Regulation of Snail in breast cancer progression and metastasis

描述（由申请人提供）：大约90%的乳腺癌死亡是由转移引起的，转移性乳腺癌患者的中位生存时间约为2年。因此，了解乳腺癌转移发生和发展的机制对预防和治疗乳腺癌具有重要意义。我们的长期目标是通过了解乳腺癌转移初始阶段的分子机制来降低乳腺癌转移的发生率。作为上皮-间质转化（epithelial-mesenchymal transition， EMT）的主开关和转移的第一步，蜗牛在转移的发生和发展中起着关键作用。Snail的过表达与乳腺癌的肿瘤分级和淋巴结转移有关，但其机制尚不清楚。我们最近证明蜗牛的活性主要受其蛋白质稳定性和细胞位置的调节。使用无偏方法-串联阵列纯化（TAP）结合质谱分析，我们确定了蜗牛与EPLINb（肿瘤中上皮蛋白丢失）的相互作用。我们发现在乳腺癌细胞系和转移性乳腺癌标本中，EPLINP的下调与Snail的上调相关。我们进一步证明了EPLINb的表达诱导了蜗牛的降解，并减轻了蜗牛介导的E-cadherin启动子的抑制。我们提出的中心假设是EPLINb作为蜗牛的负调节因子，在乳腺癌中EPLINb的缺失诱导蜗牛的稳定和核定位，从而引发乳腺癌的进展和转移。本课题旨在通过EPLINb解读Snail在乳腺癌中的功能调控，并探讨EPLINb和Snail作为乳腺癌转移标志物的预后价值。在强有力的初步数据的指导下，我们将通过追求三个具体目标来检验这一假设：(1)描绘蜗牛和EPLINb的关联所需的区域；(2)确定EPLINb的缺失是否增强了螺的稳定化；(3)明确Snail和EPLINb在小鼠和人乳腺癌中的功能调控。我们的建议具有创新性，对公共卫生具有重要意义，因为从本研究中获得的知识将扩大对转移的开始和进展的理解，并为预防和治疗乳腺癌的新干预措施带来巨大希望。

DESCRIPTION (provided by applicant): Approximately 90% of breast cancer deaths are caused by metastasis, and the median survival time for patients with metastatic breast cancer is approximately 2 years. Therefore, an understanding of the mechanisms at work in the initiation and progression of metastasis is important for prevention and treatment of breast cancer. Our long-term goal is to reduce the incidence of breast cancer metastasis by gaining an understanding of the molecular mechanism underlying the initial step of breast cancer metastasis. As the master switch for epithelial-mesenchymal transition (EMT) and the initial step of metastasis, Snail plays a critical role in the initiation and progression of metastasis. Overexpression of Snail correlates with tumor grade and nodal metastasis of breast cancer, but the mechanism remains unclear. We recently demonstrated that the activity of Snail is regulated mainly by its protein stability and cellular location. Using an unbiased approach-tandem array purification (TAP) coupled with mass spectrometry analysis, we identified the interaction of Snail with EPLINb (Epithelial Protein Lost in Neoplasm). We found that downregulation of EPLINP correlated with the upregulation of Snail in breast cancer cell lines and metastatic breast cancer specimens. We further demonstrated that expression of EPLINb induces degradation of Snail and relieves suppression of the E-cadherin promoter mediated by Snail. The central hypothesis of our proposal is that EPLINb functions as a negative regulator for Snail and that loss of EPLINb in breast cancer induces the stabilization and nuclear localization of Snail, thus triggering breast cancer progression and metastasis. The objective of this proposal is to decipher the functional regulation of Snail by EPLINb in breast cancer and explore the prognostic value of EPLINb and Snail as markers of metastasis in breast cancer. Guided by strong preliminary data, we will test this hypothesis by pursuing three specific aims: (1) to delineate the regions on Snail and EPLINb required for their association; (2) to determine whether the loss of EPLINb enhances the stabilization of Snail; and (3) to define the functional regulation of Snail and EPLINb in mouse and human breast cancer. Our proposal is innovative and significant to public health because knowledge gained from this study will expand the understanding of the initiation and progression of metastasis and holds great promise for novel interventions for preventing and treating breast cancer.