PROX1调控β-catenin在乳腺癌淋巴转移中的作用和机制研究

The mechanism of breast cancer (BRCa) is one of the hottest areas of cancer research in females, and the most common way for BRCa metastasis is via lymph nodes. Currently, epithelial mesenchymal transition (EMT) is the main theory for BRCa metastasis, but it still has limitations to illustrate why BRCa has preference to metastasis by lymph nodes. By analyzing international standard database（TCGA and GEO）, our clinic samples and molecular results, our study has successfully confirmed that PROX1 can specifically regulate the β-catenin/（ZEB1、ZEB2） and maintain mesenchymal properties. Therefore, we propose a hypothesis that "The expression of PROX1, a protein which involved in both lymphatic and cancer development, determines the EMT of BRCa and specificity of lymph nodes metastases as an upstream driver". This project will analyze roles of PROX1 in the regulation of β-catenin/（ZEB1、ZEB2） signaling during the EMT, lymphatic metastasis and chemoresistance in BRCa based on different PROX1-expressing cell models, the orthotopic animal models and clinical tissue samples. The study will clarify the novel mechanism contributing to the malignant progression of BRCa .

乳腺癌是女性肿瘤研究的热点领域之一，其最常见的转移方式为淋巴结转移。目前，上皮间质转化（EMT）是乳腺癌转移的公认学说，但并不能阐述其淋巴转移的“偏好”。我们的前期研究通过对国际通用临床数据库（TCGA和GEO）的大量数据分析和对患者肿瘤标本的检测，在分子基础上初步观察到PROX1分子可能特异性调控其下游β-catenin/（ZEB1、ZEB2）通路并维系乳腺癌细胞间质化特性。在此基础上，我们大胆提出“横跨淋巴管发育和癌症两大领域的PROX1基因的表达，是决定乳腺癌的EMT及其特异性淋巴转移的驱动因素”。本项目将以不同表达PROX1的细胞模型、SCID鼠原位瘤模型、临床组织标本为研究对象，分析PROX1调控β-catenin/（ZEB1、ZEB2）信号变化对乳腺癌上皮间质转化、淋巴转移及化疗耐药的影响，阐明对乳腺癌恶性进展调控的新机制。

目前乳腺癌临床治疗所面临的主要挑战是易复发和转移。有证据显示，乳腺癌复发、转移与EMT密切相关。课题组在前期研究中发现，PROX1可预示疾病的不良预后，其高表达与乳腺癌的侵袭转移能力呈现正相关，并伴随着核定位β-catenin的明显升高。因此我们提出假说：PROX1可通过WNT信号通路调控乳腺癌EMT，进而影响乳腺癌的恶性生物学行为。基于乳腺癌慢病毒转染并成功分选稳定干预PROX1细胞株的构建，我们对比观察了各细胞亚群，发现PROX1能够在体内外促进乳腺癌细胞EMT；利用RNA-seq和western等技术，筛选出WNT信号通路为PROX1的重要下游靶点，进一步通过免疫荧光、核浆分离等技术，证实PROX1能够上调GSK3β磷酸化，促进β-catenin磷酸化，进而抑制下游E-cadherin和激活下游vimentin，ZBE1等蛋白，起到促进乳腺癌发生发展的作用，我们的研究结果丰富了乳腺癌发生发展的机制，为乳腺癌的治疗提供了新的靶点和理论依据。