Systematic Analysis of Human Colorectal Cancer scRNA-seq Revealed Limited Pro-tumoral IL-17 Production Potential in Gamma Delta T Cells

Abstract

Gamma delta ({gamma}{delta}) T cells play a crucial role in anti-tumor immunity due to their cytotoxic properties. However, the role and extent of {gamma}{delta} T cells in production of pro-tumorigenic interleukin-17 (IL-17) within the tumor microenvironment (TME) of colorectal cancer (CRC) remains controversial. In this study, we re-analyzed nine published human CRC whole-tissue single-cell RNA sequencing (scRNA-seq) datasets, identifying 18,483 {gamma}{delta} T cells out of 951,785 total cells, in the neoplastic or adjacent normal tissue of 165 human CRC patients. Our results confirm that tumor-infiltrating {gamma}{delta} T cells exhibit high cytotoxicity-related transcription in both tumor and adjacent normal tissues, but critically, none of the {gamma}{delta} T cell clusters showed IL-17 production potential. We also identified various {gamma}{delta} T cell subsets, including Teff, TRM, Tpex, and Tex, and noted an increased expression of cytotoxic molecules in tumor-infiltrating {gamma}{delta} T cells compared to their normal area counterparts. Our work demonstrates that {gamma}{delta} T cells in CRC primarily function as cytotoxic effector cells rather than IL-17 producers, mitigating the concerns about their potential pro-tumorigenic roles in CRC, highlighting the importance of accurately characterizing these cells for cancer immunotherapy research and the unneglectable cross-species discrepancy between the mouse and human immune system in the study of cancer immunology.