Mechanism of tumor metastases suppression by Drg1

描述(申请人提供)：前列腺癌是美国男性中最常被诊断出的癌症，仅以微弱优势超过肺癌。一旦前列腺癌被诊断出来，最关键的问题是这种疾病是局部的，还是已经转移到身体的其他部位。不幸的是，目前的医学技术都没有“治愈”这种转移性疾病，已经获得转移性前列腺癌的患者的生存机会非常渺茫。因此，迫切需要开发一种新的靶向治疗转移肿瘤细胞的方法，这就需要更全面地了解转移的分子机制。我们最近发现，Drg1在前列腺癌中起着肿瘤转移抑制因子的作用。来自临床数据和体外及动物实验结果的大量证据压倒性地支持了Drg1是一种肿瘤转移抑制基因的观点，该基因的下调会加速肿瘤的转移。最关键的问题是Drg1是如何抑制肿瘤转移的。我们在研究这个问题上的主要发现有四个方面：(I)与Wnt受体LRP6相互作用，(Ii)激活Wnt抑制因子，GSK3(3)，(Iii)抑制Akt活性，(Iv)下调转移启动子ATF3的表达，以及(V)通过下调ATF3下调转移抑制基因KAI1的表达。因此，我们建议检验我们的假设，即Drg1与LRP6相互作用，通过酪氨酸磷酸化激活GSK30，并使Akt去磷酸化，从而共同导致Wnt途径的阻断(假设1)，并且这种Wnt途径的失活抑制了转移促进基因ATF3的表达，随后下调了KAI1的表达(假设2)。具体目的1旨在测试DRG-1是否通过与LRP6和GSK3相互作用而阻断Wnt途径来抑制肿瘤细胞的侵袭？体外激活。具体目的2的目的是阐明Drg1和LRP6之间的相互作用如何在动物模型中导致转移抑制。在具体目标3中，我们将检测Wnt信号分子和Drg1在前列腺癌患者临床标本中的表达状况。特异性目的4的目的是检测Drg1是否通过Wnt途径在体内外调控KAI1的表达。我们的长期目标是阐明DRG-1基因在肿瘤进展中抑制作用的分子机制，并建立DRG-1通路对前列腺癌的诊断/预后价值。我们相信，拟议的实验结果将为实现我们的最终目标--控制癌症患者的肿瘤转移--提供基础信息。

DESCRIPTION (provided by applicant): Prostate cancer is the most frequently diagnosed cancer among men in the United States, exceeding lung cancer by a narrow margin. Once prostate cancer is diagnosed, the most critical question is whether the disease is localized or it has already metastasized to other parts of the body. Unfortunately, none of the current medical technologies "cure" the metastatic disease, and the patients who have acquired metastatic prostate cancer have dismal chance of survival. Therefore, there is an urgent need for developing a novel approach of target-specific therapy to metastatic tumor cells, which requires more comprehensive understanding of the molecular mechanism of metastases. We have recently found that Drg1 acts as a tumor metastases suppressor in prostate cancer. Ample evidence from both clinical data and the results of in vitro as well as animal experiments overwhelmingly support the notion that Drg1 is a metastasis suppressor gene and that the down-regulation of the gene results in acceleration of tumor metastasis. The most crucial question is how Drg1 suppresses the tumor metastases. Our key discoveries in investigating this question are four folds: (i) interacts with Wnt receptor, LRP6, (ii) activates Wnt suppressor, GSK3(3, (iii) suppresses Akt activity, (iv) down-modulates the expression of the metastases promoter, ATF3, and (v) up-regulates the expression of the metastases suppressor gene KAI1 through ATF3 down-regulation. Therefore, we propose to test our hypothesis that Drg1 interacts with LRP6 leading to activation of GSK30 by tyrosine phosphorylation and also de-phosphorylates Akt which together results in blockade of the Wnt pathway (Hypothesis 1), and that this inactivation of the Wnt pathway suppresses the expression of the metastases promoting gene, ATF3, followed by down regulation of KAI1 (Hypothesis 2). Specific aim 1 is designed to test whether Drg-1 suppresses tumor cell invasion by blocking the Wnt pathway via interaction with LRP6 and following GSK3? activation in vitro. The purpose of the Specific aim 2 is to clarify how the interaction between Drg1 and LRP6 leads to metastasis suppression in animal models. In Specific aim 3, we will examine the status of expression of the Wnt signal molecules and Drg1 in clinical specimens from prostate cancer patients. The objective of Specific aim 4 is to examine whether Drg1 controls the KAI1 expression via Wnt pathway in vitro and in vivo. Our long-term goal is to elucidate the molecular mechanism of suppressor function of the Drg-1 gene in tumor progression and also to establish diagnostic/prognostic value of the Drg-1 pathway for prostate cancer. We believe that the results of the proposed experiments will provide fundamental information to accomplish our ultimate goal, the control of tumor metastasis in cancer patients.