A monoclonal antibody IMab-1 specifically recognizes IDH1 R132H, the most common glioma-derived mutation

Abstract

IDH1 (isocitrate dehydrogenase 1) mutations have been identified as early and frequent genetic alterations in astrocytomas, oligodendrogliomas, and oligoastrocytomas as well as secondary glioblastomas. In contrast, primary glioblastomas very rarely contain IDH1 mutations, although primary and secondary glioblastomas are histologically indistinguishable. The IDH1 mutations are remarkably specific to a single codon in the conserved and functionally important Arg132 in IDH1. In gliomas, the most frequent IDH1 mutations (>90%) were G395A (R132H). In this study, we immunized mice with R132H-containing IDH1 (IDH1 R132H) peptide. After cell fusion using Sendai virus envelope, the monoclonal antibodies (mAbs), which specifically reacted with IDH1 R132H, were screened in ELISA. One of the mAbs, IMab-1 reacted with the IDH1 R132H peptide, but not with wild type IDH1 (IDH1 wt) peptide in ELISA. In Western-blot analysis, IMab-1 reacted with only the IDH1 R132H protein, not IDH1 wt protein or the other IDH1 mutants, indicating that IMab-1 is IDH1 R132H-specific. Furthermore, IMab-1 specifically stained the IDH1 R132H-expressing cells in astrocytomas in immunohistochemistry, whereas it did not react with IDH1 R132H-negative primary glioblastoma sections. In conclusion, we established an anti-IDH1 R132H-specific monoclonal antibody IMab-1, which should be significantly useful for diagnosis and biological evaluation of mutation-bearing gliomas.