MutL homolog 1 methylation and microsatellite instability in sporadic colorectal tumors among Filipinos

Determining whether a tumor exhibits microsatellite instability (MSI) is useful in identifying patients with hereditary non-polyposis colorectal cancer and sporadic gastrointestinal cancers with defective DNA mismatch repair (MMR). The assessment of MSI status aids in establishing a clinical prognosis and may be predictive of tumor response to chemotherapy. A reference panel of five markers was suggested for MSI analysis by a National Cancer Institute (NCI) workshop in 1997 that has helped to standardize testing. But this panel of markers has limitations resulting from the inclusion of dinucleotide markers, which are less sensitive and specific for detection of tumors with MMR deficiencies compared to other types of markers that are currently available. This study demonstrates that mononucleotides are the most sensitive and specific markers for detection of tumors with defects in MMR and identifies an optimal panel of markers for detection of MSI-H tumors. A set of 266 mono-, di-, tetra- and penta-nucleotide repeat microsatellite markers were used to screen for MSI in colorectal tumors. The best markers for detection of MSI-H tumors were selected for aMSI Multiplex System, which included five mononucleotide markers:BAT-25, BAT-26, NR-21, NR-24andMONO-27. In addition, two pentanucleotide markers were added to identify sample mix-ups and/or contamination. We classified 153 colorectal tumors using the newMSI Multiplex Systemand compared the results to those obtained with a panel of 10 microsatellite markers combined with immunohistochemical (IHC) analysis. We observed 99% concordance between the two methods with nearly 100% accuracy in detection of MSI-H tumors. Approximately 5% of the MSI-H tumors had normal levels of four MMR proteins and as a result would have been misclassified based solely on IHC analysis, emphasizing the importance of performing MSI testing. The newMSI Multiplex Systemoffers several distinct advantages over other methods of MSI testing in that it is both extremely sensitive and specific and amenable to high-throughput analysis. TheMSI Multiplex Systemmeets the new recommendations proposed at the recent 2002 NCI workshop on HNPCC and MSI testing and overcomes problems inherent to the original five-marker panel. The use of a single multiplex fluorescent MSI assay reduces the time and costs involved in MSI testing with increased reliability and accuracy and thus should facilitate widespread screening for microsatellite instability in tumors of patients with gastrointestinal cancers.

Download Full-text

The Case for Universal Testing of Colorectal Tumors for Microsatellite Instability: A Coming Mismatch Between Clinical and Laboratory Testing

Digestive Diseases and Sciences ◽

10.1007/s10620-015-3739-0 ◽

2015 ◽

Vol 60 (8) ◽

pp. 2225-2227 ◽

Cited By ~ 1

Author(s):

Patrick M. Lynch

Keyword(s):

Microsatellite Instability ◽

Laboratory Testing ◽

Colorectal Tumors ◽

Universal Testing

Download Full-text

Evaluation of circulating-tumor DNA (ctDNA) as a source material for molecular phenotyping of colorectal tumors.

Journal of Clinical Oncology ◽

10.1200/jco.2015.33.3_suppl.642 ◽

2015 ◽

Vol 33 (3_suppl) ◽

pp. 642-642

Author(s):

Petra Minarikova ◽

Lucie Benesova ◽

Barbora Belsanova ◽

Tereza Halkova ◽

Jiri Cyrany ◽

...

Keyword(s):

Microsatellite Instability ◽

Peripheral Blood ◽

Cpg Island ◽

Circulating Tumor Dna ◽

Disease Stage ◽

Colorectal Tumors ◽

Minimum Requirement ◽

Spin Column ◽

Methylator Phenotype ◽

Tumor Dna

642 Background: Patients with advanced stages of colorectal cancer have elevated levels of circulating-tumor DNA (ctDNA) in peripheral blood. Its presence can facilitate acquisition of DNA material for tumor molecular profiling without the invasive procedures. In this work we present utility of ctDNA for the determination of tumor phenotype within the basic division into the mutator phenotype (microsatellite instability, MSI and chromosomal instability, CIN) or methylator phenotype (CpG island methylator phenotype, CIMP). Methods: Tumor biopsy tissue and 5mL of peripheral blood samples were prospectively collected from 148 patients with colorectal tumors. In addition, plasma was extracted from peripheral blood immediately upon collection. Samples were then transported to the molecular laboratory where DNA and ctDNA were isolated from tissue and plasma, by a modified spin-column ctDNA extraction. Somatic mutations in tumor suppressors denoting CIN phenotype were detected by denaturing capillary electrophoresis (DCE), microsatellite instability was detected by MSI Analysis System, Version 1.2 (Promega corporation, Madison, WI) and DNA methylation (CIMP phenotype) was obtained by multiplex ligation-dependent probe amplification (MRC Holland, NL). Results: The samples included 75 adenomas and 70 carcinomas. The detected rates in tissues were: 4% for MSI, 32% for CIN and 7% for CIMP in adenomas and 10% for MSI, 36% for CIN and 32% for CIMP in carcinomas. In adenomas, none of the detected molecular types could be confirmed in ctDNA. In carcinomas, the concordance between tissue and ctDNA was 25% for MSI, 23% for CIN and 60% for CIMP. The success rates were related to the ctDNA concentration yields with a minimum requirement of ~0.2ng/uL. Conclusions: ctDNA may serve as alternative source for molecular classification of colorectal tumors (MSI, CIN and CIMP). A low concordance between tissue and ctDNA was found for CIN and MSI in comparison to 60% of CIMP-phenotypes found in both tissue as well as ctDNA. The results are predominantly dictated by disease stage and the corresponding levels of ctDNA. Supported by a Czech Ministry of health grant no. 14383.

Download Full-text

Immunohistochemistry Versus Microsatellite Instability Testing in Phenotyping Colorectal Tumors

Journal of Clinical Oncology ◽

10.1200/jco.2002.20.4.1043 ◽

2002 ◽

Vol 20 (4) ◽

pp. 1043-1048 ◽

Cited By ~ 232

Author(s):

Noralane M. Lindor ◽

Lawrence J. Burgart ◽

Olga Leontovich ◽

Richard M. Goldberg ◽

Julie M. Cunningham ◽

...

Keyword(s):

Microsatellite Instability ◽

Mismatch Repair ◽

Predictive Value ◽

Dna Mismatch Repair ◽

Cost Effective ◽

Colorectal Tumors ◽

Dna Mismatch ◽

Testing Strategies ◽

Repair Deficiency ◽

Dna Mismatch Repair Deficiency

PURPOSE: To compare microsatellite instability (MSI) testing with immunohistochemical (IHC) detection of hMLH1 and hMSH2 in colorectal cancer. PATIENTS AND METHODS: Colorectal cancers from 1,144 patients were assessed for DNA mismatch repair deficiency by two methods: MSI testing and IHC detection of hMLH1 and hMSH2 gene products. High-frequency MSI (MSI-H) was defined as more than 30% instability of at least five markers; low-level MSI (MSI-L) was defined as 1% to 29% of loci unstable. RESULTS: Of 1,144 tumors tested, 818 showed intact expression of hMLH1 and hMSH2. Of these, 680 were microsatellite stable (MSS), 27 were MSI-H, and 111 were MSI-L. In all, 228 tumors showed absence of hMLH1 expression and 98 showed absence of hMSH2 expression: all were MSI-H. CONCLUSION: IHC in colorectal tumors for protein products hMLH1 and hMSH2 provides a rapid, cost-effective, sensitive (92.3%), and extremely specific (100%) method for screening for DNA mismatch repair defects. The predictive value of normal IHC for an MSS/MSI-L phenotype was 96.7%, and the predictive value of abnormal IHC was 100% for an MSI-H phenotype. Testing strategies must take into account acceptability of missing some cases of MSI-H tumors if only IHC is performed.

Download Full-text