Association of Expression of Immune Checkpoints in Tumor-Infiltrating CD4+ T Lymphocytes with Disease-Free Survival in Colorectal Cancer Patients

Objectives: The role of inhibitory immune checkpoints (ICs), which are expressed on tumor-infiltrating T lymphocytes (TILs) in colorectal cancer (CRC), and their associations with disease-free survival (DFS) have not been fully elucidated. Methods: This study evaluated the associations between ICs expressed on CD4+ TILs and DFS in forty-five treatment-naïve CRC patients. Initially, we investigated the associations of ICs, including PD-1, TIGIT, LAG-3, and TIM-3, expressed on CD4+ TILs with DFS. Results: There were no statistically significant differences in the associations between the levels of all single IC-expressing CD4+ TILs and DFS. Interestingly, when PD-1 was combined with other ICs, we found that a lack of PD-1 expression on LAG-3+CD4+ TILs (PD-1−LAG-3+) was significantly associated with shorter DFS. Additionally, a lack of expression of both PD-1 and TIGIT (PD-1−TIGIT−) on CD4+ TILs was associated with shorter DFS. Conclusion: We identified two CD4+ T-cell subpopulations (PD-1−LAG-3+ and PD-1−TIGIT−) associated with worse DFS. Our findings highlight the importance of investigating multiple IC co-expressions to determine the exact subpopulations associated with patient prognoses. This preliminary study requires further validation in a larger cohort of CRC patients.