F11R Is a Novel Monocyte Prognostic Biomarker for Malignant Glioma

Winnie W Pong,Joshua B Rubin,Todd Wylie,Jaebok Choi,John F Dipersio,Gregory N Fuller,Vincent Magrini,Obi L Griffith,Ryan J Emnett,Matthew L Cooper,Xi Feng,Dolores Hambardzumyan,Elaine R Mardis,David H Gutmann,Malachi Griffith,David Piwnica-Worms,Jason Walker,Jingqin Luo,Michael Platten

doi:10.1371/journal.pone.0077571

Abstract

ObjectiveBrain tumors (gliomas) contain large populations of infiltrating macrophages and recruited microglia, which in experimental murine glioma models promote tumor formation and progression. Among the barriers to understanding the contributions of these stromal elements to high-grade glioma (glioblastoma; GBM) biology is the relative paucity of tools to characterize infiltrating macrophages and resident microglia. In this study, we leveraged multiple RNA analysis platforms to identify new monocyte markers relevant to GBM patient outcome.MethodsHigh-confidence lists of mouse resident microglia- and bone marrow-derived macrophage-specific transcripts were generated using converging RNA-seq and microarray technologies and validated using qRT-PCR and flow cytometry. Expression of select cell surface markers was analyzed in brain-infiltrating macrophages and resident microglia in an induced GBM mouse model, while allogeneic bone marrow transplantation was performed to trace the origins of infiltrating and resident macrophages. Glioma tissue microarrays were examined by immunohistochemistry, and the Gene Expression Omnibus (GEO) database was queried to determine the prognostic value of identified microglia biomarkers in human GBM.ResultsWe generated a unique catalog of differentially-expressed bone marrow-derived monocyte and resident microglia transcripts, and demonstrated that brain-infiltrating macrophages acquire F11R expression in GBM and following bone-marrow transplantation. Moreover, mononuclear cell F11R expression positively correlates with human high-grade glioma and additionally serves as a biomarker for GBM patient survival, regardless of GBM molecular subtype.SignificanceThese studies establish F11R as a novel monocyte prognostic marker for GBM critical for defining a subpopulation of stromal cells for future potential therapeutic intervention.

Highlights

Survival for adults with the malignant brain tumor, glioblastoma multiforme (GBM), remains poor despite decades of advancements in surgery, radiation, and chemotherapy
We identified several new markers amenable to flow cytometry analysis not previously reported to be differentially expressed between microglia and bone-marrow derived monocytes (BMDM) (F11R, CD81, and CLEC12A)
We leveraged two representative transcripts to demonstrate that brain macrophages in murine GBM express F11R regardless of tissue origin

Summary

Introduction

Survival for adults with the malignant brain tumor, glioblastoma multiforme (GBM), remains poor despite decades of advancements in surgery, radiation, and chemotherapy. One underexplored strategy for treating these cancers is the targeting of stromal cell types in the tumor microenvironment. In this regard, microglia and macrophages may serve as tractable targets for stroma-directed therapy, as they comprise 30-50% of the cells in both benign and malignant gliomas [1,2]. To identify new macrophage markers relevant to high-grade glioma, we sought to discover BMDM- and brain microgliaspecific transcripts to enable an analysis of the role of these mononuclear cell populations in GBM

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Conclusion