Isocitrate Dehydrogenase-Wildtype Glioma Adapts Toward Mutant Phenotypes and Enhanced Therapy Sensitivity Under D-2-Hydroxyglutarate Exposure

Abstract

Background/Objectives: Isocitrate dehydrogenase (IDH) mutations are hallmark features in subsets of gliomas, producing the oncometabolite D-2-hydroxyglutarate (2HG). Although IDH mutations are associated with better clinical outcomes, their relationship with tumor progression is complex. This study aimed to investigate, in vitro and in vivo, the phenotypic consequences of IDH mutation and 2HG exposure in glioblastoma (GBM) under normoxic and hypoxic conditions and under temozolomide (TMZ) and radiation exposure. Methods: Experiments were conducted using IDH-wildtype (IDH-wt) and IDH-mutant (IDH-mut) glioma cell lines under controlled oxygen conditions. Functional assays included cell viability, cell cycle analysis, apoptosis profiling, migration, and surface marker expression via flow cytometry. Orthotopic xenografts were established in immunocompromised mice to assess in vivo tumor growth and morphology, followed by MRI and histological analysis. Treatments included TMZ, radiation, and 2HG at varying concentrations. Statistical analyses were performed using SPSS and RStudio. Results:IDH-wt cells exhibited faster proliferation and greater adaptability under hypoxia, while IDH-mut cells showed cell cycle arrest and limited growth. 2HG recapitulated IDH-mut features in IDH-wt cells, including increased apoptosis under TMZ, reduced proliferation, and altered CD24/CD44 expression. In vivo, IDH-wt tumors were larger and more infiltrative, while 2HG administration reduced tumor volume and promoted compact morphology. Notably, migration was initially similar across genotypes but increased in IDH-mut and 2HG-treated IDH-wt cells over time, though suppressed under therapeutic stress. Conclusions: IDH mutation and 2HG modulate glioma cell biology, including cell cycle dynamics, proliferation rates, migration, and apoptosis. While the IDH mutation and its metabolic product confer initial growth advantages, they enhance treatment sensitivity and reduce invasiveness, highlighting potential vulnerabilities for targeted therapy.

Keywords

• isocitrate dehydrogenase mutation
• <i>IDH</i>
• glioblastoma
• astrocytoma
• glioma
• 2-hydroxyglutarate