Human Isogenic Cell Line Models for Neutrophils and Myeloid-Derived Suppressor Cells

Yuting Zhang,Xin Lu,Emily Wilt

doi:10.3390/ijms21207709

Abstract

Neutrophils with immunosuppressive activity are polymorphonuclear myeloid-derived suppressor cells (MDSCs) and may contribute to the resistance to cancer immunotherapy. A major gap for understanding and targeting these cells is the paucity of cell line models with cardinal features of human immunosuppressive neutrophils and their normal counterparts, especially in an isogenic manner. To address this issue, we employ the human promyelocytic cell line HL60 and use DMSO and cytokines (granulocyte macrophage-colony stimulating factor (GM-CSF) and interleukin 6 (IL6)) to induce the formation of either neutrophils or MDSCs. The induced MDSCs are CD11b+ CD33+ HLA-DR−/low and are heterogeneous for CD15 and CD14 expression. The induced MDSCs abrogate IL2 production and activation-induced cell death of the human T cell line Jurkat stimulated by CD3/CD28 antibodies, whereas the induced neutrophils enhance IL2 production from Jurkat cells. The induced MDSCs upregulate the expression of C/EBPβ, STAT3, VEGFR1, FATP2 and S100A8. Lastly, the immunosuppressive activity of the induced MDSCs is inhibited by all-trans retinoic acid and STAT3 inhibitor BP-1-102 through cellular differentiation and dedifferentiation mechanisms, respectively. Together, our study establishes a human isogenic cell line system for neutrophils and MDSCs and this system is expected to facilitate future studies on the biology and therapeutics of human immunosuppressive neutrophils.

Highlights

In this new era of cancer immunotherapy, myeloid-derived suppressor cells (MDSCs) are increasingly recognized as a critically important immune cell population underlying the evasion of anti-tumor immunity and resistance to immunotherapy [1]
On the contrary, when HL60 was treated with dimethyl sulfoxide (DMSO) and granulocyte macrophage-colony stimulating factor (GM-CSF)+interleukin 6 (IL6) together or consecutively in either order, the cells showed decreased nucleocytoplasmic ratio and round or oval peripherally located nuclei (Figure 1C), suggesting that the cytokine cocktail interrupted the DMSO-induced differentiation of HL60 and the cells remained in an immature status
A limitation of the current study is that we only focused on the cytokine combination of GM-CSF and IL6 based on the notion that these two cytokines are known inducers of MDSCs from peripheral blood mononuclear cells (PBMCs) with strong activity and consistency [17]

Summary

Introduction

In this new era of cancer immunotherapy, myeloid-derived suppressor cells (MDSCs) are increasingly recognized as a critically important immune cell population underlying the evasion of anti-tumor immunity and resistance to immunotherapy [1]. MDSCs are a heterogeneous population of immature myeloid cells that are expanded in various pathological conditions, especially in cancer [2]. Activation of MDSCs is usually manifested by increased expression of arginase 1 (ARG1) and inducible nitric oxide synthase (iNOS, aka NOS2), as well as increased production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) [3]. MDSCs are classified as granulocytic or polymorphonuclear MDSCs (PMN-MDSCs) and monocytic MDSCs (M-MDSCs), based on morphological and phenotypical resemblance to neutrophils and monocytes, respectively.

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Results

Conclusion