Quantitative analysis and clonal characterization of T-cell receptor β repertoires in patients with advanced non-small cell lung cancer treated with cancer vaccine

Abstract

With the development of cancer immunotherapy that may activate T cells, a practical and quantitative method to improve monitoring and/or prediction of immunological response of patients as a predictive biomarker is of importance. To examine possible biomarkers for a therapeutic cancer vaccine containing a mixture of three epitope peptides derived from cell division-associated 1, lymphocyte antigen 6 complex locus K and insulin-like growth factor-II mRNA-binding protein 3, T-cell receptor β (TCRβ) repertoires of blood samples from 24 patients with human leukocyte antigen-A*2402-positive non-small cell lung cancer were characterized prior to and following 8 weeks of the cancer vaccine treatment, by applying a next-generation sequencing method. It was identified that 14 patients with overall survival (OS) times of ≥12 months had significantly lower TCRβ diversity indexes in samples prior to treatment, compared with 10 patients who succumbed within 1 year (P=0.03). In addition, patients with a high level of activated CD8⁺ T cells that are defined by a high granzyme A/CD8 ratio had favorable OS rates (log-rank test, P=0.04). The TCRβ diversity index and immunogenic gene markers following vaccine administration may serve as predictive or monitoring biomarkers for cancer vaccine treatment.

Keywords: T-cell receptor; cancer vaccine; diversity index; immunogenicity; lung cancer; next-generation sequencing; non-small cell lung cancer.

Figure 1.

TCRβ diversity index analysis. (A) Diversity index prior to treatment. (B) Diversity index following treatment. Blue: Long-term survival group (n=14). Red: Short-term survival group (n=10). Data is presented as the mean ± standard error. (C) Diversity indexes prior to and following treatment in the long-term survival group (alive ≥12 months after treatment). (D) Diversity indexes prior to and following treatment in the short-term survival group (died within 12 months). (E) Changes of TCRβ diversity index following vaccine treatment. Blue: Long-term survival group (n=14). Red: Short-term survival group (n=10; P=0.089). TCRβ, T-cell receptor β.

Figure 2.

Gene expression analysis. (A) CD8 and GZMA expression normalized to GAPDH. Green: Long-term survival group (n=14). Pink: Short-term survival group (n=10). (B) Kaplan-Meier estimator survival curve separated by the median into high and low GZMA/CD8 ratio prior to treatment (log-rank test, P=0.04). (C) CD4 expression levels and CD8/CD4 ratio in the long- and short-term survival groups prior to treatment. Green: Long-term survival group (n=14). Pink: Short-term survival group (n=10). (D) Kaplan-Meier survival curve separated by the median into high and low CD8/CD4 ratio prior to treatment. Median OS time: Low CD8/CD4 group, 316 days; high CD8/CD4 group, 598 days. GZMA, granzyme A; OS, overall survival; CD, cluster of differentiation.