Characterization Of Cd14⁺HLA-DR^-/low MDSCs And Their Significance In NSCLC Patients

Objective: Accumulating evidence has demonstrated that myeloid-derivedsuppressor cells （MDSCs）, a heterogeneous population of cells, play an importantrole in tumor immunity. However, the characteristics of these cells in humansremain controversial due to a lack of specific markers. Here, we characterizedperipheral CD14⁺HLA-DR^-/lowcells, a new human MDSC subpopulation, inpatients with non-small cell lung cancer （NSCLC）.Methods: We examined the frequency, count, phenotype, allostimulatorypotential of CD14⁺HLA-DR^-/lowcells from peripheral blood of NSCLC patients（n=89） by flow cytometry. In addition, the relationship between the MDSCpopulation and clinical data was analyzed. These cells suppressive effects on Tproliferation and IFN-γ production were determined by carboxyfuoresceinsuccinimidyl ester （CFSE） dilution and intracellular cytokine staining. Multiplecomparisons were made between the different groups with the Kruskal-Wallis Hnonparametric test. Comparison between two independent samples was performedusing the Mann-Whitney U test. Comparison between the same individual wasperformed using the Wilcoxon matched pairs T test. Correlation analysis wasperformed using Spearman’s rank correlation test. The survival curves wereestimated by the Kaplan-Meier method, and the patient survival times per groupwere compared by the log-rank test.Results: Frequency and count of CD14⁺HLA-DR^-/lowcells were significantlyincreased in the peripheral blood of NSCLC patients compared with that of thehealthy controls, which were associated with metastasis and response tochemotherapy. These cells showed decreased expression of CD16and CD86compared with HLA-DR+monocytes. Unlike classical monocytes, thesepopulations showed significantlydecreased allostimulatoryactivityand showedthe ability to inhibit autologous T cell proliferation and IFN-γ production in acell-contact dependent manner. Furthermore, we demonstrated thatCD14⁺HLA-DR^-/lowcells expressed the NADPH oxidase component gp91phoxandgenerated high level of ROS. Moreover, inactivation of ROS reversed theirimmunosuppressive capacity on T cell response.Conclusion: Our studies prove, for the first time, the existence of ROS-producingCD14⁺HLA-DR^-/lowsuppressor myeloid cells in NSCLC patients, which mediatetumor immunosuppression. The amount of these MDSCs was correlated with poorresponse to chemotherapy, representing a potential target for therapeuticintervention.