Abstract
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+Texprog) and CD8+PD1+TCF1- terminally exhausted T cells (TCF1-Texterm). 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-Texterm represented a greater proportion of CD8+PD1+Tex than TCF1+Texprog in most patients. TCF1+Texprog produced abundant TNFα, while TCF1-Texterm expressed higher levels of CD103, TIM-3, CTLA-4, and TIGIT. TCF1-Texterm 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-Texterm were accompanied by an increase in the proportion of Tregs. Therefore, it was concluded that TCF1-Texterm was the major CD8+PD1+Tex subset in the HNSCC TIME and that these cells favor patient survival. A high proportion of TCF1-Texterm was associated with greater Treg abundance.