Single-Cell Analysis Reveals Characterization of Infiltrating T Cells in Moderately Differentiated Colorectal Cancer

OBJECTIVE: This study aimed to characterize the tumor-infiltrating T cells in moderately differentiated colorectal cancer. METHODS: Using single-cell RNA sequencing data of isolated 1632 T cells from tumor tissue and 1252 T cells from the peripheral blood of CRC patients, unsupervised clustering analysis was performed to identify functionally distinct T cell populations, followed by correlations and ligand-receptor interactions across cell types. Finally, differential analysis of the tumor-infiltrating T cells between colon cancer and rectal cancer were carried out. RESULTS: A total of eight distinct T cell populations were identified from tumor tissue. Tumor-Treg showed a strong correlation with Th17 cells. CD8(+)T(RM) was positively correlated with CD8(+)IEL. Seven distinct T cell populations were identified from peripheral blood. There was a strong correlation between CD4+T(N) and CD4+blood-T(CM). Colon cancer and rectal cancer showed differences in the composition of tumor-infiltrating T cell populations. Tumor-infiltrating CD8(+)IEL cells were found in rectal cancer but not in colon cancer, while CD8(+) T(N) cells were found in the peripheral blood of colon cancer but not in that of rectal cancer. A larger number of tumor-infiltrating CD8(+) Tex (88.94%) cells were found in the colon cancer than in the rectal cancer (11.06%). The T cells of the colon and rectal cancers showed changes in gene expression pattern. CONCLUSIONS: We characterized the T cell populations in the CRC tumor tissue and peripheral blood.