Immunohistochemical expression of mismatch repair genes: a screening tool for predicting mutator phenotype in liver fluke infection-associated intrahepatic cholangiocarcinoma.
OBJECTIVE
To clarify possible contributions of DNA mismatch repair (MMR) system in carcinogenesis of liver fluke infection-associated intrahepatic cholangiocarcinoma (ICC) by using immunohistochemical assay.


METHODS
A total of 29 ICC samples, which had been assessed for genomic instability by a PCR-based method, were used for study. They were examined immunohistochemically to demonstrate protein expression of two MMR genes, hMSH2 and hMLH1. Results obtained were compared with their mutator phenotype assessed previously.


RESULTS
Either hMSH2 or hMLH1 protein was obviously expressed in 28 of 29 (96.6%) ICC samples. Positive nuclear localization of hMSH2 or hMLH1 protein was observed in 86.2% (25/29) or 93.1% (27/29) ICC cases, respectively, while their negative nuclear reactivity was only detected in 13.8% (4/29) or 6.9% (2/29) ICC cases analyzed, respectively.


CONCLUSIONS
Our study, probably for the first time, showed through immunohistochemical detection of hMSH2 and hMLH1 gene that DNA MMR system does not play a prominent role in liver fluke infection-associated cholangiocarcinogenesis. These results confirm previous findings on mutational status of these genes assessed through a PCR-based method. The immunohistochemical analysis has proven to be an effective and sensitive approach for screening MMR deficiency regardless of somatic inactivation or promoter hypermethylation of hMSH2 and/or hMLH1 gene. Furthermore, immunohistochemistry is more advantageous compared to mutator phenotyping assay in terms of simplicity, less time consuming and cost effectiveness for screening possible involvements of target MMR genes in tumorigenesis.
Liengswangwong
Upama
U
Institute of Health Research, Chulalongkorn University, Pathumwan, Bangkok and National Center for Genetic Engineering and Biotechnology, Thailand Science Park, Pathumthani.
Karalak
Anant
A
Morishita
Yukio
Y
Noguchi
Masayuki
M
Khuhaprema
Thiravud
T
Srivatanakul
Petcharin
P
Miwa
Masanao
M
D048868:Adaptor Proteins, Signal Transducing; D000328:Adult; D000368:Aged; D001650:Bile Duct Neoplasms / Q000209:etiology* / Q000235:genetics*; D001653:Bile Ducts, Intrahepatic / Q000737:chemistry* / Q000469:parasitology / Q000473:pathology; D002352:Carrier Proteins / Q000235:genetics* / Q000502:physiology; D018281:Cholangiocarcinoma / Q000209:etiology* / Q000235:genetics*; D004273:DNA, Neoplasm / Q000235:genetics; D005211:Fascioliasis / Q000150:complications*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D052138:Genes, Neoplasm / Q000235:genetics; D020022:Genetic Predisposition to Disease; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein / Q000235:genetics* / Q000502:physiology; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics* / Q000502:physiology; D010641:Phenotype
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004273:DNA, Neoplasm; C501486:MLH1 protein, human; D009687:Nuclear Proteins; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein