Abstract
Abstract Background: Glioblastoma Multiforme (GBM) is a malignant primary brain tumor. Genomic analysis of GBMs revealed somatic mutations associated with particular subtypes, which correlate with age at the time of diagnosis. Distinctive features of young adult GBMs include a mutation in Isocitrate Dehydrogenase 1 gene (IDH1-R132H) and mutations in epigenetic regulators, ATRX and H3.3G34, which define an epigenetic and biological subgroup. IDH1-R132H results in gain of an alternative enzymatic function producing an excess of the metabolite 2-hydroxglutarate (2HG) and alterations in histone methylation patterns. Animal models are critical to study and understand disease progression and pathogenesis; therefore we aimed to develop an in vivo model of young adult GBM. Objectives: Generate an animal model of young adult GBM through expression of IDH1-R132H, H3.G34 and ATRX knockdown in neonatal mouse brain using the Sleeping Beauty Transposase system. In this model we will study the effects of these genetic lesions in tumor development and DNA repair mechanisms. Experimental approach: To induce tumors we injected NRAS and shP53 plasmids in the lateral ventricle of C57BL/6 neonatal mice with or without pKT/IDH1-R132H, Pkt/H3.G34 or PT2/shATRX using the sleeping beauty transpose system. The delivery of the plasmid was confirmed by luciferase expression and tumor development was monitored by imaging. The tumors were also used to generate GBM cell for genetic analysis and moribund animals were perfused and analyzed using immunocytochemistry. Results: Pkt-IDH1-R132H expression increases the levels of H3K27me3. Currently we have five groups of animals to asses tumor progression: 1) NRAS/shP53 (n = 7) (median survival (MS) = 88 days post injection (DPI); 2) NRAS/shP53/shATRX (n = 7) (MS = 50 DPI); 3) NRAS/shP53/shATRX/IDH1-R132H (n = 18) (MS = 90 DPI); 4) NRAS/shP53/IDH1-R132H (n = 16) (MS = 100 DPI) and 5) NRAS/shP53/shATRX/H3.G34 (n = 5). Conclusion: Using the Sleeping Beauty System (SB) we expressed mutated IDH1-R132H or mutated H3.G34 together with ATRX knockdown in mice. Genetically engineering mice with IDH1-R132H have increased survival. Mice developed brain tumors harboring key features of young adult GBMs. We aim to determine the impact of these genetic lesions in median survival, tumor progression and DNA repair “in vivo”. Note: This abstract was not presented at the meeting. Citation Format: Felipe J. Nunez, Flor M. Mendez, Carl Koschmann, Alexandra Calinescu, Pedro R. Lowenstein, Maria G. Castro. Generation of a mouse model of young adult glioblatoma: In vivo expression of mutated IDH1-R132H gene using the sleeping beauty transposase system. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3033. doi:10.1158/1538-7445.AM2015-3033
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