title: hMLH1 and hMSH2 expression in human hepatocellular carcinoma.
abstract: The role of microsatellite instability (MSI) in the pathogenesis of hepatocellular carcinoma (HCC) is incompletely defined. Although high-frequency MSI (MSI-H) is infrequently seen in HCC, some studies have suggested a role for MSI in HCC development. While MSI has been clearly defined for a subset of tumors, in particular colorectal, gastric and endometrial cancers, generally accepted criteria have not been developed for other tumors. Colorectal cancers (CRC) are classified as MSI-H if >30-40% of >5 microsatellite loci analyzed show instability. The MSI-H phenotype is associated with defective DNA mismatch repair (MMR) and is observed in the majority of tumors from patients with hereditary non-polyposis colon cancer (HNPCC) and also in 15% of sporadic CRCs. Inactivating mutations of the hMLH1 or hMSH2 genes lead to defects in MMR in HNPCC. In sporadic CRCs, MMR is usually due to hypermethylation of the hMLH-1 promoter. The role of defective MMR in hepatocellular carcinogenesis is controversial. Immunohistochemistry for hMLH1 and hMSH2 reliably indicates hMLH1 or hMSH2 loss in MSI-H CRC tumors. To investigate the role of defective MMR in HCC carcinogenesis, we performed immunohistochemistry for hMLH1 and hMSH2 on 36 HCCs. BAT26, a microsatellite marker that reliably predicts MSI-H was also examined. All 36 of the tumors stained positively for both hMLH1 and hMSH2, strongly suggesting an absence of either inactivating mutations of hMLH1 and hMSH2 or promoter hypermethylation of hMLH1. None of the tumors showed MSI at the BAT26 locus. These findings suggest that defective MMR does not contribute significantly to hepatocellular carcinogenesis.
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Medical School, Clinic and Foundation, 200 First Street SW, Rochester, MN 55905, USA.
authors.forename: L
authors.initials: L
authors.lastname: Wang
authors.forename: A
authors.initials: A
authors.lastname: Bani-Hani
authors.forename: D P
authors.initials: DP
authors.lastname: Montoya
authors.forename: P C
authors.initials: PC
authors.lastname: Roche
authors.forename: S N
authors.initials: SN
authors.lastname: Thibodeau
authors.forename: L J
authors.initials: LJ
authors.lastname: Burgart
authors.forename: L R
authors.initials: LR
authors.lastname: Roberts
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D020137:Base Pair Mismatch; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins; D019175:DNA Methylation; D017931:DNA Primers / Q000737:chemistry; D004268:DNA-Binding Proteins; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism*; D008297:Male; D018895:Microsatellite Repeats; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D009367:Neoplasm Staging; D009687:Nuclear Proteins; D016133:Polymerase Chain Reaction; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein