Characteristics of T-Cell Receptor Repertoire and Correlation With EGFR Mutations in All Stages of Lung Cancer

Abstract

Lung cancer is the leading cause of cancer-related deaths worldwide, and its occurrence is related to the accumulation of gene mutations and immune escape of the tumor. Sequencing of the T-cell receptor (TCR) repertoire can reveal the immunosurveillance status of the tumor microenvironment, which is related to tumor escape and immunotherapy. This study aimed to determine the characteristics and clinical significance of the TCR repertoire in lung cancer. To comprehensively profile the TCR repertoire, results from high-throughput sequencing of samples from 93 Chinese patients with lung cancer were analyzed. We found that the TCR clonality of tissues was related to smoking, with higher clonality in patients who had quit smoking for less than 1 year. As expected, TCR clonality was correlated with stages: patients with stage IV disease showed higher clonality than others. The correlation between TCR repertoire and epidermal growth factor receptor (EGFR) status was also investigated. Patients with EGFR non-L858R mutations showed higher clonality and a lower Shannon index than other groups, including patients with EGFR L858R mutation and wild-type EGFR. Furthermore, we analyzed the TCR similarity metrics-that is, the TCR shared between postoperative peripheral blood and tissue of patients with non-distant metastasis of lung cancer. A similar trend was found, in which patients with EGFR L858R mutations had lower overlap index (OLI) and Morisita index (MOI) scores. Moreover, the OLI showed a positive correlation with several clinical characteristics, including the tumor mutational burden of tissues and the maximum somatic allele frequency of blood; OLI showed a negative correlation with the ratio of CD4+CD28+ in CD4+ cells and the ratio of CD8+CD28+ in CD8+ cells. In conclusion, TCR clonality and TCR similarity metrics correlated with clinical characteristics of patients with lung cancer. Differences in TCR clonality, Shannon index, and OLI across EGFR subtypes provide information to improve understanding about varied responses to immunotherapy in patients with different EGFR mutations.

Keywords: T-cell receptor repertoire; clonality; epidermal growth factor receptor; high-throughput sequencing; lung cancer.

Figure 1

Relationship between T-cell receptor (TCR) repertoire and individual characteristics. (A) Correlation between age and clonality or Shannon index. (B) Comparison of TCR repertoire between male and female patients. (C) Comparison of TCR repertoire between smoking and never-smoking patients. (D) Comparison of TCR repertoire between patients with adenocarcinoma (adenous) and squamous carcinoma disease. Statistical analyses were performed using the Mann-Whitney test and Spearman’s rank test. Boxes depict the interquartile range with the line at the median and the whiskers at the 5th–95th percentiles. *p < 0.05.

Figure 2

Clonality of T-cell receptor repertoire stratified by pathological stage and tumor size. (A) Comparison of clonality among different pathological stages. (B) Comparison of clonality in patients with primary tumor diameter greater than or less than 1.2 cm and without lymph node metastasis. Inset shows the correlation between tumor size and clonality in patients without lymph node metastasis. Statistical analyses were performed using the Mann-Whitney test and Spearman’s rank test. *p < 0.05.

Figure 3

Correlation between T-cell receptor repertoire and EGFR mutations. (A, G) Comparison of clonality/Shannon index among the three groups. (B, H) Differences in clonality/Shannon index within EGFR subtypes. (C, I) Comparison of clonality/Shannon index between EGFR subtype and other groups. (D, J) Differences in clonality/Shannon index among three groups of patients with stage IV disease. (E, K) Differences in clonality/Shannon index within EGFR subtype of patients with stage I–III disease. (F, L) Comparison of clonality/Shannon index between EGFR subtype and other groups of patients with stage I–III disease. Statistical analyses were performed using the Mann-Whitney test. *p < 0.05, **p < 0.01, ***p < 0.001. wt, wild type.

Figure 4

Correlation between T-cell receptor (TCR) similarity metrics and individual characteristics. (A) Correlation between age and TCR similarity metrics. (B) Comparison of TCR similarity metrics between smoking and never-smoking patients. (C) Correlation between TCR similarity metrics and tumor size. Statistical analyses were performed using the Mann-Whitney test and Spearman’s rank test. *p < 0.05, **p < 0.01. MOI, Morisita Index; OLI, Overlap Index.

Figure 5

Relationships of T-cell receptor (TCR) similarity metrics with molecular characteristics. (A) Correlation between TCR similarity metrics and tumor mutation burden (TMB) of tissues. (B) Differences in Overlap Index (OLI) among EGFR, other-driver, and negative groups, and differences in OLI among EGFR subtypes. (C) Differences in Morisita Index (MOI) among EGFR, other-driver, and negative groups, and differences in MOI among EGFR subtypes. Statistical analyses were performed using the Mann-Whitney test and Spearman’s rank test. *p < 0.05, **p < 0.01. Mut, mutation.