Role of an RNA-Binding Protein in Mammary Carcinogenesis

描述（由申请人提供）：本提案研究RNA结合癌蛋白在乳腺肿瘤发生中的作用。这种蛋白质位于细胞质中，并与胰岛素样生长因子-II、β-肌动蛋白、c-myc和其他mRNA结合。我们称之为c-myc编码区不稳定性决定簇结合蛋白或CRD-BP。因为它与c-myc mRNA编码区的不稳定决定簇结合。CRD-BP影响RNA翻译、稳定性和定位，这取决于它所结合的RNA。它在胎儿组织中大量表达，但在出生后不久被抑制。因此，它可能在胎儿生命中有特殊的作用。三项发现也将CRD-BP与乳腺癌联系起来：（a）CRD-BP在正常乳腺组织中检测不到，但存在于约60%的人类乳腺肿瘤中，（B）CRD-BP基因在约30%的人类乳腺肿瘤中扩增，（c）CRD-BP在雌性转基因小鼠中诱导乳腺腺癌。三个目标是使用转基因小鼠来研究这种RNA结合癌蛋白诱导乳腺肿瘤的途径。艾姆岛确定CRD-BP表达是否需要持续维持现有的乳腺肿瘤。转基因小鼠中的乳腺肿瘤继续表达CRD-BP，因此其存活可能依赖于CRD-BP。为了研究这一想法，目的I利用了一种小鼠模型，其中乳腺特异性CRD-BP表达由四环素类似物强力霉素（dox）诱导。预期在dox处理的小鼠中出现乳腺肿瘤。目的我接着问：这些肿瘤停止生长或倒退时，dox撤出？我们的工作假设是，当CRD-BP表达受到抑制时，肿瘤会消退。Aim II.使用微阵列分析来比较非肿瘤性乳腺组织和表达或不表达CRD-BP的小鼠的纯化乳腺上皮细胞中的基因表达谱。一些CRD-BP调控的RNA在乳腺肿瘤的诱导和维持中起着重要作用。Aim III.确定遗传和环境因素如何促进CRD-BP表达小鼠的乳腺肿瘤发生。目的是评估肿瘤抑制因子Ape和化学致癌物N-乙基-N-亚硝基脲（ENU）如何影响CRD-BP介导的肿瘤形成。我们预测Ape缺乏和ENU治疗将与CRD-BP协同增加肿瘤发病率和恶性度。许多研究充分的癌蛋白是转录因子或蛋白激酶。CRD-BP是一种不寻常的癌蛋白，因为它存在于细胞质中并与RNA结合。通过研究CRD-BP的致癌特性，它在体内影响的RNA，以及它与肿瘤诱导遗传和环境因素的相互作用，我们希望发现新的肿瘤发生途径。 修订日期：2005年10月27日（参见修订说明）

DESCRIPTION (provided by applicant): This proposal investigates the role of an RNA-binding oncoprotein in mammary tumorigenesis. This protein is located in the cytoplasm and binds to insulin-like growth factor-ll, beta-actin, c-myc, and other mRNAs. We call it the c-myc Coding Region instability Determinant-binding Protein or CRD-BP. because it binds to an instability determinant in the c-myc mRNA coding region. The CRD-BP affects RNA translation, stability, and localization, depending on the RNA to which it binds. It is expressed abundantly in fetal tissues but is repressed shortly after birth. Therefore, it probably has a special role in fetal life. Three findings also link the CRD-BP to breast cancer: (a) The CRD-BP is undetectable in normal breast tissue but is present in ~60 percent of human breast tumors, (b) The CRD-BP gene is amplified in ~30 percent of human breast tumors, (c) The CRD-BP induces mammary adenocarcinomas in female transgenic mice. Three aims use transgenic mice to investigate the pathways of mammary tumor induction by this RNA-binding oncoprotein. Aim I. Determine if CRD-BP expression is required continuously to maintain an existing mammary tumor. Mammary tumors in transgenic mice continue to express the CRD-BP and thus might be CRD-BP- dependent for their survival. To investigate this idea, Aim I exploits a mouse model in which mammary- specific CRD-BP expression is induced by doxycycline (dox), a tetracycline analog. Mammary tumors are expected to arise in dox-treated mice. Aim I then asks: Do these tumors stop growing or regress when dox is withdrawn? Our working hypothesis is that tumors will regress when CRD-BP expression is repressed. Aim II. Use microarray analysis to compare gene expression profiles in non-neoplastic mammary tissues and in purified mammary epithelial cells of mice that do or do not express the CRD-BP. Some CRD- BP-regulated RNAs could play central roles in the induction and maintenance of mammary tumors. Aim III. Determine how genetic and environmental factors contribute to mammary tumorigenesis in CRD-BP-expressing mice. The goal is to assess how the tumor suppressor Ape and the chemical carcinogen N-ethyl-N-nitrosurea (ENU) affect CRD-BP-mediated tumor formation. We predict Ape deficiency and ENU treatment will synergize with the CRD-BP to increase tumor incidence and malignancy. Many of the well-studied oncoproteins are transcription factors or protein kinases. The CRD-BP is an unusual oncoprotein, because it resides in the cytoplasm and binds to RNA. By investigating the oncogenic properties of the CRD-BP, the RNAs it affects in vivo, and its interactions with tumor-inducing genetic and environmental factors, we hope to uncover novel tumorigenesis pathways. REVISED: October 27, 2005 (see Revision Note)