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Differences in TCR repertoire and T cell activation underlie the divergent outcomes of anti-tumor immune responses in tumor-eradicating versus tumor-progressing hosts

ABSTRACT: 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.

ORGANISM(S): Mus musculus

PROVIDER: GSE164153 | GEO | 2021/01/13

REPOSITORIES: GEO

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Project description:We investigated the frequency of CX3CR1+CD8+ T cells in peripheral blood (PB) before and during immune checkpoint inhibitor (ICI) therapy, and delineated the TCR repertoire in peripheral CX3CR1+CD8+ T-cell subsets and CD8+ tumor-infiltrating lymphocytes (TILs) using preclinical models. To understand the clinical utility of CX3CR1 as a circulating T-cell biomarker, we analyzed longitudinal PB samples from non-small cell lung cancer (NSCLC) patients undergoing anti-PD-1 therapy, and evaluated predictive and prognostic value of changes in the frequency of PB CX3CR1+ CD8+ T cells Methods: Female C57BL/6 mice were inoculated subcutaneously with 5 x 10^5 MC38 tumor cells per mouse on the right flank on day 0. When tumor volume reached approximately 50 mm^3, 200 µg of anti-PD-L1 Ab (clone 10F.9G2, BioXcell) and 100 µg of anti-CTLA-4 Ab (clone 9H10, BioXcell) were administered intraperitoneally every 3 days and every other day, respectively. MC38 tumor-bearing mice were treated for 14 days, and spleens and tumors were harvested. [Tumor cells] Tumors were cut into small pieces of 2-4 mm. Single-cell suspensions were obtained by mechanical dispersion consisting of two 30-min incubations at 37°C, 5% CO2 in 5 ml RPMI 1640 (Gibco) and tumor dissociation kit (Miltenyi Biotec) in C Tubes (Miltenyi Biotec) interspersed with three mechanical dispersions on a GentleMACS dissociator (Miltenyi Biotec). The tumor cell suspensions were then filtered through a cell strainer (70 μm; BD Biosciences). An EasySep Mouse CD8a Positive Selection Kit II (STEMCELL Technologies) was used to isolate murine CD8+ tumor-infiltrating lymphocytes (TILs) for TCR sequencing. [Splenocytes] Spleens were homogenized by forcing the tissue through a cell strainer (70 μm; BD Biosciences). Red blood cells in blood and spleen were lysed using ACK Lysis Buffer (Gibco). For TCR sequencing of murine splenic CD8+ T cells, single cell suspensions from freshly isolated splenocytes were stained. CD45+ CD3+ CD8+ T cells were gated, and CD27lo CX3CR1-, CD27hi CX3CR1-, and CX3CR1+ CD8+ T cells were sorted using BD FACSAria II Cell Sorter. DNA from flow-isolated murine splenic CD8+ T cells and CD8+ TILs, and PB CD8+ T cells was extracted using QIAamp DNA Micro Kit (QIAGEN). DNA was quantified using Qubit dsDNA BR Assay (Invitrogen). Amplification and sequencing of TCRβ CDR3 regions was performed using ImmunoSEQ immune profiling system at the survey level (Adaptive Biotechnologies). Sequencing was performed on an Illumina NextSeq system using 150 cycle mid-output kit (Illumina Inc.). Processed data were uploaded to the ImmunoSEQ Platform (Adaptive Biotechnologies) for bioinformatics analysis. Processed data were downloaded and frequencies/counts for TCR clonotypes and diversity were examined by nucleotide sequences after non-productive reads were filtered out. Results: Clonally expanded TCR repertoires of CD8+ TILs are enriched in the peripheral CX3CR1+ subset during ICI therapy. ICI therapy induces high degree of TCR sequence similarity and clonality between CD8+ TILs and the peripheral CX3CR1+ CD8+ T cells.

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Differences in TCR repertoire and T cell activation underlie the divergent outcomes of anti-tumor immune responses in tumor-eradicating versus tumor-progressing hosts

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