Basic Research
Copyright ©2006 Baishideng Publishing Group Co., Limited. All rights reserved.
World J Gastroenterol. Jun 21, 2006; 12(23): 3740-3745
Published online Jun 21, 2006. doi: 10.3748/wjg.v12.i23.3740
Immunohistochemical expression of mismatch repair genes: A screening tool for predicting mutator phenotype in liver fluke infection-associated intrahepatic cholangiocarcinoma
Upama Liengswangwong, Anant Karalak, Yukio Morishita, Masayuki Noguchi, Thiravud Khuhaprema, Petcharin Srivatanakul, Masanao Miwa
Upama Liengswangwong, Institute of Health Research, Chulalongkorn University, Pathumwan, Bangkok and National Center for Genetic Engineering and Biotechnology, Thailand Science Park, Pathumthani, Thailand
Anant Karalak, Thiravud Khuhaprema, Petcharin Srivatanakul, National Cancer Institute, Bangkok, Thailand
Yukio Morishita, Masayuki Noguchi, Department of Pathology, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan
Masanao Miwa, Department of Biochemistry and Molecular Oncology, Institute of Basic Medical Sciences, University of Tsukuba, Ibaraki and Faculty of Bioscience, Nagahama Institute of Bio-Science and Technology, Nagahama, Shiga, Japan
Supported by Ministry of Education, Culture, Sports, Science and Technology of Japan
Correspondence to: Dr. Masanao Miwa, Faculty of Bioscience, Nagahama Institute of Bio-Science and Technology, Nagahama, Shiga, Japan. m_miwa@nagahama-i-bio.ac.jp
Telephone: +81-749648100 Fax: +81-749648140
Received: December 23, 2005
Revised: December 28, 2005
Accepted: February 27, 2006
Published online: June 21, 2006
Abstract

AIM: 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.

CONCLUSION: 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.

Keywords: Liver fluke infection; Cholangiocarcinoma; Mismatch repair; hMSH2; hMLH1; Immunohistochemistry; MSI; Mutator phenotype