Single-cell RNA and TCR sequencing reveals distinct systematic immune response induced by SABR with or without prior anti-PD-1 therapy

Previous studies have demonstrated that stereotactic body radiation therapy (SBRT) could activate systemic immune response, however, these researches showed limitations in comprehensively characterizing changes of T cell profile and T cell receptor (TCR). In the present study, we applied scRNA-seq and scTCR-seq to observe the dynamics of T cell and TCR repertoire from peripheral blood mononuclear cells (PBMCs) in early stage non-small-cell lung cancer (NSCLC) patients receiving SBRT with or without prior anti-PD-1 therapy, demonstrating the distinct systemic immune response between SBRT and ISBRT group. An enrichment of CD8-TE, CD8-EM, and CD4-TE clusters with increased cytotoxic and exhausted score were observed after treatment in SBRT group, while a decrease of those were presented in ISBRT group. Moreover, gene expression analysis revealed T cell mediated cytotoxicity signaling and T cell proliferation signaling were enriched in SBRT group while decreased in SBRT group. Analysis of TCR repertoire indicated a substantial alteration of TCR repertoire after treatment. The proportions of the large clone of TCR were increased after treatment in SBRT group while an opposite alteration existed in ISBRT group. After treatment, both SBRT and ISBRT group generated numerous new TCR clones which were mainly enriched in CD8 TE. Single clones and large clones were the mainly types of new TCRs in SBRT group, whereas in ISBRT group single clones accounted for the majority of new TCRs. These findings suggested that systemic immunity was activated in distinct pattern between the SBRT and ISBRT group, and provide evidence for future development of new treatment regimen.