Expression cloning of sialyltransferase involved in malignant progression of human RCC

为了鉴定α-2，3-唾液酸基转移酶参与合成单唾液酸半乳糖球状糖苷与肾癌恶性进展的关系，我们采用了表达克隆和聚合酶链式反应的方法。到目前为止，我们还没有通过表达克隆的方法获得α2，3-唾液酸基转移酶，但通过该方法得到了rRNA5‘端前体、胎盘转化生长因子β、未知基因等。我们正在研究这些基因与MSGG表达的关系，我们通过聚合酶链式反应获得了hST3Gal I和hST3Gal IV。Northern分析表明，hST3Gal I与人肾癌恶性进展无明显相关性。hST3Gal I稳定转染组无一例表达MSG，hST3Gal IV稳定转染组MSG表达中度升高，而hST3Gal IV转录本在几乎所有正常肾组织中显著升高，在大多数肿瘤组织中表达降低。提示hST3Gal IV与肾脏分化有关。根据这些结果，预计还有另一个决定MSG合成的2，3-唾液酸基转移酶。对这种推测的唾液酸基转移酶的研究仍在进行中。在本研究中，我们鉴定了N-乙酰半乳糖氨基二唾液酸型链旁糖苷(GalNAc DSPG-1)为一种新的神经节苷脂，并发现DSGG存在于中胚层来源的细胞中。我们还发现MSGG和GM3在人肾细胞癌中的表达呈负相关。

In all attempt to identify α 2, 3-sialyltransferase involved in synthesis of monosialosyl galactosyl globoside (MSGG), the first substance of globo-series ganglioside, associated with the malignant progression of human renal cell carcinoma (RCC), we utilized both expression cloning procedure and PCR method. Thus far, we could not obtain α 2, 3-sialyltransferase by expression cloning procedure, but 5' precursor of rRNA, placental transforming growth factor β, unknown cDNA, etc. were identified as concentrated cDNA by this procedure. We are now investigating the relationship between these cDNA and expression of MSGG.We obtained hST3Gal I and hST3Gal IV by PCR method. By Northern analysis, there was no clear correlation between hST3Gal I and the malignant progression of human RCC.None of the stable transfectants with hST3Gal I examined showed expression of MSGG.Stable transfectant with hST3Gal IV showed moderate increase of MSGG.However, hST3Gal IV transcript increased prominently in almost all normal renal tissues and decreased in most cases of cancer tissues. It was suggested that hST3Gal IV is associated with renal differentiation. From these results, it was anticipated that there is another a 2, 3-sialyltransferase determining the sysnthesis of MSGG.Investigation of this putative sialyltransferase is still underway. During this research, we identified N-acetyl-galactosaminyl disialosyl typel chain paragloboside (GalNAc DSPG-1) as a novel ganglioside, and found that DSGG is distributed in cells of mesoderm origin. We also found that expression of MSGG is inversely related to that of GM3 in human RCC.