Association of the T-cell receptor landscape with survival in non-small cell lung cancer.

Abstract

140 Background: Non-small cell lung cancer (NSCLC) is characterized by a high mutational load. Accordingly, it is also among the tumor types which respond best to immune checkpoint blockade, likely through its ability to enhance the anti-tumor T cell response. However, the lung is constantly exposed to the outside environment, which may result in a continuous state of inflammation targeting pathogens rather than tumor cells. Therefore, a greater understanding of the T cell receptor (TCR) landscape and phenotypes across normal lung and tumor is warranted. Methods: Here, we performed sequencing of the CDR3 variable region of the beta chain of the TCR as well as whole exome sequencing on peripheral blood, normal lung and tumor in 235 NSCLC patients. We further analyzed the immune microenvironment by Cytometry by Time-of-Flight (CyTOF) in 10 NSCLC patients with paired normal lung and tumor. Results: Comparison of the TCR repertoire showed 9% (up to 15%) of T cells were shared between normal lung and tumor, though the most dominant were generally shared (up to 95%). Interestingly, T cell clonality was higher in the normal lung than tumor in almost all patients (89%, p < 0.0001) suggesting potential differences in the ongoing immune response in different regions of the lung. A substantial number of non-synonymous exonic mutations (NSEM) were detected in tumors (average = 566 NSEM) but also in the normal lung (average = 156 NSEM), with many shared (up to 45.6%). CyTOF confirmed marked differences in the immune microenvironment, including higher frequency of VISTA+ antigen-presenting cells in the tumor (p = 0.04). Finally, analysis of clinicopathological attributes revealed a greater T cell diversity in the periphery in patients with increased overall survival (OS, p = 0.001), while patients with a more similar normal lung/tumor T cell repertoire showed decreased OS (p = 0.028). Conclusions: These results suggest that a substantial proportion of infiltrating T cells in NSCLC tumors may be lung-resident T cells associated with response to environmental factors. However, normal lung and NSCLC tumors carry T cells of distinct phenotypes, which highlights differences in the ongoing antigenic response within the lung.