Chik Jenny H L, Zhou Jerry, Moh Edward S X, Christopherson Richard, Clarke Stephen J, Molloy Mark P, Packer Nicolle H
Department of Chemistry and Biomolecular Sciences, Faculty of Science, Macquarie University, Sydney, Australia.
School of Molecular Bioscience, University of Sydney, Sydney, Australia.
J Proteomics. 2014 Aug 28;108:146-62. doi: 10.1016/j.jprot.2014.05.002. Epub 2014 May 17.
Altered glycosylation is commonly observed in colorectal cancer. In vitro models are frequently used to study this cancer but little is known about the differences that may exist between these model cell systems and tumour tissue. We have compared the membrane protein glycosylation of five colorectal cancer cell lines (SW1116, SW480, SW620, SW837, LS174T) with epithelial cells from colorectal tumours using liquid chromatography tandem mass spectrometry. Remarkably, there were five abundant O-glycans in the tumour cells that were undetected in the low-mucin producing cell lines, although two were found in the mucinous LS174T cells. The O-glycans included the well-known glycan cancer marker, sialyl-Tn, which has been associated with mucins. Using qRT-PCR, sialyl-Tn expression was found to be associated with an increase in α2,6-sialyltransferase gene (ST6GALNAC1) and a decrease in core 1 synthase gene (C1GALT1) in LS174T cells. The expression of a subset of mucins (MUC2, MUC6, MUC5B) was also correlated with sialyl-Tn expression in LS174T cells. Overall, the membrane protein glycosylation of the model cell lines was found to differ from each other and from the epithelial cells of tumour tissue. These findings should be noted in the design of biomarker discovery experiments particularly when cell surface targets are being investigated.
The extent of protein glycosylation differences between in vitro cell lines and ex vivo tumours in colorectal cancer research is unknown. Our study expands current knowledge by characterising the membrane protein glycosylation profiles of five different colorectal cancer cell lines and of epithelial cells derived from resected colorectal cancer tumour tissue, using liquid chromatography tandem mass spectrometry. The detailed structural differences found in both N- and O-linked glycan structures on the membrane glycoproteins were determined and correlated with the mRNA expression of the relevant proteins in the cell lines. The glycosylation differences found between cultured cancer cell lines and epithelial cells from tumour tissue have important implications for glycan biomarker discovery.
糖基化改变在结直肠癌中普遍存在。体外模型常用于研究这种癌症，但对于这些模型细胞系统与肿瘤组织之间可能存在的差异知之甚少。我们使用液相色谱串联质谱法，比较了五种结直肠癌细胞系（SW1116、SW480、SW620、SW837、LS174T）与结直肠肿瘤上皮细胞的膜蛋白糖基化情况。值得注意的是，肿瘤细胞中有五种丰富的O-聚糖在低黏蛋白产生的细胞系中未被检测到，不过在黏液性的LS174T细胞中发现了其中两种。这些O-聚糖包括著名的聚糖癌症标志物唾液酸化-Tn，它与黏蛋白有关。使用qRT-PCR发现，在LS174T细胞中，唾液酸化-Tn的表达与α2,6-唾液酸转移酶基因（ST6GALNAC1）的增加以及核心1合酶基因（C1GALT1）的减少有关。黏蛋白子集（MUC2、MUC6、MUC5B）的表达在LS174T细胞中也与唾液酸化-Tn的表达相关。总体而言，发现模型细胞系的膜蛋白糖基化彼此不同，且与肿瘤组织的上皮细胞不同。在生物标志物发现实验的设计中应注意这些发现，特别是在研究细胞表面靶点时。
在结直肠癌研究中，体外细胞系与离体肿瘤之间蛋白质糖基化差异的程度尚不清楚。我们的研究通过使用液相色谱串联质谱法，对五种不同的结直肠癌细胞系以及来自切除的结直肠癌肿瘤组织的上皮细胞的膜蛋白糖基化谱进行表征，扩展了当前的知识。确定了膜糖蛋白上N-和O-连接聚糖结构中发现的详细结构差异，并与细胞系中相关蛋白质的mRNA表达相关联。培养的癌细胞系与肿瘤组织上皮细胞之间发现的糖基化差异对聚糖生物标志物的发现具有重要意义。
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