Crosstalk between estrogen receptor and NFkB in target gene regulation

描述(申请人提供)：最近的证据表明，核因子？B的结构性激活与更具侵袭性的雌激素受体(ER)阳性肿瘤相关，他莫昔芬耐药性的发展，以及向雌激素非依赖性生长的进展。到目前为止，已经描述的ER和NF？B之间的串扰的主要方式是相互转录抑制，其中ER拮抗NF？B的活性，而NF？B拮抗ER的活性，但转录抑制是否有助于乳腺肿瘤的进展尚不清楚。我们的初步数据表明，ER和NF？B以协同而不是拮抗的方式对多个基因进行快速、强劲和协同上调可能是这两个因素在乳腺癌细胞中相互干扰的主要机制。此外，我们的研究结果表明，ER和核因子？B的相互作用可能在乳腺癌细胞的生存中发挥重要作用。我们的总体目标是了解ER和核因子？B协同基因调控在乳腺癌中的功能和机制意义。我们的假设是，在ER+乳腺肿瘤中，核因子？B的激活导致促进生存和耐药基因的协同上调，这有助于乳腺肿瘤的进展。为了探索这一假说，我们建议检测治疗药物对ER+乳腺癌细胞存活和肿瘤生长的影响(目标1)。在这些研究中，我们将重点关注一个协同调控的细胞生存基因在癌细胞药物反应中的作用及其在人ER阳性乳腺肿瘤中的表达。为了研究ER和NF？B协同调控基因转录的机制，我们将首先研究协同调控基因5‘侧翼区域的独特反应元件组合是否通过协同ER和NF？B DNA结合以及增强RNA Pol II的招募和激活来促进协同作用(目标2)。此外，我们还将重点研究SRC/p160共激活子和其他已知的组蛋白乙酰转移酶的基因特异性招募如何通过增强组蛋白乙酰化来促进基因协同转录(AIM 3)。我们的转录研究将与生存分析相结合，以确定是否相同的潜在机制对两者都是必不可少的。综上所述，这些研究旨在深入了解雌激素受体和核因子B之间协同串扰的分子机制，以及这种串扰在激素依赖型乳腺癌进展中的重要性。公共卫生相关性：我们已经确定了一些基因协同上调雌激素和前炎性细胞因子在乳腺癌细胞中以ER和核因子？B依赖的方式。这些基因中的许多都有可能通过各种机制促进肿瘤的进展，包括增加细胞存活率和对药物产生耐药性。我们的目的是了解ER和NF？B协同基因调控在乳腺癌中的功能和机制意义，以期利用这一新的基因调控机制来提高乳腺肿瘤对现有内分泌和化疗药物的反应性。

DESCRIPTION (provided by applicant): Recent evidence suggests that constitutive activation of NF?B is associated with more aggressive estrogen receptor (ER) positive tumors, the development of tamoxifen resistance, and progression to estrogen-independent growth. To date, the major mode of crosstalk between ER and NF?B that has been described is mutual transrepression, where ER antagonizes NF?B activity and NF?B antagonizes ER activity, but whether transrepression contributes to breast tumor progression is not known. Our preliminary data suggest that it is the rapid, robust and synergistic up-regulation of multiple genes by ER and NF?B acting in a synergistic rather than an antagonistic manner that may be the major mechanism of crosstalk between these two factors in breast cancer cells. Furthermore, our findings suggest that ER and NF?B interaction may play an essential role in breast cancer cell survival. Our overall objective is to understand the functional and mechanistic significance of synergistic gene regulation by ER and NF?B in breast cancer. Our hypothesis is that activation of NF?B in ER+ breast tumors leads to synergistic up-regulation of pro-survival and drug resistance genes, which contribute to breast tumor progression. To explore this hypothesis, we propose to examine the effect of NF?B activation and inhibition on ER+ breast cancer cell survival and tumor growth in response to therapeutic drugs (Aim 1). In these studies, we will focus our attention on the role of one synergistically regulated, cell survival gene in cancer cell drug response and its expression in human ER positive breast tumors. To investigate the mechanism by which ER and NF?B synergistically regulate gene transcription, we will first examine whether a unique combination of response elements in the 5' flanking region of synergistically regulated genes contributes to synergy through cooperative ER and NF?B DNA binding and enhanced RNA Pol II recruitment and activation (Aim 2). In addition, we will focus on how the gene specific recruitment of SRC/p160 coactivators, and other known histone acetyltransferases, contributes to synergistic gene transcription through enhanced histone acetylation (Aim 3). Our transcriptional studies will be coupled with survival assays to determine if the same underlying mechanisms are essential for both. Taken together these studies are designed to provide insight into the molecular mechanisms of synergistic crosstalk between ER and NF?B and the importance of this crosstalk in the progression of hormone-dependent breast cancer. PUBLIC HEALTH RELEVANCE: We have identified a number of genes synergistically up-regulated by estrogen and proinflammatory cytokines in breast cancer cells in an ER and NF?B dependent manner. Many of these genes have the potential to enhance tumor progression, through a variety of mechanisms including increased cell survival and the development of resistance to drugs. Our objective, which forms the basis of this proposal, is to understand the functional and mechanistic significance of synergistic gene regulation by ER and NF?B in breast cancer, with the hope that this novel mechanism of gene regulation may be exploited to improve breast tumor responsiveness to current endocrine and chemotherapeutic drugs.