The Role of E-cadherin N-glycans in Oral Cancer

描述(申请人提供)：口腔癌是最致命的癌症之一，确诊后预计只有5年的生存期。我们的研究建议通过关注人类口腔癌细胞中细胞-细胞接触的性质来阐明口腔癌的一些潜在原因。我们研究的长期目标是确定N-糖基化在口腔癌细胞中E-钙粘素介导的细胞-细胞接触形成中的作用。E-钙粘附素是口腔上皮细胞中主要的细胞-细胞黏附受体，具有肿瘤抑制作用。虽然N-糖链结构的改变早已被认为是肿瘤形成和转移的必然结果，但目前还没有关于这些结构如何影响E-钙粘附素黏附功能的信息。E-钙粘蛋白胞外结构域在同型细胞-细胞接触的形成中起作用，它有几个潜在的N-糖链加成位点，而胞浆尾巴与连接素结合，提供与肌动蛋白细胞骨架的联系。我们已经证明，在细胞增殖和迁移过程中，E-钙粘附素被广泛的N-糖基化，并存在于不稳定的细胞-细胞接触中。相反，在细胞分化的细胞中，E-钙粘附素几乎没有N-糖基化，并且存在于与肌动蛋白细胞骨架相关的稳定连接复合体中。我们在体内和体外的初步研究表明，在分化的唾液细胞中，E-钙粘素N-糖基化的不适当增加会使E-钙粘素介导的细胞-细胞接触从稳定变为微弱。重要的是，许多癌细胞具有高度N-糖基化的E-钙粘附素，存在于细胞与细胞之间的弱接触中。我们的假设是E-钙粘蛋白的N-糖基化状态调节其肿瘤抑制功能。我们建议从4个具体目标来验证这一假说：1)证明高N-糖基化的E-钙粘素是口腔癌细胞系的一个特征；2)证明高水平的E-钙粘素N-糖基化导致不稳定的E-钙粘素介导的细胞-细胞接触的形成；3)确定E-钙粘素的N-糖基化状态影响口腔癌细胞增殖和存活的信号事件；以及4)证明E-钙粘素的N-糖基化状态调节其在SCID小鼠体内的肿瘤抑制活性。我们提出的研究将增加对E-钙粘附素在口腔癌中肿瘤抑制活性的基础的理解，并将作为开发新的治疗策略的基础。

DESCRIPTION (provided by applicant): Oral cancer constitutes 1 of the most pernicious cancers with only a 5-year predicted survival following diagnosis. Our research proposes to elucidate some of the underlying causes of oral cancer by focusing on the nature of cell-cell contacts in human oral cancer cells. The long-term goal of our studies is to determine the role of N-glycosylation in the formation of E-cadherin-mediated cell-cell contacts in oral cancer cells. E-cadherin, with its documented role as a tumor suppressor, is the principal cell-cell adhesion receptor in oral epithelial cells. Although changes in N-glycan structures have long been known to be corollaries of tumor formation and metastasis, no information is available about how these structures affect E-cadherin adhesive function. E-cadherin ectodomains, which function in the formation of homotypic cell-cell contacts, have several potential N-glycan addition sites, while the cytosolic tail binds catenins that provide the linkage to the actin cytoskeleton. We have shown that during cell proliferation and migration, E-cadherin is extensively N-glycosylated and present in unstable cell-cell contacts. In contrast, in cytodifferentiated cells, E-cadherin is scarcely N-glycosylated and found in stable junctional complexes associated with the actin cytoskeleton. Our initial studies in vivo and ex vivo show that inappropriate increase in E-cadherin N-glycosylation in differentiated salivary cells reverses E-cadherin-mediated cell-cell contacts from stable to weak. Importantly, many cancer cells have highly N-glycosylated E-cadherin that is present in weak cell-cell contacts. Our hypothesis is that the N-glycosylation status of E- cadherin regulates its tumor suppressive function. We propose to test this hypothesis in 4 specific aims: 1) to demonstrate that highly N-glycosylated E-cadherin is a characteristic of oral cancer cell lines; 2) to show that high levels of E-cadherin N-glycosylation drive the formation of unstable E-cadherin-mediated cell-cell contacts; 3) to determine the signaling events through which N-glycosylation status of E-cadherin affects oral cancer cell proliferation and survival; and 4) to show that N-glycosylation status of E-cadherin regulates its tumor suppressive activity in SCID mice in vivo. Our proposed studies will increase the understanding of the basis of E-cadherin tumor suppressive activity in oral cancer and will serve as a basis for the development of novel treatment strategies.