BRAF Gene Mutation

About: BRAF Gene Mutation is a research topic. Over the lifetime, 143 publications have been published within this topic receiving 11619 citations.

Mutations of the BRAF gene in human cancer

Abstract: Cancers arise owing to the accumulation of mutations in critical genes that alter normal programmes of cell proliferation, differentiation and death. As the first stage of a systematic genome-wide screen for these genes, we have prioritized for analysis signalling pathways in which at least one gene is mutated in human cancer. The RAS RAF MEK ERK MAP kinase pathway mediates cellular responses to growth signals. RAS is mutated to an oncogenic form in about 15% of human cancer. The three RAF genes code for cytoplasmic serine/threonine kinases that are regulated by binding RAS. Here we report BRAF somatic missense mutations in 66% of malignant melanomas and at lower frequency in a wide range of human cancers. All mutations are within the kinase domain, with a single substitution (V599E) accounting for 80%. Mutated BRAF proteins have elevated kinase activity and are transforming in NIH3T3 cells. Furthermore, RAS function is not required for the growth of cancer cell lines with the V599E mutation. As BRAF is a serine/threonine kinase that is commonly activated by somatic point mutation in human cancer, it may provide new therapeutic opportunities in malignant melanoma.

High Prevalence of BRAF Gene Mutation in Papillary Thyroid Carcinomas and Thyroid Tumor Cell Lines

Abstract: The RAS-RAF-MEK-ERK-MAP kinase pathway mediates the cellular response to extracellular signals that regulate cell proliferation, differentiation, and apoptosis. Mutation of the RAS proto-oncogene occurs in various thyroid neoplasms such as papillary thyroid carcinomas (PTCs), follicular thyroid adenomas and carcinomas. A second genetic alteration frequently involved in PTC is RET/PTC rearrangements. Recent studies have shown that BRAF, which is a downstream signaling molecule of RET and RAS, is frequently mutated in melanomas. This study tests whether BRAF is also mutated in thyroid tumors and cell lines. We analyzed BRAF gene mutation at codon 599 in thyroid tumors using mutant-allele-specific PCR and in 10 thyroid tumor cell lines by DNA sequencing of the PCR-amplified exon 15. We found that BRAF was mutated in 8 of 10 thyroid tumor cell lines, including 2 of 2 papillary carcinoma cell lines, 4 of 5 anaplastic carcinoma cell lines, 1 of 2 follicular carcinoma cell lines, and 1 follicular adenoma cell line. BRAF mutation at codon 599 was detected in 21 of 56 PTC (38%) but not in 18 follicular adenomas and 6 goiters. BRAF mutation occurred in PTC at a significantly higher frequency in male patients than in female patients. To test whether BRAF mutation may cooperate with RET/PTC rearrangements in the oncogenesis of PTC, we tested whether BRAF-mutated PTCs were also positive for RET/PTC rearrangements. Immunohistochemical staining was conducted to evaluate RET/PTC rearrangements by using two different anti-RET antibodies. Surprisingly, we found that a large number of BRAF-mutated PTCs (8 of 21) also expressed RET, indicating that the RET proto-oncogene is rearranged in these BRAF-mutated PTCs. These observations suggest that mutated BRAF gene may cooperate with RET/PTC to induce the oncogenesis of PTC.

The Hippo effector YAP promotes resistance to RAF- and MEK-targeted cancer therapies

Abstract: Resistance to RAF- and MEK-targeted therapy is a major clinical challenge. RAF and MEK inhibitors are initially but only transiently effective in some but not all patients with BRAF gene mutation and are largely ineffective in those with RAS gene mutation because of resistance. Through a genetic screen in BRAF-mutant tumor cells, we show that the Hippo pathway effector YAP (encoded by YAP1) acts as a parallel survival input to promote resistance to RAF and MEK inhibitor therapy. Combined YAP and RAF or MEK inhibition was synthetically lethal not only in several BRAF-mutant tumor types but also in RAS-mutant tumors. Increased YAP in tumors harboring BRAF V600E was a biomarker of worse initial response to RAF and MEK inhibition in patients, establishing the clinical relevance of our findings. Our data identify YAP as a new mechanism of resistance to RAF- and MEK-targeted therapy. The findings unveil the synthetic lethality of combined suppression of YAP and RAF or MEK as a promising strategy to enhance treatment response and patient survival.

Impact of KRAS and BRAF Gene Mutation Status on Outcomes From the Phase III AGITG MAX Trial of Capecitabine Alone or in Combination With Bevacizumab and Mitomycin in Advanced Colorectal Cancer

Abstract: Purpose Mutations affecting the KRAS gene are established predictive markers of outcome with anti– epithelial growth factor receptor (EGFR) antibodies in advanced colorectal cancer (CRC). The relevance of these markers for anti–vascular endothelial growth factor (VEGF) therapy is controversial. This analysis was performed to assess the predictive and prognostic impact of KRAS and BRAF gene mutation status in patients receiving capecitabine with bevacizumab (CG) or capecitabine without bevacizumab in the phase III AGITG MAX (Australasian Gastrointestinal Trials Group MAX) study. Patients and Methods Mutation status was determined for 315 (66.9%) of the original 471 patients. Mutation status was correlated with efficacy outcomes (response rate, progression-free survival [PFS], and overall survival [OS]), and a predictive analyses was undertaken. Results Mutations in KRAS and BRAF genes were observed in 28.8% and 10.6% of patients, respectively. KRAS gene mutation status (wild type [WT] v mutated [MT]) had no prognostic impact for PFS (hazard ratio [HR], 0.89; CI, 0.69 to 1.14) or OS (HR, 0.97; CI, 0.73 to 1.28). BRAF mutation status (WT v MT) was not prognostic for PFS (HR, 0.80; CI, 0.54 to 1.18) but was prognostic for OS (HR, 0.49; CI, 0.33 to 0.73; P .001). By using the comparison of capecitabine versus capecitabine and bevacizumab (CB) and CB plus mitomycin (CBM), KRAS gene mutation status was not predictive of the effectiveness of bevacizumab for PFS or OS (test for interaction P .95 and 0.43, respectively). Similarly, BRAF gene mutation status was not predictive of the effectiveness of bevacizumab for PFS or OS (test for interaction P .46 and 0.32, respectively). Conclusion KRAS gene mutation status was neither prognostic for OS nor predictive of bevacizumab outcome in patients with advanced CRC. BRAF gene mutation status was prognostic for OS but was not predictive of outcome with bevacizumab. J Clin Oncol 29. © 2011 by American Society of Clinical Oncology

Clinicopathological and protein characterization of BRAF- and K-RAS-mutated colorectal cancer and implications for prognosis.

Abstract: Recent evidence highlights the potential prognostic and predictive value of BRAF and K-RAS gene alterations in patients with colorectal cancer However, a comprehensive evaluation of BRAF and K-RAS mutations and their specific clinicopathological features, histomorphological presentation and effect on protein expression have not been systematically analyzed The aim of this study was to characterize the clinicopathological, histomorphological and protein expression profiles of BRAF- and K-RAS-mutated colorectal cancers and determine their impact on patient survival Molecular analysis for microsatellite instability (MSI), K-RAS and BRAF was carried out on paraffin-embedded samples from 404 patients with primary colorectal cancer Using tissue microarrays, 36 tumor-associated and 14 lymphocyte/inflammatory-associated markers were evaluated by immunohistochemistry BRAF mutation was associated with right-sided tumor location (p > 0001), higher tumor grade (p = 0029), absence of peritumoral lymphocytic inflammation (p = 0026) and MSI-H (p > 0001) In right-sided tumors, loss of CDX2 expression was observed in 23 of 24 cases (958%) BRAF mutation was a poor prognostic indicator in patients with right-sided disease (p = 001) This result was maintained in multivariable analysis (p > 0001; HR = 282; 95% CI: 15-55) with pT, pN and vascular invasion and independent of CDX2 expression K-RAS mutation, in contrast, was not associated with any of the features analyzed BRAF gene mutation is an adverse prognostic factor in right-sided colon cancer patients independent of MSI status and, moreover, in patients with lymph node-negative disease These results indicate that molecular analysis for BRAF may be a useful biomarker for identifying patients with right-sided colon cancer with poor outcome who may benefit from a more individualized course of therapy