Nutrient Sensing and Transcriptional Regulation

摘要乳腺癌是一种异质性疾病，由几种临床和分子上截然不同的疾病组成。 子类型。与其他亚型相比，三阴性乳腺癌(TNBC)，占所有乳腺癌的15%-20% 乳腺癌发生的年龄更小，复发更频繁，存活率也更低。目前，没有 针对TNBC有靶向治疗可用。我们的短期目标是剖析 支持TNBC的发展和生存。我们的长期目标是利用这些发现来识别新的目标 适合于治疗开发。我们专注于正常细胞和癌细胞如何整合内部和 细胞外生长和营养信号，以维持生长和肿瘤形成。我们最感兴趣的是如何 扩展的Myc转录因子网络的两个成员整合了生长和营养信号。C-Myc 与Mondoa相反的功能是控制TNBC的侵略性生长和生存。在此应用程序中 我们专注于Mondoa对基因表达的控制，以及代谢如何塑造Mondoa依赖性 体外和体内转录组。Mondoa是葡萄糖依赖转录的主要调节因子，与 硫氧还蛋白相互作用蛋白(TXNIP)是其最具特征的直接和葡萄糖诱导的转录 目标。TXNIP具有多效性。在这些功能中，最具特色的是燃料选择功能。 TXNIP是一种有效的葡萄糖摄取和有氧糖酵解的抑制因子，但它也可以推动 其他燃料，如线粒体中的支链氨基酸和酮。因此，高TXNIP水平会推动 促进线粒体的氧化，同时限制葡萄糖的利用。相反，低TXNIP水平会影响燃料的使用 朝向葡萄糖，远离线粒体。我们已经证明了几个主要的癌基因阻断 Mondoa转录活性，从而降低TXNIP水平。这可能有助于致癌基因- 依赖有氧糖酵解，即华宝效应，这是癌细胞的共同特征。我们建议 为了研究燃料选择如何在体外和体内控制Mondoa转录活性，以及来自 肿瘤微环境决定了Mondoa的转录活性。在目标1中，我们将确定TXNIP、 低氧以及糖酵解和氧化磷酸化之间的平衡如何控制Mondoa 转录活性。在目标2中，我们将确定是否需要Mondoa来建立或 肿瘤发生的维持以及蒙多亚在良好灌流/充氧状态下是否转录活跃 肿瘤区域。为了检验我们发现的一般性，我们将确定Mondoa在基因表达中的作用 利用其他乳腺癌细胞系和有条件地重新编程的乳腺癌细胞进行营养传感 来自PDX型号。在目标3中，我们将使用基因组学方法来发现直接依赖Mondoa的 体内转录组，并确定这些基因如何与Mondoa合作维持TNBC 肿瘤发生学。我们还将发现Mondoa在体内转录活动所需的辅助因子 生物素亲和标记。

SUMMARY Breast cancer is a heterogeneous disease consisting of several clinically and molecularly distinct subtypes. Compared to other subtypes, Triple Negative Breast Cancer (TNBC), which represents 15-20% of all breast cancer, occurs at a younger age and recurs more frequently with a reduced survival rate. Currently, no targeted therapies are available for TNBC. Our short-term goal is to dissect the molecular pathways that support TNBC growth and survival. Our long-term goal is to leverage these discoveries to identify novel targets suitable for therapeutic development. We focus on how normal cells and cancer cells integrate intra- and extracellular growth and nutrient signals to sustain growth and tumorigenesis. We are most interested in how two members of the extended Myc network of transcription factors integrate growth and nutrient signals. c-Myc and MondoA function in opposition to control the aggressive growth and survival of TNBC. In this application we focus on the control of gene expression by MondoA and how metabolism shapes the MondoA-dependent transcriptome in vitro and in vivo. MondoA is the principal regulator of glucose-dependent transcription with Thioredoxin Interacting Protein (TXNIP) being its best-characterized direct and glucose-induced transcriptional target. TXNIP has pleiotropic function. Best characterized among these many functions is one in fuel choice. TXNIP is a potent suppressor of glucose uptake and aerobic glycolysis, but it can also drive the catabolism of other fuels such as branched chain amino acids and ketones in mitochondria. Thus, high TXNIP levels drive fuel oxidation in mitochondria, while restricting utilization of glucose. Conversely, low TXNIP levels tip fuel use towards glucose and away from mitochondria. We have shown that several predominant oncogenes block MondoA transcriptional activity, thereby decreasing TXNIP levels. This likely contributes to oncogene- dependent aerobic glycolysis, i.e. the Warburg Effect, which is a common feature of cancer cells. We propose to study how fuel choice controls MondoA transcriptional activity in vitro and in vivo and how signals from the tumor microenvironment dictate MondoA transcriptional activity. In Aim 1, we will determine how TXNIP, hypoxia and how the balance between glycolysis and oxidative phosphorylation controls MondoA transcriptional activity. In Aim 2, we will determine whether MondoA is required for the establishment or maintenance of tumorigenesis and whether MondoA is transcriptionally active in well perfused/oxygenated tumor regions. To examine the generality of our findings, we will determine MondoA’s role in gene expression and nutrient-sensing using other breast cancer cell lines and in conditionally reprogrammed breast cancer cells from PDX models. In Aim 3, we will use genomics approaches to discover the direct MondoA-dependent transcriptome in vivo and determine how these genes collaborate with MondoA to sustain TNBC tumorigenesis. We will also discover the cofactors required for MondoA transcriptional activity in vivo using biotin proximity labeling.