For the first time, the WHO (World Health Organization) Classification of Tumors of the Central Nervous System uses molecular and histological analysis together to define brain tumor entities. The new concept for how CNS tumor diagnosis should be structured, moves the IDH status into focus. The algorithm for classification of the diffuse gliomas often proceeds from IDH1 R132H histology first to molecular genetic features next.
Louis DN et al., The 2016 World Health Organization Classification of Tumors of the Central Nervous System: a summary. Acta Neuropathol. 2016, 131(6):803-820. >> Reference Link
>> Details: Anti-IDH1 R132H antibody clone H09
Figure: Immunohistochemistry of a bone marrow biopsy with anti-IDH1 R132H clone H09: Acute myelomonocytic leukemia (AML M4). (Picture courtesy of Professor Harald Stein, Pathodiagnostik Berlin, Berlin, Germany)
A few years back next generation sequencing of whole genomes from acute myeloid leukemia (AML) samples identified new mutations in the IDH1 and IDH2 gene. The mutations occur in 15-20% of newly diagnosed AML patients. IDH1/2 mutations have first been identified in gliomas and researchers wondererd how such mutations could promote malignant transformation. An important next step for understanding the contribution of IDH1 mutations to the transformed phenotype was the discovery that the amino acid substitutions in IDH mutants lead to the generation of the 2-HG “oncometabolite”. The conversion from normal a-KG to 2HG does not only prevent normal catalytic activity but results in a new function, which alters the energy balance of the Krebs cycle by competitive inhibition of dioxygenases. This leads to epigenetic reprogramming blocking diffentiation and contributing to a transformed phenotype. Very soon these mutant enzymes have been considered as clinical targets to reverse their metabolic effect. A breakthrough was presented at the 2014 EORTC-NCI-AACR Symposium on Molecular Targets and Cancer Therapeutics: The IDH1 inhibitor AG-120 shows very promising evidence for clinical activity in AML patients with IDH1 mutation. This IDH1 inhibitor together with an IDH2 inhibitor are also being studied in patients with glioma and data expected to be presented at a medical conference in 2015.
Clinical detection of mutants by sequencing is costly, technically difficult, relies on high quality DNA and often suffers from limited sensitivity (number of tumor cells in tissue is critical). Therefore it would be helpful if the mutation could be detected more easily. Histopathological data suggest the use of IDH1 R132H immunohistochemistry for clinical detection of IDH1 mutations in AML with the advantage of faster turnaround time, lower cost and the potential to detect even single positive cells.
Fig.: IHC of human IDH1 R132H in formalin-fixed paraffin-embedded brain tissue sections: The IDH1 R132H mutation specific monoclonal antibody clone H09 displays a strong and specific reaction at a 1:40 dilution. In contrast, at a 1:40 dilution antibody clone HMab-1 shows a very faint staining which remains weak even at lower dilutions of 1:20 and 1:10. All sections were stained by an indirect alkaline phosphatase method according to standard procedures with antigen retrieval by high-temperature heating in citrate buffer (pH 6.0) and counterstaining with Hematoxylin.
The exclusive production of antibody clone H09 by dianova together with its widespread commercial availability since 2010 has changed routine diagnostic neuropathology: It provides an unrevaled accuracy to the diagnosis of infiltrating gliomas (WHOII/III) and secondary gliomas. At present many companies non-exclusivly offer a different clone, HMab-1. By comparative IHC analysis we demonstrate that clone H09 displays an unchallenged staining quality at considerably higher dilution.
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>> Minireview IDH1R132H DIA-H09 2014
Craig Horbinsky, neuropathologist at the University of Kentucky, and his team developed an interactive online-tool for the selection of brain tumor cases which might benefit from additional molecular testing. The Horbinsky team established an algorithm which calculates a statistical probability score by assembling parameters which can be obtained easily by a pathologist, e.g. WHO grade and patient age. Moreover, the tool differentiates IDH1 R132H immunostain negative cases from cases without previous testing and provides separate scores. This tool might help to better triage brain tumor cases for additional molecular testing.
Online-tool for predicting likelihood of IDH1/2 mutation in glioma
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Cancer researchers from Heidelberg have been able to develop a IDH1 R123H mutation-specific vaccine. In the journal “Nature”. Platten and his co-workers report that the vaccine arrested tumor growth in mice. Moreover, they now have made the first successful step toward a vaccine that specifically targets the mutation in the tumor. “In some patients with low-grade glioma we found spontaneous immune responses against altered IDH1,” Platten says. “This is a good sign; it suggests that vaccinations based on the peptide can in fact support the body’s own immune system in fighting cancer cells.” This gives a “vaccination therapy” good chances of success, according to the Heidelberg physicians. In a clinical trial scheduled to start early next year, they plan to examine the safety of the vaccine against gliomas based on mutant IDH1 in human patients, for the first time. “Most low-grade gliomas cannot be removed completely by surgery and thus often recur,” says Prof. Wolfgang Wick, Medical Director of the Department of Neurooncology and head of the Clinical Cooperation Unit “Neurooncology” at the DKFZ. “Patients would therefore benefit tremendously from a vaccine that prevents this from happening.”
Schumacher et al. A vaccine targeting mutant IDH1 induces antitumour immunity
Nature 2014, DOI: 10.1038/nature13387
Joint press release
of the German Cancer Research Center and the Heidelberg University Hospital
dianvova, the manufacturer of the mutation specific antibody against Isocitrate Dehydrogenase 1 (IDH1) R132H has just released the new website IDH1R132H.com. This new site offers pathologists and clinicians a comprehensive overview and resources related to the use of the IDH1 R132H specific antibody clone H09 in brain tumor diagnostics.