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）结构相似，因此人们认为孤儿核受体的雌激素受体相关（ERR）亚家族起到雌激素反应性调节剂的作用。然而，现在看来，与 ER 信号传导无关的活动是 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、线粒体生物合成和脂肪酸 2-氧化的关键调节因子。除了直接的代谢领域之外，多项研究还表明 ERR1 表达与多种癌症的不良预后相关。然而，尚不清楚 ERR1 活性的哪些方面会影响肿瘤病理学。虽然大多数核受体的生物学研究依赖于产生特异性、高亲和力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用组成型活性构象的事实表明，该受体的活性主要受共激活剂的丰度和活性调节。有趣的是，ERR1 的过度表达本身并不会导致靶基因激活。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，我们已经能够使用组合肽筛选来开发 ERR1 的蛋白质配体，以设计 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。由此产生的修饰共激活剂使得能够使用阵列技术来定义 ERR1 转录组并识别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，我们开发了一种强大的元基因，使我们能够预测 ERR1 活性，并使用它来识别研究该受体的细胞模型。更重要的是，当使用宏基因探测两个独立的乳腺肿瘤阵列数据集时，它揭示了在 ER1 阳性肿瘤中，转录活性 ERR1 与阳性疾病结果相关，而在 ER1 阴性乳腺肿瘤中，相同的活性与阴性疾病结果相关。我们还在乳腺癌细胞中发现，激活 ERR1 会上调编码 TCA 循环所有限速酶和 OXPHOS 途径关键成分的 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，我们将探讨我们的矛盾发现背后的机制，这些发现将 ERR1、氧化代谢和乳腺癌的结果联系起来。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 阴性肿瘤的病理生理学之间的因果关系。

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.