Noda K, Miyoshi E, Kitada T, Nakahara S, Gao C-X, Honke K, Shiratori Y, Moriwaki H, Sasaki Y, Kasahara A, Hori M, Hayashi N, Taniguchi N
Department of Biochemistry, Division of Molecular Therapy Science, Osaka University Graduate School of Medicine, Osaka, Japan.
Tumour Biol. 2002 Jul-Aug;23(4):202-11. doi: 10.1159/000067253.
The purpose of the present study was to investigate the mechanism by which nonfucosylated alpha-fetoprotein (AFP) is converted to fucosylated AFP in human hepatoma cell lines exposed to acyclic retinoid (AR), an effective drug for the secondary prevention of hepatocellular carcinoma. AR treatment (100 microM) of HepG2 and Hep3B cells significantly increased the activity and mRNA levels of alpha1-6 fucosyltransferase (alpha1-6 FucT), the enzyme responsible for the fucosylation of AFP, leading to an increase in fucosylated glycoproteins as evidenced by lectin binding measurements. Lectin immunoelectrophoresis of AFP obtained from culture media indicated that the relative percentage of nonfucosylated AFP (L1 fraction) was decreased and alpha1-6 fucosylated AFP (L3 fraction) was increased in these hepatoma cell lines after treatment with AR. The total AFP levels were, however, markedly suppressed by AR treatment, and therefore the absolute L3 fraction on the basis of the total AFP present was extremely low. These results demonstrate that AR enhances the conversion of the L1 to the L3 fraction due to the activation of alpha1-6 FucT in human hepatoma cell lines despite clinical outcome with AR treatment and the L3 fraction of AFP. Even though the dramatic decrease in AFP is the limiting factor in the synthesis of the L3 fraction and, therefore, the absolute value of fucosylated AFP is extremely low, the conversion from L1 to L3 as judged by lectin immunoelectrophoresis represents a good marker for the progress of AR treatment.
本研究的目的是探讨在暴露于阿环维A（AR）的人肝癌细胞系中，非岩藻糖基化甲胎蛋白（AFP）转化为岩藻糖基化AFP的机制。阿环维A是一种用于肝细胞癌二级预防的有效药物。用AR（100 microM）处理HepG2和Hep3B细胞，显著增加了α1-6岩藻糖基转移酶（α1-6 FucT）的活性和mRNA水平，该酶负责AFP的岩藻糖基化，凝集素结合测量结果表明岩藻糖基化糖蛋白增加。从培养基中获得的AFP的凝集素免疫电泳表明，在这些肝癌细胞系中，用AR处理后，非岩藻糖基化AFP（L1组分）的相对百分比降低，而α1-6岩藻糖基化AFP（L3组分）增加。然而，AR处理显著抑制了总AFP水平，因此基于存在的总AFP的绝对L3组分极低。这些结果表明，尽管AR治疗的临床结果和AFP的L3组分存在差异，但AR通过激活人肝癌细胞系中的α1-6 FucT增强了L1组分向L3组分的转化。尽管AFP的显著降低是L3组分合成的限制因素，因此岩藻糖基化AFP的绝对值极低，但通过凝集素免疫电泳判断的从L1到L3的转化是AR治疗进展的良好标志物。
