Department of Chemistry, Umeå University, SE 901 87, Umeå, Sweden.
John Fulcher Neuro-Oncology Laboratory, Imperial College London, London, UK.
BMC Cancer. 2018 Feb 8;18(1):167. doi: 10.1186/s12885-018-4040-3.
Tumour cells have a high demand for arginine. However, a subset of glioblastomas has a defect in the arginine biosynthetic pathway due to epigenetic silencing of the rate limiting enzyme argininosuccinate synthetase (ASS1). These tumours are auxotrophic for arginine and susceptible to the arginine degrading enzyme, pegylated arginine deiminase (ADI-PEG20). Moreover, ASS1 deficient GBM have a worse prognosis compared to ASS1 positive tumours. Since altered tumour metabolism is one of the hallmarks of cancer we were interested to determine if these two subtypes exhibited different metabolic profiles that could allow for their non-invasive detection as well as unveil additional novel therapeutic opportunities.
We looked for basal metabolic differences using one and two-dimensional gas chromatography-time-of-flight mass spectrometry (1D/2D GC-TOFMS) followed by targeted analysis of 29 amino acids using liquid chromatography-time-of-flight mass spectrometry (LC-TOFMS). We also looked for differences upon arginine deprivation in a single ASS1 negative and positive cell line (SNB19 and U87 respectively). The acquired data was evaluated by chemometric based bioinformatic methods.
Orthogonal partial least squares-discriminant analysis (OPLS-DA) of both the 1D and 2D GC-TOFMS data revealed significant systematic difference in metabolites between the two subgroups with ASS1 positive cells generally exhibiting an overall elevation of identified metabolites, including those involved in the arginine biosynthetic pathway. Pathway and network analysis of the metabolite profile show that ASS1 negative cells have altered arginine and citrulline metabolism as well as altered amino acid metabolism. As expected, we observed significant metabolite perturbations in ASS negative cells in response to ADI-PEG20 treatment.
This study has highlighted significant differences in the metabolome of ASS1 negative and positive GBM which warrants further study to determine their diagnostic and therapeutic potential for the treatment of this devastating disease.
肿瘤细胞对精氨酸的需求很高。然而，由于限速酶精氨酸合成酶（ASS1）的表观遗传沉默，一部分胶质母细胞瘤存在精氨酸生物合成途径的缺陷。这些肿瘤对精氨酸是必需的，并且容易受到精氨酸降解酶聚乙二醇化精氨酸脱亚氨酶（ADI-PEG20）的影响。此外，与 ASS1 阳性肿瘤相比，ASS1 缺陷型 GBM 的预后更差。由于肿瘤代谢改变是癌症的标志之一，我们有兴趣确定这两种亚型是否表现出不同的代谢特征，以便能够进行非侵入性检测，并揭示额外的新的治疗机会。
我们使用一维和二维气相色谱-飞行时间质谱（1D/2D GC-TOFMS）进行基础代谢差异的研究，然后使用液相色谱-飞行时间质谱（LC-TOFMS）对 29 种氨基酸进行靶向分析。我们还观察了在单一 ASS1 阴性和阳性细胞系（分别为 SNB19 和 U87）中精氨酸剥夺后的差异。通过基于化学计量学的生物信息学方法对获得的数据进行评估。
1D 和 2D GC-TOFMS 数据的正交偏最小二乘判别分析（OPLS-DA）显示，两组之间的代谢物存在显著的系统差异，ASS1 阳性细胞通常表现出鉴定出的代谢物的整体升高，包括那些参与精氨酸生物合成途径的代谢物。代谢物谱的途径和网络分析表明，ASS1 阴性细胞的精氨酸和瓜氨酸代谢以及氨基酸代谢发生改变。正如预期的那样，我们观察到 ASS 阴性细胞在 ADI-PEG20 处理后代谢物明显受到干扰。
这项研究突出了 ASS1 阴性和阳性 GBM 代谢组之间的显著差异，这需要进一步研究，以确定它们在治疗这种毁灭性疾病方面的诊断和治疗潜力。
