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

描述（由申请人提供）：口腔癌是最致命的癌症之一，诊断后只有5年的预测生存。我们的研究建议通过关注人类口腔癌细胞中细胞间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 -钙粘蛋白介导的细胞-细胞接触形成中的作用。e -钙粘蛋白是口腔上皮细胞中主要的细胞-细胞粘附受体，具有肿瘤抑制作用。虽然n -聚糖结构的变化早已被认为是肿瘤形成和转移的必然结果，但关于这些结构如何影响e -钙粘蛋白粘附功能的信息尚不清楚。e -钙粘蛋白外结构域在形成同型细胞-细胞接触中起作用，具有几个潜在的n -聚糖添加位点，而细胞质尾部结合连环蛋白，提供与肌动蛋白细胞骨架的连接。我们已经证明，在细胞增殖和迁移过程中，e -钙粘蛋白被广泛地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 -钙粘蛋白几乎没有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物中。我们在体内和离体的初步研究表明，分化的唾液细胞中E-cadherin n-糖基化的不适当增加逆转了E-cadherin介导的细胞-细胞接触从稳定到弱。重要的是，许多癌细胞具有高度n -糖基化的e -钙粘蛋白，这种蛋白存在于弱细胞-细胞接触中。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。我们提出从四个方面验证这一假设：1)证明高度n -糖基化的e -钙粘蛋白是口腔癌细胞系的特征；2)高水平的E-cadherin n-糖基化驱动不稳定的E-cadherin介导的细胞-细胞接触的形成；3)确定E-cadherin n -糖基化状态影响口腔癌细胞增殖和存活的信号事件；4)表明E-cadherin的n -糖基化状态在体内调节其在SCID小鼠体内的肿瘤抑制活性。我们提出的研究将增加对e -钙粘蛋白在口腔癌中肿瘤抑制活性基础的理解，并将为开发新的治疗策略奠定基础。

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.