Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2013 Sep;23(5):558-64.
doi: 10.1111/bpa.12042. Epub 2013 Mar 6.

Evaluation of Histone 3 Lysine 27 Trimethylation (H3K27me3) and Enhancer of Zest 2 (EZH2) in Pediatric Glial and Glioneuronal Tumors Shows Decreased H3K27me3 in H3F3A K27M Mutant Glioblastomas

Affiliations
Free PMC article

Evaluation of Histone 3 Lysine 27 Trimethylation (H3K27me3) and Enhancer of Zest 2 (EZH2) in Pediatric Glial and Glioneuronal Tumors Shows Decreased H3K27me3 in H3F3A K27M Mutant Glioblastomas

Sriram Venneti et al. Brain Pathol. .
Free PMC article

Abstract

H3F3A mutations are seen in ∼30% of pediatric glioblastoma (GBMs) and involve either the lysine residue at position 27 (K27M) or glycine at position 34 (G34R/V). Sixteen genes encode histone H3, each variant differing in only a few amino acids. Therefore, how mutations in a single H3 gene contribute to carcinogenesis is unknown. H3F3A K27M mutations are predicted to alter methylation of H3K27. H3K27me3 is a repressive mark critical to stem cell maintenance and is mediated by EZH2, a member of the polycomb-group (PcG) family. We evaluated H3K27me3 and EZH2 expression using immunohistochemistry in 76 pediatric brain tumors. H3K27me3 was lowered/absent in tumor cells but preserved in endothelial cells and infiltrating lymphocytes in six out of 20 GBMs. H3K27me3 showed strong immunoreactivity in all other tumor subtypes. Sequencing of GBMs showed H3F3A K27M mutations in all six cases with lowered/absent H3K27me3. EZH2 expression was high in GBMs, but absent/focal in other tumors. However, no significant differences in EZH2 expression were observed between H3F3A K27M mutant and wild type GBMs, suggesting that EZH2 mediated trimethylation of H3K27 is inhibited in GBM harboring K27M mutations. Our results indicate that H3F3A K27M mutant GBMs show decreased H3K27me3 that may be of both diagnostic and biological relevance.

Keywords: EZH2; H3F3A mutations; H3K27me3; epigenetics; methylation; pediatric glioblastoma.

Conflict of interest statement

The authors of this study declare no other potential conflicts of interest.

Figures

Figure 1
Figure 1. H3K27me3 in pediatric gliomas and glioneuronal tumors
Representative images (20X) of H3K27me3 in: A. Pilocytic astrocytoma, B. Grade II diffuse astrocytoma, C. Grade II oligodendroglioma, D. Grade III anaplastic oligodendroglioma, E. Grade I ganglioglioma (arrows indicating ganglion cells), blue amorphous areas represent eosinophilic granular bodies. F. Dysembryoplastic neuroepithelial tumor (arrows indicate floating neurons).
Figure 2
Figure 2. H3K27me3 in decreased in H3F3A K27M mutant GBM compared to wild type GBM
Representative images of H3K27me3 in: A, C & E. Three H3F3A wild type GBM cases (A -10X, C -20X, E -40X), B, D & F. Three H3F3A K27M mutant GBM cases (B -10X, D -20X, F -40X, arrows indicate retained H3K27me3 staining in endothelial cells and infiltrating lymphocytes).
Figure 3
Figure 3. Mutational analyses of GBM cases
Coding exons were sequenced using Sanger sequencing. Representative plots from: A. A H3F3A wild type GBM case showing lysine (AAG, arrow) at position 27. B. A H3F3A K27M mutant GBM case showing methionine (ATG, arrow) at position 27.
Figure 4
Figure 4. Quantification of H3K27me3 and EZH2
H3K27me3 (A) and EZH2 expression (B) were quantified in pediatric gliomas and glioneuronal tumors. Differences between H3F3A K27M and wild type GBM with either marker were analyzed using Student’s t test. * p=0.01. DNET -dysembryoplastic neuroepithelial tumors, GG – ganglioglioma, Pilocytic – pilocytic astrocytoma
Figure 5
Figure 5. EZH2 expression is strongly expressed in GBMs and shows no difference between H3F3A K27M mutant or wild type GBM
Representative images (20X) of EZH2 in: A. Pilocytic astrocytoma, B. Grade III anaplastic oligodendroglioma, C. H3F3A wild type GBM, D. H3F3A K27M mutant GBM.

Similar articles

See all similar articles

Cited by 83 articles

See all "Cited by" articles

Publication types

Feedback