中文摘要：

研究表明在恶性肿瘤细胞中常见有N-糖链的异常增多。N-乙酰氨基葡萄糖转移酶Ⅱ（N-acetylglucosaminyltransferase Ⅱ,GnT-Ⅱ）是合成复合型N-糖链的关键酶,但对肿瘤细胞功能的影响尚未有报道。为了研究GnT-Ⅱ在肿瘤发生发展中的作用及其机制,采用反转录PCR（reverse transcription-PCR,RT-PCR）的方法检测了组织来源相同而恶性程度不同的小鼠乳腺癌细胞株中GnT-Ⅱ的mRNA表达水平,发现在恶性程度高的4T1细胞中GnT-Ⅱ的mRNA表达水平比恶性程度低的67NR细胞高1.53倍。以4T1细胞的cDNA为模板,PCR克隆得到GnT-Ⅱ基因,构建其表达载体pMSCV-GnT-Ⅱ,转染4T1细胞获得GnT-II过表达细胞株,并检测其增殖能力、与纤粘连蛋白的粘附能力和迁移能力。研究发现在4T1细胞中过表达GnT-Ⅱ后,细胞粘附能力降低67%,迁移能力增加82%。结果表明,GnT-Ⅱ可能在肿瘤转移过程中发挥重要作用,为研究糖链在肿瘤发生发展中的作用提供了新的靶点。

英文摘要：

It is well documented that altered biosynthesis of cell surface N-linked oligosaccharides is associated with the transformed cells and tumors. N-acetylglucosaminyltransferase Ⅱ （ GnT-Ⅱ; EC 2.4.1. 143 ） is a medial Golgi enzyme that catalyses the incorporation of a GlcNAc residue in β-1,2 linkage to the Man-α-1,6 arm of the N-glycan core. This is an essential step in the biosynthetic pathway leading from hybrid to complex N- glycans. Because functional GnT-Ⅱ is an prerequisite of N-Acetylglucosaminyltransferase Ⅴ performance, It was speculated that GnT-Ⅱ was involved in cancer development and progression. The expression of GnT-Ⅱ in mouse breast cancer cells 67NR and 4T1 which have different behavior of metastasis was analysed using RT-PCR. The amounts of GnT-Ⅱ in the highly metastatic cell 4T1 increased to 1.53 times of the lowly metastatic cell 67NR. To determine the association of GnT-Ⅱ with tumor progression, the GnT-Ⅱ encoding gene was amplified with RT-PCR and cloned into retrovirus vector pMSCV, resulting in pMSCV-GnT-Ⅱ. The recombinant plasmid was transfected into 4T1 and the transfected cells were selected in the medium containing puromycin, which were harvested to detect the adhesion ability to fibronection and the migration potential by transwell system. The cell adhesion to fibronectin was weakened by 67% and migration potential was increased by 82%. The data indicates that GnT-Ⅱ mediates cell adhesion and migration, thus may play an important role in cancer metastasis.