Targeting Malic Enzyme 3 as a Synthetic Lethality Target in Pancreatic Cancer

项目摘要/摘要 摘要胰腺导管腺癌是最常见的胰腺癌，其存活率为5年。 PDAC患者的发病率为可怕的~6%。PDAC基因组中肿瘤抑制基因的频繁缺失 基因座，最明显的是Smad4，它在大约30%的病例中纯合缺失。作为损失的 邻近的家政基因可以赋予附带致命性，我试图确定是否丢失了 代谢基因Smad4中的苹果酸酶(ME)2会产生癌症特异的代谢 以其同源异构体ME3为目标时的漏洞。利用体外和体内模型系统，I 证实ME2缺失的PDAC细胞中的ME3缺失导致细胞死亡。机械化、集成化 线粒体ME缺陷细胞的代谢和分子研究显示NADPH减少 产生和随之而来的高ROS激活AMP激活的蛋白激酶(AMPK)，进而 通过固醇调节元件结合抑制BCAT2(支链氨基酸转氨酶2)基因 蛋白1(SREBP1)-定向转录。BCAT2催化支链上的氨基转移 链氨基酸(BCAA)转化为α-酮戊二酸(αKG)，从而再生谷氨酸，谷氨酸在 部分支持从头开始的碱基合成。综上所述，这些数据表明线粒体代谢能是必需的 对胰腺癌存活率有影响，可作为治疗的脆弱性加以利用。该项目的目标是 测定甲氧西林在PDAC中的可药性。为了实现这一目标，我提出了以下建议：1)系统化 苹果酸酶作为胰腺癌治疗靶点的有效性，2)机制的理解 代谢去调控对ME3消退的影响；3)选择性ME3抑制剂的鉴定。通过向 在上述目标之上，我将进一步深入了解ME3的结构特征，并为Rational绘制一幅蓝图 针对ME3的药物设计。此外，我还将确定潜在的抵抗或代谢旁路 示踪支链氨基酸和谷氨酰胺等代谢产物治疗ME3的机制而且，我独一无二的 对BCAA法规的理解将确定针对ME3的替代靶点的新途径。最后， 将进行ME3的结构-功能分析，并验证通过电子分析确定的热门产品。

Project Summary/Abstract Pancreatic ductal adenocarcinoma (PDAC) is the most common cancer of the pancreas and 5-year survival rate for PDAC patients is a dreadful ~6%. PDAC genome sustains frequent deletion of tumor suppressor gene loci, most notably SMAD4, which is homozygously deleted in approximately 30% of cases. As loss of neighboring housekeeping genes can confer collateral lethality, I sought to determine whether loss of the metabolic gene malic enzyme (ME) 2 in the SMAD4 locus would create a cancer-specific metabolic vulnerability upon targeting its paralogous isoform ME3. Using in vitro and in vivo model system, I demonstrated that ME3 depletion in ME2 null PDAC cells causes cell death. Mechanistically, integrated metabolomic and molecular investigation of mitochondrial ME-deficient cells revealed diminished NADPH production and consequent high ROS which activates AMP activated protein kinase (AMPK), and which in turn suppresses BCAT2 (Branched chain amino acid transaminase 2) gene via sterol regulatory element-binding protein 1 (SREBP1)-directed transcription. BCAT2 catalyzes the transfer of the amino group from branched chain amino acids (BCAA) to alpha-ketoglutarate (αKG) thereby regenerating glutamate, which functions in part to support de novo nucleobase synthesis. In summary, this data shows that mitochondrial ME is required for pancreatic cancer survival and can be exploited as vulnerability for treatment. The goal of the project is to determine the druggability of ME in PDAC. In order to achieve this goal, I propose the following: 1) Systematic validation of Malic Enzyme as a therapeutic target in pancreatic cancer, 2) Mechanistic understanding of metabolic deregulation upon ME3 extinction; 3) Identification of selective ME3 inhibitors. By addressing the above aim, I will gain further insights into the structural features of ME3 and generate a blueprint for rational drug design to target ME3. Moreover, I will also identify the potential resistance or metabolic bypass mechanism of ME3 treatment by tracing metabolites such as BCAA and glutamine. Moreover, my unique understanding of the BCAA regulation will identify new avenues for targeting surrogate target of ME3. Finally, will undertake structure-function analysis of ME3 and validate the top hits identified by in-silico analysis.