Complementary analysis of microsatellite tumor profile and mismatch repair defects in colorectal carcinomas

作     者：Alfredo Blanes Salvador J Diaz-Cano 

作者机构：Department of Pathology University of Malaga School of Medicine Malaga 29010 Spain Department of Histopathology King’s College Hospital and King’s College London School of Medicine London SE5 9RS United Kingdom 

出 版 物：《World Journal of Gastroenterology》 (世界胃肠病学杂志（英文版）)

年 卷 期：2006年第12卷第37期

页      面：5932-5940页

核心收录：

学科分类：1002[医学-临床医学] 100214[医学-肿瘤学] 10[医学] 

主　　题：Colon carcinoma Microsatellites Mismatch Repair Hereditary non-polyposis colon cancer 

摘      要：Microsatellite instability (MSI) is a prognostic factor and a marker of defi cient mismatch repair (MMR) in colorectal adenocarcinomas (CRC). However, a proper application of this marker requires understanding the following: (1) The MSI concept: The PCR approach must amplify the correct locus and accurately identify the microsatellite pattern in the patient’s normal tissue. MSI is demonstrat- ed when the length of DNA sequences in a tumor differs from that of nontumor tissue. Any anomalous expansion or reduction of tandem repeats results in extra-bands normally located in the expected size range (100 bp, above or below the expected product), differ from the germline pattern by some multiple of the repeating unit, and must show appropriate stutter. (2) MSI mechanisms: MMR gene inactivation (by either mutation or protein down-regulation as frequently present in deep CRC com- partments) leads to mutation accumulation in a cell with every cellular division, resulting in malignant transforma- tion. These mechanisms can express tumor progression and result in a decreased prevalence of aneuploid cells and loss of the physiologic cell kinetic correlations in the deep CRC compartments. MSI molecular mechanisms are not necessarily independent from chromosomal in- stability and may coexist in a given CRC. (3) Because of intratumoural heterogeneity, at least two samples from each CRC should be screened, preferably from the su- perfi cial (tumor cells above the muscularis propria) and deep (tumor cells infi ltrating the muscularis propria) CRC compartments to cover the topographic tumor hetero- geneity. (4) Pathologists play a critical role in identify- ing microsatellite-unstable CRC, such as occur in young patients with synchronous or metachronous tumors or with tumors showing classic histologic features. In these cases, MSI testing and/or MMR immunohistochemistry are advisable, along with gene sequencing and genetic counseling if appropriate. MSI is an excellent functional an