Hepatocyte growth factor activator inhibitor 2/placental bikunin (HAI-2/PB) gene is frequently hypermethylated in human hepatocellular carcinoma.
To identify methylation-mediated silencing of genes in hepatocellular carcinoma ( HCC), we surveyed genes induced by treatment with 5-aza-2'-deoxycytidine (5-Aza-CdR) in six human hepatoma cell lines using cDNA microarray analysis and determined the methylation status of 5' CpG islands by bisulfite DNA sequencing or methylation-specific PCR. Fifty genes exhibited a >5-fold induction in response to treatment with 5-Aza-CdR in at least one of the hepatoma cell lines examined. Among these genes, the hepatocyte growth factor activator inhibitor 2/placental bikunin (HAI-2/PB) gene was maximally induced by 5-Aza-CdR in three of six cell lines studied ( HLE, HuH7, and Hep3B). Bisulfite sequencing revealed that the 5' CpG island of this gene was densely methylated in HLE, HuH7, and Hep3B cells. After treatment with 5-Aza-CdR, re-expression and demethylation of HAI-2/PB gene were detected in these cells. These findings suggest that HAI-2/PB expression may be inappropriately repressed by promoter hypermethylation in HCC. Methylation-specific PCR analysis demonstrated that HAI-2/PB hypermethylation occurred in 21 of 26 HCC tumors (80.8%), whereas in the corresponding nontumorous liver tissues, it was found in 7 of 26 samples (26.9%). In addition, HAI-2/PB hypermethylation was not detected in any of the seven normal liver samples from individuals without HCC. Reverse transcription-PCR analysis demonstrated that promoter hypermethylation was associated with the reduced expression of the HAI-2/PB gene in HCC tumors. In conclusion, we have found that the HAI-2/PB gene is silenced by promoter hypermethylation in human hepatoma cells by means of cDNA microarray analysis after 5-Aza-CdR treatment, and that HAI-2/PB hypermethylation occurs frequently in primary HCC tumors.[1]References
- Hepatocyte growth factor activator inhibitor 2/placental bikunin (HAI-2/PB) gene is frequently hypermethylated in human hepatocellular carcinoma. Fukai, K., Yokosuka, O., Chiba, T., Hirasawa, Y., Tada, M., Imazeki, F., Kataoka, H., Saisho, H. Cancer Res. (2003) [Pubmed]
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