IDH1突变增强胶质瘤谷氨酰胺依赖的机制和作用研究

Isocitrate dehydrogenase 1/2 (IDH1/2) mutation is one of the most frequent genetic changes in Grade II and III glioma. Mutant IDH1/2 gains a new enzymatic activity, and reduces α-ketoglutarate (α-KG) to 2-hydroxyglutarate (2HG) instead of converting isocitrate to α-KG. This competitive inhibition of α-KG by 2-HG causes widespread epigenetic changes, suggesting that 2-HG may function as an oncometabolite. Our recent results showed that IDH1(R132H) mutant colon cancer cells and IDH1(R132H) overexpressing glioma cells were more sensitive to the deprivation of glutamine compared to control cells. Moreover, the primary glial cells with IDH1(R132H) mutation consumed more glutamine, and also become more sensitive to the deprivation of glutamine, and these enzymes involved in glutamine metabolism were changed. These data indicated that IDH1 mutation could enhance the glutamine addiction. However, the details and roles of glutamine addiction enhanced by mutant IDH1 are still unknown, and the metabolic mechanism should also be clarified. Using IDH1 mutant glioma, IDH1(R132H) knock-in mouse and glioma cells with overexpressed IDH1(R132H), we will determine the degree and critical processes of glutamine addiction induced by DH1 mutation, and illuminate how IDH1 mutation enhance the glutamine addiction in glioma, and discuss whether intervention of glutamine metabolism could be used in the therapy of IDH1 mutant glioma. These results should be helpful for us to clarify the significance of IDH1/2 mutation in glioma, and to identify new metabolic targets for the therapy of IDH1 mutant glioma.

IDH1/2突变是胶质瘤最重要的遗传学改变之一。突变型IDH1/2能够催化α-酮戊二酸（α-KG）转变为癌代谢物2-羟基戊二酸（2-HG），而2-HG与肿瘤表观遗传学改变密切相关。我们最近研究发现，IDH1突变胶质瘤细胞的生长依赖培养液中谷氨酰胺（Gln）水平，且IDH1突变肿瘤细胞和胶质细胞对Gln缺乏均更加敏感。此外，IDH1突变原代胶质细胞的Gln消耗速度增加，且Gln代谢相关分子表达水平明显改变。这些结果表明，IDH1突变能够增强胶质瘤的谷氨酰胺依赖（Addiction），但尚不清楚其在胶质瘤发生中的作用，以及产生的主要机制。本研究将分析IDH1突变增强胶质瘤谷氨酰胺依赖的程度和关键步骤，阐明发生的代谢机制，并研究干预谷氨酰胺代谢能否应用于IDH1突变胶质瘤的治疗。本研究对认识IDH1/2突变在胶质瘤发生中的作用具有重要意义，也为IDH1突变胶质瘤的治疗提供的靶途径和靶分子。

IDH1/2突变是胶质瘤中的重要的遗传学改变，2HG是其中重要的癌代谢产物。我们在本课题研究中发现IDH突变导致小鼠脑发育异常，脑组织代谢异常，特别是与谷氨酰胺（Gln）相关的各条代谢途径，包括三羧酸循环代谢以及各类氨基酸的代谢；进一步，在IDH突变的原代胶质细胞的基础上，我们发现IDH突变的胶质（瘤）谷氨酰胺的分解加速，三羧酸循环代谢过程降低，电子传递链复合物功能异常，影响胶（瘤）细胞的增殖生长；同时发现2HG影响胶质细胞内谷氨酰胺合成，谷氨酰胺合成酶（GS）的活性被2HG竞争性抑制，我们从体外细胞实验，酶活性检测以及蛋白结构预测方面都进行了验证；最后，在IDH突变胶质瘤组织中检测GS与IDH突变的调控关系，发现IDH突变与GS呈现互斥的组织分布特点，GS主要分布在GFAP阳性的星型胶质细胞中。本研究对深入理解IDH1突变胶质瘤谷氨酰胺代谢重编程提供了重要的数据和理论支持。