Loss of Nkx3.1-an Initiating Event in Prostate Cancer

描述（由申请人提供）：前列腺癌是男性中最常见的非皮肤癌，也是美国癌症死亡的第二大原因。与大多数人类癌症一样，前列腺肿瘤的发生需要多种遗传病变的连续积累。肿瘤发生的多步骤性已被广泛接受，但对导致癌前病变的起始步骤知之甚少。肿瘤抑制基因座的单倍不足是肿瘤发生的一个潜在的中心机制。在前列腺中，肿瘤的发生通常与NKX3.1基因座的杂合性缺失有关。在小鼠中，编码同源结构域蛋白的Nkx3.1的单倍体丢失足以引起前列腺上皮增生和最终PIN形成。在Myc过表达和Pten功能丧失的前列腺癌小鼠模型中，Nkx3.1表达在肿瘤发生的早期阶段丢失。我们的中心假设是NKXS.1在前列腺中起着“守门人”的作用，它的丢失是前列腺癌的主要起始事件。为了验证这一假设，我们计划在几种小鼠模型中研究NKX3.1在前列腺中的过表达是否可以预防前列腺癌的发展。我们还将尝试鉴定NKX3.1的效应子，这些效应子将提供NKX3.1与异常增殖之间的联系。对于这项研究，我们将通过一系列分析，包括表达谱，比较基因组分析，染色质免疫沉淀和报告基因测定，确定直接由NKX3.1调控的基因。最后，我们将确定NkxS.1缺失对前列腺上皮细胞增殖的影响是否通过mTOR激活的改变介导。我们还将尝试使用mTOR抑制剂预防Nkx3.1缺陷小鼠的增生。对于这些研究，我们将利用多种技术的组合，包括计算技术、慢病毒介导的过表达和使用siRNA的敲低、诱变以及在体外和使用转基因小鼠进行的功能测定。

DESCRIPTION (provided by applicant): Prostate cancer is the most common non-skin cancer in men and the second-leading cause of death from cancer in the US. As with most human cancers, prostate tumorigenesis requires the sequential accumulation of multiple genetic lesions. The multistep nature of tumorigenesis is widely accepted; however little is known about the initiation steps that lead to pre-malignant alterations. Haploinsufficiency at tumor suppressor loci presents a potential central mechanism for tumor initiation. In the prostate, tumor initiation is often linked to loss-of-heterozygosity at the NKX3.1 locus. In mice, haploid loss ofNkx3.1, which encodes a homeodomain protein, is sufficient to cause prostate epithelial hyperplasia and eventual PIN formation. In both the Myc overexpression and Pten loss-of-function mouse models of prostate cancer, Nkx3.1 expression is lost in the early stages of tumorigenesis. Our central hypothesis is that NKXS.1 serves a 'gatekeeper' function in the prostate and that its loss is a major initiating event in prostate cancer. To test this hypothesis, we plan to investigate whether overexpression of NKX3.1 in the prostate can prevent the development of prostate cancer in several mouse models. We will also attempt to identify effectors of NKX3.1 that would provide a link between it and abnormal proliferation. For this search, we will identify genes that are directly regulated by NKX3.1 through a series of analyses including expression profiling, comparative genomic analysis chromatin immunoprecipitation and reporter gene assays. Finally, we will determine whether the effects of NkxS.1 loss on prostate epithelial cell proliferation are mediated through alterations in mTOR activation. We will also attempt to prevent hyperplasia in Nkx3.1 -deficient mice using mTOR inhibitors. For these studies, we will utilize a combination of techniques, including computational techniques, lentivirus mediated overexpression and knockdown using siRNA, mutagenesis, and functional assays conducted in vitro and using transgenic mice.