Metabolic dependencies and neural progenitor dysregulation: driving forces in paediatric high-grade glioma development

Paediatric high-grade gliomas (pHGGs) are the most lethal brain tumours in children, characterised by profound epigenetic dysregulation and limited treatment options. The 2021 WHO Classification has established a molecular framework that distinguishes pHGGs as biologically distinct from adult glioblastoma, recognising four major subtypes: H3K27-altered diffuse midline glioma, H3G34-mutant diffuse hemispheric glioma, infant-type hemispheric glioma, and the rare IDH-mutant gliomas. Each subtype exhibits unique epigenetic landscapes, metabolic dependencies, and therapeutic vulnerabilities, necessitating subtype-specific treatment strategies. This review explores the molecular classification of pHGGs and examines the critical role of the tumour microenvironment in disease progression. We focus on glioma stem cells as central drivers of tumour initiation, maintenance, and therapeutic resistance, highlighting their remarkable cellular plasticity and ability to dynamically transition between different states. Particular attention is given to metabolic reprogramming in pHGGs, including alterations in glucose and lipid metabolism, and the exceptional metabolic flexibility of glioma stem cells that enables adaptation to microenvironmental pressures. Importantly, we discuss the intimate crosstalk between metabolism and epigenetic regulation, whereby metabolites serve as essential cofactors for chromatin-modifying enzymes-exemplified by α-ketoglutarate maintaining low H3K27me3 in H3K27M tumours and 2-hydroxyglutarate driving hypermethylation in IDH-mutant gliomas. We review preclinical models that have advanced pHGG research and discuss emerging immunotherapeutic approaches, including CAR T-cell therapies and oncolytic viruses. By synthesising current understanding of pHGG biology, this review aims to identify promising therapeutic avenues that exploit the unique metabolic and epigenetic vulnerabilities of each molecular subtype.