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

由于它们在结构上与典型的雌激素受体(ERα和ER&946；)相似，所以它一直是 认为雌激素受体相关(ERR)家族的孤儿核受体的功能与 雌激素反应的调节器。然而，现在看来，与ER信号无关的活动是 错误生物学的一个同样重要的方面。最值得注意的是，已经表明ERRpha是一个关键的调节因子 氧化代谢，线粒体生物发生和脂肪酸的氧化。在直接的领域之外 新陈代谢方面，几项研究也表明，ERRpha的表达与阴性 多种癌症的预后。然而，目前尚不清楚ERRpha活性的哪个方面会影响肿瘤 病理学。尽管对大多数核受体生物学的研究依赖于产生特定的、 作为高亲和力的激动剂和拮抗剂，ERRpha已被证明是一个困难的药物靶点。非典型的 ERRpha的配体结合口袋，以及ERRpha似乎在 缺乏明显的配基，表明该受体的活性主要受 共激活子的丰度和活性。有趣的是，ERRpha本身的过度表达并不会导致 靶基因激活。相反，我们的研究表明，转录活动通常需要它的一个 伴随辅因子PGC-1α或PGC-1的表达。基于这一发现，我们已经能够开发出 用组合多肽筛选法构建ERRpha的蛋白质配体 因此，它以一种高度选择性的方式与ERRpha相互作用。所得到的经修改的辅助激活剂被启用 使用阵列技术定义ERRpha转录组并识别乳腺癌中的几条途径 参与该受体的细胞(即HER2信号)。使用我们拥有的这些基因表达数据 开发了一种强大的元基因，使我们能够预测ERRpha活性，并用它来鉴定细胞 研究这种受体的模型。更重要的是，当后生基因被用来探测两个 独立的乳腺肿瘤阵列数据集，它揭示了在ERpha阳性肿瘤中转录活性的ERRpha 与阳性的疾病结局有关，而同样的活动与阴性的疾病有关 ERα阴性乳腺肿瘤的预后。我们还在乳腺癌细胞中展示了激活的 ERRpha上调编码TCA循环所有限速酶的mRNAs的表达，并 OXPHOS途径的关键组成部分。此外，乳房中TCA基因特征的分析 肿瘤研究表明，在ERα阴性的乳房中，其表达也与阴性结果有关 肿瘤。鉴于肿瘤通常被认为依赖于糖酵解代谢，我们将探索 我们矛盾的发现背后的机制将ERRpha、氧化代谢和乳房结局联系起来 癌症。在这项研究中，我们建议使用细胞和动物模型来评估因果关系。 ERα阳性和阴性肿瘤中ERRpha活性与病理生理学的关系

Because of their structural similarity to the canonical estrogen receptors (ERalpha and ERβ), 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 ERRalpha is a key regulator of oxidative metabolism, mitochondrial biogenesis and β-oxidation of fatty acids. Outside of the direct realm of metabolism, it has also been shown in several studies that ERRalpha expression correlates with negative prognosis in a variety of cancers. It is not known however, what aspect of ERRalpha 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, ERRalpha has proven to be a difficult pharmaceutical target. The atypical ligand-binding pocket of ERRalpha, and the fact that ERRalpha 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 ERRalpha 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-1alpha or PGC-1β, be expressed. Building on this finding, we have been able to develop ¿protein ligands¿ for ERRalpha using combinatorial peptide screens to engineer the NR interacting surfaces of PGC1alpha so that it interacts in a highly selective manner with ERRalpha. The resultant modified coactivator enabled the use of array technology to define the ERRalpha 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 ERRalpha 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 ERalpha-positive tumors transcriptionally active ERRalpha is associated with a positive disease outcome whereas the same activity is associated with a negative disease outcome in ERalpha-negative breast tumors. We have also shown in breast cancer cells that activated ERRalpha 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 ERalpha-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 ERRalpha, 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 ERRalpha activity and the pathophysiology of both ERalpha-positive and ERalpha-negative tumors.