Noda K, Miyoshi E, Uozumi N, Yanagidani S, Ikeda Y, Gao C, Suzuki K, Yoshihara H, Yoshikawa K, Kawano K, Hayashi N, Hori M, Taniguchi N
Department of Biochemistry, Osaka University Medical School, Japan.
Hepatology. 1998 Oct;28(4):944-52. doi: 10.1002/hep.510280408.
The 1-6 fucosylated -fetoprotein (AFP) present in serum of patients with hepatocellular carcinoma (HCC) has been employed for the differential clinical diagnosis of HCC from chronic liver diseases. The molecular mechanism by which this alteration occurs, however, remains largely unknown. To address this issue, we purified GDP-L-Fuc:N-acetyl-beta-D-glucosaminide 1-6 fucosyltransferase (1-6 FucT), an enzyme involved in the 1-6 fucosylation of N-glycans from porcine brain, as well as from a human gastric cancer cell line, and cloned their genes. In this study, levels of 1-6 FucT mRNA expression and the activity of this enzyme for 12 human HCC tissues were examined and compared with that in surrounding tissues and normal livers. The mean +/- SD for 1-6 FucT activity was 78 +/- 41 pmol/h/mg in normal control liver, 202 +/- 127 pmol/h/mg in adjacent uninvolved liver tissues (chronic hepatitis: 181 +/- 106 pmol/h/mg; liver cirrhosis: 233 +/- 164 pmol/h/mg), and 195 +/- 72 pmol/h/mg in HCC tissues. The mRNA expression of 1-6 FucT was also enhanced in proportion to enzymatic activity except for a few cases, suggesting that 1-6 FucT expression is increased in chronic liver diseases, especially liver cirrhosis. Transfection of 1-6 FucT gene into cultured rat hepatocytes markedly increased 1-6 FucT activity and led to an increase in lens culinaris agglutinin (LCA) binding proteins in both cell lysates and condition media. When the 1-6 FucT gene was transfected into a human HCC cell line, Hep3B, which originally showed low levels of 1-6 FucT expression, 1-6-fucosylated AFP was dramatically increased in the condition media. Collectively, these results suggest that the enhancement of 1-6 FucT expression increased the fucosylation of several proteins, including AFP, and that the level of 1-6-fucosylated AFP in patients with HCC was in part caused by up-regulation of the 1-6 FucT gene expression.
肝细胞癌（HCC）患者血清中存在的1-6岩藻糖基化甲胎蛋白（AFP）已被用于HCC与慢性肝病的鉴别临床诊断。然而，这种改变发生的分子机制在很大程度上仍然未知。为了解决这个问题，我们从猪脑以及人胃癌细胞系中纯化了GDP-L-岩藻糖：N-乙酰-β-D-氨基葡萄糖1-6岩藻糖基转移酶（1-6 FucT），它是一种参与N-聚糖1-6岩藻糖基化的酶，并克隆了它们的基因。在本研究中，检测了12个人类HCC组织中1-6 FucT mRNA表达水平和该酶的活性，并与周围组织和正常肝脏中的水平进行比较。正常对照肝脏中1-6 FucT活性的平均值±标准差为78±41 pmol/h/mg，相邻未受累肝脏组织中为202±127 pmol/h/mg（慢性肝炎：181±106 pmol/h/mg；肝硬化：233±164 pmol/h/mg），HCC组织中为195±72 pmol/h/mg。除少数情况外，1-6 FucT的mRNA表达也与酶活性成比例增强，这表明1-6 FucT表达在慢性肝病尤其是肝硬化中增加。将1-6 FucT基因转染到培养的大鼠肝细胞中显著增加了1-6 FucT活性，并导致细胞裂解物和条件培养基中扁豆凝集素（LCA）结合蛋白增加。当将1-6 FucT基因转染到最初显示1-6 FucT表达水平较低的人HCC细胞系Hep3B中时，条件培养基中1-6-岩藻糖基化AFP显著增加。总体而言，这些结果表明1-6 FucT表达的增强增加了包括AFP在内的几种蛋白质的岩藻糖基化，并且HCC患者中1-6-岩藻糖基化AFP的水平部分是由1-6 FucT基因表达上调引起的。
