Abstract
BACKGROUND: Lung cancer is among the most common malignant tumors worldwide. Circulating mucosal-associated invariant T (cMAIT) cells play an important role in cancer. This study investigated the biological and clinical significance of cMAIT cells in lung cancer. METHODS: Fasting peripheral blood mononuclear cells (PBMCs) were extracted from 30 newly diagnosed lung cancer patients and 30 healthy controls. The percentages of cMAIT among the CD3(+)T cells, their absolute values, and subpopulation distribution in both groups were compared by flow cytometry. The correlations of cMAIT with the neutrophil-to-lymphocyte ratio (NLR) and the expression of programmed cell death-ligand 1 (PD-L1) were analyzed. Enzyme-linked immunosorbent assay (ELISA) was used to detect plasma interleukin-6 (IL-6), interleukin-8 (IL-8), and interferon-γ (IFN-γ) levels in lung cancer patients and healthy controls. The percentage of MAIT cells in the tumor tissues and adjacent normal lung tissues was measured by flow cytometry. RESULTS: The percentages and absolute values of the cMAIT in lung cancer patients were lower than in healthy subjects (P<0.001, P<0.01, respectively). The CD8(+)CD4(-) subgroup was dominant in both groups. There was no significant difference in percentages of the CD8(+)CD4(-) subgroup between lung cancer patients and healthy subjects (P=0.63), but the absolute values of CD8(+)CD4(-) cells were lower in lung cancer patients (P<0.05). The percentages and absolute values of cMAIT in lung cancer patients were negatively correlated with NLR (r=-0.537; P<0.01 and r=-0.423; P<0.05, respectively). The cMAIT cell percentage did not correlate with PD-L1 tumor expression (r=-0.1740; P=0.59) and with the PD-L1 expression level (P>0.99). No differences were found in the plasma IL-6, IL-8, and IFN-γ levels in lung cancer patients and healthy controls (P=0.63, P=0.052, P=0.13, respectively). The percentage of mucosal-associated invariant T (MAIT) cells in lung cancer tissues was higher than in the adjacent normal lung tissues (1.44% vs. 1.29%, P=0.044). CONCLUSIONS: Lower percentage and absolute values of cMAIT in lung cancer patients may be due to their migration into tissues. The number of cMAIT in lung cancer patients may potentially be considered as a prognostic indicator.