Characterizing the role of MSRA in pancreatic tumorigenesis

项目总结 胰腺导管腺癌(PDA)是一种侵袭性的恶性肿瘤，在很大程度上仍无法治愈。KRAS 原癌基因在95%的PDA中发生突变，是PDA生长和维持的有力驱动因素。致癌作用 KRAS诱导了对PDA生长至关重要的代谢途径的深刻重新布线。有趣的是，这 重新布线会产生代谢副产物，包括可能会氧化的活性氧物种(ROS) 大分子，导致基因组不稳定和有毒的细胞损伤。然而，除了这些， 不分青红皂白的活动，ROS也可以通过氧化翻译后修饰启动氧化还原信号 指蛋白质类半胱氨酸，在半胱氨酸的还原状态和氧化状态之间切换构成 一种可以调节蛋白质结构和/或功能的“氧化还原开关”。实际上，用我们的胰腺 器官模型(Cell，2015)，我们先前表明致癌的KRAS促进胰腺肿瘤的发生 部分是通过调节参与翻译的特定蛋白质上半胱氨酸的循环还原/氧化 机械(Cell，2016)，从而促进蛋白质合成(Cell，2016)、葡萄糖代谢和肿瘤生长 (《自然通讯》，2019)。虽然半胱氨酸因其氧化敏感性而广为人知，但它经常 没有意识到蛋氨酸，另一种含硫的氨基酸，很容易被氧化成蛋氨酸 亚砜，并被氧化还原酶蛋氨酸亚砜还原酶A(MSRA)还原。用纸巾 患者来源的胰腺肿瘤和邻近正常组织的微阵列，我们观察到一个分期依赖的 肿瘤组织中MSRA蛋白表达减少。一直以来，小鼠MSRA的急性敲除使用 癌前胰腺类器官中的CRISPR/Cas9在体外和体内提供了迁移优势。因此， 我们假设氧化还原信号是通过蛋氨酸的氧化翻译后修饰实现的。 残留物(Met-oxPTM)是一种未知的支持胰腺转移的机制。 在此，我们建议i)定义调控PDA中MSRA表达的机制，ii)表征 氧化型蛋氨酸肽在动脉导管未闭转移中的功能和临床意义 描述由Met-oxPTM在PDA单元中创建的目标漏洞的特征。

PROJECT SUMMARY Pancreatic ductal adenocarcinoma (PDA) is an aggressive malignancy that remains largely incurable. The KRAS oncogene is mutated in 95% of PDAs and acts as a potent driver of PDA growth and maintenance. Oncogenic KRAS induces a profound rewiring of metabolic pathways that are essential for PDA growth. Interestingly, this rewiring generates metabolic by-products, including reactive oxygen species (ROS), that can potentially oxidize macromolecules, resulting in genomic instability and toxic cellular damage. However, in addition to these indiscriminate activities, ROS can also initiate redox signaling through oxidative post-translational modifications of proteinaceous cysteines, such that toggling between the reduced and oxidized states of cysteine constitutes a “redox switch” that can regulate the structure and/or function of a protein. Indeed, using our pancreatic organoid model (Cell, 2015), we previously showed that oncogenic KRAS promotes pancreatic tumorigenesis in part by regulating the cyclic reduction/oxidation of cysteines on select proteins involved in the translation machinery (Cell, 2016), thereby promoting protein synthesis (Cell, 2016), glucose metabolism, and tumor growth (Nature Communications, 2019). While cysteine is well-recognized for its susceptibility to oxidation, it is often not appreciated that methionine, the other sulfur-containing amino acid, can be readily oxidized to methionine sulfoxide, and reduced by the oxidoreductase, methionine sulfoxide reductase A (MSRA). Using a tissue microarray of patient-derived pancreatic tumors and adjacent normal tissues, we observed a stage-dependent decrease in MSRA protein expression in tumor tissues. Consistently, acute knockout of murine MSRA using CRISPR/Cas9 in premalignant pancreatic organoids provides a migratory advantage in vitro and in vivo. Thus, we hypothesize that redox signaling through oxidative post-translational modification of methionine residues (Met-oxPTM) represents an unexplored mechanism that supports pancreatic metastasis. Herein, we propose to i) define the mechanism regulating MSRA expression in PDA, ii) characterize the functional and clinical significance of oxidized methionine peptides in PDA metastasis, and iii) define and characterize targetable vulnerabilities created by Met-oxPTM in PDA cells.