<b/> BRAF mutations in colorectal cancer portend a poor prognosis, with first-line treatment often involving triplet or quadruplet chemotherapy, and single-agent targeted therapy with BRAF inhibitors failing to demonstrate clinical activity.
<i>BRAF</i><sup>V600E</sup> mutations occur in ∼10% of colorectal cancer cases, are associated with poor survival, and have limited responses to BRAF/MEK inhibition with or without EGFR inhibition.
Colorectal cancer (CRC) mortality was not associated with the traditional, alternate, or serrated pathways, but was associated with a subset of pathway-unassigned tumors (MSS or MSI low, CIMP negative, BRAF mutation negative, and KRAS mutation positive) (n = 96 cases; relative risk = 1.76; 95% confidence interval, 1.07-2.89, compared with the traditional pathway).
Colorectal cancers with BRAFD594G mutations exhibit similar clinicopathological features, microsatellite instability status, and prognosis as those with BRAF wild-type.
Colorectal cancer (CRC) growth and progression is frequently driven by RAS pathway activation through upstream growth factor receptor activation or through mutational activation of KRAS or BRAF.
Colorectal cancers (CRCs) initiate through distinct mutations, including in APC pathway components leading to tubular adenomas (TAs); in BRAF, with epigenetic silencing of CDX2, leading to serrated adenomas (SAs); and in the DNA mismatch repair machinery driving microsatellite instability (MSI).
Colorectal cancer (CRC) is categorized by alteration of vital pathways such as β-catenin (CTNNB1) mutations, WNT signaling activation, tumor protein 53 (TP53) inactivation, BRAF, Adenomatous polyposis coli (APC) inactivation, KRAS, dysregulation of epithelial to mesenchymal transition (EMT) genes, MYC amplification, etc.
BRAF-V600E mutations were analysed by automatic sequencing in colorectal cancers from 206 sporadic cases with MSI-H and 111 HNPCC cases with known germline mutations in MLH1 and MSH2.
B-RAF mutations, predominantly the specific V600E mutation and additional alterations in exons 11 and 15, were frequently detected in malignant melanomas, papillary thyroid tumors, and colorectal cancers with microsatellite instability (MSI).
BRAF mutation testing has therefore been proposed as a means to more definitively identify and exclude sporadic MSI-H CRC cases from germline MMR gene testing.
BRAFV600E mutation was analyzed in CRC patients with MMR deficiencies (microsatellite instability and/or lack of MLH1/MSH2 protein expression) in the EPICOLON population-based study.
BRAF mutation and CIMP+ are therefore likely to be involved in an alternate, albeit rare, pathway to APC inactivation during the development of CRC in younger patients.
BRAFV600E is the predominantly occurring mutation of the cytoplasmic kinase BRAF, and, in colorectal cancer, its determination provides a diagnostic exclusion criterion for hereditary nonpolyposis colorectal cancer.
BRAFV600E mutation was found in 15.6% of colorectal cancers but at higher frequencies in cancers with proximal location, poor differentiation and microsatellite instability (MSI) (all p < 0.001).
BRAF(V600E) was associated with inferior overall survival in metastatic CRC (HR = 2.02; 95% CI 1.26-3.26), particularly evident in patients treated with chemotherapy, and is independent of MSI status.
BRAF mutations are specific for serrated adenocarcinoma and identify a subset of serrated adenocarcinomas with gene methylation and a tendency for MSI-H. A high frequency of KRAS mutations in serrated adenocarcinomas suggests that a significant proportion of KRAS-mutated CRCs originate from serrated precursors, thus challenging the traditional model of Vogelstein.
BRAF mutation and the loss of MLH1 protein were observed in the colorectal cancer, but not in the other serrated polyps around the colorectal cancer, suggesting that colorectal cancer with microsatellite instability develops rapidly from a specific serrated polyp with distinct molecular properties.