELE, and PTGS2 are downregulated. Following SPAG5 knockdown, proliferation, migration, and invasion were inhibited in both cell lines. Conclusions: A reliable prognostic model screened from a stress granule-related gene set was established. Experimental data linking this model to the immune microenvironment and epithelial differentiation support the notion that SPAG5 is an oncogenic factor, suggesting that SPAG5 warrants further investigation as a potential prognostic biomarker, though prospective validation is required before clinical translation.