Elevated Asparagine Biosynthesis Drives Brain Tumor Stem Cell Metabolic Plasticity and Resistance to Oxidative Stress

Asparagine synthetase (ASNS) is a gene on the long arm of chromosome 7 that is copy number amplified in the majority of glioblastomas. ASNS copy number amplification is associated with a significantly decreased survival. Using patient-derived glioma stem cells (GSCs), we showed significant metabolic alterations occur in gliomas when perturbing the expression of asparagine synthetase, which is not merely restricted to amino acid homeostasis. ASNS-high GSCs maintained a slower basal metabolic profile yet readily shifted to a greatly increased capacity for glycolysis and oxidative phosphorylation when needed. This led ASNS-high cells to a greater ability to proliferate and spread into brain tissue. Finally, we demonstrate that these changes confer resistance to cellular stress, notably oxidative stress, through adaptive redox homeostasis which led to radiation resistance. Furthermore, ASNS overexpression led to modifications of the one-carbon metabolism to promote a more antioxidant tumor environment revealing a metabolic vulnerability that may be therapeutically exploited. Overall design: RNA sequencing on glioma stem cells (ASNS-high and -low) underwent irradiation and cultured for 0, 3 and 14 days with control cells without irradiation.

天冬酰胺合成酶（Asparagine synthetase, ASNS）是位于7号染色体长臂上的基因，在绝大多数胶质母细胞瘤中存在拷贝数扩增。ASNS拷贝数扩增与患者生存期显著缩短相关。本研究借助患者来源的神经胶质瘤干细胞（glioma stem cells, GSCs），证实扰动天冬酰胺合成酶的表达后，胶质瘤会出现显著的代谢改变，且这类改变不仅局限于氨基酸稳态调控。高表达ASNS的GSCs呈现出更为缓慢的基础代谢特征，但在需求触发时可快速切换为糖酵解与氧化磷酸化能力大幅提升的代谢模式。这使得高表达ASNS的细胞具备更强的增殖能力与脑组织侵袭能力。最后，本研究证实上述代谢改变可通过适应性氧化还原稳态赋予细胞对应激（尤其是氧化应激）的抵抗能力，进而产生辐射抵抗效应。此外，ASNS过表达会改变一碳代谢通路，营造出更具抗氧化特性的肿瘤微环境，这一现象揭示了一种可被开发为治疗靶点的代谢脆弱性。实验整体设计：对分别高表达与低表达ASNS的神经胶质瘤干细胞进行辐照处理，并设置未辐照的对照组细胞，分别培养0、3、14天后进行RNA测序。