Conventional and Tissue Microarray Immunohistochemical Expression Analysis of Mismatch Repair in Hereditary Colorectal Tumors

Abstract

Immunohistochemistry (IHC) of mismatch repair (MMR) proteins in colorectal tumors together with microsatellite analysis (MSI) can be helpful in identi-fying families eligible for mutation analysis. The aims were to determine sensitivity of IHC for MLH1, MSH2, and MSH6 and MSI analysis in tumors from known MMR gene mutation carriers; and to evaluate the use of tissue microarrays for IHC (IHC-TMA) of colon tumors in its ability to identify potential carriers of MMR gene mutations, and compare it with IHC on whole slides. IHC on whole slides was performed in colorectal tumors from 45 carriers of a germline mutation in one of the MMR genes. The TMA cohort consisted of 129 colon tumors from (suspected) hereditary nonpolyposis colorectal cancer (HNPCC) patients. Whole slide IHC analysis had a sensitivity of 89% in detecting MMR deficiency in carriers of a pathogenic MMR mutation. Sensitivity by MSI analysis was 93%. IHC can also be used to predict which gene is expected to harbor the mutation: for MLH1, MSH2, and MSH6, IHC on whole slides would have correctly predicted the mutation in 48%, 92%, and 75% of the cases, respectively. We propose a scheme for the diagnostic approach of families with (suspected) HNPCC. Comparison of the IHC results based on whole slides versus TMA, showed a concordance of 85%, 95%, and 75% for MLH, MSH2, and MSH6, respectively. This study therefore shows that IHC-TMA can be reliably used to simultaneously screen a large number of tumors from (suspected) HNPCC patients, at first in a research setting. Colorectal cancer (CRC) is the second most common cause of death because of malignancy in the Western world. The cause of CRC is multifactorial, involving hereditary and environmental factors and somatic genetic changes during tumor progression. 1 A family history of CRC is a clinically significant risk factor and may be found in up to 15% of all patients with CRC. 2 The most common hereditary CRC syndromes are familial adenomatous polyposis coli (FAP), accounting for Ͻ1% of CRC cases and HNPCC (hereditary nonpolyposis colorectal cancer), accounting for 1 to 6% of the cases. 3 HNPCC is an autosomal dominantly inherited disorder that is clinically defined by the Amsterdam Criteria. 4,5 In HNPCC, germline mutations have been identified in four DNA mismatch repair (MMR) genes, MSH2, 6 MLH1, 7 PMS2, 8 and MSH6. 9 -14 In 50 to 70% of the families fulfilling the Amsterdam criteria a germline mutation is detected in MLH1 or MSH2. 15,16 Germline mutations have been found in MSH6 in families with atypical HNPCC, ie, not entirely fulfilling the Amsterdam criteria. [11][12][13][14] Microsatellite instability (MSI) in colorectal tumors, first reported in 1993, [17][18][19] is caused by a failure of the DNA MMR machinery to repair errors occurring during DNA replication and leading to length alterations in simple, repetitive microsatellite sequences distributed throughout the genome. 20 According to international guidelines, a panel of five specific microsatellite markers has been recommended for MSI evalua...

Novel strategy for optimal sequential application of clinical criteria, immunohistochemistry and microsatellite analysis in the diagnosis of hereditary nonpolyposis colorectal cancer

“…15,16 Another predictive but less expensive screening method is the analysis of tumor tissue for reduction or loss of expression of mismatch repair proteins by immunohistochemical staining with monoclonal antibodies. 17,18 In contrast to microsatellite analysis, this method provides also information about the mismatch repair gene that is likely to be affected.…”

Prognostic implication of laminin-5 gamma 2 chain expression in the invasive front of colorectal cancers, disclosed by area-specific four-point tissue microarrays

“…20 The utility of TMAs has been proved in a number of immunohistochemical studies of various cancer types. [21][22][23][24] However, from the viewpoint of tumor heterogeneity, it is still doubtful whether each tissue core specimen measuring 0.6-2.0 mm in diameter in a tumor represents the characteristics of the whole tumor.…”

A founder MLH1 mutation in Lynch syndrome families from Piedmont, Italy, is associated with an increased risk of pancreatic tumours and diverse immunohistochemical patterns

“…Unusual staining patterns have been previously reported and do not seem to depend on the anti-MLH1 antibody used [50]. It has been suggested that different kinds of second hits can result in variable MLH1 immunostaining patterns in tumours of individuals carrying the same germinal mutation [51].…”