Transgenic analysis of Smad tumor suppressor genes

描述（由申请人提供）： 转化生长因子-β（TGF-β）的Smad家族成员 信号转换器在多种组织中起肿瘤抑制剂的作用。 Smad 2或Smad 4的纯合突变在50%的胰腺中检测到，20%的胰腺中检测到。 结肠癌和10%的肺肿瘤。然而，TGF-β信号和靶基因 通常抑制这些组织中增殖的药物是未知的。作为 结果，Smad突变导致肿瘤的机制也是 未知由于缺乏这方面的资料，目前的假设是， 所有Smad肿瘤突变都是功能缺失突变，它们都导致 通过一种单一的机制作用于肿瘤。在具体目标1中，我们测试了 假设。我们将确定是否有任何Smad肿瘤等位基因是获得性的。 功能突变为此，我们将利用 Smad家族，同源家族成员跨 物种我们将表达从人类肿瘤中分离的Smad突变等位基因， 果蝇我们将比较Smad突变等位基因产生的表型， 我们最近发表的Smad野生型等位基因产生的表型。 我们的初步研究表明，假设的第一部分是错误的。 我们已经确定了Smad 4的功能突变的增益。在Aim Specific 2中，我们 将检验假设的第二部分。我们来指挥？机制 行动？筛选以鉴定参与Smad功能获得突变体的基因 表型。我们将分离出增强或抑制 功能表型，然后克隆负责基因。基本原理是 果蝇基因，增强Smad获得的功能表型可能有 在肿瘤发生中辅助Smad突变体的人类同源物和 抑制这些表型具有拮抗肿瘤形成同源物。 涉及不同表型的筛选可以识别不同的基因组 提示Smad突变体通过多种机制诱导肿瘤。本研究 将提供前所未有的洞察Smad突变等位基因和机制， 它们用来产生肿瘤。这些知识可以用来确定Smad是否 蛋白质应该被开发作为抗癌药物发现的目标。

DESCRIPTION (provided by applicant): Members of the Smad family of Transforming Growth Factor-beta (TGF-beta) signal transducers act as tumor suppressors in a variety of tissues. Homozygous mutations in Smad2 or Smad4 are detected in 50% of pancreas, 20% of colon and 10% of lung tumors. However, the TGF-beta signals and target genes that normally suppress proliferation in these tissues are unknown. As a result, the mechanism by which Smad mutations result in tumors is also unknown. In the absence of this information, the current hypothesis is that all Smad tumor mutations are loss of function mutations and that they all lead to tumors via a single mechanism. In Specific Aim 1 we test the first part of the hypothesis. We will determine if any Smad tumor alleles are gain of function mutations. To do this we will exploit a well- established feature of the Smad family, the ability of homologous family members to function across species. We will express Smad mutant alleles isolated from human tumors in Drosophila. We will compare phenotypes generated by the Smad mutant alleles to the phenotypes generated by Smad wild type alleles we have recently published. Our preliminary studies show that the first part of the hypothesis is false. We have identified a gain of function mutation in Smad4. In Specific Aim 2 we will test the second part of the hypothesis. We will conduct ?mechanism of action? screens to identify genes involved in Smad gain of function mutant phenotypes. We will isolate mutations that enhance or suppress the gain of function phenotype and then clone the responsible gene. The rationale is that Drosophila genes that enhance Smad gain of function phenotypes likely have human homologs that assist Smad mutants in tumorigenesis and genes that suppress these phenotypes have homologs that antagonize tumor formation. Screens involving different phenotypes may identify distinct sets of genes suggesting that Smad mutants induce tumors by multiple mechanisms. This study will provide unprecedented insight into Smad mutant alleles and the mechanisms they use to generate tumors. This knowledge can be used to determine if Smad proteins should be exploited as anti-cancer drug discovery targets.