Validation of the Estrogen Related Receptor as a therapeutic target in cancer

描述（由申请人提供）：由于它们与典型雌激素受体（ER1和ER2）的结构相似，人们一直认为孤儿核受体的雌激素受体相关（ERR）亚家族是雌激素反应性的调节剂。然而，现在看来，与内质网信号无关的活动是ERR生物学的一个同样重要的方面。最值得注意的是，研究表明ERR1是氧化代谢、线粒体生物发生和脂肪酸2氧化的关键调节因子。在代谢的直接领域之外，一些研究也表明，在多种癌症中，ERR1表达与不良预后相关。然而，ERR1活性的哪个方面影响肿瘤病理尚不清楚。尽管大多数核受体的生物学研究依赖于产生特异性、高亲和力的激动剂和拮抗剂的能力，但ERR1已被证明是一个困难的药物靶点。ERR1的非典型配体结合口袋，以及ERR1在没有明显配体的情况下似乎采取构成活性构象的事实表明，该受体的活性主要由辅激活因子的丰度和活性调节。有趣的是，ERR1本身的过表达并不会导致靶基因的激活。相反，我们的研究表明，转录活性通常需要其伴随的辅助因子之一PGC-11或PGC-12的表达。基于这一发现，我们已经能够开发ERR1的蛋白质配体，使用组合肽筛选来设计PGC11的NR相互作用表面，使其以高度选择性的方式与ERR1相互作用。由此产生的修饰的共激活子能够使用阵列技术来定义ERR1转录组，并确定乳腺癌细胞中该受体参与的几种途径（即HER2信号传导）。利用这些基因表达数据，我们开发了一个强大的元基因，使我们能够预测ERR1的活性，并利用它来识别研究这种受体的细胞模型。更重要的是，当metagene用于探测两个独立的乳腺肿瘤阵列数据集时，它揭示了er1阳性肿瘤中转录活性的ERR1与阳性疾病结局相关，而er1阴性乳腺肿瘤中相同的活性与阴性疾病结局相关。我们还发现，在乳腺癌细胞中，激活ERR1可上调编码TCA循环中所有限速酶和OXPHOS通路关键组分的mrna的表达。此外，对乳腺肿瘤中TCA基因特征的分析表明，其表达也与er1阴性乳腺肿瘤的阴性结果相关。鉴于肿瘤通常被认为依赖于糖酵解代谢，我们将探索将ERR1、氧化代谢和乳腺癌预后联系起来的矛盾发现背后的机制。在这项研究中，我们建议使用细胞和动物模型来评估ERR1活性与er1阳性和er1阴性肿瘤病理生理之间的因果关系。

DESCRIPTION (provided by applicant): Because of their structural similarity to the canonical estrogen receptors (ER1 and ER2), it has been considered that the estrogen receptor related (ERR) sub-family of orphan nuclear receptors function as regulators of estrogen responsiveness. It now appears, however, that activities unrelated to ER signaling are an equally important facet of ERR biology. Most notably, it has been shown that ERR1 is a key regulator of oxidative metabolism, mitochondrial biogenesis and 2-oxidation of fatty acids. Outside of the direct realm of metabolism, it has also been shown in several studies that ERR1 expression correlates with negative prognosis in a variety of cancers. It is not known however, what aspect of ERR1 activity impacts tumor pathology. Whereas the study of the biology of most nuclear receptors relies on the ability to generate specific, high affinity agonists and antagonists, ERR1 has proven to be a difficult pharmaceutical target. The atypical ligand-binding pocket of ERR1, and the fact that ERR1 appears to adopt a constitutively active conformation in the absence of an apparent ligand, indicates that the activity of this receptor is regulated primarily by the abundance and activity of coactivators. Interestingly, overexpression of ERR1 in and of itself does not lead to target gene activation. Rather, our studies reveal that transcriptional activity usually requires that one of its attendant cofactors, PGC-11 or PGC-12, be expressed. Building on this finding, we have been able to develop protein ligands for ERR1 using combinatorial peptide screens to engineer the NR interacting surfaces of PGC11 so that it interacts in a highly selective manner with ERR1. The resultant modified coactivator enabled the use of array technology to define the ERR1 transcriptome and identify several pathways in breast cancer cells in which this receptor is engaged (i.e. HER2 signaling). Using this gene expression data we have developed a robust metagene that enables us to predict ERR1 activity and have used this to identity cellular models in which to study this receptor. More importantly, when the metagene was used to probe two independent breast tumor array datasets, it revealed that in ER1-positive tumors transcriptionally active ERR1 is associated with a positive disease outcome whereas the same activity is associated with a negative disease outcome in ER1-negative breast tumors. We have also shown in breast cancer cells that activated ERR1 upregulates expression of the mRNAs encoding all of the rate-limiting enzymes of the TCA cycle and the key components of the OXPHOS pathway. Furthermore, analysis of the TCA gene signature in breast tumors revealed that its expression was also associated with a negative outcome in ER1-negative breast tumors. Given that tumors are generally thought to rely on glycolytic metabolism, we will explore the mechanisms underlying our paradoxical findings that link ERR1, oxidative metabolism and outcomes in breast cancer. In this study we propose to use both cellular and animal models to assess the cause and effect relationship between ERR1 activity and the pathophysiology of both ER1-positive and ER1-negative tumors.