Molecular Etiology of Enchondromatosis

摘要 超过3%的人患有内生性软骨瘤(ECA)，这是一种由细胞组成的骨骼良性肿瘤 从生长板中衍生出来的，会引起疼痛、畸形，并可能导致病理性骨折。 内生性软骨瘤可进展为恶性软骨肉瘤(CSA)。编码异柠檬酸的基因突变 脱氢酶(IDH1和2)在ECA和CSA中占很大比例。在我们之前的工作中，我们 发现IDH突变抑制生长板软骨细胞分化，且软骨细胞特异性条件 IDH1突变小鼠产生ECAs。突变体IDH独特地产生代谢物2-羟基戊二酸(2-HG)，但 我们和其他人发现，阻断2-HG的产生在药理上不会改变CsA细胞的活力。 虽然2-HG具有表观遗传效应，这在肿瘤的启动过程中可能是重要的，但肿瘤的维持必须依赖于 其他因素。由于IDH在新陈代谢中起重要作用，相关的代谢变化可能会推动 观察到的表型。我们在表达突变IDH的细胞中发现了高水平的糖原。糖原也是 发现于生长板的增殖和前期肥大细胞中。在我们之前的工作中，我们发现 IDH突变的软骨细胞内胆固醇的生物合成被激活，它也被调节在 生长板，其活性与糖原水平相关。这增加了细胞内 固醇调节元件结合蛋白(SREBP)激活的胆固醇生物合成 转录，也调节糖原。我们的前提是糖原是Pre-Pre的重要能量来源 肥大和肥大的生长板软骨细胞和糖原储存是维持 ECA和CsA的肿瘤表型。我们还提出糖原耗竭可以抑制肿瘤。 表型。在这项建议中，我们将研究是什么调节生长板中的糖原，ECA和CsA，以及 测定这些生长板和肿瘤性软骨细胞中糖原的功能。 为了确定是什么调节生长板、ECA和CsA中的糖原，我们优先考虑了已知的 调节在生长板和IDH突变中差异调节的糖原。蛋白 磷酸酶1调节亚基3C(PPP1R3C)就是这样一个基因， 在其启动子区域包含SREBP结合位点。我们的初步数据表明，SREBP调节 PPP1R3C，然后调节糖原。我们的研究将使用来自人类肿瘤和基因的细胞系 改良内生性软骨瘤小鼠以确定糖原和PPP1R3C在生长中的作用 板块、ECA和CsA。此外，我们还将研究SREBP如何调节PPP1R3C和糖原。糖原 合成酶将被基因删除，或者我们将用抑制糖原合成和分解的药物来抑制细胞。 这些数据将提供临床前信息，为ECA和CsA的新疗法奠定基础。

Abstract More than 3% of the population develops an enchondroma (ECA), a benign tumor in bone composed of cells derived from the growth plate that can cause pain, deformity, and can be responsible for pathologic fractures. Enchondromas can progress to malignant chondrosarcoma (CSA). Mutations in genes encoding isocitrate dehydrogenase (IDH1 and 2) were identified in a large proportion of ECAs and CSAs. In our prior work, we found that IDH mutations inhibit growth plate chondrocyte differentiation, and chondrocyte-specific conditional Idh1 mutant mice develop ECAs. Mutant IDH uniquely produces the metabolite 2-hydroxyglutarate (2-HG), but we and others found that blocking the production of 2-HG pharmacologically does not alter CSA cell viability. While 2-HG has epigenetic effects that are likely important in tumor initiation, tumor maintenance must rely on other factors. Since IDH plays an important role in in metabolism, associated metabolic changes could drive the observed phenotype. We found high levels of glycogen in cells expressing a mutant IDH. Glycogen is also found in proliferating and pre-hypertrophic cells of the growth plate. In our previous work, we found that intracellular cholesterol biosynthesis was activated in IDH mutant chondrocytes and that it is also regulated in the growth plate, and its activity corelates with glycogen levels. This raises the possibility that intracellular cholesterol biosynthesis, which is activated by Sterol regulatory-element binding proteins (SREBP) transcription, also regulates glycogen. Our premise is that glycogen is an important energy source for pre- hypertrophic and hypertrophic growth plate chondrocytes and that glycogen stores are required to maintain the neoplastic phenotype in ECA and CSA. We also propose that glycogen depletion can suppress the neoplastic phenotype. In this proposal we will study what regulates glycogen in the growth plate, ECA and CSA, and determine the function of glycogen in these growth plate and neoplastic chondrocytes. To determine what regulates glycogen in the growth plate, ECA, and CSA, we prioritized genes known to regulate glycogen that were differentially regulated in the growth plate and by IDH mutations. Protein phosphatase 1 regulatory subunit 3C (PPP1R3C) is one such gene which is differentially and interestingly, contains SREBP binding sites in its promoter region. Our preliminary data suggest that SREBP regulates PPP1R3C which then regulates glycogen. Our studies will use cell lines from human tumors and genetically modified mice that develop enchondromas to define the function of glycogen and PPP1R3C in the growth plate, ECA, and CSA. In addition, we will study how SREBP regulates PPP1R3C and glycogen. Glycogen synthase will be deleted genetically, or we will cells with drugs that inhibit glycogen synthesis and breakdown. This data will provide pre-clinical information on which to base novel therapies for ECA and CSA.