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.