Expression cloning of carbohydrate sufotransferase and its implication in cancer metastasis

我们试图分离编码人磺基转移酶的cDNA克隆，该克隆可以合成硫酸化的LacCer。在这项研究中，我们利用我们实验室建立的抗硫酸酯糖脂的单抗的哺乳动物表达系统，发现转基因细胞从头开始表达。然而，我们仍在获得编码人硫转移酶结构基因的cDNA。同时，我们研究了最近克隆的GalCer硫转移酶在人肝和肝癌细胞系中的表达模式。在Northern blotts中，该基因在人肝癌细胞系中的表达与这些细胞中的磺基糖脂产物有关。这一结果可能表明该基因编码的酶可以合成硫酸化的LacCer，这个问题应该通过对该基因衍生的酶功能的分析来解决。在酸性糖脂和糖蛋白中，唾液酸化的糖结构具有与硫酸糖脂一样的细胞黏附功能，我们研究了与这些产物相关的糖基转移酶的表达实际上在癌症相关和细胞特异性的条件下受到调节。尤其是在肿瘤病毒转录激活剂的影响下，一些转移酶参与了唾液酸化Le^x的合成，从而介导了白细胞和白血病细胞与内皮细胞的黏附。

We have tried to isolate a cDNA clone encoding human sulfotransferase, which could synthesize sulfated LacCer. In this research, we used a mammalian expression system with monoclonal antibodies which were established against sulfated glycolipids in our laboratory, and found that de novo expression of transgected cells. However, we are still in the way to get a cDNA that represent a tructural gene encoding a human sulfotransferase.At the same time, we have investigated expression pattern of the GalCer sulfotransferase which was recently cloned, among human liver and hepatoma cell lines. In Northern blots, the gene was expressed in human hepatoma cell lines in relation to product of sulfoglycolipids in these cells. This result might suggest that the enzyme encoded by the gene could synthesize sulfated LacCer, and this issue should be resolved upon analysis of enxymatic function derived from this gene.Among acidic glycolipids and glycoproteins, sialylated glyco-structures have function of cell adhesion like sulfated glycolipids, and we have investigated that expression of glycosyltransferases related to these products were actually regulatted in cancer-related and cell-specific condition. Especially some transferase is under the influence of the transcription activator of the oncovirus in synthesis of sialyl Le^x which mediates adhesion of leukocytes and leukemic cells to endothelium.