Elucidating and targeting the molecular foundations of IDH Mutant glioma

描述(申请人提供)：胶质母细胞瘤(GBM)是一种几乎普遍致命的中枢神经系统(CNS)原发恶性肿瘤。我们的长期目标是了解胶质瘤发生的分子机制，并利用这些信息为GBM患者开发更好的治疗方式。最近的研究表明，基底膜由几个亚群组成，每个亚群都由不同的基因改变驱动。基底节细胞亚群是一个独特的类型，包括具有异柠檬酸脱氢酶(IDH)1和2突变、PDGF途径激活和胶质瘤高甲基化表型(G-CIMP)的肿瘤。这些变化可能是可逆的，并有望成为潜在的目标。然而，突变体IDH介导的转化的作用机制仍不清楚。最近，我们的研究小组已经证明IDH突变的作用是通过重塑表观基因组来建立G-CIMP并阻止分化。这一应用的中心假设是，突变的idh诱导的表观基因组变化是这一GBM子集发育的关键事件。这项建议的目的是了解突变型IDH诱导的胶质瘤形成的分子基础，并通过追求3个特定的目标来评估靶向这一改变的有效性。在目标1中，我们将阐明突变体IDH1相关表观遗传重新编程背后的染色质状态动力学。这里的工作假设是IDH突变通过重塑表观基因组并阻止分化来发挥作用，这种影响可能是可逆的。我们将系统地阐明IDH1突变引起的染色质状态变化的全球细节和单个效应基因的水平。我们将询问突变IDH诱导的效应的可逆性。在目标2中，我们将描述IDH1突变和IDH1突变相关基因改变之间的致癌协同性。我们的数据表明，突变的IDH1通过促进去分化状态发挥作用，但不会单独改变细胞。我们的假设是IDH1突变与其他复发的遗传损伤合作实现转化。我们将定义这种致癌背景下的租户。我们将使用人类星形胶质细胞和小鼠RCAS-TVA系统来研究相关病变与突变的IDH1在转化中的合作能力。在目标3中，我们将通过表观遗传疗法优化依赖于IDH1的突变生物改变的靶向。由于IDH诱导的改变原则上是可逆的，我们假设突变的IDH1的影响可以通过靶向小分子逆转，这将使组织特异性因子能够驱动分化。单独使用突变的IDH1抑制剂(AGI-5198)抑制突变的IDH1可以阻止2-HG的产生，但对肿瘤生长的影响很小。相比之下，DNMT和H3K9甲基酶抑制剂(DAC、Bix)直接逆转病理性甲基化，对IDH突变细胞非常有效。我们将使用这两种方法来优化治疗策略。使用体外和小鼠模型，我们将单独使用DNA/组蛋白甲基化抑制剂，并与AGI-5198联合使用，以逆转突变的IDH1的影响。

DESCRIPTION (provided by applicant): Glioblastoma (GBM) is a primary malignancy of the central nervous system (CNS) that is nearly universally fatal. Our long-term goal is to understand the molecular mechanisms that underlie gliomagenesis and to use this information to develop better therapeutic modalities for GBM patients. Recent work has demonstrated that GBMs consist of several subgroups, each driven by different genetic alterations. The proneural subgroup of GBMs is a distinct class that includes tumors with isocitrate dehydrogenase (IDH) 1 and 2 mutation, PDGF pathway activation, and the glioma hypermethylator phenotype (G-CIMP). These alterations are potentially reversible and hold great promise as potential targets. However, the mechanisms of action underlying mutant IDH-mediated transformation remain unclear. Recently, our groups have shown that IDH mutation functions by remodeling the epigenome to establish G-CIMP and institute a block to differentiation. The central hypothesis of this application is that mutant IDH-induced epigenomic changes are critical events underlying the development of this subset of GBMs. The objective of this proposal is to understand the molecular foundations of mutant IDH-induced gliomagenesis and to evaluate the utility of targeting this alteration by pursuing 3 Specific Aims. In Aim 1, we will elucidate the chromatin state dynamics underlying mutant IDH1- associated epigenetic reprogramming. The working hypothesis here is that IDH mutation acts by remodeling the epigenome and blocking differentiation, an effect that may be reversible. We will systematically elucidate the details of IDH1 mutation-induced chromatin state changes globally and at the level of individual effector genes. We will interrogate the reversibility of mutant IDH-induced effects. In Aim 2, we will characterize oncogenic cooperativity between IDH1 mutation and IDH1 mutation-associated genetic alterations. Our data indicates that mutant IDH1 acts by promoting a dedifferentiated state, but does not transform cells alone. Our hypothesis here is that IDH1 mutation cooperates with other recurring genetic lesions to achieve transformation. We will define the tenants of this oncogenic context. We will investigate the ability of associated lesions to cooperate with mutant IDH1 in transformation using human astrocytes and the murine RCAS-TVA system. In Aim 3, we will optimize targeting of mutant IDH1-dependent biological alterations with epigenetic therapy. Since IDH-induced changes are in principle reversible, we hypothesize that the effects of mutant IDH1 can be reversed using targeted small molecules, which will then enable tissue-specific factors to drive differentiation. Inhibition of mutant IDH1 alone using a mutant IDH1 inhibitor (AGI-5198) blocks 2-HG production but affects tumor growth only modestly. In contrast, DNMT and H3K9 methylase inhibitors (DAC, BIX) directly reverse pathologic methylation and are very potent against IDH mutant cells. We will use these two approaches to optimize a therapeutic strategy. Using both in vitro and mouse models, we will use DNA/ histone methylation inhibitors, alone and in combination with AGI-5198, to reverse the effects of mutant IDH1.