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Updated: May 11, 2026
Quantitative Immunohistochemistry of the Cellular Microenvironment in Patient Glioblastoma Resections
Published on: July 31, 2017
Microglia-specificity of different markers is overridden in glioblastoma specimens
Alexander D Bungert1,2,3, Aminaa Sanchin1,4, Anne Blank1
1Department of Experimental Neurosurgery, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Charitéplatz 1, 10117, Berlin, Germany.
Abstract:
Microglia are the resident immune cells of the central nervous system. When glioblastoma develops, microglia and peripheral macrophages accumulate within the tumor tissue. Since both cell populations presumably exhibit different functional properties with anti- and pro-tumor characteristics, it is essential to distinguish between these cell populations accurately. The widespread and extensive use of single-cell technologies allowed the discovery of novel microglial markers like Sall1, Tmem119, P2ry12 and Hexb that were used for discrimination of populations. In our study, these markers were tested on protein level using immunofluorescence staining. This method permits easy identification by co-staining with IBA1 as lineage marker for myeloid cells. Bone marrow chimeras served as differentiation control. Staining showed ubiquitous marker expression of microglia in both murine naïve brains and human epilepsy specimens. However, experiments using a murine glioblastoma model demonstrated that macrophages can also express these markers after infiltrating the brain and tumor tissue. Furthermore, the level of expression varies spatially, decreasing towards the intratumoral area. In vitro experiments confirmed positive staining results for both microglia and macrophages. Furthermore, cultivation with tumor-conditioned medium led to downregulation of microglial markers. Consequently, the concept that SALL1, TMEM119, P2RY12, and HEXB are exclusive markers for microglia depends strongly on the experimental and pathological conditions, and should not be generalized. Under neuroinflammatory conditions, cell specificity of the examined markers largely diminishes and both microglia and macrophages show ubiquitous expression. Considering this fact should lead to a context dependent application when using these markers to identify myeloid cell populations within the brain.
Insights
Novel microglial markers like Sall1, Tmem119, P2ry12, and Hexb are not exclusive to microglia in glioblastoma models. Macrophages can also express these markers, necessitating context-dependent interpretation for accurate myeloid cell identification.
Area of Science:
- Neuroscience
- Immunology
- Oncology
Background:
- Microglia are central nervous system immune cells; glioblastoma attracts microglia and macrophages.
- Distinguishing these myeloid cells is crucial due to their opposing anti- and pro-tumor roles.
- Novel markers (Sall1, Tmem119, P2ry12, Hexb) were identified for microglial discrimination.
Purpose of the Study:
- To validate the specificity of novel microglial markers (Sall1, Tmem119, P2ry12, Hexb) in glioblastoma models.
- To assess the expression of these markers on both microglia and infiltrating macrophages.
- To determine the influence of tumor microenvironment on marker expression.
Main Methods:
- Immunofluorescence staining of brain tissue and cell cultures.
- Utilized IBA1 as a myeloid lineage marker.
- Employed bone marrow chimeras for differentiation control.
- In vitro experiments with tumor-conditioned medium.
Main Results:
- Ubiquitous expression of Sall1, Tmem119, P2ry12, and Hexb in normal brain microglia and human epilepsy specimens.
- Macrophages infiltrating murine glioblastoma models also expressed these markers.
- Marker expression decreased spatially towards the tumor core.
- In vitro, both microglia and macrophages stained positive; tumor medium downregulated microglial markers.
Conclusions:
- The exclusivity of Sall1, Tmem119, P2ry12, and Hexb as microglial markers is condition-dependent and cannot be generalized.
- Under neuroinflammatory conditions, these markers show ubiquitous expression in both microglia and macrophages.
- Application of these markers for myeloid cell identification in the brain requires careful consideration of the experimental and pathological context.
