Single-Cell Atlas Reveals Complexity of the Immunosuppressive Microenvironment of Initial and Recurrent Glioblastoma.

Weilun Fu,Jiangfei Wang,Jizong Zhao,Shuo Wang,Dexi Chen,Wenjing Wang,Yong Cao,Zihan Yan,Ran Huo,Jie Wang,Yuming Jiao,Hao Li

doi:10.3389/fimmu.2020.00835

Abstract

The Glioblastoma (GBM) immune microenvironment plays a critical role in tumor development, progression, and prognosis. A comprehensive understanding of the intricate milieu and its interactions remains unclear, and single-cell analysis is crucially needed. Leveraging mass cytometry (CyTOF), we analyzed immunocytes from 13 initial and three recurrent GBM samples and their matched peripheral blood mononuclear cells (pPBMCs). Using a panel of 30 markers, we provide a high-dimensional view of the complex GBM immune microenvironment. Hematoxylin and eosin staining and polychromatic immunofluorescence were used for verification of the key findings. In the initial and recurrent GBMs, glioma-associated microglia/macrophages (GAMs) constituted 59.05 and 27.87% of the immunocytes, respectively; programmed cell death-ligand 1 (PD-L1), T cell immunoglobulin domain and mucin domain-3 (TIM-3), lymphocyte activation gene-3 (LAG-3), interleukin-10 (IL-10) and transforming growth factor-β (TGFβ) demonstrated different expression levels in the GAMs among the patients. GAMs could be subdivided into different subgroups with different phenotypes. Both the exhausted T cell and regulatory T (Treg) cell percentages were significantly higher in tumors than in pPBMCs. The natural killer (NK) cells that infiltrated into the tumor lesions expressed higher levels of CXC chemokine receptor 3 (CXCR3), as these cells expressed lower levels of interferon-γ (IFNγ). The immune microenvironment in the initial and recurrent GBMs displayed similar suppressive changes. Our study confirmed that GAMs, as the dominant infiltrating immunocytes, present great inter- and intra-tumoral heterogeneity and that GAMs, increased exhausted T cells, infiltrating Tregs, and nonfunctional NK cells contribute to local immune suppressive characteristics. Recurrent GBMs share similar immune signatures with the initial GBMs except the proportion of GAMs decreases.

Highlights

IntroductionGlioblastoma (GBM) is the most common and aggressive primary brain tumor [1]
MATERIALS AND METHODSGlioblastoma (GBM) is the most common and aggressive primary brain tumor [1]
The GBM immune microenvironment plays a critical role in tumor development, progression, and prognosis

Summary

Introduction

Glioblastoma (GBM) is the most common and aggressive primary brain tumor [1] Because of their malignant growth and invasion into the brain parenchyma coupled with resistance to therapy, GBMs are among the deadliest of all tumors [2]. Produced factors and their crosstalk with the extracellular matrix drive and reprogram infiltrating immune cells to acquire distinct functional phenotypes [6]. These infiltrating immune cells have been shown to engage in reciprocal interactions with neoplastic tumor cells to play a crucial role in tumor growth, metastasis, and response to treatment [7]

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Conclusion