Aiming to uncover host-intrinsic causes of heterogeneous responses to immunotherapies, Woolaver et al. utilized a mouse squamous cell carcinoma GEMM cell line transplanted into identical recipients that resulted in uncontrolled growth in ~75% of animals (progressors), but CD8+ T cell-dependent spontaneous elimination with long term memory in the rest (regressors). Single cell TCR and RNASeq of TILs and splenic T cells revealed clonotype expansion in both progressors and regressors with very limited overlap of expanded TCR clonotypes between any mice, including predicted antigen specificity. Regressor T cells achieved a more activated state.
Contributed by Ed Fritsch
BACKGROUND: Antitumor immunity is highly heterogeneous between individuals; however, underlying mechanisms remain elusive, despite their potential to improve personalized cancer immunotherapy. Head and neck squamous cell carcinomas (HNSCCs) vary significantly in immune infiltration and therapeutic responses between patients, demanding a mouse model with appropriate heterogeneity to investigate mechanistic differences. METHODS: We developed a unique HNSCC mouse model to investigate underlying mechanisms of heterogeneous antitumor immunity. This model system may provide a better control for tumor-intrinsic and host-genetic variables, thereby uncovering the contribution of the adaptive immunity to tumor eradication. We employed single-cell T-cell receptor (TCR) sequencing coupled with single-cell RNA sequencing to identify the difference in TCR repertoire of CD8 tumor-infiltrating lymphocytes (TILs) and the unique activation states linked with different TCR clonotypes. RESULTS: We discovered that genetically identical wild-type recipient mice responded heterogeneously to the same squamous cell carcinoma tumors orthotopically transplanted into the buccal mucosa. While tumors initially grew in 100% of recipients and most developed aggressive tumors, ~25% of recipients reproducibly eradicated tumors without intervention. Heterogeneous antitumor responses were dependent on CD8 T cells. Consistently, CD8 TILs in regressing tumors were significantly increased and more activated. Single-cell TCR-sequencing revealed that CD8 TILs from both growing and regressing tumors displayed evidence of clonal expansion compared with splenic controls. However, top TCR clonotypes and TCR specificity groups appear to be mutually exclusive between regressing and growing TILs. Furthermore, many TCRα/TCRβ sequences only occur in one recipient. By coupling single-cell transcriptomic analysis with unique TCR clonotypes, we found that top TCR clonotypes clustered in distinct activation states in regressing versus growing TILs. Intriguingly, the few TCR clonotypes shared between regressors and progressors differed greatly in their activation states, suggesting a more dominant influence from tumor microenvironment than TCR itself on T cell activation status. CONCLUSIONS: We reveal that intrinsic differences in the TCR repertoire of TILs and their different transcriptional trajectories may underlie the heterogeneous antitumor immune responses in different hosts. We suggest that antitumor immune responses are highly individualized and different hosts employ different TCR specificities against the same tumors, which may have important implications for developing personalized cancer immunotherapy.
Author Info: (1) Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA. (2) Immunology and Microbiology, University of Colorado Anschutz Medical Cam
Author Info: (1) Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA. (2) Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA. (3) Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA. (4) Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA. (5) Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA. (6) Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA. (7) Pediatrics, Biostatistics and Informatics, Cancer Center Biostatistics Core, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA. (8) Pediatrics, Biostatistics and Informatics, Cancer Center Biostatistics Core, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA. (9) Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA. (10) Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA. (11) Pathology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA. (12) Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA jing.wang@CUanschutz.edu.
