Abstract 5057: Single cell RNA sequencing reveals altered natural killer-like, effector CD8+ T lymphocytes in smokers

Abstract

Abstract Tobacco smoke exposure is a risk factor for many human diseases and the global disease burden attributed to smoking remains substantial. In addition to DNA damage, smoking-induced epigenetic changes may contribute to etiology of complex smoking-associated diseases. Smoking alters the epigenome and transcriptome of human blood leukocytes. However, interpretation of bulk genomic approaches is limited because changes could indicate altered distribution of cell (sub)populations or changes in expression within (sub)populations. To characterize smoking-related gene expression changes in primary immune cells, we performed single cell RNA sequencing on human peripheral blood mononuclear cells (PBMCs) from smokers (n=4) and nonsmokers (n=4). Transcriptomes of 45,965 cells (78,183 reads per cell) revealed an altered population of Natural Killer (NK)-like T lymphocytes in smokers. Compared to NK cells, the NK-like T cell cluster had elevated expression of CD8A, CD8B, CD3D, CD3E, CD3G, CD6, and CD2, indicative of CD8+ T lymphocytes. Relatively rare in nonsmokers (2.2%), the transcriptionally unique subset of CD8+ T cells comprised 8.7% of PBMCs in smokers. Among CD8+ T cell subtypes, the increase in NK-like CD8+ T cells (Mann-Whitney p = 0.03) corresponded with a decrease in Naïve CD8+ T cells (p = 0.03). We did not observe changes in the frequencies of two additional CD8+ T cell clusters or in the overall frequency of CD8+ T cells. Mass cytometry of a 26-antibody leukocyte panel confirmed no differences in the frequencies of total CD8+ T (CD3+/CD8+/CD56-), total NKT (CD3+/CD56+) or CD8+ NKT (CD3+/CD8+/CD56+) cells between smokers and nonsmokers. This suggests smoking is associated with an increased number of CD8+ T cells that share characteristics with NK cells, but are not NKT cells. Consistent with an NK-like phenotype, altered effector CD8+ T cells had elevated expression of genes reported to be upregulated in T cells reprogrammed to NK-like cells. Compared to other effector CD8+ T cells, altered effector CD8+ T cells had reduced IL7R and increased FCGR3A (CD16), IFNG (interferon gamma), GZMB (granzyme B), and PRF1 (perforin) expression. In mice, granzyme B and perforin expressing CD8+ T cells contribute to the development of atherosclerotic plaques. Our data highlights a potential link between smoking-induced functional changes in human CD8+ T cells and atherosclerosis and /or immune surveillance in cancer. Citation Format: Suzanne N. Martos, Michelle R. Campbell, Marie A. Iannone, Gary S. Pittman, Ma Wan, Douglas A. Bell. Single cell RNA sequencing reveals altered natural killer-like, effector CD8+ T lymphocytes in smokers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5057.