Overexpression of glutamine synthetase in human primary liver cancer.
OBJECTIVE
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
Our results show an overexpression of GS in human primary liver cancers and, thus, point to its potential involvement in hepatocyte transformation.
Christa
L
L
Institut de la Santé et de la Recherche Médicale U370, CHU Necker, Paris, France.
Simon
M T
MT
Flinois
J P
JP
Gebhardt
R
R
Brechot
C
C
Lasserre
C
C
D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D002471:Cell Transformation, Neoplastic / Q000473:pathology; D004273:DNA, Neoplasm / Q000032:analysis / Q000235:genetics; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D005974:Glutamate-Ammonia Ligase / Q000032:analysis / Q000235:genetics* / Q000502:physiology; D006801:Humans; D008099:Liver / Q000737:chemistry / Q000473:pathology; D008113:Liver Neoplasms / Q000201:enzymology* / Q000235:genetics*; D008297:Male; D008969:Molecular Sequence Data; D012334:RNA, Neoplasm / Q000032:analysis / Q000235:genetics; D014158:Transcription, Genetic
D004273:DNA, Neoplasm; D012334:RNA, Neoplasm; D005974:Glutamate-Ammonia Ligase