A novel monoclonal antibody GMab-m1 specifically recognizes IDH1-R132G mutation

Isocitrate dehydrogenase 1 (IDH1) mutations occur in gliomas, acute myeloid leukemias, and cartilaginous tumors. While IDH1 catalyzes the oxidative carboxylation of isocitrate to α-ketoglutarate in cytosol, mutated IDH1 proteins possess the ability to change α-ketoglutarate into onco-metabolite R(-)-2-hydroxyglutarate (2-HG). To data, two monoclonal antibodies (mAbs), which are specific for IDH1 mutations have been established: clone HMab-1 against IDH1-R132H and clone SMab-1 against IDH1-R132S. However, specific mAbs against IDH1-R132G, which are useful for immunohistochemical analysis, have not been reported. To establish IDH1-R132G-specific mAbs, we immunized mice with IDH1-R132G-containing peptides. Established mAb GMab-m1 reacted with the IDH1-R132G peptide, but not with IDH1-wild type (WT) in ELISA. Western-blot analysis also showed that GMab-m1 reacted with the IDH1-R132G recombinant proteins, not with IDH1-WT or other IDH1 mutants, indicating that GMab-m1 is IDH1-R132G-specific. Furthermore, GMab-m1 specifically stained the IDH1-R132G-expressing glioma cells in immunohistochemistry. This is the first report to establish anti-IDH1-R132G-specific mAbs, which is useful in immunohistochemistry of IDH1-R132G-bearing tumors.