Christa L, Simon M T, Flinois J P, Gebhardt R, Brechot C, Lasserre C
Institut de la Santé et de la Recherche Médicale U370, CHU Necker, Paris, France.
Gastroenterology. 1994 May;106(5):1312-20. doi: 10.1016/0016-5085(94)90024-8.
BACKGROUND/AIMS: We have identified several clones specifically expressed during malignant cell proliferation by screening a complementary DNA library constructed from a human primary liver cancer with subtractive probes. One clone was identified as the glutamine synthetase (GS) transcript. Its expression is tightly regulated during development, especially in the hepatic lobule. Because this enzyme is involved in nitrogen homeostasis, it might contribute to tumor development/progression in primary liver cancer.
We compared the expression of GS messenger RNA (mRNA) and protein in tumorous and nontumorous liver from 34 patients with primary liver cancers, using a combination of Northern blot, dot blot, western blot, and determination of GS enzyme activity.
GS mRNA was higher in tumors versus nontumors in 23 of 34 primary liver cancer samples. GS activity was higher in 6 of 8 selected primary liver cancer samples with high RNA levels. GS protein levels were proportional to enzyme activity. A major GS transcript of 2.8 kilobase was detected by Northern blotting and sequencing. This comprised the minor 1.8-kb transcript and a long 3' untranslated region; the latter contained an AT-rich zone, fully conserved in the chicken, mouse, and rat, which might be important for stability.
Our results show an overexpression of GS in human primary liver cancers and, thus, point to its potential involvement in hepatocyte transformation.
背景/目的：通过用消减探针筛选由人原发性肝癌构建的互补DNA文库，我们鉴定出了几个在恶性细胞增殖过程中特异性表达的克隆。其中一个克隆被鉴定为谷氨酰胺合成酶（GS）转录本。其表达在发育过程中受到严格调控，尤其是在肝小叶中。由于这种酶参与氮稳态，它可能在原发性肝癌的肿瘤发生/进展中起作用。
我们结合Northern印迹、斑点印迹、蛋白质印迹以及GS酶活性测定，比较了34例原发性肝癌患者肿瘤和非肿瘤肝脏中GS信使核糖核酸（mRNA）和蛋白质的表达。
在34例原发性肝癌样本中的23例中，肿瘤组织中的GS mRNA高于非肿瘤组织。在8例RNA水平高的选定原发性肝癌样本中的6例中，GS活性较高。GS蛋白水平与酶活性成正比。通过Northern印迹和测序检测到一个2.8千碱基的主要GS转录本。它由较小的1.8千碱基转录本和一个长的3'非翻译区组成；后者包含一个富含AT的区域，在鸡、小鼠和大鼠中完全保守，这可能对稳定性很重要。
我们的结果显示GS在人原发性肝癌中过表达，因此表明其可能参与肝细胞转化。
