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Updated: Oct 21, 2025
Live-3D-Cell Immunocytochemistry Assays of Pediatric Diffuse Midline Glioma
Published on: November 11, 2021
Inhibition of microglial EZH2 leads to anti-tumoral effects in pediatric diffuse midline gliomas
Lily Keane1, Mathilde Cheray1, Dalel Saidi1
1Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
Background:
Diffuse intrinsic pontine gliomas (DIPG), within diffuse midline gliomas are aggressive pediatric brain tumors characterized by histone H3-K27M mutation. Small-molecule inhibitors for the EZH2-H3K27 histone methyltransferase have shown promise in preclinical animal models of DIPG, despite having little effect on DIPG cells in vitro. Therefore, we hypothesized that the effect of EZH2 inhibition could be mediated through targeting of this histone modifying enzyme in tumor-associated microglia.
Methods:
Primary DIPG tissues, and cocultures between microglia and patient-derived DIPG or -pediatric high-grade glioma (pHGG) cell lines, were used to establish the H3-K27M status of each cell type. Antisense RNA strategies were used to target EZH2 gene expression in both microglia and glioma cells. Microglia anti-tumoral properties were assessed by gene expression profile, tumor cell invasion capacity, microglial phagocytic activity, and associated tumor cell death.
Results:
In primary DIPG tissues, microglia do not carry the H3-K27M mutation, otherwise characteristic of the cancer cells. Activation of a microglial tumor-supportive phenotype by pHGG, independently of their H3-K27M status, is associated with a transient H3K27me3 downregulation. Repression of EZH2 in DIPG cells has no impact on tumor cell survival or their ability to activate microglia. However, repression of EZH2 in microglia induces an anti-tumor phenotype resulting in decreased cancer cell invasion capability, increased microglial phagocytosis, and tumor-related cell death.
Conclusions:
These results indicate that microglia, beyond the tumor cells, contribute to the observed response of DIPG to EZH2 inhibition. Results highlight the potential importance of microglia as a new therapeutic avenue in DIPG.
Insights
Targeting EZH2 in microglia, not tumor cells, shows promise for treating diffuse intrinsic pontine gliomas (DIPG). This approach activates microglia's anti-tumor properties, offering a new therapeutic strategy for this aggressive pediatric brain cancer.
Area of Science:
- Oncology
- Neuro-oncology
- Immunology
Background:
- Diffuse intrinsic pontine gliomas (DIPG) are aggressive pediatric brain tumors characterized by the H3-K27M mutation.
- While EZH2 inhibitors show preclinical promise, their efficacy in DIPG cells in vitro is limited.
- This suggests a potential role for targeting EZH2 in tumor-associated microglia.
Purpose of the Study:
- To investigate the role of EZH2 in microglia within the context of DIPG.
- To determine if targeting EZH2 in microglia can elicit an anti-tumoral response in DIPG.
Main Methods:
- Utilized primary DIPG tissues and cocultures of microglia with patient-derived DIPG/pediatric high-grade glioma (pHGG) cell lines.
- Employed antisense RNA strategies to target EZH2 gene expression in both microglia and glioma cells.
- Assessed microglial anti-tumoral properties via gene expression, tumor cell invasion, phagocytosis, and cell death.
Main Results:
- Microglia in DIPG tissues lack the H3-K27M mutation found in cancer cells.
- Repressing EZH2 in DIPG cells did not affect tumor cell survival or microglial activation.
- Repressing EZH2 in microglia induced an anti-tumor phenotype, reducing invasion, increasing phagocytosis, and promoting tumor cell death.
Conclusions:
- Microglia, in addition to tumor cells, contribute to DIPG response to EZH2 inhibition.
- Microglia represent a potential novel therapeutic target for DIPG treatment.
