In 2021, the World Health Organization classified isocitrate dehydrogenase (IDH) mutant gliomas as a distinct subgroup of tumors with genetic changes sufficient to enable a complete diagnosis. Patients with an IDH mutant glioma have improved survival which has been further enhanced by the advent of targeted therapies. IDH enzymes contribute to cellular metabolism, and mutations to specific catalytic residues result in the neomorphic production of D-2-hydroxyglutarate (D-2-HG). The accumulation of D-2-HG results in epigenetic alterations, oncogenesis and impacts the tumor microenvironment via immunological modulations. Here, we summarize the molecular, cellular, and clinical implications of IDH mutations in gliomas as well as current diagnostic techniques.

In 2021, the World Health Organization classified isocitrate dehydrogenase (IDH) mutant gliomas as a distinct subgroup of tumors with genetic changes sufficient to enable a complete diagnosis. Patients with an IDH mutant glioma have improved survival which has been further enhanced by the advent of targeted therapies. IDH enzymes contribute to cellular metabolism, and mutations to specific catalytic residues result in the neomorphic production of D-2-hydroxyglutarate (D-2-HG). The accumulation of D-2-HG results in epigenetic alterations, oncogenesis and impacts the tumor microenvironment via immunological modulations. Here, we summarize the molecular, cellular, and clinical implications of IDH mutations in gliomas as well as current diagnostic techniques.

D-2-hydroxyglutarate (D-2-HG) is an oncometabolite that accumulates due to mutations in isocitrate dehydrogenase 1 and 2 (IDH1/2). D-2-HG may be used as a surrogate marker for IDH1/2 mutant cancers, yet simple and specific methods for D-2-HG detection are limited. Here, we present the development and characterization of a genetically encoded fluorescent sensor of D-2-HG (D2HGlo). D2HGlo responds to clinically relevant concentrations of D-2-HG, demonstrates exceptional selectivity and can quantify D-2-HG in various body fluids and glioma tumor supernatants. Additionally, analysis of tumor lysates using D2HGlo accurately predicted the IDH mutational status of gliomas. The successful quantification of D-2-HG within contrived samples suggests that D2HGlo may facilitate the detection and monitoring of IDH mutant cancers through liquid biopsies following further validation. In addition to D2HGlo’s potential clinical utility, we also present findings for its adaptation to the cellular environment. To assess D-2-HG production in living immortalized glioma cells, we engineered D2HGlo sensors that localize to subcellular compartments, which yielded findings of elevated D-2-HG in the cytosol, mitochondria, and nucleus of IDH1 mutant cells. D2HGlo was used to perform a side-by-side comparison of cytosolic and secreted D-2-HG to reveal that glycolysis, but not glutamine catabolism, drives D-2-HG production in IDH1 mutant cells.

D-2-hydroxyglutarate (D-2-HG) is an oncometabolite that accumulates due to mutations in isocitrate dehydrogenase 1 and 2 ( IDH1/2 ). D-2-HG may be used as a surrogate marker for IDH1/2 mutant cancers, yet simple and specific methods for D-2-HG detection are limited. Here, we present the development and characterization of a genetically encoded fluorescent sensor of D-2-HG (D2HGlo). D2HGlo responds to clinically relevant concentrations of D-2-HG, demonstrates exceptional selectivity and can quantify D-2-HG in various body fluids and glioma tumor supernatants. Additionally, analysis of tumor lysates using D2HGlo accurately predicted the IDH mutational status of gliomas. Collectively, these results suggest that D2HGlo may be an in vitro diagnostic device for the detection and monitoring of IDH mutant cancers through liquid biopsies. In addition to D2HGlo’s clinical utility, we also present preliminary findings for its adaptation to the cellular environment. To assess D-2-HG production in living immortalized glioma cells, we engineered D2HGlo sensors that localize to subcellular compartments, which yielded findings of elevated D-2-HG in the cytosol, mitochondria, and nucleus of IDH1 mutant cells.