Investigating a Novel Glutamine Metabolism Pathway in Pancreatic Cancer

 描述（由申请人提供）：胰腺导管腺癌（PDAC）是一种致命的疾病，迫切需要新的治疗方法。我们以前的工作表明，PDAC具有改变的代谢，并且致癌Kras在这种代谢重编程中起关键作用。重要的是，我们已经确定了一种新的，谷氨酰胺（Gln）依赖性途径，这是必要的PDAC的增长，通过产生NADPH的氧化还原平衡的维持（称为谷氨酰胺-氧化还原途径）。该途径依赖于致癌Kras，并且对于PDAC在体外和体内的生长是绝对必要的，同时在正常细胞中被抑制。因此，可能存在可接近的治疗窗口。我们已经表明，致癌Kras通过调节两种关键代谢酶GOT 1和GLUD 1的相对表达来控制Gln-氧化还原途径的通量，从而促进GOT 1对Gln衍生的天冬氨酸的转氨作用，并抑制GLUD 1对谷氨酸向α-酮戊二酸的典型转化。最终，NADPH和丙酮酸由苹果酸酶（ME 1）产生。此外，我们的数据表明，绝大多数由ME 1产生的Gln衍生的丙酮酸盐不通过乳酸脱氢酶转化为乳酸盐。具体地，同位素分析表明，丙酮酸盐池直接隧道进入线粒体，在线粒体中它可以被丙酮酸羧化酶（PC）作用。总之，这支持了ME 1、线粒体丙酮酸转运蛋白（MPC 1/2）和可能的PC之间存在复合物的想法。与这一概念相一致，我们已经表明，抑制MPC 1或PC的结果在一个显着的积累完全标记的天冬氨酸在谷氨酰胺示踪研究，这表明谷氨酰胺氧化还原途径已被抑制。在此背景下，我们提出了一系列深入的机制研究，以阐明：i）致癌Kras对该途径的调节; ii）该途径与PDAC中其他ROS清除途径的整合; iii）丙酮酸终产物的代谢命运，以及iv）体内PDAC微环境对这种独特Gln代谢的影响。鉴于开发Kras抑制剂的困难，靶向生长所需的Kras调节代谢途径可能为这种毁灭性癌症提供新的攻击切入点。因此，一个完整的了解这种新的谷氨酰胺-氧化还原途径将是至关重要的，将这些发现转化为临床。 SA 1.探讨致癌Kras对谷氨酰胺代谢和氧化还原平衡的调节作用。 SA 2.研究苹果酸酶衍生的丙酮酸在PDAC谷氨酰胺代谢中的去向。 SA 3.探讨在基础和应激条件下，PDAC微环境如何影响体内谷氨酰胺代谢和氧化还原平衡。

 DESCRIPTION (provided by applicant): Pancreatic ductal adenocarcinoma (PDAC) is a deadly disease and new therapies are desperately needed. Our previous work has shown that PDAC have an altered metabolism and that oncogenic Kras plays a key role in this metabolic reprogramming. Importantly, we have identified a novel, glutamine (Gln) -dependent pathway that is necessary for PDAC growth through the generation of NADPH for the maintenance of redox balance (referred to as the Gln-redox pathway). This pathway is dependent on oncogenic Kras and is absolutely essential for PDAC growth both in vitro and in vivo, while being dispensable in normal cells. Thus, there may be an accessible therapeutic window. We have shown that oncogenic Kras controls flux through the Gln-redox pathway by regulating the relative expression of two key metabolic enzymes; GOT1 and GLUD1, thereby promoting the transamination of Gln-derived aspartate by GOT1 and repressing the canonical conversion of glutamate to alpha-ketoglutarate by GLUD1. Ultimately, NADPH and pyruvate are produced by malic enzyme (ME1). Additionally, our data demonstrate that the overwhelming majority of Gln- derived pyruvate produced by ME1 is not converted to lactate via lactate dehydrogenase. Specifically the isotopomer analyses suggest that this pool of pyruvate is directly tunneled into the mitochondria where it can be acted upon by pyruvate carboxylase (PC). Together, this supports the idea that a complex exists between ME1, the mitochondrial pyruvate transporter (MPC1/2), and possibly PC. Consistent with this concept, we have shown that suppression of either MPC1 or PC results in a significant accumulation of fully labeled aspartate in Gln tracing studies, suggesting that the Gln-redox pathway has been inhibited. Against this backdrop, we propose a series of in-depth, mechanistic studies to elucidate: i) the regulation of the pathway by oncogenic Kras; ii) the integration of this pathway with other ROS scavenging pathways in PDAC; iii) the metabolic fate of the pyruvate end product, and iv) the impact of the PDAC microenvironment in vivo on this unique Gln metabolism. Given the difficulties in developing inhibitors to Kras, targeting Kras-regulated metabolic pathways that are required for growth may provide novel entry points of attack in this devastating cancer. Thus, a complete understanding of this novel Gln-redox pathway will be critical to translate these findings to the clinic. SA1. T explore the regulation of glutamine metabolism and redox balance by oncogenic Kras. SA2. To investigate the fate of malic enzyme derived pyruvate in PDAC glutamine metabolism. SA3. To explore how the PDAC microenvironment impacts glutamine metabolism and redox balance in vivo under basal and stress conditions.