IDH1 R132H decreases proliferation of glioma cell lines in vitro and in vivo

Abstract Objective: A high percentage of grade II and III gliomas have mutations in the gene encoding isocitrate dehydrogenase ( IDH1 ). This mutation is always a heterozygous point mutation that affects the amino acid arginine at position 132 and results in loss of its native enzymatic activity and gain of alternative enzymatic activity (producing D‐2‐hydroxyglutarate). The objective of this study was to investigate the cellular effects of R132H mutations in IDH1 . Methods: Functional consequences of IDH1 R132H mutations were examined among others using fluorescence‐activated cell sorting, kinome and expression arrays, biochemical assays, and intracranial injections on 3 different (glioma) cell lines with stable overexpression of IDH1 R132H . Results: IDH1 R132H overexpression in established glioma cell lines in vitro resulted in a marked decrease in proliferation, decreased Akt phosphorylation, altered morphology, and a more contact‐dependent cell migration. The reduced proliferation is related to accumulation of D‐2‐hydroxyglutarate that is produced by IDH1 R132H . Mice injected with IDH1 R132H U87 cells have prolonged survival compared to mice injected with IDH1 wt or green fluorescent protein–expressing U87 cells. Interpretation: Our results demonstrate that IDH1 R132H dominantly reduces aggressiveness of established glioma cell lines in vitro and in vivo. In addition, the IDH1 R132H ‐IDH1 wt heterodimer has higher enzymatic activity than the IDH1 R132H ‐IDH1 R132H homodimer. Our observations in model systems of glioma might lead to a better understanding of the biology of IDH1 mutant gliomas, which are typically low grade and often slow growing. Ann Neurol 2011;69:455–463