Targeting SUV4-20H2-mediated H4K20 methylation restrains growth and migration in pediatric high-grade astrocytomas.
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Pediatric astrocytomas are characterized by increased molecular and clinical heterogeneity with epigenetic alterations contributing to aggressiveness and therapy resistance. The repressive histone mark H4K20 trimethylation (H4K20me3) and the methyltransferase SUV4-20H2 (KMT5C) are critical regulators of chromatin integrity and genome stability, with limited investigation in pediatric astrocytomas. KMT5C mRNA levels were evaluated in a publicly available pediatric gliomas database using bioinformatic analysis. Investigation of SUV4-20H2 and H4K20me3 expression was performed in a cohort of 43 pediatric astrocytoma tissues by immunohistochemistry. Their functional role and mechanism of action was investigated in pediatric glioma cell lines by using the substrate-competitive inhibitor of SUV4-20, A-196. Cell viability, apoptosis and migration were assessed using XTT, cleaved PARP, and wound healing assays, respectively. Effects of treatment on H4K20 methylation, DNA damage, mitotic stress [Polo-like kinase (PLK1) expression], and invasion markers (N-cadherin, β-catenin expression) were examined by western immunoblotting. KMT5C mRNA was significantly enriched in pediatric high-grade astrocytomas compared to low-grade tumors. A significant elevation of SUV4-20H2 and H4K20me3 expression was detected in astrocytoma tissues indicating epigenetic dysregulation contributing to malignancy. Treatment with A-196 reduced cell proliferation of pediatric glioma cell lines and induced apoptosis in a dose-dependent manner. It further impaired cell migration, accompanied by reduced N-cadherin and β-catenin expression. Mechanistically, inhibition of SUV4-20 depleted H4K20me3, inducing chromatin destabilization, replication-associated DNA damage and was associated with increased PLK1 expression, consistent with activation of a mitotic stress response. Our findings indicate that SUV4-20H2-mediated H4K20 activity in pediatric high-grade astrocytomas maintains their growth and migratory potential by regulating chromatin integrity and may serve as potential therapeutic target.