IDH1 Mutation in Cancer
OncogeneIsocitrate Dehydrogenase 1
IDH1 mutations produce the oncometabolite 2-hydroxyglutarate, which alters DNA methylation and blocks cell differentiation. IDH1 mutations define a distinct subtype of glioma and AML with better prognosis.
What Is IDH1?
IDH1 (Isocitrate Dehydrogenase 1) encodes a metabolic enzyme that catalyzes the oxidative decarboxylation of isocitrate to α-ketoglutarate (α-KG) in the cytoplasm. Oncogenic IDH1 mutations are neomorphic: rather than losing enzyme function, the mutant IDH1 gains a new activity: converting α-KG to 2-hydroxyglutarate (2-HG), an oncometabolite. 2-HG accumulation inhibits α-KG-dependent dioxygenases, causing widespread epigenetic dysregulation through DNA and histone hypermethylation.
IDH1 Mutations in Brain Tumors
IDH1 mutations are a defining molecular feature of lower-grade gliomas and secondary glioblastoma. The R132H mutation accounts for over 90% of IDH1 mutations in gliomas. IDH1 mutations are found in approximately 70-80% of grade II-III gliomas (astrocytomas, oligodendrogliomas), ~10% of glioblastomas (mostly secondary), and ~20% of intrahepatic cholangiocarcinomas. They are also present in ~15% of acute myeloid leukemias. The 2021 WHO Classification of CNS tumors uses IDH mutation status as a primary classifier for adult-type diffuse gliomas.
Prognostic and Therapeutic Implications
IDH1 mutation is one of the strongest positive prognostic markers in gliomas. IDH-mutant gliomas have significantly better overall survival compared to IDH-wildtype tumors (median OS ~7 years vs ~1.5 years for glioblastoma). Vorasidenib, an oral dual IDH1/IDH2 inhibitor, was approved in 2024 for IDH-mutant grade 2 gliomas and is the first targeted therapy for these tumors. Ivosidenib is approved for IDH1-mutant cholangiocarcinoma and AML.
Morphological Associations
IDH1-mutant gliomas display distinctive histological features: diffuse infiltrative growth with less necrosis and microvascular proliferation than IDH-wildtype glioblastoma. IDH-mutant astrocytomas show characteristic nuclear atypia patterns, while oligodendrogliomas exhibit the classic "fried egg" morphology. HistoAtlas quantifies these morphological differences across cancer types using computational analysis of H&E-stained whole slide images.
Frequently Asked Questions
What is an IDH1 mutation?
An IDH1 mutation is a change in the IDH1 gene that causes the enzyme to produce an abnormal metabolite called 2-hydroxyglutarate (2-HG), which disrupts normal cell development through epigenetic changes. IDH1 mutations are most common in brain tumors (gliomas), where the R132H mutation defines a distinct disease entity with better prognosis.
What is IDH1 mutation in brain tumors?
IDH1 mutations are found in 70-80% of lower-grade gliomas (grade II-III) and about 10% of glioblastomas. IDH1-mutant brain tumors are a molecularly distinct category in the WHO Classification, with significantly better prognosis than IDH-wildtype tumors. The R132H mutation accounts for over 90% of IDH1 mutations in gliomas.
What is IDH1 mutation treatment?
Vorasidenib, an oral dual IDH1/IDH2 inhibitor, was approved in 2024 for IDH-mutant grade 2 gliomas, the first targeted therapy for these tumors. Ivosidenib is approved for IDH1-mutant cholangiocarcinoma and acute myeloid leukemia. Standard glioma treatments (surgery, radiation, temozolomide) remain the backbone of care.
Does IDH1 mutation affect survival?
Yes. IDH1 mutation is one of the strongest positive prognostic markers in gliomas. IDH-mutant lower-grade gliomas have a median survival of ~7 years, compared to ~1.5 years for IDH-wildtype glioblastoma. HistoAtlas provides survival curves comparing IDH1-mutant vs wild-type tumors across 33 TCGA cancer types.