Increased circulating monocyte MDSCs positively correlate with serum Interleukin-10 in metastatic melanoma patients

Abstract

Numerous immunosuppressive cells such as myeloid-derived suppressor cells (MDSCs) and inhibitory cytokines identified in melanoma microenvironment have the important role in immune escape. Therefore, in this study we analyzed monocytic (m)MDSCs in peripheral blood of metastatic melanoma (MM) patients. In peripheral blood of 35 MM patients and 30 healthy controls we analyzed percentage of CD14 + HLA-DR- mMDSCs in monocyte gate and the mean fluorescence intensity of Foxp3 in CD25 + CD4 + regulatory T cells by Flow cytometry. Serum levels of transforming growth factor beta, interferon-gamma, interleukin (IL)-6, IL-8, IL-10 are measured by ELISA assays. In this study MM patients have significantly higher percentage of CD14 + HLA-DR- mMDSCs, as well as increased the baseline mMDSC/PBMC subset (NK, T, B cells, monocytes) ratio. Although there is no significant difference in the percentage of mMDSCs between groups of MM patients with different localization of distant metastasis, patients with elevated serum lactate dehydrogenase (LDH) have statistically significant higher percentage of these cells compared to LDH negative patients. Furthermore, in MM patients there is statistically significant positive correlation between values of IL-10 and the percentage of mMDSCs, only. Therefore, therapeutics that target circulating mMDSCs and IL-10 may have a big importance in the improvement of antitumor immunity in MM patients.

Keywords: cytokine; interleukin-10; metastatic melanoma patients; myeloid-derived suppressor cells; regulatory t cells.

Figure 1.

Mm patients compared to HC have significantly higher a) percentage of CD14 + HLA-DR- mMDSCs (**p < 0.01, Mann–Whitney exact test) and b) mean fluorescence intensity (MFI) of Foxp3 in CD25 + CD4 + tregs (*p ≤ 0.05, Mann–Whitney exact test); c) Representative flow cytometric dot plots of mMDSCs analysed in monocyte gate the results are estimated by flow cytometry and shown as mean values ± se for 35 MM patients and 30 HC for mMDSCs analysis and 10 MM patients and 10 HC for Foxp3 analysis.

Figure 2

The baseline mMDSC/PBMC subset ratio is significantly increased (*p ≤ 0.05, **p < 0.01 Mann–Whitney exact test) in MM patients compared to HC. Results are expressed in indexes calculated as the percentage of mMDSC for each MM patient and HC devides with the percenatage of appropriate PBMC subset (CD3-CD56 + NK, CD3 + CD8 + CTL, CD3 + CD4 + Th, CD19 + B cells, monocytes). Results are shown as mean ± SE for 30 MM patients and 25 HC.

Figure 3

a) There is no significant difference (p > 0.05, Mann–Whitney exact test) in the percentage of mMDSCs between groups of MM patients according to localization of distant metastasis (M1a + M1b, M1c, M1d); b) LDH + MM patients have statistically significant higher percentage of mMDSCs (*p ≤ 0.05, Mann–Whitney exact test) compared to LDH- patients. The results are shown as mean values ± SE for 35 MM patients and 30 HC.

Figure 4

In MM patients there is statistically significant positive correlation (p ≤ 0.05, Spearman's rank correlation) between serum values of IL-10 estimated by ELISA and the percentage of mMDSCs estimated by flow cytometry in monocyte gate. These parameters were analysed in 35 MM patients.