Novel synthetic tools for mucin glycobiology

描述(申请人提供)：细胞表面糖基化异常已成为癌症的新标志。粘蛋白1的短糖形式表达增加和密度改变是癌变和癌前病变中常见的改变。尽管O-连接的N-乙酰半乳糖胺(TN)、唾液酸封盖的TN(STN)的功能尚不清楚，但汤姆森-弗里登瑞克(Tf)抗原已被证明积极参与肿瘤转移，通过与内源性�-半乳糖苷特异性凝集素Galectin-3(GAL-3)结合促进几个关键的细胞间相互作用。反过来，GAL-3促进癌细胞的侵袭和转移。由于Tf抗原和GAL-3之间的相互作用可能是异型癌-血管内皮细胞黏附和血管内转移沉积形成的重要早期步骤，在分子水平上彻底了解这一过程对于将其用于生物医学应用至关重要。我们推测，葡聚糖提呈和O-连接的葡聚糖密度模式对GAL-3识别肿瘤相关MUC1的Tf抗原有重要影响。我们最近的突破性发现表明，天然多肽支架呈现的葡聚糖配体与GAL-3结合高度相关，并为设计GAL-3抑制剂的变构靶向提供了机会。在这项提议中，我们将准备一个MUC1衍生的糖肽位置扫描组合文库，展示天然的、不同的和异常的肿瘤相关O-糖链表位(目标1)。合成的糖肽库将使用基于AlphaScreen技术的新型珠基邻近分析来筛选GAL-3结合。已确定的单个糖肽与GAL-3和一组Galectins(GAL-1、GAL-4、GAL-7和GAL-3CRD结构域)的结合亲和力和选择性将由ITC确定，并将在更具生理学相关性的环境中使用代表糖链天然复杂性的癌细胞系(目标2)。基于MUC1的糖肽对GAL-3显示出良好的效力和选择性，将被用来探索与肿瘤侵袭和转移相关的肿瘤细胞功能(目标3)。这些研究将通过确定MUC1-GAL-3相互作用在肿瘤进展和转移形成中的作用和特异性，为研究异常的MUC1糖基化的功能意义提供深入的见解。我们的长期目标是研究MUC1-GAL-3相互作用相对于其他参与识别和结合肿瘤相关形式的MUC1的凝集素样受体的特异性，评估MUC1/GAL-3相互作用的其他功能，如它们在免疫调节中的作用，并利用已确定的结构设计和开发具有理想药理学特征的基于小分子的选择性和有效的GAL-3抑制剂，用于新的抗癌治疗策略的临床前评估。

DESCRIPTION (provided by applicant): Aberrant cell surface glycosylation has emerged as a new hallmark of cancer. The increased expression and altered density of shorter glycoforms of mucin 1 (MUC1) are commonly observed changes in malignant and premalignant epithelia. Whereas the functional role of O-linked N-acetylgalactosamine (Tn), sialic acid capped Tn (sTn) remains unclear, Thomsen-Friedenreich (TF) antigen has been shown to be actively involved in tumor metastasis, promoting several key cell-cell interactions via association with the endogenous �- galactoside-specific lectin, galectin-3 (gal-3). In turn, gal-3 promotes cancer cell invasion and metastasis. Since the interaction between TF antigen and gal-3 potentially represents an important early step in heterotypic cancer-endothelial adhesion and the formation of intravascular metastatic deposits, a thorough understanding of this process at the molecular level is essential for it to be used for biomedical applications. We hypothesize that glycan presentation and the density patterns of O-linked glycans have a major impact on recognition of TF antigen of cancer-associated MUC1 by gal-3. Our recent breakthrough findings have shown that the presentation of the glycan ligand by the natural peptide scaffold is highly relevant for gal-3 binding and provides opportunities for allosteric site targeting in the design of gal-3 inhibitors. Within this proposal, we will prepare a MUC1-derived glycopeptide positional scanning combinatorial library displaying native-like heterogeneous and aberrant tumor-associated O-glycan epitopes (Aim 1). Synthesized glycopeptide libraries will be screened for gal-3 binding using a novel bead-based proximity assay based on AlphaScreen technology. The binding affinities and selectivity of the identified individual glycopeptides for gal-3 and a panelof galectins (gal-1, gal-4, gal-7, and gal-3 CRD domain) will be determined by ITC and in a more physiologically relevant setting, using cancer cell lines representing the natural complexity of glycan chains (Aim 2). MUC1-based glycopeptides that show good potency and selectivity for gal-3 will be probed for tumor cell functions relevant to tumor invasion and metastasis (Aim 3). These studies will provide insights into the functional significance of the aberrant MUC1 glycosylation by defining the role and specificity of MUC1-gal-3 interactions in cancer progression and metastasis formation. Our long-term goals are to study the specificity of MUC1-gal-3 interactions in relation to other lectin-like receptors involved in recognition and binding o tumor- associated forms of MUC1, assess other functions of MUC1/gal-3 interactions such as their role in immune modulation, and to use identified structures in design and development of small molecule-based selective and potent gal-3 inhibitors with desirable pharmacological profiles for preclinical evaluation of a novel anti-cancer therapeutic strategy.