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Clonal replacement of tumor-specific T cells following PD-1 blockade [single cells]

ABSTRACT: Immunotherapies that block inhibitory checkpoint receptors on T cells have transformed the clinical care of cancer patients. However, the clonal origin of tumor-specific T cells following checkpoint blockade in patients remains unclear. Here, we performed paired single-cell RNA- and T cell receptor (TCR)- sequencing on site-matched tumors from patients with basal cell carcinoma (BCC) pre- and post-anti-PD-1 therapy. Tracking TCR clonotypes and transcriptome phenotypes revealed a coupling of tumor-recognition, clonal expansion, and T cell dysfunction: the response to treatment was accompanied by a clonal expansion of CD8+CD39+ T cells, which co-expressed markers of chronic T cell activation and exhaustion. However, this response was not accompanied by an expansion of pre-existing tumor-specific T cell clonotypes; rather, expanded T cell clones post-therapy comprised novel clonotypes, which were not previously observed in the same tumor. Clonal replacement of T cells was preferentially observed in tumor-specific exhausted CD8+ T cells, compared to other distinct T cell phenotypes, and was more evident in patients who exhibited a clinical response to treatment. These results, enabled by single-cell multi-omic profiling of clinical samples, demonstrate that the chronic activation of pre-existing tumor-infiltrating T cells may limit their re-invigoration following checkpoint blockade, and that a successful response relies on the expansion of a distinct repertoire of tumor-specific T cell clones.

ORGANISM(S): Homo sapiens

PROVIDER: GSE123813 | GEO | 2019/05/24

REPOSITORIES: GEO

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Project description:Background: Anti-tumor 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 anti-tumor 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 SCC 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 anti-tumor 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 TCRa/TCRb 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 vs. 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 anti-tumor immune responses in different hosts. We suggest that anti-tumor 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.

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Clonal replacement of tumor-specific T cells following PD-1 blockade [single cells]

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