Investigating the role of KLRG1 in regulatory T-cells and implications for anti-tumor immunity in Non-small Cell Lung Cancer

Abstract Although it is well established that CD4+CD25+Foxp3+ regulatory T cells (Tregs) dampen anti-tumor T cell responses in cancer, their molecular signature and clonal heterogeneity in NSCLC remains poorly understood. In this study, comparative phenotypic assessment of tumor and lymphoid tissue resident Tregs in KRAS/p53 mutant NSCLC mouse model revealed the presence of a distinct tumor infiltrating Treg population which express KLRG1. Compared to their counterparts, tumor associated KLRG1+ Treg showed higher expression of inhibitory receptors and activation markers, suggesting that KLRG1+ Tregs represent an activated subpopulation which may contribute to immunosuppression. Ex-vivo Treg suppression assay revealed that tumor associated KLGR1+ Tregs exhibited higher suppressive activity compared to KLRG1-Tregs. Although T cell development was normal in in-house generated KLRG1 KO mice including thymic and peripheral Treg numbers, KLRG1 KO Tregs showed less suppressive capacity compared to wild type, implying KLRG1 in Tregs functional program. Furthermore, α-KLRG1 antibody treatment in lung tumor bearing KP mice showed prolonged survival, accompanied by reduced proportion of KLRG1+ Tregs in the tumor. Finally, immunogenomic characterization of KLRG1 KO/wt and tumor infiltrating KLRG1+/− Tregs revealed distinct gene expression patterns and associated immune pathways. Collectively, our findings indicate that KLRG1 is not critical for Treg development and maintenance but may play a non-redundant role in Tregs differentiation and function in inflammatory settings. Therefore, targeting KLRG1 to curtail the inhibitory function of the highly suppressive KLRG1+ Treg subset could facilitate antitumor responses in NSCLC.