Mechanism of tumor metastases suppression by Drg1

描述（由申请人提供）：前列腺癌是美国男性中最常诊断的癌症，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，目前的医疗技术都没有“治愈”转移性疾病，并且已经获得转移性前列腺癌的患者的生存机会很低。因此，迫切需要开发一种针对转移性肿瘤细胞的靶向特异性治疗的新方法，这需要更全面地了解转移的分子机制。我们最近发现Drg 1在前列腺癌中作为肿瘤转移抑制因子。来自临床数据和体外以及动物实验结果的充分证据压倒性地支持Drg 1是转移抑制基因并且该基因的下调导致肿瘤转移加速的概念。最关键的问题是Drg 1如何抑制肿瘤转移。我们在研究这个问题中的关键发现是四个方面：（i）与Wnt受体LRP 6相互作用，（ii）激活Wnt抑制因子GSK 3 β，（iii）抑制Akt活性，（iv）下调转移启动子ATF 3的表达，和（v）通过ATF 3下调上调转移抑制基因KAI 1的表达。因此，我们建议验证我们的假设，即Drg 1与LRP 6相互作用，通过酪氨酸磷酸化激活GSK 30，并使Akt去磷酸化，共同导致Wnt途径阻断（假设1），Wnt途径的失活抑制了转移促进基因ATF 3的表达，随后下调KAI 1（假设2）。特异性目的1旨在检测Drg-1是否通过与LRP 6相互作用和随后的GSK 3阻断Wnt通路来抑制肿瘤细胞侵袭？体外活化。具体目标2的目的是阐明Drg 1和LRP 6之间的相互作用如何导致动物模型中的转移抑制。在具体目标3中，我们将检查来自前列腺癌患者的临床标本中Wnt信号分子和Drg 1的表达状况。具体目的4的目的是检查Drg 1是否通过Wnt途径在体外和体内控制KAI 1表达。我们的长期目标是阐明Drg-1基因在肿瘤进展中抑制功能的分子机制，并建立Drg-1通路对前列腺癌的诊断/预后价值。我们相信，所提出的实验的结果将提供基本的信息，以实现我们的最终目标，控制癌症患者的肿瘤转移。

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.