Role of Nmi in retarding breast tumor growth.

描述（由申请人提供）：我们实验室的研究重点是了解N-Myc相互作用因子（Nmi）在癌症生物学中的作用[1]。当我们看到它在侵袭性乳腺癌细胞系中的表达减少时，我们对这种分子的兴趣被激发了。有趣的是，虽然，Nmi的表达可以诱导在这些细胞中使用干扰素？(IFN-?) [1]的文件。我们发现诱导的mRNA具有野生型序列，这意味着诱导的Nmi蛋白能够具有正常的生物学活性。为了测试其功能作用，我们在人乳腺癌细胞系MDA-MB- 231中组成型表达Nmi。对表达子的功能研究表明，Nmi降低了肿瘤细胞在锚定非依赖性条件下侵袭和生长的能力。裸鼠异种移植研究表明，Nmi表达子在体内具有降低的肿瘤生长[1]。 对这些表达子的进一步分析显示，Dickkopf-1（Dkk 1），一种可溶性Wnt/？在表达Nmi的克隆中，连环蛋白信号通路显著上调，同时Wnt通路的关键转录辅因子？连环蛋白。Dkk 1已被报道抑制原发性肿瘤生长率在几项研究涉及乳腺癌[2，3]，是一个因素牵连的抗肿瘤作用引起的干扰素-？[4]的文件。Wnt/？-连环蛋白信号传导在发育以及细胞增殖中是重要的。虽然先前显示Wnt/β-CD在结肠癌进展中起关键作用，但Wnt/β-CD的作用仍有待进一步研究。乳腺癌中的连环蛋白信号传导尚未明确定义[5]。 这项拟议工作的总体目标是了解Wnt/？-通过Nmi的连环蛋白信号传导，并确定该途径在抑制乳腺肿瘤生长中的作用。 假设 抑制Wnt/β-通过上调Dkk 1调节连环蛋白信号通路对Nmi在减少肿瘤生长中的作用至关重要。 目的1：为了验证敲低Nmi表达将激活Wnt/β-SMA的假设，连环蛋白信号传导。 目的2：探讨Dkk 1和？Nmi的catenin。 目的3：探讨Dkk 1在Nmi抑制肿瘤生长中的作用。 目的4：确定Nmi表达缺失与活化的Wnt/β之间的相关性。患者来源的乳腺癌标本中的连环蛋白信号传导。 公共卫生相关性：我们的初步数据表明，Nmi在延缓乳腺肿瘤生长方面具有功能性作用。该提案将研究带到了下一个重要步骤，即建立Nmi的翻译潜力及其调节的下游事件。本研究的重点是Wnt/？-连环蛋白途径Nmi上调Wnt通路抑制因子Dkk 1，这使我们推测Nmi下调Wnt/？连环蛋白信号传导，导致乳腺癌恶性活动降低。

DESCRIPTION (provided by applicant): Research in our laboratory focuses on understanding the role of N-Myc interactor (Nmi) in cancer biology [1]. Our interest in this molecule was triggered when we saw that its expression was diminished in aggressive breast cancer cell lines. Interestingly though, Nmi expression could be induced in these cells using interferon-? (IFN-?) [1]. We found that the induced mRNA had a wild type sequence, implying that the induced Nmi protein was capable of its normal biological activities. To test its functional role, we constitutively expressed Nmi in the human breast cancer cell line, MDA-MB- 231. Functional studies of the expressors showed that Nmi reduced the ability of tumor cells to invade and grow under anchorage independent conditions. Xenograft studies in nude mice showed that Nmi expressors had reduced tumor growth in vivo [1]. Further analysis of these expressors revealed that Dickkopf-1 (Dkk1), a soluble inhibitor of the Wnt/?- catenin signaling pathway, was significantly upregulated in the Nmi expressing clones concurrent with reduced levels of the critical transcription co-factor of Wnt pathway, ?-catenin. Dkk1 has been reported to suppress primary tumor growth rates in several studies involving breast cancer [2, 3] and is a factor implicated in the anti-tumor effects elicited by IFN-? [4]. Wnt/?-catenin signaling is important in development as well as cell proliferation. While previously shown to be a critical player in colon cancer progression, the role of Wnt/?-catenin signaling in breast cancer is not clearly defined [5]. The overall objective of this proposed work is to understand the regulation of Wnt/?-catenin signaling by Nmi and to determine the role of this pathway in suppression of breast tumor growth. HYPOTHESIS Inhibition of the Wnt/?-catenin signaling pathway by upregulation of Dkk1 is critical to the role of Nmi in reducing tumor growth. Aim 1: To test the hypothesis that knockdown of Nmi expression will activate the Wnt/?-catenin signaling. Aim 2: To determine the mechanism of regulation of Dkk1 and ?-catenin by Nmi. Aim 3: To evaluate the role of Dkk1 in mediating the retardation of tumor growth by Nmi. Aim 4: To determine correlation between loss of Nmi expression and activated Wnt/?-catenin signaling in patient derived breast cancer specimens. PUBLIC HEALTH RELEVANCE: Our preliminary data demonstrates a functional role of Nmi in retarding breast tumor growth. This proposal takes the research to a next essential step in establishing the translational potential of Nmi and the downstream events that it regulates. The focus of this research is the Wnt/?-catenin pathway. Nmi up-regulates Dkk1, a secreted inhibitor of Wnt pathway, leading us to propose that Nmi down regulates Wnt/?-catenin signaling, resulting in reduced malignant activity of breast cancer.