Brief Reports
Copyright ©2005 Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. May 14, 2005; 11(18): 2781-2783
Published online May 14, 2005. doi: 10.3748/wjg.v11.i18.2781
Dinucleotide microsatellite repeats are essential for the diagnosis of microsatellite instability in colorectal cancer in Asian patients
Manuel Salto-Tellez, Soo-Yong Tan, Lily-Lily Chiu, Evelyn Siew-Chuan Koay
Manuel Salto-Tellez, Evelyn Siew-Chuan Koay, Department of Pathology, National University of Singapore and Molecular Diagnosis Centre, Department of Laboratory Medicine, National University Hospital, Singapore
Soo-Yong Tan, Department of Pathology, Tan Tock Seng Hospital, Singapore
Lily-Lily Chiu, Molecular Diagnosis Centre, Department of Laboratory Medicine, National University Hospital, Singapore
Author contributions: All authors contributed equally to the work.
Supported by the Health Services Development Program, Ministry of Health, Singapore (Project Reference No.: HSDP01N02). The study was carried out following the ethical approval of our Institutional Review Board (IRB Reference Code 03.104)
Correspondence to: Associate Professor Evelyn Siew-Chuan Koay, Department of Pathology, National University of Singapore, 5 Lower Kent Ridge Road, 119074 Singapore. patkoaye@nus.edu.sg
Telephone: +65-67724564 Fax: +65-67751757
Received: October 23, 2004
Revised: October 24, 2004
Accepted: December 1, 2004
Published online: May 14, 2005
Abstract

AIM: The molecular diagnosis of microsatellite instability (MSI) in colorectal cancer (CRC) is based on the analysis of five microsatellite markers. Among them, the two mononu-cleotide microsatellite repeats are considered more infor-mative for this analysis than the three dinucleotide ones. The aim of this study is to establish the most relevant markers for MSI analysis in colorectal cancers from Asian patients.

METHODS: The MSI analysis of 143 CRC cases in a routine molecular diagnostic laboratory was reviewed. Analysis by fluorescence-based PCR of the five recommended micros-atellites was performed, followed by data interpretation according to internationally accepted guidelines. The results were analyzed to address (1) the rate of success in the analysis of histopathological samples not specifically prepared for molecular analysis; (2) the relative importance of individual markers in the diagnosis of high-MSI (H-MSI).

RESULTS: MSI analysis was unsuccessful in 34 cases (24%), but for tissues archived in recent years the unsuccessful rate was 5%. We found the D2S123 marker the most vulnerable to inadequate tissue preservation, failing to amplify in 58 instances. Approximately 30% (32/109) of the cases were H-MSI, while 7/109 (6%) were low-MSI. A detailed analysis of the H-MSI cases revealed that the dinucleotide repeats (and D5S346 in particular) were more relevant than the mononucleotide repeats in assigning the correct MSI status.

CONCLUSION: The analysis of dinucleotide repeats is essential for the establishment of MSI status in Asian CRC patients.

Keywords: Microsatellite instability; Dinucleotide repeats; Reference registration