👤 Spyros Sgouros

Pediatric diffuse high-grade gliomas (pHGGs) are heterogeneous and infiltrative tumors with poor prognosis. Recent molecular characterization of pHGGs has revealed an altered epigenetic profile with aberrant post-translational modifications and increased histone 3 lysine 9 trimethylation (H3K9) to be implicated in their pathology. Herein, we investigate the expression and biological role of the methyltransferase suppressor of variegation 3-9 homolog 1 (SUV39H1) in regulating key cancer hallmarks, including cell proliferation, motility, and epithelial-mesenchymal transition (EMT) gene regulation of pHGG. Bioinformatic analysis of SUV39H1 mRNA levels was performed in a public database of pediatric gliomas with respective controls. SUV39H1 protein expression was further investigated in a cohort of 24 pHGG tissues and controls by immunohistochemistry and western immunoblotting, followed by correlation analysis with patients' clinicopathological features. Gene silencing of SUV39H1 was performed in patient-derived pHGG cell lines (SJ-GBM2 and CHLA-200) to investigate their functional role in cell proliferation, migration, cell adhesion, and EMT markers. SUV39H1 mRNA was found enriched in pHGG tissues compared to normal brain, with pathway analyses (GO and KEGG) revealing a significant correlation with cell adhesion and focal adhesion pathways in SUV39H1-high pHGG. Immunohistochemical analysis of the pHGG cohort detected significantly increased SUV39H1 protein expression in pHGG tissues, followed by elevated H3K9me3 expression compared to normal brain tissues. Moreover, SUV39H1 and H3K9me3 levels were higher in pHGG with H3K27M mutation compared to H3-WT tumors and correlated with worst patients' survival. Gene silencing of SUV39H1 in SJ-GBM2 and CHLA-200 cells induced a significant decrease in cell viability and cell migration, followed by reduced expression of vimentin, β-catenin, and TCF4 protein levels. Furthermore, SUV39H1 silencing reduced the mRNA levels of EMT marker genes CDH2, SNAI1, and MARCKS. Our findings demonstrate that SUV39H1 regulates cell proliferation and adhesion in pHGG, contributing to epithelial-mesenchymal transition through regulation of β-catenin/TCF4 axis, presenting a promising therapeutic target to be investigated further. KEY MESSAGES: SUV39H1 gene expression is enriched in pHGG compared to normal brain. SUV39H1 expression is increased in pHGG tissues along with H3K9me3 expression. Gene silencing of SUV39H1 reduces cell viability and migration. SUV39H1 silencing decreased expression of vimentin, β-catenin and TCF4. SUV39H1 silencing reduced EMT marker genes CDH2, SNAI1 and MARCKS. SUV39H1 has an oncogenic role in pHGG and presents a promising therapeutic target. Show less

Pediatric high-grade gliomas (pHGGs) are heterogeneous, diffuse, and highly infiltrative tumors with dismal prognosis. Aberrant post-translational histone modifications with elevated histone 3 lysine trimethylation (H3K9me3) have been recently implicated in pHGGs' pathology, conferring to tumor heterogeneity. The present study investigates the potential involvement of H3K9me3 methyltransferase SETDB1 in the cellular function, progression, and clinical significance of pHGG. The bioinformatic analysis detected SETDB1 enrichment in pediatric gliomas compared to the normal brain, as well as positive and negative correlations with a proneural and mesenchymal signature, respectively. In our cohort of pHGGs, SETDB1 expression was significantly increased compared to pLGG and normal brain tissue and correlated with p53 expression, as well as reduced patients' survival. In accordance, H3K9me3 levels were also elevated in pHGG compared to the normal brain and were associated with worse patient survival. Gene silencing of SETDB1 in two patient-derived pHGG cell lines showed a significant reduction in cell viability followed by reduced cell proliferation and increased apoptosis. SETDB1 silencing further reduced cell migration of pHGG cells and the expression of the mesenchymal markers N-cadherin and vimentin. mRNA analysis of epithelial-mesenchymal transition (EMT) markers upon SETDB1 silencing showed a reduction in SNAI1 levels and downregulation of CDH2 along with the EMT regulator gene MARCKS. In addition, SETDB1 silencing significantly increased the bivalent tumor suppressor gene SLC17A7 mRNA levels in both cell lines, indicating its implication in the oncogenic process.Altogether, our findings demonstrate a predominant oncogenic role of SETDB1 in pHGG which along with elevated H3K9me3 levels correlate significantly to tumor progression and inferior patients' survival. There is evidence that targeting SETDB1 may effectively inhibit pHGG progression, providing a novel insight into the therapeutic strategies for pediatric gliomas. KEY MESSAGES: SETDB1 gene expression is enriched in pHGG compared to normal brain. SETDB1 expression is increased in pHGG tissues and associates with reduced patients' survival. Gene silencing of SETDB1 reduces cell viability and migration. SETDB1 silencing affects mesenchymal markers expression. SETDB1 silencing upregulates SLC17A7 levels. SETDB1 has an oncogenic role in pHGG. Show less