Identification of the subpopulations of myeloid-derived suppressor cells and the function study in elderly tumor-bearing mice / 中华老年医学杂志

ABSTRACT

Objective To investigate the level of subpopulations of myeloid-derived suppressor cells (MDSCs) in elderly tumor-bearing mice versus elderly tumor-free mice,and to study the difference in immune suppressive functions between different subpopulations and their mechanisms.Methods A total of 20 healthy C57BL/6 elderly mice(aged 18-20 months) were randomly chosen to establish Lewis lung cancer models.The amount of monocytic-MDSCs (MO-MDSCs) and polymorphonuclear granulocytic-MDSCs(PMN-MDSCs) in tumor-free and tumor-bearing elderly mice was evaluated by using flow cytometry.MO-MDSCs and PMN-MDSCs were separated with Magnetic-Activated Cell Sorting (MACS) MicroBeads and their morphological characteristics were observed after May-Grunwald-Giemsa staining.The effects of MO-MDSCs and PMN-MDSCs on the proliferation of T cells were determined by Brdu-enzyme-linked immunosorbent assay(ELISA).And the immune suppressive mediators secreted by the subpopulations were detected by Real-time polymerase chain reaction(PCR).Results Compared to the tumor-free group,the proportion of MO-MDSCs in the spleen of tumorbearing group were increased [(12.44± 1.20) ％ vs.(38.42±3.66) ％,t=5.67,P＜0.001],while PMN-MDSCs were not [(10.34±0.68) ％ vs.(12.18±1.27) ％,t=2.21,P=0.09].The result of Brdu-ELISA showed that MO-MDSCs could suppress the proliferation of T cells [(0.30 ± 0.18) vs.(3.38±0.96),t=8.33,P＜0.001],while PMN MDSCs could not [(2.69±0.45)vs.(3.38±0.96),t =1.72,P=0.11].The result of PCR showed that as compared with PMN-MDSCs,Mo-MDSCs had the increased expression levels of arginase-1 (ARG-1),inducible nitric oxide synthase (iNOS),interleukin-10 (IL-10),interferon-γ(IFN-γ) (t =4.31,8.89,1.70,3.13,respectively,P ＜ 0.01 or 0.05),while the expression levels of interleukin-13 (IL-13),transforming growth factor-β(TGF-β) had no differences (t=4.94 and 2.75,P =0.39 and0.47).Conclusions MO-MDSCs are significantly increased in elderly Lewis lung cancer mice models.MO-MDSCs could mediate lung tumor evasion by suppressing the proliferation of T cells through highly expressing ARG-1,iNOS,IL-10 and IFN-γ.