The Significance Of Two Subsets Myeloid-derived Suppressor Cells In The Peripheral Blood Of Patients With Non-small Cell Lung Cancer

Background and objectivesLung cancer is one of the most common cancers. The combination of surgeryand chemotherapy is the standard schedule to lung cancer. However, lots of patientswith lung cancer have lost operation opportunity when diagnosed. And a little parteven if treated by surgery still had a high rate of recurrence and metastasis. It isextremely urgent that to develop the effective adjuvant treatment. In recent years,tumor biological immunotherapy has gradually appeared in the clinical application,but the early tumor biological treatment strategies have focused on elevating thepatient’s antitumor immunity. Recently, many studies suggest immunosuppressionand immune escape is the crucial factors of biological immunotherapy. With theresearch on tumor immunology and tumor microenvironment, the cause toimmunosuppressive status of cancer patients is increasingly clear. Myeloid-derivedsuppressor cells (MDSCs) in the peripheral blood and tumor tissue from lung cancerpatients have a higher level compared to health donors, which is involved in theimmune suppression and immune escape to influencing the antitumor effect.There are many studies about the phenotype and function of MDSCs.According to the different surface marker, MDSCs is divided into monocytic andgranulocytic MDSC. And the phenotype and distribution of MDSCs are dissimilar indifferent malignant tumor. Han-Pin, Kuo et al. using CD14and CD11b as surfacemarker showed that human MDSCs comprised two distinct subpopulations with aprecise phenotype and fate：CD14+CD11b+cells (M-MDSC) and CD14-CD11b+cell (G-MDSC). It is demonstrated that MDSCs is abnormal accumulated in variety of malignant tumor and associated with the prognosis of patients. But studies ofM-MDSC and G-MDSC in non-small cell lung cancer (NSCLC) patients are limited.So in the experiment, we attempted to investigate the difference of two MDSCssubsets accotding to Han-Pin, Kuo et al. in the peripheral blood of NSCLC patientsand their potential clinical significance. Furthermore, the analysis of theirmechanism is needed, in order to provide new targeted therapy for NSCLC.Methods6ml peripheral blood from NSCLC patients and health donor were collectedand then peripheral blood mononuclear cells (PBMC) were obtained by densitygradient centrifugation. The frequency of CD14+CD11b+cell (M-MDSC) andCD14-CD11b+cell (G-MDSC) were determined by Flow cytomertry (FCM), inaddition, the expression of Tim3, PD-1and CTLA-4on CD4+and CD8+T cellswere detected. M-MDSC and G-MDSC were purified by MASC and FASC. Next,the exoression of ARG1, HIF-1, COX-2and IL-10on the purified two subsets wereanalysized by real-time PCR. Two groups of MDSCs were co-cultured with CD8+Tcell and tumor cells to observe the proliferation and apoptosis of CD8+T cell andtumor cells. The ratio of M-MDSC and G-MDSC in peripheral blood from patientsafter chemotherapy was detected using FCM.Results1. The frequency of G-MDSC was higher than that of M-MDSC in patients withnon-small cell lung cancer (P=0.031), whereas G-MDSC was lower thanM-MDSC in healthy donors (P=0.023). G-MDSC was significantly elevated inpatients compared to healthy donors (P<0.001). However, there was nosignificant difference in frequency of M-MDSC between the two groups.2. Compared with health donors, G-MDSC from NSCLC patients expressedhigher level of ARG1, HIF-1, and IL-10, but M-MDSC expressed higherlevel of COX-2and IL-10(P<0.05). In NSCLC patients, G-MDSC was withhigher level of ARG1but lower of COX-2than M-MDSC (P<0.05). 3. G-MDSC and M-MDSC from NSCLC patients had a significant inhibition tothe proliferation of CD8+T cells than that from health controls (P<0.05).Furthermore, the effect of inhibition was associated with the proportion ofMDSCs.4. G-MDSC and M-MDSC effectively reduced the apoptosis of tumor cells bychemotherapy (P<0.001), and promoted its proliferation (P<0.05).5. After chemotherapy, G-MDSC was greatly reduced in stable disease (SD) andPartial response (PR) groups (P<0.05), whereas progressive disease (PD)group showed no significant change. However, M-MDSC had no difference inall groups. After the four cycles of chemotherapy, G-MDSC from patients inPR group was much lower than that in SD and PD group (F=7.353, P=0.004).6. Before the first chemotherapy, the NSCLC patients with high level ofG-MDSC showed poor response to chemotherapy (2=4.180, P=0.041).Conclusion1. As a group of suppressive immune cells, MDSCs were excessive accumulationin non-small cell lung cancer.2. Two subsets of MDSCs played an immunosuppressive role through differentmechanisms.3. The frequency of G-MDSC of peripheral blood from patients with NSCLCcould be a predictor of prognosis.