Single-Cell Sequencing Reveals γδT Cell Heterogeneity Under Distinct Microsatellite Statuses as a Potential Biomarker for Immunotherapy and Prognosis in Colorectal Cancer.

Background: Colorectal cancer (CRC) continues to represent one of the most common and lethal malignant tumors globally. Notably, only patients diagnosed with microsatellite instability-high (MSI-H) colorectal cancer derive substantial clinical benefits from immune checkpoint inhibitor therapy. As critical immune cells that infiltrate tumors, γδT cells are tightly linked to the therapeutic response in colorectal cancer patients with microsatellite instability (MSI) colorectal cancer. However, the heterogeneous characteristics of γδT cells in colorectal cancer with different microsatellite statuses and their specific roles in regulating immunotherapy responses remain unclear. Methods: We performed dimensionality reduction and clustering analysis on γδT cells from a single-cell RNA sequencing dataset to explore diversity and functional characteristics of distinct γδT cell subsets. Meanwhile, bulk transcriptome data were applied to further investigate the immune infiltration, clinical characteristics, and immune checkpoint molecule expression in CRC patients stratified by distinct γδT cell subpopulations. Results: We identified five γδT cell subsets, among which the C4_CXCL13 γδT cell subsets was enriched in MSI CRC and exhibited an exhausted-like T cell phenotype while retaining robust cytotoxic function. A signature score based on these 17 marker genes was associated with survival, immune infiltration, and therapeutic response, thus representing a potentially valuable independent prognostic factor. Conclusions: The C4_CXCL13 γδT cell subset represents a characteristic subset in MSI CRC and is closely associated with clinical prognosis and benefit from immunotherapy. It represents a potential clinical marker for classifying patients and estimating the response to immunotherapy, offering a novel target for personalized immunotherapy in CRC.