Abstract
Immune checkpoint inhibitors (ICIs) offer significant clinical benefits to a subset of cancer patients via the induction of a systemic T cell-mediated anti-cancer immune response. Thus, the dynamic characterization of T cell repertoires in the peripheral blood has the potential to demonstrate noninvasive predictive biomarkers for the clinical efficacy of ICIs. In this study, we collected tumor tissues and peripheral blood samples from 25 patients with advanced kidney cancer before anti-programmed cell death protein 1 (PD-1) treatment and 1, 3, and 6 months after treatment initiation. Furthermore, we applied a next-generation sequencing approach to characterize T cell receptor (TCR) alpha and beta repertoires. TCR repertoire analysis revealed that the responders to anti-PD-1 showed an expansion of certain T cell clones even in the blood, as evidenced by the significant decrease in the TCR diversity index and increase in the number of expanded TCR clonotypes 1 month after treatment. Interestingly, these expanded TCR clonotypes in the peripheral blood were significantly shared with tumor-infiltrating T cells in responders, indicating that they have many circulating T cells that may recognize cancer antigens. Expression analysis also revealed that 1 month after treatment, T cells from the peripheral blood of responders showed significantly elevated transcriptional levels of Granzyme B, Perforin, CD39, and PD-1, markers of cancer-associated antigen-specific T cells. Altogether, we propose that global TCR repertoire analysis may allow identifying early surrogate biomarkers in the peripheral blood for predicting clinical responses to anti-PD-1 monotherapy.