Background: Immune aberrations have been demonstrated in tumorogenesis, and myeloid-derived suppressor cells (MDSC) have shown to play a pivotal role in mediating immune suppression in animal models of human tumors. In the present study, we explored the clinical relevance of CD11b+/CD14 -/CD15+/CD33+ MDSCs and the association of MDSCs with CD8+ cytotoxic T lymphocytes in patients with non-small-cell lung cancer (NSCLC). Patients and methods: The population of CD11b+/CD14- cells in peripheral blood mononuclear cells (PBMNC) was determined in 173 patients with NSCLC and 42 control subjects. The expression of CD15, CD33, IL-4R, INF-γR, iNOS and l-arginase were analyzed. Cocultures with CD8+ T lymphocytes and Jurkat cells were developed to determine the impact of MDSCs on the expression of CD3ζ of CD8+ T lymphocytes. Results: Patients with treatment-naïve, advanced-stage NSCLC (n = 87) had an increased subpopulation of CD11b +/CD14-/CD15+/CD33+ cells in the PBMNCs with characteristics of MDSCs (P <0.0001). The CD11b +/CD14- cells in PBMNC also express IL-4R and INF-γR and can suppress CD3ζ expression in CD8+ T lymphocytes. The subpopulation of CD11b+/CD14- cells in PBMNC was decreased in the advanced-stage NSCLC patients who had responsiveness to chemotherapy (n = 41, P <0.0001) and in the early-stage NSCLC patients after removal of tumor (n = 8, P = 0.0391). Notably, a negative association existed between the population of CD11b+/CD14- cells in PBMNC and the frequency of CD8+ T lymphocytes (n = 48, r = -0.3141, P = 0.0297). Conclusions: Our study provided evidence of an increased pool of CD11b +/CD14-/CD15+/CD33+ MDSCs in the peripheral blood of NSCLC patients. For the suppressive effect of the cells on CD8+ T lymphocytes, these findings suggest the important role of the CD11b+/CD14-/CD15+/CD33+ MDSCs in mediating immunosuppression in NSCLC.
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