Moreira Franco Yollanda E, Alves Maria Jose, Uno Miyuki, Moretti Isabele Fattori, Trombetta-Lima Marina, de Siqueira Santos Suzana, Dos Santos Ancely Ferreira, Arini Gabriel Santos, Baptista Mauricio S, Lerario Antonio Marcondes, Oba-Shinjo Sueli Mieko, Marie Suely Kazue Nagahashi
Laboratory of Molecular and Cellular Biology (LIM 15), Department of Neurology, Faculdade de Medicina FMUSP, Universidade de São Paulo, São Paulo, 01246-903, Brazil.
Department of Molecular Pharmacology, University of Groningen, 9713 Av, Groningen, The Netherlands.
Cancer Metab. 2021 Apr 28;9(1):18. doi: 10.1186/s40170-021-00255-8.
Glioblastoma is the most frequent and high-grade adult malignant central nervous system tumor. The prognosis is still poor despite the use of combined therapy involving maximal surgical resection, radiotherapy, and chemotherapy. Metabolic reprogramming currently is recognized as one of the hallmarks of cancer. Glutamine metabolism through glutaminolysis has been associated with tumor cell maintenance and survival, and with antioxidative stress through glutathione (GSH) synthesis.
In the present study, we analyzed the glutaminolysis-related gene expression levels in our cohort of 153 astrocytomas of different malignant grades and 22 non-neoplastic brain samples through qRT-PCR. Additionally, we investigated the protein expression profile of the key regulator of glutaminolysis (GLS), glutamate dehydrogenase (GLUD1), and glutamate pyruvate transaminase (GPT2) in these samples. We also investigated the glutathione synthase (GS) protein profile and the GSH levels in different grades of astrocytomas. The differential gene expressions were validated in silico on the TCGA database.
We found an increase of glutaminase isoform 2 gene (GLSiso2) expression in all grades of astrocytoma compared to non-neoplastic brain tissue, with a gradual expression increment in parallel to malignancy. Genes coding for GLUD1 and GPT2 expression levels varied according to the grade of malignancy, being downregulated in glioblastoma, and upregulated in lower grades of astrocytoma (AGII-AGIII). Significant low GLUD1 and GPT2 protein levels were observed in the mesenchymal subtype of GBM.
In glioblastoma, particularly in the mesenchymal subtype, the downregulation of both genes and proteins (GLUD1 and GPT2) increases the source of glutamate for GSH synthesis and enhances tumor cell fitness due to increased antioxidative capacity. In contrast, in lower-grade astrocytoma, mainly in those harboring the IDH1 mutation, the gene expression profile indicates that tumor cells might be sensitized to oxidative stress due to reduced GSH synthesis. The measurement of GLUD1 and GPT2 metabolic substrates, ammonia, and alanine, by noninvasive MR spectroscopy, may potentially allow the identification of IDH1 AGII and AGIII progression towards secondary GBM.
胶质母细胞瘤是最常见的高级别成人恶性中枢神经系统肿瘤。尽管采用了包括最大程度手术切除、放疗和化疗在内的联合治疗，其预后仍然很差。代谢重编程目前被认为是癌症的标志之一。通过谷氨酰胺分解的谷氨酰胺代谢与肿瘤细胞的维持和存活相关，并通过谷胱甘肽（GSH）合成与抗氧化应激相关。
在本研究中，我们通过qRT-PCR分析了153例不同恶性级别的星形细胞瘤队列和22例非肿瘤性脑样本中谷氨酰胺分解相关基因的表达水平。此外，我们研究了这些样本中谷氨酰胺分解关键调节因子（GLS）、谷氨酸脱氢酶（GLUD1）和谷氨酸丙酮酸转氨酶（GPT2）的蛋白表达谱。我们还研究了不同级别星形细胞瘤中的谷胱甘肽合成酶（GS）蛋白谱和GSH水平。在TCGA数据库上对差异基因表达进行了计算机验证。
我们发现与非肿瘤性脑组织相比，所有级别的星形细胞瘤中谷氨酰胺酶同工型2基因（GLSiso2）表达均增加，且其表达随恶性程度的增加而逐渐升高。编码GLUD1和GPT2表达水平的基因根据恶性程度而变化，在胶质母细胞瘤中下调，在较低级别的星形细胞瘤（AGII-AGIII）中上调。在GBM的间充质亚型中观察到显著低的GLUD1和GPT2蛋白水平。
在胶质母细胞瘤中，特别是在间充质亚型中，两种基因和蛋白（GLUD1和GPT2）的下调增加了GSH合成的谷氨酸来源，并由于抗氧化能力的增强而提高了肿瘤细胞的适应性。相反，在低级别星形细胞瘤中，主要是那些携带IDH1突变的肿瘤，基因表达谱表明肿瘤细胞可能因GSH合成减少而对氧化应激敏感。通过无创磁共振波谱测量GLUD1和GPT2的代谢底物、氨和丙氨酸，可能有助于识别IDH1 AGII和AGIII向继发性GBM的进展。
