Integration of Single-Cell RNA Sequencing Data and Bulk Sequencing Data to Characterise the CD8+ T-Cell Exhaustion Mediated Immune Microenvironment in CRC.

CD8+ T cells are crucial for the anti-tumour immune response, and their exhaustion contributes to poor prognosis and limited immunotherapy efficacy in colorectal cancer (CRC). In this study, we examined the immune microenvironment of CRC by integrating single-cell RNA sequencing (scRNA-seq) and bulk sequencing data. T-cell subtypes in tumour tissues were analysed using CellMarker 2.0 and scType, and an intercellular communication network was constructed through CellChat. Our analysis revealed that exhausted CD8+ T cells exhibit strong interactions with epithelial cells, primarily via the MIF-(CD74 + CXCR4), MIF-(CD74 + CD44) and CD99-CD99 pathways. Based on CD8+ T-cell exhaustion markers, we developed a prognostic model using XGBoost, which demonstrated promising predictive capabilities for CRC prognosis and immunotherapy response. Functional assays showed that MIF knock-down significantly inhibited CRC cell proliferation and invasion. Our findings suggest that MIF and CD99 are key regulators of CD8+ T-cell exhaustion in CRC. This study provides novel insights into the mechanisms underlying T-cell exhaustion in CRC and offers potential biomarkers for improving immunotherapy outcomes.