A map of the spatial distribution and tumour‐associated macrophage states in glioblastoma and grade 4 IDH‐mutant astrocytoma

Abstract

Tumour‐associated macrophages (TAMs) abundantly infiltrate high‐grade gliomas and orchestrate immune response, but their diversity in isocitrate dehydrogenase (IDH)‐differential grade 4 gliomas remains largely unknown. This study aimed to dissect the transcriptional states, spatial distribution, and clinicopathological significance of distinct monocyte‐derived TAM (Mo‐TAM) and microglia‐derived TAM (Mg‐TAM) clusters across glioblastoma‐IDH‐wild type and astrocytoma‐IDH‐mutant‐grade 4 (Astro‐IDH‐mut‐G4). Single‐cell RNA sequencing was performed on four cases of human glioblastoma and three cases of Astro‐IDH‐mut‐G4. Cell clustering, single‐cell regulatory network inference, and gene set enrichment analysis were performed to characterize the functional states of myeloid clusters. The spatial distribution of TAM subsets was determined in human glioma tissues using multiplex immunostaining. The prognostic value of different TAM‐cluster specific gene sets was evaluated in the TCGA glioma cohort. Profiling and unbiased clustering of 24,227 myeloid cells from glioblastoma and Astro‐IDH‐mut‐G4 identified nine myeloid cell clusters including monocytes, six Mo/Mg‐TAM subsets, dendritic cells, and proliferative myeloid clusters. Different Mo/Mg‐TAM clusters manifest functional and transcriptional diversity controlled by specific regulons. Multiplex immunostaining of subset‐specific markers identified spatial enrichment of distinct TAM clusters at peri‐vascular/necrotic areas in tumour parenchyma or at the tumour–brain interface. Glioblastoma harboured a substantially higher number of monocytes and Mo‐TAM‐inflammatory clusters, whereas Astro‐IDH‐mut‐G4 had a higher proportion of TAM subsets mediating antigen presentation. Glioblastomas with a higher proportion of monocytes exhibited a mesenchymal signature, increased angiogenesis, and worse patient outcome. Our findings provide insight into myeloid cell diversity and its clinical relevance in IDH‐differential grade 4 gliomas, and may serve as a resource for immunotherapy development. © 2022 The Pathological Society of Great Britain and Ireland.

TREM2 promotes glioma progression and angiogenesis mediated by microglia/brain macrophages

“…However, the Iba1‐fluorescent area is not significantly different between the two genotypes in the tumor‐brain interface, the ABR1‐4 (Figure 2c,d), and the contralateral area (Figure 2b,d). Notably, the distribution of GAMs at the tumor‐brain interface is denser compared to the rim of the tumor (Figure 2c,d), similar to the data that have been reported in patient glioblastoma tissue (Yin et al, 2022), indicating that the GL261 glioblastoma mouse model represents the clinical features of GAMs distribution.…”

Macrophages and microglia in glioblastoma: heterogeneity, plasticity, and therapy

“…Moreover, the strict sample preparation requirement for large-scale scRNA-Seq analysis on human GBM tumor tissues is still challenging ( 107 , 108 ). Finally, the spatial distribution of TAMs can generate additional heterogeneity, since specific local niches are able to affect TAM distribution and functional polarization ( 109 , 110 ). For example, IBA1 + TMEM119 – CXCL3 + macrophages are predominantly located at perinecrotic areas and express genes involved in inflammatory program and glycolysis, whereas IBA1 + TMEM119 + CCL4 + microglia are enriched at the tumor-brain interface and express chemoattractant-encoding genes involved in T cell recruitment ( 110 ).…”

“…Finally, the spatial distribution of TAMs can generate additional heterogeneity, since specific local niches are able to affect TAM distribution and functional polarization ( 109 , 110 ). For example, IBA1 + TMEM119 – CXCL3 + macrophages are predominantly located at perinecrotic areas and express genes involved in inflammatory program and glycolysis, whereas IBA1 + TMEM119 + CCL4 + microglia are enriched at the tumor-brain interface and express chemoattractant-encoding genes involved in T cell recruitment ( 110 ). Characterization of TAM spatial distribution and identification of the context-dependent niche signals that drive TAM activation and polarization are two remaining challenges.…”

Identification of the novel prognostic biomarker, MLLT11, reveals its relationship with immune checkpoint markers in glioma

“…Previous studies have found that there were a large number of TAMs in GBM. There is a correlation between TAM density and glioma grade, indicating that TAMs support tumor development (51,52). Interestingly, negative correlations were found in this study between MLLT11 expression and M2 macrophages, as well as M1 macrophages.…”