Molecular mechanisms responsible for low grade glioma (LGG) pathogenesis remain poorly understood.1-6 We hypothesize that the identification of molecular pathways underlying LGG will lead to the discovery of more specific and effective novel therapeutic approaches for patients with LGG. The investigation of the molecular pathways which play a role in the pathogenesis of LGG requires accurate genetic and epigenetic models. Ideally, the models should recapitulate the salient features of LGG and develop within the brain's microenvironment in an immune-competent host. Our lab has created genetically engineered LGG mouse models employing the Sleeping Beauty (SB) transposase system.7,8 Experimental tumors harbor genetic lesions characteristic of a subtype of LGG, i.e., mutant isocitrate dehydrogenase (mIDH1) co-expressed with mutations in ATRX and TP53. The host in this tumor model exhibits an intact immune system. This allows a detailed study of all aspects of LGG biology in vivo, including interactions with the tumor immune microenvironment (TME). In this model, animals harboring intracranial mIDH1 LGG display increased median survival (MS). Mutant IDH1 exhibits an enzymatic activity that converts ?-ketoglutarate (?KG) to a new metabolite, 2-hydroxyglutarate (2HG).9-12 2HG inhibits TET methylcytosine dioxygenases (Tet2), as well as the JumonjiC domain-containing (JmjC) histone demethylases. This leads to DNA and histone 3 (H3) hypermethylation,9,10 resulting in epigenetic reprograming of the tumor cells' transcriptome. Our central hypothesis is that the epigenetic reprogramming elicited by H3 hypermethylation activates downstream pathways that confer a survival advantage in our genetically engineered animal model. In SA1 and SA2, we aim to elucidate the role played by mIDH1 in DNA repair pathways, genomic stability, and response to DNA damaging agents by employing state-of-the-art techniques such as ChIP-seq (genome regions enriched for H3me3), RNA-seq (tumor cells' transcriptome), and Bru-seq (temporal gene expression profiles). To identify the effects of mDH1 on the incidence of single nucleotide variants we will perform whole cancer genome sequencing. The findings from the experimental LGG model will also be validated in human-derived LGG stem cells. In SA 3, we will investigate how mIDH1, through epigenetic reprograming, can modify the immune suppressive TME. We will also investigate phenotypic and functional changes in tumor antigen-specific T-cells in the TME, bone marrow, blood and spleen. Finally, we will investigate how mIDH1-mediated epigenetic reprograming enhances the therapeutic efficacy of a novel immune-mediated gene therapy approach currently being tested in a Phase I trial for glioma patients at our Institution.13-18

Public Health Relevance

Recent whole genome sequencing has revealed that lower grade primary brain tumors (LGG) harbor distinct mutations and molecular profiles. We aim to study a subtype of LGG which harbors ATRX mutation (mATRX), p53 mutation and mutation in the enzyme, isocitrate dehydrogenase 1 (mIDH1). ATRX is a histone chaperone; mIDH1 acquires a gain-of-function mutation that produces 2-hydroxyglutarate (2HG), an inhibitor of histone and DNA demethylases, leading to epigenetic reprograming. Our goal is to assess the molecular mechanisms by which mATRX and mIDH1 impact the biology of LGGs, influence the tumor immune microenvironment and the response to treatment, including immune-mediated therapeutic approaches.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
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Special Emphasis Panel (ZRG1)
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Fountain, Jane W
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University of Michigan Ann Arbor
Schools of Medicine
Ann Arbor
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Haase, Santiago; Garcia-Fabiani, María Belén; Carney, Stephen et al. (2018) Mutant ATRX: uncovering a new therapeutic target for glioma. Expert Opin Ther Targets 22:599-613
Kamran, Neha; Li, Youping; Sierra, Maria et al. (2018) Melanoma induced immunosuppression is mediated by hematopoietic dysregulation. Oncoimmunology 7:e1408750
Mendez, Flor M; Núñez, Felipe J; Zorrilla-Veloz, Rocío I et al. (2018) Native Chromatin Immunoprecipitation Using Murine Brain Tumor Neurospheres. J Vis Exp :
Kamran, Neha; Alghamri, Mahmoud S; Nunez, Felipe J et al. (2018) Current state and future prospects of immunotherapy for glioma. Immunotherapy 10:317-339
Kamran, Neha; Chandran, Mayuri; Lowenstein, Pedro R et al. (2018) Immature myeloid cells in the tumor microenvironment: Implications for immunotherapy. Clin Immunol 189:34-42