Therapeutic targeting of glutamine metabolism in MDS

 描述（由申请人提供）：癌细胞的代谢重编程对于促进其增殖和抵抗微环境压力的存活至关重要。谷氨酰胺（Gln）是一种必需氨基酸，在增殖癌细胞的代谢中发挥独特作用，提供维持细胞增殖的构件并调节氧化还原稳态和信号转导途径。谷氨酰胺酶（GLS）是一种通过将谷氨酰胺转化为谷氨酸来启动这一过程的酶，谷氨酸随后用于支持肿瘤细胞生长和存活的多个反应，包括能量的产生（TCA循环），氨基酸的合成和谷胱甘肽的产生。重要的是，还显示GLS抑制可降低肿瘤中的2 HG水平，从而增加泰特活性并导致甲基化降低。我们小组和其他人的最新发现表明，AML细胞依赖于Gln作为生长和存活的主要碳源。用新型选择性小分子抑制剂CB-839抑制转氨酶或用诱导型shRNA沉默GLS表达抑制了白血病细胞系和原代AML细胞亚组中的线粒体呼吸，减少了细胞生长并诱导了细胞凋亡。此外，白血病细胞与骨髓来源的间充质干细胞的共培养引起基质和癌症两者中的代谢重编程，其中糖酵解基质部分地通过供应谷氨酰胺来支持白血病细胞的氧化代谢。 骨髓增生异常综合征（MDS）是一种无法治愈的恶性肿瘤，需要更新的治疗靶点。我们的初步数据表明，GLS在具有复杂细胞遗传学的AML中过表达，在高风险MDS干细胞中过表达，并且与MDS患者的预后不良相关。我们假设，转氨酶是MDS的治疗靶点，代谢重编程参与MDS向AML的转化。我们建议在小鼠模型中监测MDS向AML转化过程中的代谢变化，并确定抑制β-内酰胺分解是否会抑制进展。该项目将（1）表征谷氨酰胺依赖性MDS亚型;（2）确定机制并研究新型、有效、口服生物可利用的GLS抑制剂CB-839在MDS模型中的临床前疗效;（3）在I/II期临床试验中测试CB-839与5-氮杂胞苷联合治疗中度和高危MDS患者的疗效。我们将专门确定这种组合在消除MDS干细胞方面的功效，并分析其对甲基化状态的影响。由于DNA的高甲基化是MDS的重要标志，因此两种低甲基化方法的组合（通过不同的作用机制）将在MDS中潜在有效。拟议的工作将产生一个更好的理解代谢途径在MDS。

 DESCRIPTION (provided by applicant): Metabolic reprogramming by cancer cells is critical to facilitate their proliferation and survival against micro environmental stresses. Glutamine (Gln) i an essential amino acid that plays a unique role in the metabolism of proliferating cancer cells, providing building blocks to sustain cell proliferation and regulating redox homeostasis and signal transduction pathways. Glutaminase (GLS) is an enzyme that initiates this process by converting glutamine to glutamate which is subsequently used in multiple reactions that support tumor cell growth and survival, including the generation of energy (TCA cycle), synthesis of amino acids and production of glutathione. Importantly, it has also been shown that GLS inhibition can reduce 2HG levels in tumors thus increasing TET activity and leading to decreased methylation. Recent findings from our group and others indicate that AML cells depend on Gln as a major carbon source for growth and survival. Inhibition of glutaminase with novel selective small molecule inhibitor CB-839, or silencing GLS expression with inducible shRNA inhibited mitochondrial respiration, reduced cell growth and induced apoptosis in a subset of leukemia cell lines and primary AML cells. Further, co-culture of leukemia cells with bone marrow-derived mesenchymal stem cells caused metabolic reprogramming in both, stroma and cancer, whereby glycolytic stroma supported oxidative metabolism of leukemic cells, in part by supplying glutamine. Myelodysplastic syndromes (MDS) are incurable malignancies that need newer therapeutic targets. Our preliminary data demonstrate that GLS is overexpressed in AML with complex cytogenetics, in high risk MDS stem cells and is associated with worse prognosis in MDS patients. We hypothesize that the glutaminase is a therapeutic target in MDS and metabolic reprogramming involved in transformation of MDS into AML. We propose to monitor the changes in metabolism in the conversion of MDS to AML in mouse models and determine if inhibiting glutaminolysis inhibits progression. This project will (1) characterize glutamine-dependent MDS subtypes; (2) determine mechanisms and investigate pre-clinical efficacy of the novel, potent, orally bioavailable GLS inhibitor CB-839 in MDS models; and (3) test therapeutic efficacy of CB-839 combined with 5-azacytidine in a Phase I/II clinical trial in patients with intermediate and high-risk MDS. We will specifically determine the efficacy of this combination in eliminating MDS stem cells, and analyze the effects on their methylation states. Since hypermethylation of DNA is an important hallmark of MDS, a combination of two hypomethylating approaches (via distinct mechanisms of action) will be potentially efficacious in MDS. The proposed work will generate a better understanding of the metabolic pathways in MDS.