Associations of different immune checkpoints-expressing CD4 Treg/ T cell subsets with disease-free survival in colorectal cancer patients.

There are different subsets of T regulatory cells (Tregs), orchestrating critical roles in the regulation of anti-tumor immunity in colorectal cancer (CRC). In this study, we report that a high frequency of circulating CD4FoxP3 Tregs was associated with poorer disease-free survival (DFS), while their higher frequencies in tumor-infiltrating CD4 Tregs was associated with better DFS. We further investigated such associations with four Tregs/T cells expressing or lacking FoxP3 and Helios (FoxP3Helios). For the first time, we report that a high frequency of circulating CD4FoxP3Helios Tregs was associated with poorer DFS, while a high frequency of tumor-infiltrating CD4FoxP3Helios T cells was associated with poorer DFS. In the four FoxP3Helios T cell subsets expressing any of the immune checkpoints (ICs) investigated, we found that a high frequency of CD4FoxP3HeliosPD-1 Tregs in circulation was associated with worse DFS. We also found that high frequencies of FoxP3HeliosCTLA-4 Tregs, FoxP3HeliosCTLA-4 Tregs, and FoxP3HeliosCTLA-4 CD4 T cells in circulation were associated with worse DFS. In contrast, high frequencies of CD4TIM-3 T cells, FoxP3HeliosTIM-3 Tregs, and FoxP3HeliosTIM-3 CD4 T cells in circulation were associated with longer DFS. Our data show that certain CD4 Treg/T cell subsets could serve as independent predictive biomarkers in CRC patients. Identification of the exact subpopulations contributing to clinical outcomes is critical for prognoses and therapeutic targeting.