IDH1 R132H Decreases Proliferation of Glioma Cell Lines In Vitro and In Vivo

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 IDH(1R132H)-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