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Infrequent widespread microsatellite instability in hepatocellular carcinomas
H Yamamoto1, F Itoh, H Fukushima
1First Department of Internal Medicine, Sapporo Medical University, South-1, West-16, Chuo-ku, Sapporo 060-8543, Japan.
International Journal of Oncology
|February 17, 2000
Summary
Microsatellite instability (MSI) due to DNA mismatch repair (MMR) defects is common in some cancers but not significant in Japanese liver cancer. Our study found no evidence of widespread MSI or MMR gene defects in hepatocellular carcinoma.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Microsatellite instability (MSI) and DNA mismatch repair (MMR) defects are hallmarks of hereditary non-polyposis colorectal cancer and some sporadic tumors.
- While well-characterized in gastrointestinal cancers, the role of MSI and MMR defects in hepatocarcinogenesis remains largely unexplored.
Purpose of the Study:
- To investigate the incidence and underlying mechanisms of MSI and DNA MMR defects in Japanese hepatocellular carcinoma (HCC).
- To determine if MSI plays a significant role in the development of liver cancer.
Main Methods:
- Analysis of 55 Japanese HCC tissues and 9 liver cancer cell lines.
- Assessment of MSI using microsatellite analysis (BAT26, BAT25, BAT34C4).
- Evaluation of DNA MMR defects through loss of heterozygosity (LOH), MMR gene mutation analysis, hMLH1 promoter methylation, and frameshift mutations in target genes.
- Examination of beta2-microglobulin gene mutations.
Main Results:
- None of the analyzed HCC tissues or cell lines exhibited shortened unstable alleles for MSI markers (BAT26, BAT25, BAT34C4).
- Loss of heterozygosity at MMR genes was infrequent (4.4–7.1%), with no mutations detected in MMR genes.
- No evidence of hMLH1 hypermethylation or frameshift mutations in target genes was found.
- Mutations in the beta2-microglobulin gene were absent.
Conclusions:
- Widespread MSI resulting from defective DNA MMR plays a minimal role, if any, in the pathogenesis of Japanese hepatocellular carcinoma.
- The findings suggest that alternative molecular pathways are primarily responsible for hepatocarcinogenesis in this population.