Role of an RNA-Binding Protein in Mammary Carcinogenesis

本研究旨在探讨RNA结合癌蛋白在乳腺肿瘤发生中的作用。这 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。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。在胎儿组织中大量表达 但在出生后不久就受到抑制。因此，它可能在胎儿生命中有特殊的作用。三个发现也 将CRD-BP与乳腺癌联系起来：（a）CRD-BP在正常乳腺组织中无法检测到，但在 （B）CRD-BP基因在约30%的人乳腺肿瘤中扩增，（c）CRD-BP基因在约60%的人乳腺肿瘤中扩增，（d）CRD-BP基因在约30%的人乳腺肿瘤中扩增，（e）CRD-BP基因在约30%的人乳腺肿瘤中扩增。 CRD-BP在雌性转基因小鼠中诱导乳腺癌。三个目标使用转基因小鼠 探讨这种RNA结合癌蛋白诱导乳腺肿瘤的途径。 艾姆岛确定是否需要持续表达CRD-BP以维持现有乳腺癌 肿瘤转基因小鼠中的乳腺肿瘤继续表达CRD-BP，因此可能是CRD-BP- 依赖于他们的生存。为了研究这一想法，Aim 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。乳腺肿瘤是 预期在dox处理的小鼠中出现。目的我然后问：这些肿瘤停止生长或退化时， 撤回了吗我们的工作假设是，当CRD-BP表达受到抑制时，肿瘤会消退。 Aim II.应用基因芯片技术比较乳腺癌基因表达谱的差异 组织和纯化的小鼠乳腺上皮细胞中表达或不表达CRD-BP。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乳腺肿瘤的发生， CRD-BP表达小鼠。目的是评估肿瘤抑制因子猿和化学物质 致癌物N-乙基-N-亚硝基脲（ENU）影响CRD-BP介导的肿瘤形成。我们预测Apeficiency ENU治疗将与CRD-BP协同作用，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是一个 这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。通过研究致癌的 CRD-BP的性质，它在体内影响的RNA，以及它与肿瘤诱导遗传和 环境因素，我们希望发现新的肿瘤发生途径。

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, p-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 fetaltissues 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% of human breast tumors, (b) The CRD-BP gene is amplified in -30% 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 nori-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 Apedeficiency 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.