We have previously demonstrated that the prognostic significance of tumour-infiltrating CD8+ T cells significantly differs according to histological type and patient smoking habits in non-small cell lung cancer (NSCLC). This work suggested that infiltrating CD8+ T cells may not be activated sufficiently in the immunosuppressive microenvironment in non-smokers with adenocarcinoma. To understand the immunogenic microenvironment in NSCLC, we characterised immune cells comprehensively by performing an immunohistochemical evaluation using an alternative counting method and multicolour staining method (n = 234), and assessed immune-related gene expression by using genetic analytical approaches (n = 58). We found that high infiltration of activated CD8+ T cells expressing interferon gamma (IFN-γ) and granzyme was correlated with postoperative survival in patients with non-adenocarcinoma. On the contrary, CD8+ T-cell accumulation was identified as a worse prognostic factor in patients with adenocarcinoma, particularly in non-smokers. Infiltrating CD8+ T cells were significantly less activated in this microenvironment with high expression of various immunoregulation genes. Potentially immunoregulatory CD8+ FOXP3+ T cells and immunodysfunctional CD8+ GATA3+ T cells were increased in adenocarcinoma of non-smokers. CD4+ FOXP3+ regulatory T cells expressing chemokine receptor-4 (CCR4)- and chemokine ligand (CCL17)-expressing CD163+ M2-like macrophages also accumulated correlatively and significantly in adenocarcinoma of non-smokers. These characteristic immune cells may promote tumour progression possibly by creating an immunosuppressive microenvironment in non-smoking patients with lung adenocarcinoma. Our findings may be helpful for refining the current strategy of personalised immunotherapy including immune-checkpoint blockade therapy for NSCLC.
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