Checkpoint blockade induceds CD8+ T cell differentiation in responders in head and neck cancers

Outcomes for locally advanced or recurrent/ metastatic head and neck squamous cell carcinomas (HNSCCs) remain unfavorable despite recent advances with immune checkpoint blockade (ICB). Preclinical studies using model antigens identified that anti-PD1 therapy translates to a productive anti-tumor T cell response with a critical role of CD8+TCF7+PD1+ T cells. Such studies on heterogeneity and clonal dynamics of global tumor infiltrating T lymphocytes (TILs) in the anti-PD1 and anti-CTLA4 response have not been explored in HNSCC. Here, we first generated a novel isogenic HNSCC anti-PD1 sensitive/resistant model. Transcriptomic analysis identified an immune cell exclusion program in adaptively resistant cells. Tumor microenvironment characterization using mass cytometry and targeted depletion revealed the contribution of Tregs and M2-like macrophages in anti-PD1 resistance. Paired single-cell RNA and TCR sequencing on tumor infiltrating immune cells from anti-CTLA4 or anti-PD1 responsive and anti-PD1 resistant HNSCC models identified a spectrum of CD8+ TIL subsets including TCF7+PD1- (naive/memory-like), TCF7+PD1+ (progenitor exhausted), and TCF7-PD1+ (terminally exhausted). Mapping TCR shared fractions identified that successful anti-PD1 or anti-CTLA4 therapy induced higher post-treatment T cell lineage transitions. A TIL differentiation signature was associated with improved responses in multiple ICB clinical trials. These results demonstrate distinct differentiation dynamics of CD8+ TILs in novel ICB responsive and resistant HNSCC models, highlighting critical aspects of CD8+ TIL differentiation in response to ICB.