A comprehensive profile of TCF1 + progenitor and TCF1 - terminally exhausted PD-1 + CD8 + T cells in head and neck squamous cell carcinoma: implications for prognosis and immunotherapy.

The heterogeneity of exhausted T cells (Tex) is a critical determinant of immune checkpoint blockade therapy efficacy. However, few studies have explored exhausted T cell subpopulations in human cancers. In the present study, we examined samples from two cohorts of 175 patients with head and neck squamous cell cancer (HNSCC) by multiplex immunohistochemistry (mIHC) to investigate two subsets of Tex, CD8 + PD1 + TCF1 + progenitor exhausted T cells (TCF1 + Tex prog ) and CD8 + PD1 + TCF1 - terminally exhausted T cells (TCF1 - Tex term ). Moreover, fresh tumor samples from 34 patients with HNSCC were examined by flow cytometry and immunohistochemistry to further investigate their properties and cytotoxic capabilities and their correlation with regulatory T cells (Tregs) in the tumor immune microenvironment (TIME). mIHC and flow cytometry analysis showed that TCF1 - Tex term represented a greater proportion of CD8 + PD1 + Tex than TCF1 + Tex prog in most patients. TCF1 + Tex prog produced abundant TNFα, while TCF1 - Tex term expressed higher levels of CD103, TIM-3, CTLA-4, and TIGIT. TCF1 - Tex term exhibited a polyfunctional TNFα + GZMB + IFNγ + phenotype; and were associated with better overall survival and recurrence-free survival. The results also indicated that larger proportions of TCF1 - Tex term were accompanied by an increase in the proportion of Tregs. Therefore, it was concluded that TCF1 - Tex term was the major CD8 + PD1 + Tex subset in the HNSCC TIME and that these cells favor patient survival. A high proportion of TCF1 - Tex term was associated with greater Treg abundance.