Abstract
The R132H mutation of cytosolic isocitrate dehydrogenase (IDH1) is present in the majority of low grade gliomas. Immunotherapy in these tumors has an interesting, still unexploited, therapeutic potential, as they are less immunosuppressive than glioblastomas.Using site-directed mutagenesis we introduced the R132H mutation into the murine glioma cell line GL261, creating mIDH1-GL261. Presence of the mutation was confirmed by immunoblotting and production of the oncometabolite 2-hydroxyglutarate (2HG), demonstrated by mass spectrometry (LC-MS/MS) performed on cell supernatant. In vitro mIDH1-GL261 had different morphology but similar growth rate than parental GL261 (p-GL261). After intracranial injection, MRI suggested that the initial growth rate was slower in mIDH1-GL261 than p-GL261 gliomas but overall survival was similar. mIDH1-GL261 gliomas showed evidence of R132H expression and of intratumoral 2HG production (evaluated by MRS and LC-MS/MS). Immunizations were performed nine days after intracranial implantation of mIDH1- or p-GL261 cells by three subcutaneous injections of five different peptides encompassing the IDH1 mutation site, all emulsified with Montanide ISA-51, in association with GM-CSF. Control mice were injected with four ovalbumin peptides or vehicle. Mice with mIDH1-GL261 but not p-GL261 gliomas treated with mIDH1 peptides survived longer than controls; 25% of them were cured. Immunized mice showed higher amounts of peripheral CD8+ T cells, higher production of IFN-γ, and evidence of anti-mIDH1 antibodies. Immunizations led to intratumoral up-regulation of IFN-γ, granzyme-b and perforin-1 and down-regulation of TGF-β2 and IL-10.These results support the translational potential of immunotherapeutic targeting of gliomas carrying IDH1 mutations.Electronic supplementary materialThe online version of this article (doi:10.1186/s40478-014-0180-0) contains supplementary material, which is available to authorized users.
Highlights
The new era of cancer genomics, due to the revolution of generation sequencing, was heralded in 2008 by the discovery of mutations in the IDH1 gene in glioblastomas (GBM) [1]
Our results show for the first time in an intracranial glioma model that the R132H mutation, can be effectively targeted by the immune system, allowing a significant prolongation of survival and the cure of 25% of the mice
The mIDH1-GL261 model we have used has obvious differences with human gliomas, as it is established in a malignant glioma while in humans IDH1 mutations take place early in development of low grade gliomas
Summary
The new era of cancer genomics, due to the revolution of generation sequencing, was heralded in 2008 by the discovery of mutations in the IDH1 gene in glioblastomas (GBM) [1]. It was found that IDH1 mutations are present in the large majority of low grade gliomas (LGG) and define secondary GBM more rigorously than before [2]. A new function of IDH1 was found as a consequence of the R132H mutation that affects the active site of the enzyme [3]. New drugs that are acting on the novel function of IDH1 are under development and are initially tested in patients [11]. The diagnosis of the mutation in peripheral blood as well as the detection of increased levels of 2HG by MRI in the brain are actively pursued and initial results are available [12,13]
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