Expression and Clinical Significance of CD8+Natural Killer T Cell Stimulatory Receptor NKG2D in Peripheral Blood of Lung Cancer Patients

Abstract

Background and objective NKG2D-expressing CD8+NKT cells and soluble major histocompatibility complex class I-related chain A (sMICA) is one of recently emerged general interests in tumor research area. The aim of this study is to investigate the levels of NKG2D-expressing CD8+NKT cells in peripheral blood of lung cancer patients, which are remarkably related to clinical significance, and to analyze the correlation between NKG2D-expressing CD8+NKT cells and sMICA levels, and to explore the role of NKG2D and sMICA in immune surveillance. Methods Flow cytometry was used to determine the percentage of NKG2D-expressing CD8+NKT cells, and ELISA was used to measure the levels of sMICA in peripheral blood of 82 untreated lung cancer patients and 45 healthy controls. The association of NKG2D levels with clinical features was analyzed. Results The expression of NKG2D on CD8+NKT cells in lung cancer group was significantly lower than that in healthy group, with statistically significant difference (P < 0.001). And with the increase of TNM stage, NKG2D expression rate reduced gradually. NKG2D expression in stage IV disease was significantly lower than which stage I-II and III disease (P < 0.001). The expression of NKG2D on CD8+NKT cells was remarkably lower in that in smokers than that in non-smokers, with statistically significant difference (P < 0.05). NKG2D exhibited negative correlation with sMICA (r=-0.598, P < 0.001). Conclusion Lung cancer has low expression of NKG2D in CD8+NKT cells which correlate with pathological stage. Detection of NKG2D and sMICA might be helpful to understand immune functions and provide evaluation of combined treatment for clinical cancer