Role of the lncRNA BORG in Breast Cancer Metastatic Progression and Recurrence

虽然转移是乳腺癌(BC)最致命的特征，但我们对 管理这一事件的分子机制仍然不完整。有趣的是，许多BCS传播很长时间 在他们的原发肿瘤出现症状之前。事实上，约50%的女性被诊断患有卵巢小肿瘤 乳房(4毫米)的骨髓中已经含有播散性癌细胞。此外，这些 微转移潜伏数年后再次出现为不治之症，从而逃脱了临床检测 对最初对原发肿瘤有效的化疗不敏感的继发性肿瘤。 根除乳腺癌的一大障碍反映了与乳腺癌如何获得相关知识的匮乏 转移和复发的表型，这是科学和医学无法检测和治疗的基础 潜伏性微转移。这些知识缺陷对于三阴性乳腺癌来说尤其成问题 (TNBCs)，侵袭性很强，容易迅速复发；它们也缺乏FDA批准的靶向 必要的治疗，以提高他们令人沮丧的总体存活率。长的非编码RNA(LncRNA)具有 最近作为染色质重塑和基因表达的强大全球调节者在不同的 生理环境，包括细胞和组织的动态平衡、胚胎发生和发育。此外，一个 越来越多的与人类疾病中lncRNAs的病理生理学相关的科学证据引导我们 假设发育和进展中的TNBCs劫持了全球染色质重新编程的能力 LncRNAs，从而引发转移潜伏期的出现和致命性疾病的复发。 因此，我们鉴定了Borg(BMP/OP-Responsive gene，Borg)，它是一种强大的致癌lncRNA，其 异常表达与上皮-间充质转化获得和转移相关 (A)人和小鼠TNBCs细胞的表型；(B)人乳腺肿瘤及其相应的中枢神经系统 (C)与正常乳腺相比的人乳腺癌患者来源的异种移植(PDX)模型 上皮细胞。此外，Borg足以驱动潜伏的播散性TNBCs细胞重新激活 体外和体内的增殖计划，与表观基因组重编程操纵子相关的事件 抑制细胞衰老程序，并激活细胞生存程序。基于这些和其他 初步发现，我们假设Borg通过(I)重塑 表观基因组重新激活增殖程序，绕过静止和衰老相关的程序 转录本，和(Ii)促进与获得的生存信号系统的诱导 耐药表型。这些假设将通过两个具体目标来解决。目标一号将决定 Borg：TRIM28复合体形成和驱动TNBC转移和复发的机制。我们会 确定绑定TRIM28所需的最小Borg行列式，以及TRIM28中绑定的结构域 博格。此外，我们将通过执行TRIM28和TRIM28来映射博格引起的染色质变化 在博格人熟练和缺陷的TNBCs中进行H3K4me1芯片序列分析，研究结果将在人类身上得到验证 乳腺癌标本。目标2将确定Borg：RPA1复合体和NF-kB 促进TNBC存活和化疗耐药。类似于目标1，我们将确定最小Borg序列 绑定RPA1所必需的，反之亦然，RPA1中与Borg相互作用的区域。预防的影响 Borg：RPA1复合体的形成对TNBC存活和化疗耐药性的影响将被确定，以及RPA1的作用 ATM在调节TRIM28和RPA1与博格结合时的相互作用。最后，这些因素的影响 将在体外和临床前对介导TNBC耐药的事件进行评估。 治疗试验。总的来说，在这一创新应用中获得的发现将提供新的分子洞察力 Borg是如何驱动TNBC获得转移、复发和耐药表型的。

Although metastasis is the most lethal characteristic of breast cancer (BC), our understanding of the molecular mechanisms that govern this event remains incomplete. Interestingly, many BCs disseminate long before their primary tumors become symptomatic. In fact, ~50% of women diagnosed with small tumors of the breast (4 mm) already harbor disseminated carcinoma cells in their bone marrow. Moreover, these micrometastases escape clinical detection by remaining latent for years before reemerging as incurable secondary tumors that are insensitive to chemotherapies that were originally effective against the primary tumor. A major barrier to eradicating BC reflects the paucity of knowledge related to how mammary tumors acquire metastatic and recurrent phenotypes, which underlies the inability of science and medicine to detect and treat latent micrometastases. These knowledge deficits are especially problematic for triple-negative breast cancers (TNBCs), which are highly aggressive and prone to rapid relapse; they also lack FDA-approved targeted therapies necessary to improve their dismal overall survival rates. Long noncoding RNAs (lncRNAs) have recently emerged as powerful global regulators of chromatin remodeling and gene expression in diverse physiological settings, including cell and tissue homeostasis, embryogenesis and development. Moreover, an ever expanding array of scientific evidence related to the pathophysiology of lncRNAs in human disease led us to postulate that developing and progressing TNBCs hijack the global chromatin reprogramming ability of lncRNAs, thereby eliciting emergence from metastatic latency and initiating lethal disease recurrence. Accordingly, we identified BORG (BMP/OP-Responsive Gene (BORG), as a powerful oncogenic lncRNA whose aberrant expression correlated with the acquisition of EMT (epithelial-mesenchymal transition) and metastatic phenotypes in (a) human and murine TNBCs cells; (b) human breast tumors and their corresponding CNS metastases; and (c) patient-derived xenograft (PDX) models of human BC as compared to normal breast epithelial cells. Additionally, BORG is sufficient in driving latent disseminated TNBCs cells to reactivate proliferative programs both in vitro and in vivo, events associated with epigenomic reprogramming operant in repressing cellular senescence programs, and in activating cell survival programs. Based on these and other preliminary findings, we hypothesize that BORG drives TNBC metastasis and recurrence by (i) remodeling the epigenome to reactivate proliferative programs that circumvent quiescence- and senescence-associated transcriptomes, and (ii) promoting the induction of survival signaling systems coupled to the acquisition of chemoresistant phenotypes. These hypotheses will be addressed by two Specific Aims. Aim 1 will determine the mechanisms whereby BORG:TRIM28 complexes form and drive TNBC metastasis and recurrence. We will identify the minimal BORG determinants necessary to bind TRIM28, as well as the domains in TRIM28 that bind BORG. Additionally, we will map the chromatin alterations provoked by BORG by performing TRIM28 and H3K4me1 ChIP-seq analyses in BORG-proficient and -deficient TNBCs, findings that will be validated in human breast cancer specimens. Aim 2 will determine the mechanisms whereby BORG:RPA1 complexes and NF-kB promote TNBC survival and chemoresistance. Similar to Aim 1, we will identify the minimal BORG sequences necessary to bind RPA1, and conversely, the regions in RPA1 that interact with BORG. The impact of preventing BORG:RPA1 complex formation on TNBC survival and chemoresistance will be determined, as will the role of ATM in regulating the interplay between TRIM28 and RPA1 when bound to BORG. Finally, the impact of these events in mediating TNBC resistance to cytotoxic chemotherapy will be assessed in vitro, and in preclinical therapy trials. Collectively, the findings obtained in this innovative application will provide novel molecular insights into how BORG drives TNBC to acquire metastatic, recurrent, and chemoresistant phenotypes.