A subset of pediatric chordomas with atypical histomorphologic features needs to be identified, as they behave in an aggressive manner and require adjuvant therapy. Pediatric chordomas more frequently show p53 expression, INI1 loss, and higher MIB-1 LI as compared with adults, whereas EGFR expression is common to both.

No abstract

Elevated expression of enhancer of zeste homolog 2 (EZH2), a histone H3K27 methyltransferase, was observed in gliomas harboring telomerase reverse transcriptase (TERT) promoter mutations. Given the known involvement of TERT and EZH2 in glioma progression, the correlation between the two and subsequently its involvement in metabolic programming was investigated. Inhibition of human telomerase reverse transcriptase either pharmacologically or through genetic manipulation not only decreased EZH2 expression, but also (i) abrogated FASN levels, (ii) decreased de novo fatty acid accumulation, and (iii) increased ataxia-telangiectasia-mutated (ATM) phosphorylation levels. Conversely, diminished TERT and FASN levels upon siRNA-mediated EZH2 knockdown indicated a positive correlation between TERT and EZH2. Interestingly, ATM kinase inhibitor rescued TERT inhibition-mediated decrease in FASN and EZH2 levels. Importantly, TERT promoter mutant tumors exhibited greater microsatellite instability, heightened FASN levels and lipid accumulation. Coherent with in vitro findings, pharmacological inhibition of TERT by costunolide decreased lipid accumulation and elevated ATM expression in heterotypic xenograft glioma mouse model. By bringing TERT-EZH2 network at the forefront as driver of dysregulated metabolism, our findings highlight the non-canonical but distinct role of TERT in metabolic reprogramming and DNA damage responses in glioblastoma.

Enhancer of zeste homolog-2(EZH2) is a key epigenetic regulator that functions as oncogene and also known for inducing altered trimethylation of histone at lysine-27 (H3K27me3) mark in various tumors. However, H3K27me3 targets and their precise relationship with gene expression are largely unknown in astrocytic tumors. In this study, we checked EZH2 messenger RNA and protein expression in 90 astrocytic tumors of different grades using quantitative PCR and immunohistochemistry, respectively. Further, genome-wide ChIP-seq analysis for H3K27me3 modification was also performed on 11 glioblastomas (GBMs) and 2 diffuse astrocytoma (DA) samples. Our results showed EZH2 to be highly overexpressed in astrocytic tumors with a significant positive correlation with grade. Interestingly, ChIP-seq mapping revealed distinct differences in genes and pathways targeted by these H3K27me3 modifications between GBM versus DA. Neuroactive ligand receptor pathway was found most enriched in GBM (P = 9.4 × 10-25), whereas DA were found to be enriched in metabolic pathways. Also, GBM showed a higher enrichment of H3K27me3 targets reported in embryonic stem cells and glioma stem cells as compared with DAs. Our results show majority of these H3K27me3 target genes were downregulated, not only due to H3K27me3 modification but also due to concomitant DNA methylation. Further, H3K27me3 modification-associated gene silencing was not restricted to promoter but also present in gene body and transcription start site regions. To the best of our knowledge, this is the first high-resolution genome-wide mapping of H3K27me3 modification in adult astrocytic primary tissue samples of human, highlighting the differences between grades. Interestingly, we identified SLC25A23 as important target of H3K27me3 modification, which was downregulated in GBM and its low expression was associated with poor prognosis in GBMs.

Ependymomas (EPN) show site specific genetic alterations and a recent DNA methylation profiling study identified nine molecular subgroups. C11orf95-RELA and YAP1 fusions characterise the RELA and YAP1 molecular subgroups, respectively, of supratentorial (ST)-EPNs. Current guidelines recommend molecular subgrouping over histological grade for accurate prognostication. Clinicopathological features of ST-EPNs in correlation with C11orf95-RELA and YAP1 fusions have been assessed in only few studies. We aimed to study these fusions in EPNs, and identify diagnostic and prognostic markers. qRT-PCR and Sanger Sequencing for the detection of C11orf95-RELA, YAP1-MAMLD1 and YAP1-FAM118B fusion transcripts, gene expression analysis for NFKB1, and immunohistochemistry for p53, MIB-1, nestin, VEGF, and L1CAM were performed. 88 EPNs (10-Grade I and 78-Grade II/III) from all sites were included. RELA fusions were unique to Grade II/III ST-EPNs, detected in 81.4% (22/27) and 18.5% (5/27) of pediatric and adult ST-EPNs respectively. ST-EPNs harbouring RELA fusions showed frequent grade III histology (81.5%), clear cell morphology (70.3%), upregulated NFKB1 expression, MIB-1 labelling indices (LI) ≥ 10% (77.8%), and immunopositivity for nestin (95.7%), VEGF (72%), L1CAM (79%), and p53 (64%). Presence of RELA fusions, L1CAM immunopositivity and MIB-1 LI ≥ 10% associated with poor outcome. L1CAM showed 81% concordance with RELA fusions. YAP1-MAMLD1 fusion was identified in a single RELA fusion negative adult anaplastic ST-EPN. RELA fusions are frequent in ST-EPNs and associate with poor outcome. L1CAM is a surrogate immunohistochemical marker. RELA fusion positive ST-EPNs strongly express nestin indicating increased stemness. Further evaluation of the interactions between NFKB and stem cell pathways is warranted.

Loss of SMARCB1/INI1 expression is considered to be a hallmark for childhood chordomas (CCs). Although mutation/loss of 22q has strongly established the loss of SMARCB1/INI1 in cancers, the cause in CCs remains elusive. Recent studies suggest role of miRNAs in regulation of SMARCB1/INI1 expressions. We examined 5 reported/target predicted miRNAs to SMARCB1/INI1 in SMARCB1/INI1 immunonegative and immunopositive cases, and found upregulation of miR-671-5p and miR-193a-5p in SMARCB1/INI1-immunonegative cases. Notably, these two miRNAs were significantly predicted to target TGF-β signaling, suggestive of dysregulation of developmental and osteoblast regulation pathway in CCs. Overall, we suggest miR-671-5p- and miR-193a-5p-mediated epigenetic mode of SMARCB1/INI1 loss and downregulated TGF-β pathway in CCs.

The factors involved in cell differentiation have recently garnered interest for their role in inhibition of pathogenesis in various tumors. However, their role in glioblastoma (GBM) remains poorly understood. We analyzed The Cancer Genome Atlas (TCGA) GBM data and found significant downregulation of neurogenic differentiation factor NeuroD2 in GBM patients. Low levels of NeuroD2 were found to be correlated with poor overall survival of GBM patients in TCGA dataset as well as in our cohort. Interestingly, NeuroD2 was shown to be transcriptionally induced by p53 and post-transcriptionally targeted by hypoxia- inducible miRNA, miR-210. NeuroD2 overexpression diminished GBM aggressiveness by inhibiting cell proliferation, migration and promoting apoptosis under hypoxia. NeuroD2 overexpressing GBM cells failed to form three-dimensional (3D)-tumor spheroids and displayed reduced migration in a 3D gelatin matrix. NeuroD2 gene signature was enriched in pathways belonging to cytokine-cytokine receptor interaction, TNF-signaling, PI3K-AKT signaling, focal adhesion and ECM-receptor interaction. Overall, our study identifies a novel role of NeuroD2 as a tumor suppressor and prognostic biomarker in GBM the levels of which are tightly regulated by p53 and miR-210. Overexpressing NeuroD2 may potentially be a simple and efficient therapeutic strategy to inhibit the malignant phenotype of GBM cells.

No abstract