BRAF mutation detection in hairy cell leukaemia from archival haematolymphoid specimens

BRAF V600E mutation detection in hairy cell leukemia-utility of archival DNA from bone marrow aspirate/imprint smear and amplification refractory mutation system

BRAF V600E is a disease defining mutation for hairy cell leukemia (HCL), which helps in its diagnosis and differentiation from morphologically similar splenic marginal zone lymphoma (SMZL) and HCL-variant (HCL-v). Forty eight cases:HCL(n = 34), SMZL(n = 11) and HCL-v(n = 3) were included. Of these, 32 were retrospective and 16 were prospective. DNA was extracted, in retrospective cases from cells obtained by smears from bone marrow aspirate/trephine imprint (BMA/BMTx) slides, and in prospective cases from peripheral blood (PB)/BMA samples. BRAF V600E mutation testing was done using ARMS-PCR. BRAF V600E mutation was positive in all HCL and negative in all SMZL and HCL-v cases. DNA extracted from BMA/BMTx slides gave results comparable to DNA extracted from PB/BMA samples. Median age of presentation for HCL (53 years) and SMZL (56 years) were quite similar, however, HCL-v (71 years) cases presented at an older age. Statistically significant differences between the three groups were seen for total leucocyte, platelet, absolute lymphocyte and monocyte counts, bone marrow-infiltration pattern, reticulin fibrosis, and an expression of CD11c, CD25, CD103, CD123, and CD200. The use of BMA/BMTx smears for DNA extraction was found to be a useful alternative to DNA extraction from formalin-fixed paraffin-embedded biopsy sections. ARMS-PCR is an efficient and specific technique to detect BRAF V600E mutation in HCL patients.

Concomitant BRAF Mutation in Hairy Cell Leukemia and Papillary Thyroid Cancer: Case Report

Hairy cell leukemia (HCL) is rare type of leukemia. This neoplasm is well-known to present with pancytopenia and splenomegaly. HCL is associated with BRAF mutation in 100% of cases. It is also associated with hematological and oncological malignancies such as melanoma and papillary thyroid cancer. Although the association of both cancers (HCL and papillary thyroid cancer) with BRAF mutation is well established in the literature, as far as we know it has not been reported before in the same patient. Here we report 48-year-old male diagnosed with HCL and papillary thyroid cancer and who is BRAF positive in both diagnostic tissues.

New treatment options in hairy cell leukemia with focus on BRAF inhibitors

Hairy cell leukemia (HCL) responds initially very well to chemotherapy with purine analogues. However, up to 50% of patients relapse, often multiple times, and become progressively less sensitive to these myelotoxic and immune-suppressive drugs. At progression, viable therapeutic strategies include addition of rituximab to purine analogues, and treatment with the anti-CD22 immunotoxin moxetumomab pasudotox, which has been recently approved by the FDA in HCL patients after at least two prior therapies. Identification of the BRAF-V600E kinase mutation as the genetic cause of HCL has opened the way, in the relapsed/refractory experimental setting, to targeted and non-myelotoxic effective strategies that are based on inhibition of BRAF with vemurafenib, co-inhibition of BRAF and its target MEK with dabrafenib and trametinib, and BRAF inhibition with vemurafenib combined with anti-CD20 immunotherapy. In particular, vemurafenib plus rituximab is emerging as a short, safe, chemotherapy-free regimen able to induce deep complete remissions in most HCL patients refractory to, or relapsed multiple times, after chemo(immuno)therapy.

The prevalence of BRAF V600E mutation in hairy cell leukemia: A systematic review and meta-analysis study

Background: BRAF V600E mutations were recently identified in the leukemic cells from patients with hairy cell leukemia (HCL) that this mutation in exon 15 is considered the disease-defining mutation in HCL. Objectives: This meta-analysis aimed to report the prevalence of BRAF V600E mutation in HCL patients. Methods: Three databases including PubMed, Scopus, and Web of Science up to 2017 were searched for the prevalence of BRAF mutation in HCL patients. A random effects meta-analysis was performed using the Comprehensive Meta-Analysis software version 2.0 with the event rate (ER) and 95% confidence interval (95% CI). Results: Out of 552 articles identified from the search, 11 were included included and were analyzed for meta-analysis study. The studies in meta-analysis included 437 patients with HCL, of which 353 (80.8%) patients had BRAF V600E mutation. The pooled ER of the studies was 81.5% (95% CI: 69.5%–89.5%). The Begg's test did not show publication bias, but the Egger's test showed publication bias. Conclusions: With regard to the mentioned limitations, the prevalence of BRAF mutation in HCL patients was >80%. In future studies, considering sex, age, and other variables can exactly show the correlation between these variables with the detection of BRAF mutation.

Droplet digital polymerase chain reaction assay and peptide nucleic acid-locked nucleic acid clamp method for RHOA mutation detection in angioimmunoblastic T-cell lymphoma

Angioimmunoblastic T‐cell lymphoma (AITL) is a subtype of nodal peripheral T‐cell lymphoma (PTCL). Somatic RHOA mutations, most frequently found at the hotspot site c.50G > T, p.Gly17Val (G17V RHOA mutation) are a genetic hallmark of AITL. Detection of the G17V RHOA mutations assists prompt and appropriate diagnosis of AITL. However, an optimal detection method for the G17V RHOA mutation remains to be elucidated. We compared the sensitivity and concordance of next‐generation sequencing (NGS), droplet digital PCR (ddPCR) and peptide nucleic acid‐locked nucleic acid (PNA‐LNA) clamp method for detecting the G17V RHOA mutation. G17V RHOA mutations were identified in 27 of 67 (40.3%) PTCL samples using NGS. ddPCR and PNA‐LNA clamp method both detected G17V mutations in 4 samples in addition to those detected with NGS (31 of 67, 46.3%). Additionally, variant allele frequencies with ddPCR and those with NGS showed high concordance (P < .001). Three other RHOA mutations involving the p.Gly17 position (c.[49G > T;50G > T], p.Gly17Leu in PTCL198; c.[50G > T;51A > C], p.Gly17Val in PTCL216; and c.50G > A, p.Gly17Glu in PTCL223) were detected using NGS. These sequence changes could not appropriately be detected using the ddPCR assay and the PNA‐LNA clamp method although both indicated that the samples might have mutations. In total, 34 out of 67 PTCL samples (50.7%) had RHOA mutations at the p.Gly17 position. In conclusion, our results suggested that a combination of ddPCR/PNA‐LNA clamp methods and NGS are best method to assist the diagnosis of AITL by detecting RHOA mutations at the p.Gly17 position.

BRAF V600E mutation in hairy cell leukemia: from bench to bedside

Hairy cell leukemia (HCL) is a distinct clinicopathological entity whose underlying genetic lesion has remained a mystery for over half a century. The BRAF V600E mutation is now recognized as the causal genetic event of HCL because it is somatic, present in the entire tumor clone, detectable in almost all cases at diagnosis (encompassing the whole disease spectrum), and stable at relapse. BRAF V600E leads to the constitutive activation of the RAF-MEK-extracellular signal-regulated kinase (ERK) signaling pathway which represents the key event in the molecular pathogenesis of HCL. KLF2 and CDNK1B (p27) mutations may cooperate with BRAF V600E in promoting leukemic transformation. Sensitive molecular assays for detecting BRAF V600E allow HCL (highly responsive to purine analogs) to be better distinguished from HCL-like disorders, which are treated differently. In vitro preclinical studies on purified HCL cells proved that BRAF and MEK inhibitors can induce marked dephosphorylation of MEK/ERK, silencing of RAF-MEK-ERK pathway transcriptional output, loss of the HCL-specific gene expression profile signature, change of morphology from “hairy” to “smooth,” and eventually apoptosis. The overall response rate of refractory/relapsed HCL patients to the BRAF inhibitor vemurafenib approached 100%, with 35% to 40% complete remissions (CRs). The median relapse free-survival was about 19 months in patients who had achieved CR and 6 months in those who had obtained a partial response. Future therapeutic perspectives include: (1) combining BRAF inhibitors with MEK inhibitors or immunotherapy (anti-CD20 monoclonal antibody) to increase the percentage of CRs and (2) better understanding of the molecular mechanisms underlying resistance of HCL cells to BRAF inhibitors.