BRAF mutation in sporadic colorectal cancer and Lynch syndrome

Abstract

The aim of the study was to detect mutations of BRAF oncogene in colorectal cancer and to use this information to identify Lynch syndrome patients. Consecutive cases of primary colorectal cancer (n = 137) were analyzed for MLH1 protein expression using immunohistochemistry (IHC). BRAF V600E mutation was detected by IHC using a specific monoclonal antibody (VE1) and by qPCR. All MLH1 protein-negative cases were subjected to microsatellite instability analysis and MLH1 promoter methylation assay. MLH1 protein expression deficiency and high microsatellite instability (MSI-H) were detected in 18 of the 137 (13.1%) consecutive colorectal cancer specimens. Detection of the BRAF V600E mutation by IHC was 100% sensitive and specific as compared to qPCR, and this mutation was frequently present in the MSI-H group (77.8%; 14/18) and less frequently in the microsatellite-stable group (7.6%; 9/118). All BRAF V600E mutated cases of the MSI-H group presented with a MLH1 promoter methylation (14/14) as detected by methylation-specific multiplex ligation-dependent probe amplification. When BRAF was wild type in the MSI-H group, only one MLH1 promoter methylation was detected (1/4), and of the remaining three cases without MLH1 methylation, two were identified to harbor an MLH1 mutation consistent with Lynch syndrome. Finally, 11 previously confirmed Lynch syndrome cases were analyzed for BRAF V600E mutation, and all of them were wild type. In conclusion, detection of BRAF V600E in colorectal cancer specimens by IHC is sensitive and specific and may help to identify Lynch syndrome patients.

A Further Investigation of Combined Mismatch Repair and BRAFV600E Mutation Specific Immunohistochemistry as a Predictor of Overall Survival in Colorectal Carcinoma

“…In 11 studies BRAFV600E mutation specific IHC has either outperformed or performed comparably to molecular techniques [2], [7], [8], [9], [10], [11], [12], [13], [14],[15],[16] whereas in two studies mutation specific IHC was found to be less reliable. [17], [18] A fair reading of the literature would support the approach taken by Kuan et al, [12] that mutation specific IHC is reliable but requires rigorous technical optimization and ongoing quality assurance including the performance of molecular testing in equivocal cases.…”

“…In the interim, the combination of BRAFV600E and MMR IHC still has a clear role in the triaging of patients with CRC encountered in routine clinical practice for formal molecular testing for Lynch Syndrome. [2], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16] The strong likelihood that this approach can also have the added benefit of predicting outcome can be considered a likely downstream benefit of universal screening for Lynch Syndrome by immunohistochemistry.…”

Tumor and Patient Characteristics of Individuals with Mismatch Repair Deficient Colorectal Cancer

“…Sporadic MSI CRC are associated with BRAF V600E mutations [28] and occur preferably in older patients [42]. Since BRAF V600E mutations virtually exclude LS, it as a suitable test to differentiate between sporadic CRC with hMLH1 mutation and LS [43]. In this study, all patients with MMR-D who fulfilled AC, BG and rBG had no mutation in BRAF V600E.…”

BRAFV600E immunohistochemistry in conjunction with mismatch repair status predicts survival in patients with colorectal cancer

“…2, 8, 9, 10 To date, its main suggested utility has been to triage molecular testing for Lynch syndrome in mismatch repair-deficient tumors. It has been proposed that if BRAFV600E immunohistochemistry were performed universally in all tumors, it could also be used to detect the poor prognosis mismatch repair-proficient BRAFV600E mutant colorectal carcinomas.…”