Nutrient Sensing and Transcriptional Regulation

乳腺癌是一种异质性疾病，由几种临床和分子上不同的 亚型与其他亚型相比，三阴性乳腺癌（TNBC）占所有乳腺癌的15-20%。 乳腺癌发生在较年轻的年龄，复发更频繁，生存率降低。当前没有任何 靶向疗法可用于TNBC。我们的短期目标是剖析 支持TNBC的增长和生存。我们的长期目标是利用这些发现来确定新的目标 适合治疗发展。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发生。我们最感兴趣的是 转录因子的扩展Myc网络的两个成员整合生长和营养信号。c-Myc 和MondoA的功能相反，以控制TNBC的侵袭性生长和存活。本申请中 我们专注于MondoA对基因表达的控制，以及代谢如何塑造MondoA依赖的基因表达。 体外和体内转录组。MondoA是葡萄糖依赖性转录的主要调节因子， 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因子， 目标TXNIP具有多效性。在这些功能中，最具特点的是燃料选择。 TXNIP是葡萄糖摄取和有氧糖酵解的有效抑制剂，但它也可以驱动 其他燃料如支链氨基酸和线粒体中的酮。因此，高TXNIP水平驱动 线粒体中的燃料氧化，同时限制葡萄糖的利用。相反，低TXNIP水平提示燃料使用 而不是线粒体。我们已经证明了几种主要的癌基因阻断了 MondoA转录活性，从而降低TXNIP水平。这可能有助于癌基因- 依赖性有氧糖酵解，即瓦尔堡效应，这是癌细胞的共同特征。我们提出 研究燃料的选择如何控制MondoA在体外和体内的转录活性，以及来自细胞的信号如何影响MondoA的转录活性。 肿瘤微环境决定MondoA转录活性。在目标1中，我们将确定TXNIP， 缺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MondoA在良好灌注/氧合的细胞中是否具有转录活性 肿瘤区域。为了检验我们发现的普遍性，我们将确定MondoA在基因表达中的作用。 以及利用其他乳腺癌细胞系和条件性重编程乳腺癌细胞进行营养感测 PDX模型在目标3中，我们将使用基因组学方法来发现直接依赖于MondoA的 体内转录组，并确定这些基因如何与MondoA协作以维持TNBC 肿瘤发生我们还将发现MondoA体内转录活性所需的辅因子， 生物素邻近标记。

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.