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Infrequent microsatellite instability in liver fluke infection-associated intrahepatic cholangiocarcinomas from
Upama Liengswangwong1, Takayuki Nitta, Hironobu Kashiwagi
1Institute of Health Research, Chulalongkorn University, Pathumwan, Bankok, Thailand.
Abstract:
The liver fluke infection-associated intrahepatic cholangiocarcinoma (ICC) is a major liver cancer in Northeast Thailand. The molecular basis of this ICC is poorly understood. To address possible roles of the DNA mismatch repair (MMR) system in ICC carcinogenesis, a fluorescence-labeling PCR/laser scanning technique with high sensitivity was employed to analyze genomic instability in the nuclear DNA (nDNA) and mitochondrial DNA (mtDNA) in 24 fresh and 13 formalin-fixed, paraffin-embedded tissues of ICC and their corresponding normal parts. Microsatellite instability (MSI) was assessed in nDNA, using 12 highly polymorphic loci including 5 Bethesda markers. These loci were mainly related to major MMR genes, hMSH2 and hMLH1. Also 3 (C)n and/or (C)n(A)n repeat instability at 1 noncoding region in the displacement-loop (D-loop) and 2 coding sequences in NADH dehydrogenase subunit 1 and subunit 5 gene in mtDNA were analyzed. MSI was only detected in 1 (2.7%), 6 (16.7%), 1 (2.9%), 1 (2.9%) or 2 (6.3%) out of 37, 36, 35, 35 or 32 cases at BAT-25, D2S123, D3S1611, D11S904 or D17S250, respectively. LOH was found at D3S1298, D3S1561, D5S346 and TP53 in 4 (18.2%) out of 22, 2 (18.2%) out of 11, 6 (33.3%) out of 18 and 3 (12.5%) out of 24 informative cases, respectively. In mtDNA, none except a single case out of the 37 (2.7%) exhibited repeat sequence instability in the D-loop. We conclude that the liver fluke infection-associated ICC in Thailand is classified as low frequency MSI or microsatellite stable type and that DNA MMR system, through hMSH2 and hMLH1 gene mutations, does not play a major role in its carcinogenesis.
Insights
Liver fluke-associated intrahepatic cholangiocarcinoma (ICC) in Thailand shows low microsatellite instability (MSI). The DNA mismatch repair (MMR) system, including hMSH2 and hMLH1 genes, does not appear to be a major factor in this cancer
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Intrahepatic cholangiocarcinoma (ICC) linked to liver fluke infection is prevalent in Northeast Thailand.
- The molecular mechanisms underlying ICC development remain largely unknown.
- The DNA mismatch repair (MMR) system's role in ICC carcinogenesis requires investigation.
Purpose of the Study:
- To investigate the potential involvement of the DNA mismatch repair (MMR) system in the development of liver fluke-associated ICC.
- To analyze genomic instability in both nuclear DNA (nDNA) and mitochondrial DNA (mtDNA) of ICC tissues.
- To assess microsatellite instability (MSI) and loss of heterozygosity (LOH) in relation to MMR genes.
Main Methods:
- Utilized a sensitive fluorescence-labeling PCR and laser scanning technique.
- Analyzed MSI in nDNA using 12 polymorphic microsatellite loci, including Bethesda markers, focusing on hMSH2 and hMLH1.
- Examined repeat sequence instability in mitochondrial DNA (mtDNA) regions (D-loop, NADH dehydrogenase subunits 1 and 5).
Main Results:
- Microsatellite instability (MSI) was detected at low frequencies in nDNA across several markers (e.g., 2.7% at BAT-25, 16.7% at D2S123).
- Loss of heterozygosity (LOH) was observed in specific loci (D3S1298, D3S1561, D5S346) and TP53.
- Mitochondrial DNA (mtDNA) showed minimal repeat sequence instability, with only one case exhibiting instability in the D-loop.
Conclusions:
- Liver fluke-associated ICC in Thailand is characterized by low MSI, classifying it as microsatellite stable.
- The DNA MMR system, particularly through hMSH2 and hMLH1 gene mutations, does not play a significant role in the carcinogenesis of this ICC subtype.
- Further research into other molecular pathways is warranted to understand ICC development in this region.
