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Characterization of glycine-N-methyltransferase-gene expression in human hepatocellular carcinoma
Y M Chen1, J Y Shiu, S J Tzeng
1Division of Preventative Medicine, Institute of Public Health, School of Medicine, National Yang-Ming University, Taipei, Taiwan, Republic of China. arthur@ym.edu.tw
Abstract:
Messenger RNA differential display was used to study liver-gene expression in paired tumor and non-tumor tissues from hepatocellular carcinoma (HCC) patients. mRNA differential display and Northern-blot analyses showed that a 0.8-kb cDNA fragment was diminished or absent from the tumorous tissues of 7 HCC patients. The cDNA fragment was sequenced and found to have 98.7% nucleotide sequence homology with human glycine-N-methyltransferase cDNA (GNMT). In addition, there was no detectable level of GNMT expression in 4 human HCC cell lines, SK-Hep1, Hep 3B, HuH-7 and HA22T, examined by Northern-blot assay. A full-length GNMT cDNA clone-9-1-2 was obtained by screening a Taiwanese liver cDNA library. In comparison with the GNMT cDNA sequence reported elsewhere, clone 9-1-2 had 4 nucleotide differences resulting in 1 amino-acid change. Immunohistochemical staining with rabbit anti-recombinant GNMT serum showed that GNMT protein almost completely disappeared in liver-cancer cells, while it was abundant in the non-tumorous liver cells. Down-regulation of GNMT gene expression may be involved in the pathogenesis of liver cancer.
Insights
Researchers investigated liver gene expression in hepatocellular carcinoma (HCC) patients. They found glycine-N-methyltransferase (GNMT) gene expression was significantly reduced in tumor tissues, suggesting its role in liver cancer development.
Area of Science:
- Molecular Biology
- Oncology
- Biochemistry
Background:
- Hepatocellular carcinoma (HCC) is a major global health concern.
- Understanding liver gene expression alterations is crucial for identifying cancer mechanisms.
Purpose of the Study:
- To investigate differential gene expression in HCC tumor versus non-tumor tissues.
- To identify specific genes potentially involved in HCC pathogenesis.
Main Methods:
- Messenger RNA (mRNA) differential display and Northern-blot analyses were employed.
- cDNA sequencing and screening of a liver cDNA library were performed.
- Immunohistochemical staining was used to assess protein levels.
Main Results:
- A 0.8-kb cDNA fragment, homologous to human glycine-N-methyltransferase (GNMT), was diminished or absent in HCC tumor tissues.
- GNMT expression was undetectable in four human HCC cell lines.
- GNMT protein was significantly reduced in liver cancer cells compared to non-tumorous liver cells.
Conclusions:
- Down-regulation of GNMT gene expression is potentially involved in the pathogenesis of liver cancer.
- GNMT may serve as a biomarker or therapeutic target in HCC.