谷氨酰胺酶2(GLS2)的分子调控机制及其在MYCN扩增的神经母细胞瘤发生发展过程中的功能研究

Neuroblastoma is one of the most frequent solid tumors in infants and children. Amplification of the MYCN oncogene in human neuroblastoma predicts poor prognosis and resistance to therapy. Therefore, a complete understanding of the pathogenic mechanisms responsible for this type of cancer is of great emergence. In this regard, we previously showed that MYCN-amplified neuroblastoma cells constantly require large amounts of glutamine to sustain their viability. However, how MYCN-amplified neuroblastoma cells utilize glutamine metabolism to support unabated growth remains unclear thus far. To this end, we identified expression of glutaminase 2 (GLS2), a critical enzyme involved in the first step in glutaminolysis, was significantly elevated in MYCN-amplified neuroblastomas in comparison with non-amplified ones. Inhibition of GLS2 activity induced significant cell death, suggesting GLS2-mediated glutaminolysis is essential for MYCN-amplified neuroblastoma cells. Combining approaches of molecular cell biology, metabolomics and animal modeling, we aim to (1) investigate molecular mechanisms whereby N-Myc activates GLS2 expression; (2) examine how GLS2 affects TCA cycle metabolites and chemoresistance; and (3) evaluate the in-vivo pathogenic roles of GLS2 in MYCN-transgenic neuroblastoma tumor model. Our studies will decipher novel mechanisms by which N-Myc regulates glutamine metabolism through direct GLS2 activation. More importantly, these results also provide strong rationales for developing highly specific small-molecule inhibitors against GLS2 in treating MYCN-amplified neuroblastomas, which are resistant to routine chemotherapies.

神经母细胞瘤是儿童常见的恶性实体肿瘤。 其中，MYCN扩增的神经母细胞瘤恶性程度极高，治疗效果和预后差，尚无有效的靶向药物。 因此，深入研究此类肿瘤的病理机制以期找到有效的治疗手段至关重要。 申请人前期证明MYCN扩增的神经母细胞瘤细胞高度依赖谷氨酰胺存活，而且发现谷氨酰胺酶2(GLS2)在这类肿瘤中过表达。体外抑制GLS2显著诱导MYCN扩增的神经母细胞瘤细胞死亡。然而，GLS2在此类肿瘤中的调控机制和生物学功能尚不明确。据此，拟采用分子细胞生物学、代谢组学和模式动物等学科交叉的研究方法，深入研究(1) N-Myc激活GLS2的分子机制；(2) GLS2对谷氨酰胺代谢和化疗抵抗的影响；(3) GLS2对神经母细胞瘤在体内发生发展的影响。该项目的实施有望揭示GLS2表达调控的新机制，为MYCN扩增的神经母细胞瘤的治疗提供潜在的治疗靶点。

MYCN扩增的神经母细胞瘤高度依赖谷氨酰胺代谢且恶性程度极高。这类肿瘤异常高表达GLS2，然而，GLS2在此类肿瘤中的分子调控机制和生物学功能尚未明确。本项目旨在探讨GLS2的分子调控机制及其通过代谢重编程调节神经母细胞瘤发生发展的病理机制，重点研究以下四方面的内容：（1）癌蛋白N-Myc通过激活GLS2调控神经母细胞瘤谷氨酰胺代谢；（2）PLK1-N-Myc通路调控GLS2促进神经母细胞瘤发生发展的分子新机制；（3）miRNA-137-ASCT2通路调控神经母细胞瘤谷氨酰胺代谢重编程的分子机制；（4）硼替佐米通过协同MYC诱导MYC扩增神经母细胞瘤死亡的分子机制。通过以上四方面深入研究，申请人取得了很好的进展，并以通讯作者身份在主流期刊发表研究论文4篇，包括1篇Molecular Cell，1篇Oncogene，1篇Oncogenesis和1篇Oncotarget。这些研究不仅系统阐述了GLS2的分子调控新机制，而且为以GLS2为靶点的肿瘤治疗提供了科学依据。