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Distinct population of immune suppressive macrophages differentiate from monocytic myeloid-derived suppressor cells in cancer

ABSTRACT: Here, we report that functional heterogeneity of macrophages in cancer could be determined by the nature of their precursors: monocytes (Mon) and monocytic myeloid-derived suppressor cells (M-MDSC). Macrophages differentiated from M-MDSC, but not from Mon were immune suppressive with genomic profile matching that of M-MDSC. Immune suppressive activity of M-MDSC derived macrophages was dependent on the persistent expression of S100A9 protein in these cells. S100A9 also promoted M2 polarization of macrophages. Tissue resident and Mon derived macrophages lacked expression of this protein. S100A9 dependent immune suppressive activity of macrophage was mediated via transcription factor CEBP/β. The presence of S100A9 positive macrophages in tumor tissues was associated with shorter survival in patients with head and neck cancer and poor response to PD-1 antibody treatment in patients with metastatic melanoma. Thus, this study revealed the pathway of the development of immune suppressive macrophages and suggested approach to their selective targeting.

ORGANISM(S): Homo sapiens

PROVIDER: GSE162353 | GEO | 2020/12/14

REPOSITORIES: GEO

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Project description:Myeloid-derived suppressor cells (MDSCs) are immature myeloid cells that accumulate in the tumor microenvironment of most cancer patients. There MDSCs suppress both adaptive and innate immune responses, hindering immunotherapies. Moreover, many cancers are accompanied by inflammation, a processes that further intensifies MDSC suppressive activity, causing aggressive tumor progression and metastasis. MDSCs collected from tumor-bearing mice profusely release nano-scale membrane-bound extracellular vesicles, called exosomes, which carry biologically active proteins between cells and contribute directly to the immune suppressive functions of MDSC. Many studies on other cell types have shown that exosomes may also carry microRNAs (miRNAs) and messenger RNAs (mRNAs) which can also be transferred to surrounding and distant cells. However, to the best of our knowledge, the miRNA and mRNA cargo of MDSC-derived exosomes has not yet been interrogated. This study aims to identify and quantify the cargo of MDSC and their immunosuppressive exosomes to gather knowledge that can offer insights on the mechanisms by which MDSCs contribute to immune suppression, focusing on the role of exosomes as intercellular communication mediators in the tumor microenvironment. In order to achieve our objective a well-established mouse model based on a conventional mammary carcinoma (4T1 cells) and heightened inflammation (4T1 transduced to express the cytokine interleukin-1b) was used. We provide evidence that MDSC-derived exosomes carry proteins, mRNAs and miRNAs. Relative quantitation demonstrated quantitative differences between the exosome cargo and the cargo of their parental cells, supporting the hypothesis that selective loading into the exosomes is possible. Additionally, quantitative and functional analyses of the exosome cargo generated under conventional and heightened inflammation conditions are consistent with clinical observations that inflammation is linked to cancer development.

Project description:The role of myeloid cells in supporting cancer growth is well established. Most work has focused on myeloid-derived suppressor cells (MDSC) that accumulate in tumor-bearing animals, but tumor-associated neutrophils (TAN) are also known to be capable of augmenting tumor growth. However, little is known about their evolution, phenotype, and relationship to naive neutrophils (NN) and to the granulocytic fraction of MDSC (G-MDSC). In the current study, a transcriptomics approach was used in mice to compare these cell types. Our data show that the three populations of neutrophils are significantly different in their mRNA profiles with NN and G-MDSC being more closely related to each other than to TAN. Structural genes and genes related to cell-cytotoxicity (i.e. respiratory burst) were significantly down-regulated in TAN. In contrast, many immune-related genes and pathways, including genes related to the antigen presenting complex (e.g. all six MHC-II complex genes), and cytokines (e.g. TNF-a, IL-1-a/b), were up-regulated in G-MDSC, and further up-regulated in TAN. Thirteen of the 25 chemokines tested were markedly up-regulated in TAN compared to NN, including striking up-regulation of chemoattractants for T/B-cells, neutrophils and macrophages. This study characterizes different populations of neutrophils related to cancer, pointing out the major differences between TAN and the other neutrophil populations. Various types of myeloid cells have been shown to promote tumor progression by direct immune suppression and by production of angiogenic factors, matrix-degrading enzymes, or growth factors. In untreated tumors, neutrophils have been reported to produce angiogenic factors and matrix-degrading enzymes, support the acquisition of a metastatic phenotype, and suppress the anti-tumor immune response. Neutrophils, like all other leukocytes, move into tissues from the blood under the influence of specific chemokines (e.g. KC/CXCL-1, MIP-2a/CXCL-2 and GCP-2/CXCL-6), cytokines (e.g. TNFa and IFN-x), and cell adhesion molecules located on their own surface (e.g. CD11b) and on the surface of endothelial cells (e.g. selectins, ICAM-1 and PECAM-1). When they traffic into tumors, they are referred to as TAN. In mice, TAN can be defined by the specific surface markers CD11b and Ly6G with low expression of macrophage markers such as F4/80. Myeloid-derived suppressor cells (MDSC) are a heterogeneous population of immune suppressive cells that are produced excessively in cancer. They comprise at least two subsets -granulocytic (Ly6G+, G-MDSC) and monocytic cells (Ly6C+, M-MDSC), potentially with different immunosuppressive properties. It has been previously shown that MDSC can enter tumors and differentiate to mature macrophages (TAM) or neutrophils (TAN). However, since no definitive markers have been established, it is unknown whether intratumoral N2 neutrophils (N2 TAN) are granulocytic MDSC from spleen that are attracted to the tumor or if they are typical blood-derived neutrophils that are then converted to an N2 phenotype by the tumor microenvironment, specifically by the high local concentrations of TGF-b. The purpose of this study was to use a transcriptomics approach to gain further information about TANs by comparing the RNA profile of these cells to naive bone-marrow neutrophils (NN) and to the granulocytic fraction of myeloid derived suppressor cells (G-MDSC). We examined which pathways and gene-groups varied amongst these 3 populations of neutrophils and performed a detailed analysis on pathways related to the main functions of neutrophils, such as respiratory burst, granule proteins, phagocytosis, apoptosis, structural genes, antigen presentation and specific immune effects. Our data defines TAN as a unique population of neutrophils, quite distinct from both NN and G-MDSC.

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Distinct population of immune suppressive macrophages differentiate from monocytic myeloid-derived suppressor cells in cancer

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