Single-Cell Sequencing and Mendelian Randomization Reveal T Cell Nuclear Factor Genes in Hepatocellular Carcinoma Progression.

This study integrates single-cell RNA sequencing with Mendelian randomization to elucidate the role of nuclear factor of activated T cells (NFAT)-related genes in the progression of hepatocellular carcinoma (HCC). The GSE162616 dataset was analyzed to identify differentially expressed cells and NFAT-related genes through quality control, clustering, and -score algorithms. Mendelian randomization analysis of expression quantitative trait loci (eQTL) data was performed to identify hub genes causally linked to HCC. Validation in The Cancer Genome Atlas-Liver Hepatocellular Carcinoma cohort included survival analysis, clinical correlation, and nomogram construction. Sixteen cell clusters were resolved and annotated into five types: natural killer (NK) cells, T cells, B cells, hepatocytes, and monocytes. Differentially expressed NFAT-related genes were predominantly enriched in immune and cytokine pathways. Three genes-CACYBP, CTLA4, and RGCC-were identified as causally associated with HCC and designated as hub genes. T cells and NK cells emerged as key cellular populations, and pseudotime analysis delineated T cell differentiation trajectories. Cell-cell communication analysis revealed robust interactions between NK and B cells and between NK and T cells, primarily via the MIF-(CD74+CXCR4) axis. All three hub genes were upregulated in HCC tissues. A nomogram integrating these genes exhibited excellent diagnostic performance (AUC = 0.9). These results establish CACYBP and RGCC as risk factors and CTLA4 as a protective factor for HCC. The nomogram offers a potential tool for early diagnosis and immunotherapy guidance. Our findings highlight the value of integrating single-cell transcriptomics with Mendelian randomization for prioritizing causal genes and provide novel insights into NFAT-mediated immune regulation in HCC.