Prognostic signature and immune microenvironment characterization in colorectal cancer based on interleukin-related genes.

[BACKGROUND] Colorectal cancer (CRC) exhibits substantial prognostic heterogeneity, and immune checkpoint inhibitors benefit only approximately 10%-15% of patients with mismatch repair-deficient/microsatellite instability-high (dMMR/MSI-H) status. Therefore, there is an urgent need for risk stratification tools that are both biologically interpretable and clinically applicable.

[METHODS] We integrated transcriptomic and clinical data from the TCGA-COAD/READ and GEO-GSE39582 cohorts, comprising 1209 cases, and identified 25 interleukin-related genes (IRGs). Using consensus clustering, we defined two distinct molecular subtypes. In the training cohort, LASSO-Cox regression identified 12 IRGs for constructing a prognostic risk score model, which was subsequently validated in both an independent cohort and the combined dataset. The immune-stromal microenvironment was characterized using CIBERSORT, Single-sample Gene Set Enrichment Analysis (ssGSEA), and the ESTIMATE algorithm. IL20RB expression was assessed via Quantitative PCR (qPCR) and Immunohistochemistry (IHC), and its functional role was evaluated through small interfering RNA (siRNA)-mediated knockdown assays.

[RESULTS] The risk model achieved AUC values of 0.683, 0.684, and 0.629 for 1-, 3-, and 5-year OS, respectively, in the combined cohort. After adjustment for TNM stage and age, the risk score remained an independent prognostic factor. The high-risk group exhibited an "immune-cold, stroma-rich" phenotype, characterized by enrichment of M2 macrophages and neutrophils. In contrast, the low-risk group displayed an "immune-inflamed" phenotype, with increased infiltration of CD8⁺ T cells and NK cells. IL20RB was significantly overexpressed in CRC tissues and cell lines, and its knockdown suppressed cell proliferation, migration, and invasion.

[CONCLUSION] A new prognostic model based on IRG was established and validated in CRC, demonstrating its ability to forecast OS and to effectively differentiate between immune-inflamed ("hot") and non-inflamed ("cold") tumor microenvironments. The overexpression and functional relevance of IL20RB suggest its involvement in the immune-cold, stroma-rich phenotype, providing experimental evidence and a foundation for further investigation into IL-related signaling pathways in CRC progression and targeted therapy.