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BRAF V600 mutations in Langerhans cell histiocytosis with a simple and unique assay.

ABSTRACT: BRAF (V-raf murine sarcoma viral oncogene homolog B1) is a serine-threonine protein kinase involved in cell survival, proliferation, and differentiation. The most common missense mutation of BRAF (mainly V600E) contributes to the incidence of various cancers, including Langerhans cell histiocytosis (LCH). BRAF inhibitors molecularly targeting the V600E mutation have been developed to counteract the effect of the mutation. To ensure the administration of effective pharmacotherapy, it is therefore imperative to develop an effective assay to screen LCH patients for the V600E mutation. However, tumor tissues of LCH typically contain many inflammatory cells which make a correct judgement of the mutation status difficult in the DNA sequence analysis.In this study, we present a new, highly sensitive analyzing method combining PCR, restriction enzyme digestion, and a sequencing assay using DNA extracted from formalin-fixed paraffin-embedded (FFPE) tissue specimens. TspRI is a restriction enzyme that cleaves the sequence encompassing the wild-type BRAF codon 600 into two fragments, which cannot be used as a template for subsequent BRAF PCR amplification. We therefore evaluated the sensitivity of BRAF V600 mutation detection by amplifying the primary PCR product digested with TspRI and sequencing the secondary PCR products. The V600E mutation was detected in FFPE tissue samples from 32 LCH patients; our assay was able to identify mutations in four samples that gave inconclusive results, and ten that were negative, according to standard PCR and sequencing.We presented a new and highly sensitive method to detect BRAF V600 mutations. This screening method is expected to play an important role to select the most effective therapies.

SUBMITTER: Tatsuno M

PROVIDER: S-EPMC4837618 | biostudies-literature | 2016 Apr

REPOSITORIES: biostudies-literature

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BRAF V600 mutations in Langerhans cell histiocytosis with a simple and unique assay.

Tatsuno Michiko M Shioda Yoko Y Iwafuchi Hideto H Yamazaki Shigeki S Iijima Kenta K Takahashi Chiaki C Ono Hiromi H Uchida Kiyono K Okamura Osamu O Matubayashi Mamoru M Okuyama Torayuki T Matsumoto Kimikazu K Yoshioka Takako T Nakazawa Atsuko A

Diagnostic pathology 20160419

<h4>Background</h4>BRAF (V-raf murine sarcoma viral oncogene homolog B1) is a serine-threonine protein kinase involved in cell survival, proliferation, and differentiation. The most common missense mutation of BRAF (mainly V600E) contributes to the incidence of various cancers, including Langerhans cell histiocytosis (LCH). BRAF inhibitors molecularly targeting the V600E mutation have been developed to counteract the effect of the mutation. To ensure the administration of effective pharmacothera ...[more]

PMID: 27094161

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Project description:Importance:The histiocytic neoplasms Erdheim-Chester disease (ECD) and Langerhans cell histiocytosis (LCH) are highly enriched for BRAF V600 mutations and have been previously shown to be responsive to treatment with vemurafenib, an inhibitor of the BRAF V600 kinase. However, the long-term efficacy and safety of prolonged vemurafenib use in these patients are not defined. Here we analyze the final efficacy and safety data for vemurafenib in patients with ECD and LCH enrolled in the VE-BASKET study. Objective:To determine the efficacy and safety of vemurafenib in adults with ECD or LCH enrolled in the VE-BASKET study. Design, Setting, and Participants:The VE-BASKET study was an open-label, nonrandomized, multicohort study for patients with nonmelanoma cancers harboring the BRAF V600 mutation. Patients with BRAF V600-mutant ECD or LCH were enrolled in an "other solid tumor" cohort of the VE-BASKET study, and they were enrolled in the present study. Interventions:Patients received vemurafenib, 960 mg, twice daily continuously until disease progression, study withdrawal, or occurrence of intolerable adverse effects. Main Outcomes and Measures:The primary end point was confirmed objective response rate (ORR) by Response Evaluation Criteria in Solid Tumors (RECIST, version 1.1). Secondary end points included progression-free survival (PFS), overall survival (OS), metabolic response by modified positron-emission tomography (PET) Response Criteria in Solid Tumors (PERCIST) using 18F-fluorodeoxyglucose (FDG)-PET/computed tomography (CT), and safety. Results:A total of 26 patients from the VE-BASKET trial (22 with ECD, 4 with LCH) were included in the present study (14 women and 12 men; median age, 61 years; age range, 51-74 years). The confirmed ORR was 61.5% (95% CI, 40.6%-79.8%) in the overall cohort and 54.5% (95% CI, 32.2%-75.6%) in patients with ECD. All evaluable patients achieved stable disease or better. The median PFS and OS had not been reached in the overall cohort at study closure despite a median follow-up of 28.8 months; 2-year PFS was 86% (95% CI, 72%-100%), and 2-year OS was 96% (95% CI, 87%-100%). All 15 patients evaluated by FDG-PET/CT achieved a metabolic response, including 12 patients (80%) with a complete metabolic response. The most common adverse events (AEs) in the overall cohort included arthralgia, maculopapular rash, fatigue, alopecia, prolonged QT interval, skin papilloma, and hyperkeratosis. Hypertension and dermatologic AEs occurred at higher rates than those reported in metastatic melanoma. Conclusions and Relevance:In this study, vemurafenib had prolonged efficacy in patients with BRAF V600-mutant ECD and LCH and warrants consideration as a new standard of care for these patients.

Project description:Resistance to therapy with BRAF kinase inhibitors is associated with reactivation of the mitogen-activated protein kinase (MAPK) pathway. To address this problem, we conducted a phase 1 and 2 trial of combined treatment with dabrafenib, a selective BRAF inhibitor, and trametinib, a selective MAPK kinase (MEK) inhibitor.In this open-label study involving 247 patients with metastatic melanoma and BRAF V600 mutations, we evaluated the pharmacokinetic activity and safety of oral dabrafenib (75 or 150 mg twice daily) and trametinib (1, 1.5, or 2 mg daily) in 85 patients and then randomly assigned 162 patients to receive combination therapy with dabrafenib (150 mg) plus trametinib (1 or 2 mg) or dabrafenib monotherapy. The primary end points were the incidence of cutaneous squamous-cell carcinoma, survival free of melanoma progression, and response. Secondary end points were overall survival and pharmacokinetic activity.Dose-limiting toxic effects were infrequently observed in patients receiving combination therapy with 150 mg of dabrafenib and 2 mg of trametinib (combination 150/2). Cutaneous squamous-cell carcinoma was seen in 7% of patients receiving combination 150/2 and in 19% receiving monotherapy (P=0.09), whereas pyrexia was more common in the combination 150/2 group than in the monotherapy group (71% vs. 26%). Median progression-free survival in the combination 150/2 group was 9.4 months, as compared with 5.8 months in the monotherapy group (hazard ratio for progression or death, 0.39; 95% confidence interval, 0.25 to 0.62; P<0.001). The rate of complete or partial response with combination 150/2 therapy was 76%, as compared with 54% with monotherapy (P=0.03).Dabrafenib and trametinib were safely combined at full monotherapy doses. The rate of pyrexia was increased with combination therapy, whereas the rate of proliferative skin lesions was nonsignificantly reduced. Progression-free survival was significantly improved. (Funded by GlaxoSmithKline; ClinicalTrials.gov number, NCT01072175.).

Dataset Information

BRAF V600 mutations in Langerhans cell histiocytosis with a simple and unique assay.

Publications

BRAF V600 mutations in Langerhans cell histiocytosis with a simple and unique assay.

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