Radiotherapy and CTLA-4 blockade shape the TCR repertoire of tumor-infiltrating T cells
Menée à l'aide d'un modèle murin de carcinome, cette étude montre que la radiothérapie et l'inhibition de CTLA-4 ont un effet sur la diversité du répertoire du récepteur TCR des lymphocytes T infiltrant la tumeur
Immune checkpoint inhibitors activate T cells to reject tumors. Unique tumor mutations are key T-cell targets, but a comprehensive understanding of the nature of a successful antitumor T-cell response is lacking. To investigate the T-cell receptor (TCR) repertoire associated with treatment success versus failure we used a well-characterized mouse carcinoma that is rejected by CD8 T cells in mice treated with radiotherapy (RT) and anti-CTLA-4 in combination, but not as monotherapy, and comprehensively analyzed tumor-infiltrating lymphocytes (TILs) by high-throughput sequencing of the TCR
Β CDR3 region. The combined treatment increased TIL density and CD8/CD4 ratio. Assessment of the frequency of T cell clones indicated that anti-CTLA-4 resulted in fewer clones and a more oligoclonal repertoire compared to untreated tumors. In contrast, RT increased the CD8/CD4 ratio and broadened the TCR repertoire, and when used in combination with anti-CTLA-4, these selected T cell clones proliferated. Hierarchical clustering of CDR3 sequences showed a treatment-specific clustering of TCRs that were shared by different mice. Abundant clonotypes were commonly shared between animals and yet treatment-specific. Analysis of amino-acid sequence similarities revealed a significant increase in the number and richness of dominant CDR3 motifs in tumors treated with RT+anti-CTLA-4 compared to control. The repertoire of TCRs reactive with a single tumor antigen recognized by CD8+ T cells was heterogeneous but highly clonal, irrespective of treatment. Overall, data support a model whereby a diverse TCR repertoire is required to achieve tumor rejection and may underlie the synergy between RT and CTLA-4 blockade.