The localization of beta 1,4-galactosyltransferase and its significance for malignancy

本研究探讨了肿瘤相关半乳糖基转移酶（GAT）作为卵巢肿瘤标志物的作用，半乳糖基转移酶（GalT）的亚细胞定位，以及GalT在高尔基体中的滞留机制。1）为了用双抗体夹心酶联免疫法检测卵巢癌患者腹水中的GAT，我们制备了抗卵巢癌患者腹水中GAT的单克隆抗体Mab 8513和Mab 8628。血清GAT检测卵巢癌的阳性率为52.9%，良性肿瘤的假阳性率为5.7%，提示GAT对卵巢癌的诊断特异性较低。2)用Mab 8628进行的组织化学分析表明，在cacer细胞的核上区有强阳性反应，这与免疫电镜观察到的高尔基体的反侧相一致。3)用转染人半乳糖基转移酶野生型和突变型cDNA的Cos-1细胞进行的免疫组化实验表明，膜锚定结构域中的氨基酸残基Cys和His是GalT驻留在高尔基体上所必需的。

In this study, 1) usefulness of galactosyltranseferase associated with tumor (GAT) as a tumor marker for ovarian tumors, 2) subcellular localization of galactosyltransferase(GalT), and 3) the mechanism for thetention of Galt in Golgi apparatus were investigated. Their outlines were described as follows ; 1) In order to measure GAT with double-denterminant enzyme immunoassay, we utilized monoclonal antibodies(Mabs) terned Mab8513 and Mab8628 generated against the GalT extracted from ascites of ovarian cancer patients. Assay of the serum-GAT levels showed favorite rate (52.9%) in ovarian cancers and extremely low false positive rate (5.7%) in benign tumors, indicating GAT to ve useful in terms of very low specificity for ovarian cancers. 2) Histochemical analysis using Mab8628 demonstrated a strong positive reaction in the suprasuclear area of cacer cells which coincided with trans-side of the Golgi apparatus as observed with immunoelectron microscopy. 3) Immunohistochemical expmination using Cos-1 cells transfected with wild and mutated cDNA for human galacrosyltransferase demonstrated that amino acid residues, Cys and His in a membrane-anchoring domain are necessaty for GalT to reside on the Golgi.