Functional Role of Metadherin Subcellular Localization in Breast Cancer

描述（由申请人提供）：拟议的研究旨在增加对转移的分子理解-转移是导致大多数癌症相关死亡和发病率的过程。我们实验室最近的工作确定了Metadherin （MTDH）基因是预后不良乳腺癌复发性基因组扩增的靶标。我们确定MTDH是一种双功能基因，它通过介导癌细胞粘附到肺内皮来促进转移，同时促进化疗耐药的增加。因此，MTDH是临床医生非常感兴趣的潜在的极好的药物靶点；然而，mtdh介导的转移和化疗耐药的分子机制必须首先被揭示。该研究将利用体外生物化学、体内癌症进展模型和广泛的人类乳腺癌组织样本临床相关性分析相结合的方法，对MTDH功能进行严格的机制分析。总体目标是确定在哪些细胞区室中以及与哪些相互作用的伙伴MTDH促进其多种表型。作为第一步，我将使用免疫荧光和免疫印迹分析来研究内源性MTDH在早期和晚期乳腺癌细胞系以及大规模临床乳腺癌样本中的定位。我还将研究MTDH定位的功能作用，通过评估其在化疗药物治疗前后以及是否附着在肺内皮细胞上的亚细胞定位。其次，我将通过研究在相关细胞系中表达具有核通路阻断的MTDH变体的表型后果来确定核定位MTDH的作用。核阻断MTDH的功能将通过一系列体外和体内化疗耐药、粘附和转移试验来评估。最后，我将使用分离的癌细胞样本进行gst下拉和共免疫沉淀实验，以确定MTDH在不同细胞区室中与之相互作用的蛋白质。然后，我将通过用shRNA敲除它们并通过上述功能分析测试后续效果来测试这些相互作用伙伴的功能意义。公共卫生相关性：转移是癌症进展中最致命但最不为人所知的方面。临床癌症治疗的改善依赖于对转移的分子理解的进展。通过研究Metadherin基因促进化疗耐药、转移性乳腺癌的分子机制，我的目标是为基础生物医学研究转化为拯救生命的临床治疗提供支持。

DESCRIPTION (provided by applicant): The proposed research aims to increase the molecular understanding of metastasis - a process that accounts for most of cancer-related death and morbidity. Recent work in our laboratory identified the gene Metadherin (MTDH) as the target of recurrent genomic amplification in poor prognosis breast cancer. We determined MTDH to be a dual-functional gene that enhances metastasis by mediating cancer cell adhesion to the lung endothelium while simultaneously promoting increased chemoresistance. As such, MTDH is potentially an excellent drug target of great interest to clinicians; however the molecular mechanisms underlying MTDH-mediated metastasis and chemoresistance must first be uncovered. The proposed study will initiate a rigorous mechanistic analysis of MTDH functionality using a combined approach that will utilize in vitro biochemistry, in vivo models of cancer progression, and extensive clinical correlation analyses with human breast cancer tissue samples. The overarching goal is to determine in what cellular compartments and with which interacting partners MTDH promotes its multiple phenotypes. As a first step, I will use immunofluorescence and immunoblotting analyses to investigate endogenous MTDH localization in early and late stage breast cancer cell lines and in a large-scale set of clinical breast cancer samples. I will also investigate the functional role of MTDH localization by assessing its subcellular localization before and after chemotherapeutic drug treatment and with or without attachment to lung endothelial cells. Secondly, I will determine the role of nuclear-localized MTDH by investigating the phenotypic consequences of expressing a variant of MTDH with blocked nuclear access in relevant cell lines. Functionality of nuclear-blocked MTDH will be assessed in a set in vitro and in vivo chemoresistance, adhesion, and metastasis assays. Finally, I will perform GST-pulldown and co-immunoprecipitation experiments using fractionated cancer cell samples to determine the proteins with which MTDH interacts in various cellular compartments. I will then test the functional significance of these interacting partners by knocking them down with shRNA and testing subsequent effects via the aforementioned functional assays. PUBLIC HEALTH RELEVANCE: Metastasis is the most deadly yet least understood aspect of cancer progression. Improvements in clinical cancer treatment rely on advances in the molecular understanding of metastasis. By studying the molecular mechanisms through which a gene called Metadherin promotes chemoresistant, metastatic breast cancer, I aim to provide support for the translation of basic biomedical research into clinical therapeutics that saves lives.