Significant differences in T cell receptor repertoires in lung adenocarcinomas with and without epidermal growth factor receptor mutations

Recent clinical trials of non-small cell lung cancer with immune checkpoint inhibitors revealed that patients with epidermal growth factor receptor (EGFR) mutations had more unfavorable outcomes compared with those with wild-type EGFR. However, the underlying mechanism for the link between EGFR mutations and immune resistance remains unclear. We performed T cell receptor (TCR) repertoire analysis of resected lung adenocarcinoma tissues with and without EGFR mutations to investigate the characteristics of TCR repertoires. We collected a total of 39 paired (normal and tumor) lung tissue samples (20 had EGFR mutations) and conducted TCR repertoire analysis as well as whole-exome sequencing (WES) and transcriptome analysis. The TCR diversity index in EGFR-mutant tumors was significantly higher than that in EGFR-wild-type tumors (median [range] 552 [162-1,135] vs 230 [30-764]; P < .01), suggesting higher T cell clonal expansion in EGFR-wild-type tumors than in EGFR-mutant tumors. In WES, EGFR-mutant tumors showed lower numbers of non-synonymous mutations and predicted neoantigens than EGFR-wild-type tumors (P < .01, P = .03, respectively). The number of non-synonymous mutations revealed a positive correlation with the sum of frequencies of the TCRβ clonotypes of 1% or higher in tumors (r = .52, P = .04). The present study demonstrates significant differences in TCR repertoires and the number of predicted neoantigens between EGFR-mutant and wild-type lung tumors. Our findings provide important information for understanding the molecular mechanism behind EGFR-mutant patients showing unfavorable responses to immune checkpoint inhibitors.