T cell receptor β-chain repertoire analysis to reveal potential predictive biomarker for the use of immune checkpoint blockade in patients with advanced solid tumors.

Abstract

e14152 Background: Immune checkpoint blockade (ICB) targeted to CTLA-4, PD-1, and PD-L1 can promote antitumor T cell immunity and clinical responses. Tracking the dynamic changes of the T Cell Receptor (TCR) Immune Repertoire can reflect the evolution of the immune system in tumor immunotherapy patients, predict the immune response to ICB, and provide high-value information for clinical monitoring of immune function status of cancer patients to make effective clinical decisions. The purpose of this study was to explore the correlation between the peripheral blood TCR repertoire dynamic changes and the immune response of patients with anti-PD-1/PD-L1, and to accurately guide the individualized treatment of immunotherapy. Methods: We sequenced the TCRβ genes from T cells contained in peripheral blood mononuclear cells (PBMCs) from 24 advanced solid tumors patients (PD/7, PR/4, SD/13) treated with immune checkpoint blockade. Peripheral blood samples were collected from baseline, 8-week, and 16-week after treatment for each patient. bioinformatic analysis was used to detect the diversity and clonality changes of TCRβ-CDR3 sequence before and after treatment with ICB in patients, and provide auxiliary technology for further guiding clinical tumor immunotherapy. Results: The analysis result of Chao index showed that the TCR-CDR3 diversity in the PR group was significantly increased after treatment than SD or PD group. (pvalue = 0.001), and the number of CDR3 aa clonotypes also increased significantly (pvalue = 0.012). A total of 61 Vβ gene fragments and 15 Jβ gene fragments were uniquely identified during immunotherapy . There was a significant difference in the number of Vβ gene fragments between baseline samples and after treatment in PR group (pvalue = 0.042). Conclusions: In this project, PBMC samples was used to evaluate the changes of TCR repertoire between before and after treatment with immune checkpoint blockade in advanced solid tumor patients. The immune function status was significantly changed before and after treatment. Patients with PR had significantly increased diversity in TCR repertoire than patients with SD or PD. The results provide T cell receptor β-chain repertoire sequencing and analysis has potential to assess whether immune checkpoint blockade promotes global T cell expansion and/or loss of T cell clonotype diversity, and to identify predictive biomarker for the use of immune checkpoint blockade.