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

Background: 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 a critical role of CD8+TCF7+PD1+ T cells in anti-PD1 response. Studies on the heterogeneity and clonal dynamics of global tumor infiltrating T lymphocytes (TILs) in the HNSCC anti-PD1 and anti-CTLA4 response have not been explored. Results: In this study, we generated isogenic HNSCC anti-PD1 sensitive/resistant models that bore distinct cancer cell intrinsic transcriptomic programs. 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 ICB responsive and resistant HNSCC models identified a spectrum of CD8+ TIL subsets including TCF7+PD1- (naïve/memory-like), TCF7+PD1+ (progenitor exhausted), and TCF7-PD1+ (terminally exhausted). Mapping TCR shared fractions between these subsets identified that successful anti-PD1 or anti-CTLA4 therapy induced higher post-treatment T cell lineage transitions. A TIL differentiation gene signature was associated with better responses in multiple ICB clinical trials. Conclusions: Together, analyses integrating scRNAseq and TCRseq 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. Overall design: profiling tumor infiltrating T cells scRNA and TCR-seq in responding and resistance conditions, as well as bulk RNAseq of bulk tumors and cell lines