Role of menin in islet cell biology and tumorigenesis

描述(申请人提供)：多发性内分泌瘤，I型(MEN1)，是一种遗传性癌症，以多发性肿瘤为特征，主要累及内分泌腺。MEN1的基因是一种经典的肿瘤抑制基因，它编码一种名为Menin的核蛋白。受影响个体的肿瘤发生在野生型等位基因丢失后，遵循经典的肿瘤抑制模型。虽然一些相互作用的蛋白质已经为脑膜素提供了功能上的洞察，但目前还不清楚脑膜素的丢失是如何导致肿瘤形成的。我们最近开发了MEN1的小鼠模型。这些小鼠发展出一种内分泌肿瘤谱，忠实地概括了相应的人类状况，因此是追求与MEN1肿瘤抑制基因作用有关的三个目标的极佳资源。在特定的目标1中，我将确定MEN1基因敲除小鼠胰腺内分泌肿瘤中替代薄荷素的后果。这一目标将通过在可诱导启动子的控制下使用含有MEN1基因的转基因小鼠来实现。虽然有多项研究表明，一个或多个激活的癌基因的逆转可以导致肿瘤消退，但到目前为止，还没有人报道过重新表达缺失的抑癌基因在癌症中的后果。在特定的目标2中，1将深入了解MEN1基因的缺失是如何导致仅在特定组织中发生肿瘤的。MEN1是一种普遍表达的基因。为了做到这一点，我设计了肝脏薄荷素纯合缺失的小鼠，这是一种在MEN1中通常不容易发生肿瘤的组织。有趣的是，MEN1阴性的肝脏看起来完全正常，在整个成年期都没有肿瘤。为了深入了解MEN1中组织特异性肿瘤表型的悖论，我将比较来自肝脏的野生型和MEN1零表达谱与内分泌胰腺产生的表达谱，内分泌胰腺是MEN1中易发生肿瘤的组织。我推测，在MEN1缺失的肝脏和内分泌胰腺中显示表达差异的基因的识别将为MEN1的组织特异性提供重要线索。在特定的目标3，1将利用一种方法，结合染色质免疫沉淀和微阵列技术(ChlP-芯片)，以确定转录共同调节的基因，由薄荷素。重要的是，我提供了初步数据，其中包含18,000个基因启动子的微阵列被用于鉴定与薄荷素结合的&gt；50个启动子。这些结果不仅说明了这种方法的有效性和可行性，而且也为人类提供了新的机制洞察力。一种全面的方法来确定其他由薄荷素共同调节的基因，不仅将增加我们对薄荷素如何调控细胞增殖的理解，就像目标1中所研究的那样，而且还将通过提供关于MEN1中组织特异性肿瘤表型悖论的线索，很好地补充目标2。

DESCRIPTION (provided by applicant): Multiple endocrine neoplasia, type I (MEN1), is a form of inherited cancer characterized by multiple tumors primarily involving the endocrine glands. The gene for MEN1 is a classic tumor suppressor gene that encodes a nuclear protein called menin. Tumors in affected individuals occur after loss of the wild-type allele, following the classic tumor suppressor model. Although a number of interacting proteins have provided functional insights to menin, it is not clear how the loss of menin causes tumor formation. We recently developed mouse models for MEN1. These mice develop an endocrine tumor spectrum that faithfully recapitulates the corresponding human condition, and therefore are excellent resources to pursue three aims pertaining to the action of the Men1 tumor suppressor gene. In Specific Aim 1, I will determine the consequence of replacing menin in pancreatic endocrine tumors of Men1 knockout mice. This aim will be addressed using transgenic mice containing the Men1 gene under the control of an inducible promoter. Although there are several studies suggesting that the reversal of one or more activated oncogenes can cause tumor regression, so far no one has reported the consequences of re-expressing a deleted tumor suppressor gene in cancer. In Specific Aim 2,1 will gain insights into how the loss of MEN1, a ubiquitously expressed gene, gives rise to tumors only in a defined set of tissues. To do this, I have engineered mice that are homozygous null for menin in liver, a tissue not normally predisposed to developing tumors in MEN1. Interestingly, Men1-null livers appear entirely normal and remain tumor free throughout adulthood. To gain insights to the paradox of the tissue-specific tumor phenotype in MEN1, I will compare wild-type and Men1-null expression profiles from liver to those generated from endocrine pancreas, a tissue that is susceptible to developing tumors in MEN1. I hypothesize that the identification of genes that show expression differences in Men1-null livers and endocrine pancreas will provide vital clues to tissue specificity in MEN1. In Specific Aim 3,1 will take advantage of an approach that couples chromatin immunoprecipitation with microarray technology (ChlP-chip) to identify genes that are transcriptionally co-regulated by menin. Importantly, I present preliminary data in which microarrays containing >18,000 gene promoters were used to identify >50 promoters bound by menin. These results not only illustrate the power and feasibility of this approach, but also provide new mechanistic insights to menin. A comprehensive approach to identify additional genes that are co-regulated by menin will not only increase our understanding of how menin regulates cell proliferation, as studied in Aim 1, but will also nicely complement Aim 2 by providing clues to the paradox of tissue-specific tumor phenotype in MEN1.