Therapeutic targeting of glutamine metabolism in MDS

 描述(由申请人提供)：癌细胞的代谢重新编程对于促进它们的增殖和抵抗微环境压力的生存至关重要。谷氨酰胺(Gln)是一种必需氨基酸，在癌细胞增殖代谢中发挥独特作用，为维持细胞增殖、调节氧化还原动态平衡和信号转导通路提供基石。谷氨酰胺酶(GLS)是一种酶，通过将谷氨酰胺转化为谷氨酸来启动这一过程，谷氨酸随后被用于支持肿瘤细胞生长和存活的多种反应，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，GLS抑制也被证明可以降低肿瘤中2HG的水平，从而增加Tet的活性，并导致甲基化减少。我们小组和其他人的最新发现表明，AML细胞依赖谷氨酰胺作为生长和生存的主要碳源。用新型选择性小分子抑制剂CB-839抑制谷氨酰胺酶，或用可诱导的shRNA沉默GLS的表达，可抑制线粒体呼吸，减少细胞生长，并诱导白血病细胞亚群和原代AML细胞凋亡。此外，白血病细胞与骨髓间充质干细胞共培养导致基质和癌症的代谢重新编程，由此糖酵解基质支持白血病细胞的氧化代谢，部分是通过提供谷氨酰胺。骨髓增生异常综合征(MDS)是一种无法治愈的恶性肿瘤，需要新的治疗靶点。我们的初步数据表明，GLS在具有复杂细胞遗传学的AML中高表达，在高危MDS干细胞中表达，并与MDS患者的预后不良有关。我们假设谷氨酰胺酶是MDS的治疗靶点，代谢重编程参与了MDS向AML的转化。我们建议在小鼠模型中监测MDS向AML转化过程中代谢的变化，并确定抑制谷氨酰胺分解是否抑制进展。该项目将(1)确定谷氨酰胺依赖MDS亚型的特征；(2)确定新型、有效的口服生物可利用GLS抑制剂CB-839在MDS模型中的作用机制并调查其临床前疗效；以及(3)在I/II期临床试验中测试CB-839与5-azacytidine联合治疗中高风险MDS的疗效。我们将专门确定这种组合在消除MDS干细胞方面的效果，并分析它们对甲基化状态的影响。由于DNA的高甲基化是MDS的一个重要标志，两种低甲基化方法的组合(通过不同的作用机制)将在MDS中潜在地有效。这项拟议的工作将使人们更好地了解MDS的代谢途径。

 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.