Conserved minimal CD8 cytotoxic immune-state unit in an IL18R1-associated immune program in hepatocellular carcinoma

BACKGROUND AND AIMS: The conserved human correlate of interleukin-18 receptor 1 (IL-18R1)-associated immune states in hepatocellular carcinoma (HCC) remains undefined. We aimed to identify a minimal, reproducible, immune-state component associated with IL18R1 across independent human HCC cohorts and evaluate its clinical relevance. METHODS: Publicly available single-cell RNA sequencing datasets from five independent HCC cohorts were analyzed using a unified framework. Paired tumor-adjacent cohorts were prioritized for primary analyses, whereas tumor-only cohorts served as supportive datasets. CD8 T cells were stratified by IL18R1 expression, and tumor-specific enrichment was quantified using difference-in-differences. We validated the spatial transcriptomics using a murine liver tumor Xenium dataset. Clinical relevance was evaluated using The Cancer Genome Atlas Liver Hepatocellular Carcinoma (TCGA-LIHC) bulk RNA-seq data. RESULTS: IL18R1-positive CD8 T cells exhibited a tumor-specific, C-C motif chemokine ligand 5 (CCL5)-centered cytotoxic transcriptional program, consistently enriched across datasets. Alternative IL18R1 stratification confirmed the identified immune program's robustness. Spatial transcriptomics localized this cytotoxic state in tumor-associated CD8 T cells and highlighted increased expression of Ccl5 and Cxcr3. Tumor-only cohorts demonstrated substantial heterogeneity, highlighting the importance of paired cohort design. In TCGA-LIHC, a composite CCL5-centered cytotoxic core score, not CCL5 alone, was associated with improved overall survival, although this attenuated after adjusting for clinical covariates. CONCLUSIONS: The dominant human correlate of an IL18R1-associated immune state in HCC is a compact, CCL5-centered CD8 cytotoxic module, not a broad inflammatory response. This spatially validated unit provides a reproducible framework for HCC immune-state characterization and stratification.