State Key Laboratory of Proteomics, Beijing Proteome Research Center, Beijing Institute of Radiation Medicine, Beijing, People's Republic of China.
Glycoconj J. 2012 Aug;29(5-6):411-24. doi: 10.1007/s10719-012-9420-3. Epub 2012 Jul 1.
Cell surface glycoproteins are one of the most frequently observed phenomena correlated with malignant growth. Hepatocellular carcinoma (HCC) is one of the most malignant tumors in the world. The majority of hepatocellular carcinoma cell surface proteins are modified by glycosylation in the process of tumor invasion and metastasis. Therefore, characterization of cell surface glycoproteins can provide important information for diagnosis and treatment of liver cancer, and also represent a promising source of potential diagnostic biomarkers and therapeutic targets for hepatocellular carcinoma. However, cell surface glycoproteins of HCC have been seldom identified by proteomics approaches because of their hydrophobic nature, poor solubility, and low abundance. The recently developed cell surface-capturing (CSC) technique was an approach specifically targeted at membrane glycoproteins involving the affinity capture of membrane glycoproteins using glycan biotinylation labeling on intact cell surfaces. To characterize the cell surface glycoproteome and probe the mechanism of tumor invasion and metastasis of HCC, we have modified and evaluated the cell surface-capturing strategy, and applied it for surface glycoproteomic analysis of hepatocellular carcinoma cells. In total, 119 glycosylation sites on 116 unique glycopeptides were identified, corresponding to 79 different protein species. Of these, 65 (54.6%) new predicted glycosylation sites were identified that had not previously been determined experimentally. Among the identified glycoproteins, 82% were classified as membrane proteins by a database search, 68% had transmembrane domains (TMDs), and 24% were predicted to contain 2-13 TMDs. Moreover, a total of 26 CD antigens with 50 glycopeptides were detected in the membrane glycoproteins of hepatocellular carcinoma cells, comprising 43% of the total glycopeptides identified. Many of these identified glycoproteins are associated with cancer such as CD44, CD147 and EGFR. This is a systematic characterization of cell surface glycoproteins of HCC. The membrane glycoproteins identified in this study provide very useful information for probing the mechanism of liver cancer invasion and metastasis.
细胞表面糖蛋白是与恶性生长最相关的现象之一。肝细胞癌（HCC）是世界上最恶性的肿瘤之一。在肿瘤侵袭和转移过程中，大多数肝癌细胞表面蛋白通过糖基化修饰。因此，细胞表面糖蛋白的特征可以为肝癌的诊断和治疗提供重要信息，也是肝癌潜在诊断生物标志物和治疗靶点的有希望的来源。然而，由于其疏水性、低溶解度和低丰度，细胞表面糖蛋白的 HCC 很少通过蛋白质组学方法鉴定。最近开发的细胞表面捕获（CSC）技术是一种专门针对膜糖蛋白的方法，涉及使用完整细胞表面上的聚糖生物素化标记对膜糖蛋白进行亲和捕获。为了描述细胞表面糖蛋白质组并探讨 HCC 肿瘤侵袭和转移的机制，我们对细胞表面捕获策略进行了改进和评估，并将其应用于肝癌细胞的表面糖蛋白质组学分析。总共鉴定了 116 种独特糖肽上的 119 个糖基化位点，对应于 79 种不同的蛋白质。其中，65 个（54.6%）新预测的糖基化位点是以前未通过实验确定的。在鉴定的糖蛋白中，通过数据库搜索将 82%分类为膜蛋白，68%具有跨膜结构域（TMD），24%预测含有 2-13 个 TMD。此外，在肝癌细胞的膜糖蛋白中检测到总共 26 个 CD 抗原，带有 50 个糖肽，占鉴定的总糖肽的 43%。这些鉴定的糖蛋白中有许多与癌症有关，如 CD44、CD147 和 EGFR。这是对 HCC 细胞表面糖蛋白的系统描述。本研究中鉴定的膜糖蛋白为探讨肝癌侵袭和转移的机制提供了非常有用的信息。
