HCL - Molecular Biology


Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Sulfonamides
  • Remission Induction
  • Cancer DNA
  • Recurrence
  • Young Adult
  • Flow Cytometry
  • B-Lymphocytes
  • Immunoglobulin Variable Region
  • Polymerase Chain Reaction
  • Gene Rearrangement, B-Lymphocyte, Heavy Chain
  • DNA Mutational Analysis
  • Biomarkers, Tumor
  • T-Lymphocytes
  • Single Nucleotide Polymorphism
  • Receptors, Antigen, B-Cell
  • Bone Marrow
  • Chromosome Aberrations
  • CD22
  • Somatic Hypermutation, Immunoglobulin
  • Immunophenotyping
  • Cancer RNA
  • Sensitivity and Specificity
  • VDJ Exons
  • Antineoplastic Agents
  • Karyotyping
  • Genes, Immunoglobulin
  • Nucleic Acid Hybridization
  • Alleles
  • Acute Lymphocytic Leukaemia
  • Immunoglobulin Heavy Chains
  • Y Chromosome
  • Hairy Cell Leukemia
  • B-Cell Lymphoma
  • Reticulin
  • p53 Protein
  • Cladribine
  • Chronic Lymphocytic Leukemia
  • FISH
  • Gene Rearrangement
  • Base Sequence
Tag cloud generated 29 August, 2019 using data from PubMed, MeSH and CancerIndex

Mutated Genes and Abnormal Protein Expression (3)

How to use this data tableClicking on the Gene or Topic will take you to a separate more detailed page. Sort this list by clicking on a column heading e.g. 'Gene' or 'Topic'.

CD22 19q13.12 SIGLEC2, SIGLEC-2 -CD22 and Hairy Cell Leukemia
TP53 17p13.1 P53, BCC7, LFS1, TRP53 -TP53 AND Hairy Cell Leukemia
ITGAX 16p11.2 CD11C, SLEB6 -ITGAX and Hairy Cell Leukemia

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications

Cardus B, Colling R, Hamblin A, Soilleux E
Comparison of methodologies for the detection of
J Clin Pathol. 2019; 72(6):406-411 [PubMed] Related Publications

Bibi A, Java S, Chaudhary S, et al.
Indian J Pathol Microbiol. 2018 Oct-Dec; 61(4):532-536 [PubMed] Related Publications
Background: BRAFV600E mutation has been reported as a unique genetic lesion of hairy cell leukemia (HCL), a subset of which lacks this lesion and shows adverse outcomes.
Aims: To determine the prevalence of BRAFV600E in HCL from our center and derive clinicopathological correlation, if any.
Materials and Methods: A 9-year retrospective analysis of 46 consecutive cases of HCL diagnosed on morphology and immunophenotyping was done. Stained smears were used as samples for amplification refractory mutation system polymerase-chain reaction using fluorescent primers for mutation detection.
Results: BRAFV600E mutation was detected in 41/46 patients (89.1%) while absent in control samples of chronic lymphocytic leukemia. Cases mimicking HCL-variant clinically or immunophenotypically too showed the presence of this mutation. HCL with mutated BRAF presented at a younger age. No statistical difference in blood counts, tumor load, and immunophenotype patterns existed among BRAF mutated and unmutated group. Nine patients (45%) with mutated BRAF had residual disease following treatment with cladribine.
Conclusion: BRAFV600E mutation analysis has a definitive role in the diagnosis of HCL.

Itamura H, Ide M, Sato A, et al.
Identification of the BRAF V600E mutation in Japanese patients with hairy cell leukemia and related diseases using a quenching probe method.
Int J Hematol. 2018; 108(4):416-422 [PubMed] Related Publications
Hairy cell leukemia (HCL) is a rare B-cell lymphoid malignancy that is difficult to distinguish from other morphological variants. The frequency of HCL has not been determined accurately in Japan. Recent studies revealed that the BRAF V600E mutation is the causal genetic event in HCL. We assessed the BRAF mutation in Japanese patients with HCL and related diseases using the quenching probe (QP) method, a single-nucleotide polymorphism detection system, and evaluated the incidence rate of HCL among Japanese patients with chronic lymphocytic leukemia, and related diseases. We identified 18 cases (33.3%) harboring the BRAF mutation among 54 patients diagnosed with, or suspected of having HCL. Of BRAF V600E-positive patients, 7 were only detected using the QP method, not by direct sequencing, whereas 11 were positive using both tests. In a larger cohort of Japanese patients diagnosed with chronic lymphoid leukemia or related diseases, the frequency of HCL was 4%. Patients with the BRAF V600E mutation had a significantly higher frequency of neutropenia, thrombocytopenia, and elevated soluble interleukin-2 receptor and common B-cell surface markers than patients without the mutation. Our results confirm that BRAF V600E-positive HCL is a relatively rare disorder in the Japanese leukemia patient population.

Angelova EA, Medeiros LJ, Wang W, et al.
Clinicopathologic and molecular features in hairy cell leukemia-variant: single institutional experience.
Mod Pathol. 2018; 31(11):1717-1732 [PubMed] Related Publications
Hairy cell leukemia-variant is rare. Only a small number of cases have been reported in the literature with little cytogenetic or molecular data available. In this study, we describe the clinicopathologic and genetic features of 23 patients with hairy cell leukemia-variant (16 men and 7 women) with a median age of 70 years. Most patients had splenomegaly (90%), leukocytosis (77%), and lymphocytosis (82%); no patients had monocytopenia. Histologically, the bone marrow biopsy specimens showed a mixed pattern of predominantly interstitial and lesser intrasinusoidal infiltration by leukemic cells. In bone marrow aspirate smears most cells had villous cytoplasmic features and a small nucleolus. We describe unusual sites of hairy cell leukemia-variant involvement in 4 patients, including brain, omentum, terminal ileum, and skin at the time of initial presentation. Immunophenotyping showed monotypic B-cells positive for pan B-cell antigens, CD11c, and CD103, and negative for CD25 and annexin A1. Conventional cytogenetic or fluorescence in situ hybridization analysis showed deletions of 17p13/TP53 and 11q22/ATM gene in 5/12 (42%) and 2/9 (22%) cases, respectively. Sequencing of the variable region of IGVH showed mutations (>2% deviation from germline) in 40% of the cases assessed. MAP2K1 mutation (p.C121S) was seen in 1 of 14 (7%) patients tested. No BRAF V600E mutations were detected. The patients were treated in a heterogeneous manner, but most often with therapies designed for classical hairy cell leukemia and the 5-year overall survival was 84%. In summary, hairy cell leukemia-variant exhibits a heterogeneous spectrum of clinical, morphologic, immunophenotypic, and genetic features that may overlap with classic hairy cell leukemia and other hairy cell-like B-cell neoplasms. A subset of patients can have an aggressive clinical course. In our experience MAP2K1 mutations are uncommon in this disease.

Vacca D, Cancila V, Gulino A, et al.
Real-time detection of BRAF V600E mutation from archival hairy cell leukemia FFPE tissue by nanopore sequencing.
Mol Biol Rep. 2018; 45(1):1-7 [PubMed] Related Publications
The MinION is a miniaturized high-throughput next generation sequencing platform of novel conception. The use of nucleic acids derived from formalin-fixed paraffin-embedded samples is highly desirable, but their adoption for molecular assays is hurdled by the high degree of fragmentation and by the chemical-induced mutations stemming from the fixation protocols. In order to investigate the suitability of MinION sequencing on formalin-fixed paraffin-embedded samples, the presence and frequency of BRAF c.1799T > A mutation was investigated in two archival tissue specimens of Hairy cell leukemia and Hairy cell leukemia Variant. Despite the poor quality of the starting DNA, BRAF mutation was successfully detected in the Hairy cell leukemia sample with around 50% of the reads obtained within 2 h of the sequencing start. Notably, the mutational burden of the Hairy cell leukemia sample as derived from nanopore sequencing proved to be comparable to a sensitive method for the detection of point mutations, namely the Digital PCR, using a validated assay. Nanopore sequencing can be adopted for targeted sequencing of genetic lesions on critical DNA samples such as those extracted from archival routine formalin-fixed paraffin-embedded samples. This result let speculating about the possibility that the nanopore sequencing could be trustably adopted for the real-time targeted sequencing of genetic lesions. Our report opens the window for the adoption of nanopore sequencing in molecular pathology for research and diagnostics.

Durham BH, Getta B, Dietrich S, et al.
Genomic analysis of hairy cell leukemia identifies novel recurrent genetic alterations.
Blood. 2017; 130(14):1644-1648 [PubMed] Free Access to Full Article Related Publications
Classical hairy cell leukemia (cHCL) is characterized by a near 100% frequency of the

Tiacci E, Pettirossi V, Schiavoni G, Falini B
Genomics of Hairy Cell Leukemia.
J Clin Oncol. 2017; 35(9):1002-1010 [PubMed] Free Access to Full Article Related Publications
Hairy cell leukemia (HCL) is a chronic mature B-cell neoplasm with unique clinicopathologic features and an initial exquisite sensitivity to chemotherapy with purine analogs; however, the disease relapses, often repeatedly. The enigmatic pathogenesis of HCL was recently clarified by the discovery of its underlying genetic cause, the BRAF-V600E kinase-activating mutation, which is somatically and clonally present in almost all patients through the entire disease spectrum and clinical course. By aberrantly activating the RAF-MEK-ERK signaling pathway, BRAF-V600E shapes key biologic features of HCL, including its specific expression signature, hairy morphology, and antiapoptotic behavior. Accompanying mutations of the KLF2 transcription factor or the CDKN1B/p27 cell cycle inhibitor are recurrent in 16% of patients with HCL and likely cooperate with BRAF-V600E in HCL pathogenesis. Conversely, BRAF-V600E is absent in other B-cell neoplasms, including mimickers of HCL that require different treatments (eg, HCL-variant and splenic marginal zone lymphoma). Thus, testing for BRAF-V600E allows for a genetics-based differential diagnosis between HCL and HCL-like tumors, even noninvasively in routine blood samples. BRAF-V600E also represents a new therapeutic target. Patients' leukemic cells exposed ex vivo to BRAF inhibitors are spoiled of their HCL identity and then undergo apoptosis. In clinical trials of patients with HCL who have experienced multiple relapses after purine analogs or who are refractory to purine analogs, a short course of the oral BRAF inhibitor vemurafenib produced an almost 100% response rate, including complete remission rates of 35% to 42%, without myelotoxicity. To further improve on these results, it will be important to clarify the mechanisms of incomplete leukemic cell eradication by vemurafenib and to explore chemotherapy-free combinations of a BRAF inhibitor with other targeted agents (eg, a MEK inhibitor and/or an anti-CD20 monoclonal antibody).

Jud S, Goede JS, Senn O, et al.
sIL2R ratio as early marker for response in hairy cell leukemia and the prognostic relevance of IL28B genotype to interferon-α therapy.
Ann Hematol. 2017; 96(5):757-763 [PubMed] Related Publications
Interferon-α (IFNα) was the first effective drug therapy for hairy cell leukemia (HCL). Nowadays, it is used as an alternative treatment in selected patients. Due to unlimited treatment time, monitoring and early prediction of response are important. Moreover, IFNα is used in the therapy of chronic hepatitis C, where a single nucleotide polymorphism of interleukin-28B gene (IL28B) correlates with therapy response. The role of this polymorphism in therapy response of IFNα-treated patients with HCL is unknown. Thirty-seven HCL patients treated between 1978 and 2014 were included in this study. Treatment strategy and response parameters (blood cell counts, soluble interleukin-2 receptor (sIL2R), and bone marrow examination) have been assessed. Relative decrease of sIL2R was correlated with outcome parameters. Response parameters of IFNα-treated patients were correlated with IL28B polymorphism. Twenty-one patients were analyzed for the correlation of sIL2R ratio and outcome. After 1 and 3 months of therapy (IFNα or cladribine (CDA)), the median sIL2R level showed a relative decrease of 79 and 91%. These decreases significantly correlate with time to complete remission (CR, p = 0.029 and p = 0.018). Correlation analyses of IL28B genotype with outcome parameters are not significant. Six patients (16%) were diagnosed with secondary malignancies, and one death was registered (median follow-up time 14 years). IFNα is a safe, effective, and well-tolerated long-term treatment in HCL. Relative decreases of sIL2R levels correlate with time to CR and are useful as early predictor for response. There is no significant correlation between IL28B polymorphism and treatment response to IFNα. Graphical abstract.

Falini B, Martelli MP, Tiacci E
BRAF V600E mutation in hairy cell leukemia: from bench to bedside.
Blood. 2016; 128(15):1918-1927 [PubMed] Related Publications
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.

Weston-Bell NJ, Tapper W, Gibson J, et al.
Exome Sequencing in Classic Hairy Cell Leukaemia Reveals Widespread Variation in Acquired Somatic Mutations between Individual Tumours Apart from the Signature BRAF V(600)E Lesion.
PLoS One. 2016; 11(2):e0149162 [PubMed] Free Access to Full Article Related Publications
In classic Hairy cell leukaemia (HCLc), a single case has thus far been interrogated by whole exome sequencing (WES) in a treatment naive patient, in which BRAF V(600)E was identified as an acquired somatic mutation and confirmed as occurring near-universally in this form of disease by conventional PCR-based cohort screens. It left open however the question whether other genome-wide mutations may also commonly occur at high frequency in presentation HCLc disease. To address this, we have carried out WES of 5 such typical HCLc cases, using highly purified splenic tumour cells paired with autologous T cells for germline. Apart from BRAF V(600)E, no other recurrent somatic mutation was identified in these HCLc exomes, thereby excluding additional acquired mutations as also prevalent at a near-universal frequency in this form of the disease. These data then place mutant BRAF at the centre of the neoplastic drive in HCLc. A comparison of our exome data with emerging genetic findings in HCL indicates that additional somatic mutations may however occur recurrently in smaller subsets of disease. As mutant BRAF alone is insufficient to drive malignant transformation in other histological cancers, it suggests that individual tumours utilise largely differing patterns of genetic somatic mutations to coalesce with BRAF V(600)E to drive pathogenesis of malignant HCLc disease.

Arons E, Zhou H, Edelman DC, et al.
Impact of telomere length on survival in classic and variant hairy cell leukemia.
Leuk Res. 2015; 39(12):1360-6 [PubMed] Free Access to Full Article Related Publications
Telomeres, which protect the ends of chromosomes, are shortened in several hematologic malignancies, often with adverse prognostic implications, but their effect on prognosis of classic and variant hairy cell leukemia (HCL and HCLv) has not been reported. HCL/HCLv genomic DNA from 46 patients was studied by PCR to determine the ratio of telomere to single copy gene number (T/S). T/S was unrelated to diagnosis of HCL or HCLv (p=0.27), but shorter T/S was associated with unmutated immunoglobulin rearrangements (p=0.033) and age above the median at diagnosis (p=0.017). Low T/S was associated with shorter overall survival from diagnosis (OS), particularly T/S <0.655 (p=0.0064, adjusted p=0.019). Shorter OS was also associated with presence of unmutated (p<0.0001) or IGHV4-34+ (p<0.0001) rearrangements, or increasing age (p=0.0002). Multivariable analysis with Cox modeling showed that short T/S along with either unmutated or IGHV4-34+ rearrangements remained associated with reduced OS (p=0.0071, p=0.0024, respectively) after age adjustment. While T/S is relatively long in HCL and the disease usually indolent with excellent survival, shortened telomeres in HCL/HCLv are associated with decreased survival. Shortened T/S could represent a risk factor needing further investigation/intervention to determine if non-chemotherapy treatment options, in addition to or instead of chemotherapy, might be particularly useful.

Robak T, Smolewski P
New mutation in hairy cell leukemia.
Blood. 2015; 126(8):930-1 [PubMed] Related Publications
In this issue of Blood, Dietrich et al make the first observation of the presence of deleterious CDKN1B mutation in 16% of patients with hairy cell leukemia (HCL). Furthermore, in the majority of patients, the CDKN1B mutation was clonal, suggesting that this mutation plays a role in the pathogenesis of HCL.

Turakhia S, Lanigan C, Hamadeh F, et al.
Immunohistochemistry for BRAF V600E in the Differential Diagnosis of Hairy Cell Leukemia vs Other Splenic B-Cell Lymphomas.
Am J Clin Pathol. 2015; 144(1):87-93 [PubMed] Related Publications
OBJECTIVES: Recent reports have used immunohistochemistry (IHC) with a mutation-specific antibody to detect the BRAF V600E mutation, which is found in nearly all cases of hairy cell leukemia (HCL). To date, however, only a small number of non-HCL, splenic B-cell lymphomas have been examined by IHC.
METHODS: We analyzed 121 cases, including 26 HCLs, 52 non-HCL splenic lymphomas, 22 chronic lymphocytic leukemias/small lymphocytic lymphomas (CLLs/SLLs), and 21 plasma cell neoplasms (PCNs) for BRAF V600E expression by IHC. Molecular testing for BRAF V600E was performed in a subset of cases, using allele-specific polymerase chain reaction and/or Sanger sequencing.
RESULTS: Twenty-six (100%) of 26 HCL cases were positive by IHC vs one (1%) of 95 non-HCL cases. Positive staining was identified in one (2%) of 44 splenic marginal zone lymphomas (SMZLs), while each of 22 CLLs/SLLs, 21 PCNs, six unclassifiable splenic lymphomas, and two HCL variants were negative. IHC and molecular results were concordant in all cases examined (21 HCLs and 21 non-HCLs, including the BRAF+ SMZLs).
CONCLUSIONS: The detection of BRAF V600E by IHC is useful in the distinction of HCLs from other splenic-based lymphomas, although the identification of at least rare SMZLs containing this abnormality illustrates the continuing need for a multiparameter approach to diagnosis.

Dietrich S, Hüllein J, Lee SC, et al.
Recurrent CDKN1B (p27) mutations in hairy cell leukemia.
Blood. 2015; 126(8):1005-8 [PubMed] Related Publications
Hairy cell leukemia (HCL) is marked by near 100% mutational frequency of BRAFV600E mutations. Recurrent cooperating genetic events that may contribute to HCL pathogenesis or affect the clinical course of HCL are currently not described. Therefore, we performed whole exome sequencing to explore the mutational landscape of purine analog refractory HCL. In addition to the disease-defining BRAFV600E mutations, we identified mutations in EZH2, ARID1A, and recurrent inactivating mutations of the cell cycle inhibitor CDKN1B (p27). Targeted deep sequencing of CDKN1B in a larger cohort of HCL patients identify deleterious CDKN1B mutations in 16% of patients with HCL (n = 13 of 81). In 11 of 13 patients the CDKN1B mutation was clonal, implying an early role of CDKN1B mutations in the pathogenesis of HCL. CDKN1B mutations were not found to impact clinical characteristics or outcome in this cohort. These data identify HCL as having the highest frequency of CDKN1B mutations among cancers and identify CDNK1B as the second most common mutated gene in HCL. Moreover, given the known function of CDNK1B, these data suggest a novel role for alterations in regulation of cell cycle and senescence in HCL with CDKN1B mutations.

Okada K, Kunitomi A, Sakai K, et al.
Hairy Cell Leukemia with Systemic Lymphadenopathy: Detection of BRAF Mutations in Both Lymph Node and Peripheral Blood Specimens.
Intern Med. 2015; 54(11):1397-402 [PubMed] Related Publications
A 47-year-old woman with pancytopenia, excessive systemic lymphadenopathy and splenomegaly was referred to our hospital. The peripheral blood (PB) smear findings indicated neutropenia with lymphoid cells exhibiting hairy projections, while the histological findings of the cervical lymph node (LN) suggested hairy cell leukemia (HCL). In addition, the BRAF V600E mutation was detected, and the immunoglobulin gene rearrangement patterns were identical in both the cervical LN and PB specimens. Based on these findings, we diagnosed the patient with systemic lymphadenopathy due to HCL. This is the first report of a BRAF mutation detected in both the PB and LN at the onset of HCL.

Thomas C, Amanuel B, Finlayson J, et al.
BRAF mutation detection in hairy cell leukaemia from archival haematolymphoid specimens.
Pathology. 2015; 47(4):349-54 [PubMed] Related Publications
Hairy cell leukaemia (HCL) is a rare, indolent chronic B-cell leukaemia accounting for approximately 2% of all adult leukaemias. The recent association of the BRAF p.Val600Glu (V600E) mutation in HCL makes it a valuable molecular diagnostic marker. We compared the ability of Sanger sequencing, fluorescent single-strand conformational polymorphism (F-SSCP) and high resolution melting (HRM) analysis to detect BRAF mutations in 20 cases of HCL consisting of four archival Romanowsky stained air-dried peripheral blood and bone marrow aspirate smears, 12 mercury fixed decalcified bone marrow trephine biopsies, three formalin fixed, paraffin embedded (FFPE) splenectomy samples and one fresh peripheral blood sample. DNA was amplified and BRAF mutation status determined by the three methods above. V600E mutation was identified in 94%, 89% and 72% of HCL cases by F-SSCP, HRM and Sanger sequencing, respectively. In one case, in addition to the p.Val600Glu mutation, a p.Lys601Thr (K601T) mutation was identified. DNA from archival slide scrapings, mercury-fixed and FFPE tissue can be used to identify BRAF mutations with high sensitivity, especially using HRM/F-SSCP. The V600E mutation can be used as a supplementary molecular marker to aid in the diagnosis of HCL and the presence of the mutation may provide a target for therapy.

Klapper W, Kreipe H
[Diagnostic molecular pathology of lymphatic and myeloid neoplasms].
Pathologe. 2015; 36(2):164-70 [PubMed] Related Publications
Molecular pathology has been an integral part of the diagnostics of tumors of the hematopoietic system substantially longer than for solid neoplasms. In contrast to solid tumors, the primary objective of molecular pathology in hematopoietic neoplasms is not the prediction of drug efficacy but the diagnosis itself by excluding reactive proliferation and by using molecular features for tumor classification. In the case of malignant lymphomas, the most commonly applied molecular tests are those for gene rearrangements for immunoglobulin heavy chains and T-cell receptors. However, this article puts the focus on new and diagnostically relevant assays in hematopathology. Among these are mutations of MYD88 codon 265 in lymphoplasmacytic lymphomas, B-raf V600E in hairy cell leukemia and Stat3 exon 21 in indolent T-cell lymphomas. In myeloproliferative neoplasms, MPL W515, calreticulin exon 9 and the BCR-ABL and JAK2 V617F junctions are the most frequently analyzed differentiation series. In myelodysplastic and myeloproliferative neoplasms, SRSF2, SETBP1 and CSF3R mutations provide important differential diagnostic information. Genes mutated in myelodysplastic syndromes (MDS) are particularly diverse but their analysis significantly improves the differential diagnostics between reactive conditions and MDS. The most frequent changes in MDS include mutations of TET2 and various genes encoding splicing factors.

Kreitman RJ
Removing a hair of doubt about BRAF targeting.
Blood. 2015; 125(8):1199-200 [PubMed] Free Access to Full Article Related Publications
In this issue of Blood, Pettirossi et al, including Drs Tiacci and Falini, who led the effort in 2011 defining the BRAF-V600E driving mutation in hairy cell leukemia (HCL),provide extensive laboratory studies showing that inhibitors of BRAF-V600E and/or mitogen-activated protein kinase kinase (MEK) reach their targets and cause HCL cell death

Pettirossi V, Santi A, Imperi E, et al.
BRAF inhibitors reverse the unique molecular signature and phenotype of hairy cell leukemia and exert potent antileukemic activity.
Blood. 2015; 125(8):1207-16 [PubMed] Free Access to Full Article Related Publications
Hairy cell leukemia (HCL) shows unique clinicopathological and biological features. HCL responds well to purine analogs but relapses are frequent and novel therapies are required. BRAF-V600E is the key driver mutation in HCL and distinguishes it from other B-cell lymphomas, including HCL-like leukemias/lymphomas (HCL-variant and splenic marginal zone lymphoma). The kinase-activating BRAF-V600E mutation also represents an ideal therapeutic target in HCL. Here, we investigated the biological and therapeutic importance of the activated BRAF-mitogen-activated protein kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) pathway in HCL by exposing in vitro primary leukemic cells purified from 26 patients to clinically available BRAF (vemurafenib; dabrafenib) or MEK (trametinib) inhibitors. Results were validated in vivo in samples from vemurafenib-treated HCL patients within a phase 2 clinical trial. BRAF and MEK inhibitors caused, specifically in HCL (but not HCL-like) cells, marked MEK/ERK dephosphorylation, silencing of the BRAF-MEK-ERK pathway transcriptional output, loss of the HCL-specific gene expression signature, downregulation of the HCL markers CD25, tartrate-resistant acid phosphatase, and cyclin D1, smoothening of leukemic cells' hairy surface, and, eventually, apoptosis. Apoptosis was partially blunted by coculture with bone marrow stromal cells antagonizing MEK-ERK dephosphorylation. This protective effect could be counteracted by combined BRAF and MEK inhibition. Our results strongly support and inform the clinical use of BRAF and MEK inhibitors in HCL.

So CC, Chan A, Chung LP, et al.
A comparison of high resolution melting, allele-specific priming and Sanger sequencing for the detection of BRAFV600E mutation in hairy cell leukaemia from different haematological specimens.
Pathology. 2014; 46(6):533-7 [PubMed] Related Publications
The BRAFV600E mutation is a highly sensitive and specific marker for the diagnosis of hairy cell leukaemia (HCL) and a potential therapeutic target. We assessed the performance of high resolution melting (HRM), allele-specific priming (ASP) and Sanger sequencing (SS) for BRAFV600E detection in 17 unenriched samples from 15 HCL patients: blood (n = 7), marrow aspirate (n = 3), ethylenediaminetetraacetic acid (EDTA)-decalcified trephine biopsy (n = 2), formic acid (FA)-decalcified trephine biopsy (n = 5). Our results showed that for blood and marrow aspirate samples, both HRM and ASP had a very high analytical sensitivity (1%) in clinical specimens and excellent diagnostic sensitivity (100%) and specificity (100%) in analysable samples. Sanger sequencing had a lower analytical sensitivity (4%), resulting in false-negative analysis in samples with a low tumour cell percentage. High resolution melting was technically the simplest and had the shortest turn-around time (2 hours). Analysis of decalcified trephine biopsies was more difficult because of suboptimal DNA preservation. Although Sanger sequencing was least demanding on sample DNA quality for a successful analysis, none of the three techniques showed satisfactory diagnostic performance on trephine biopsies. Therefore, careful selection of a suitable sample type and testing platform is important to optimise the detection of this important mutation in HCL.

Arons E, Adams S, Venzon DJ, et al.
Class II human leucocyte antigen DRB1*11 in hairy cell leukaemia patients with and without haemolytic uraemic syndrome.
Br J Haematol. 2014; 166(5):729-38 [PubMed] Free Access to Full Article Related Publications
Frequencies of human leucocyte antigens (HLA) were determined in 287 classic hairy cell leukaemia (HCL) patients. With respect to both population (n = 287) and allele (2n = 574) frequency respectively, the most common HLA class I and II antigens expressed were HLA-A*02 (49·1% and 28·6%), HLA-B*07 (21·3% and 11·1%), HLA-C*07 (46·7 and 28·2%), HLA-DQB1*03 (62·7% and 37·3%), HLA-DRB1*11 (30·0% and 16·0%) and HLA-DRB4*01 (45·3% and 29·6%). In comparing 6-14 databases of control Caucasians to 267 Caucasian HCL patients, only HLA-DRB1*11 was consistently over-represented in HCL, 31·1% of patients vs. 17-19·9% of controls (P = 0·0055 to <0·0001) and 16·5% of alleles vs. 6·5-12·3% of control alleles (P = 0·022 to <0·0001). HLA-DRB1*11 is a known risk factor for acquired thrombotic microangiopathy. Anti-CD22 recombinant immunotoxin BL22 in HCL was associated with a 12% incidence of completely reversible grade 3-4 haemolytic uraemic syndrome (HUS), mainly during the second or third retreatment cycle. Of 49 HCL patients receiving ≥2 cycles of BL22, 7 (14%) had HUS and HLA-DRB1*11 was expressed in 71% of 7 with HUS compared with only 21% of 42 without (P = 0·015). These data suggest that DBR1*11 may be a marker for increased susceptibility to HCL and, among HCL patients, could be a risk factor for BL22-induced HUS.

Chung SS, Kim E, Park JH, et al.
Hematopoietic stem cell origin of BRAFV600E mutations in hairy cell leukemia.
Sci Transl Med. 2014; 6(238):238ra71 [PubMed] Free Access to Full Article Related Publications
Hairy cell leukemia (HCL) is a chronic lymphoproliferative disorder characterized by somatic BRAFV600E mutations. The malignant cell in HCL has immunophenotypic features of a mature B cell, but no normal counterpart along the continuum of developing B lymphocytes has been delineated as the cell of origin. We find that the BRAFV600E mutation is present in hematopoietic stem cells (HSCs) in HCL patients, and that these patients exhibit marked alterations in hematopoietic stem/progenitor cell (HSPC) frequencies. Quantitative sequencing analysis revealed a mean BRAFV600E-mutant allele frequency of 4.97% in HSCs from HCL patients. Moreover, transplantation of BRAFV600E-mutant HSCs from an HCL patient into immunodeficient mice resulted in stable engraftment of BRAFV600E-mutant human hematopoietic cells, revealing the functional self-renewal capacity of HCL HSCs. Consistent with the human genetic data, expression of BRafV600E in murine HSPCs resulted in a lethal hematopoietic disorder characterized by splenomegaly, anemia, thrombocytopenia, increased circulating soluble CD25, and increased clonogenic capacity of B lineage cells-all classic features of human HCL. In contrast, restricting expression of BRafV600E to the mature B cell compartment did not result in disease. Treatment of HCL patients with vemurafenib, an inhibitor of mutated BRAF, resulted in normalization of HSPC frequencies and increased myeloid and erythroid output from HSPCs. These findings link the pathogenesis of HCL to somatic mutations that arise in HSPCs and further suggest that chronic lymphoid malignancies may be initiated by aberrant HSCs.

Sári E, Nagy ZG, Baghy K, et al.
Treatment of refractory hairy cell leukemia with a BRAF-inhibitor: lessons to be learnt.
Pathol Oncol Res. 2014; 20(4):973-80 [PubMed] Related Publications
Hairy cell leukemia is a rare chronic lymphoproliferative disorder with indolent but progressive clinical course. Patients require treatment when they have significant cytopenia or recurrent infections. The gold standard treatment are purine nucleoside analogues (cladribine and pentostatine), with these agents the rate of complete remission can approach even 95 %. The differential diagnosis between classical hairy cell leukemia and other, rare splenic lymphomas that can mimic this disease might be really challenging. Splenic lymphoma with villous lymphocytes and other new, provisional WHO entities share some, but not all immunophenotypical features with hairy cell leukemia. The correct diagnosis is of an extreme importance as these entities require different treatment. Thus further investigation in the pathogenesis of hairy cell leukemia is required in order to solve this challenge. Discovery of the BRAF V600E mutation as a disease-defining genetic event in hairy cell leukemia can be helpful in both differential diagnosis and treatment of this disease. We report the case of three hairy cell leukemia patients, whose diagnosis or treatment was based on this newly discovered somatic mutation, but the treatment results and side effects were individual.

Sakata-Yanagimoto M, Enami T, Yokoyama Y, Chiba S
Disease-specific mutations in mature lymphoid neoplasms: recent advances.
Cancer Sci. 2014; 105(6):623-9 [PubMed] Free Access to Full Article Related Publications
Mature lymphoid neoplasms (MLN) are clinically and pathologically more complex than precursor lymphoid neoplasms. Until recently, molecular characterization of MLN was mainly based on cytogenetics/fluorescence in situ hybridization, allele copy number, and mRNA expression, approaches that yielded scanty gene mutation information. Use of massive parallel sequencing technologies has changed this outcome, and now many gene mutations have been discovered. Some of these are considerably frequent in, and substantially specific to, distinct MLN subtypes, and occur at single or several hotspots. They include the V600E BRAF mutation in hairy cell leukemia, the L265P MYD88 mutation in Waldenström macroglobulinemia, the G17V RHOA mutation in angioimmunoblastic T-cell lymphoma and peripheral T-cell lymphoma, not otherwise specified, and the Y640F//D661Y/V/H/I//N647I STAT3 mutations in T-cell large granular lymphocytic leukemia. Detecting these mutations is highly valuable in diagnosing MLN subtypes. Defining these mutations also sheds light on the molecular pathogenesis of MLN, furthering development of molecular targeting therapies. In this review, we focus on the disease-specific gene mutations in MLN discovered by recent massive sequencing technologies.

Zhang Y, Liu H, Qi J, et al.
[Detection of BRAF V600E mutation in hairy cell leukemia by high- resolution melting analysis].
Zhonghua Xue Ye Xue Za Zhi. 2014; 35(3):207-9 [PubMed] Related Publications
OBJECTIVE: To explore the feasibility and diagnostic implication of BRAF V600E mutation identified by high-resolution melting (HRM) assay in patients with hairy cell leukemia (HCL).
METHODS: The V600E mutation of BRAF exon 15 in four HCL patients were detected by HRM assay and patients' clinical data were retrospectively analyzed.
RESULTS: All four HCL patients were positive for the BRAF V600E mutation, which were identical to the results of DNA sequencing.
CONCLUSION: The HRM assay for BRAF V600E mutation provides a useful tool to aid the laboratory diagnosis of HCL with easy operability, accuracy, and low cost.

Weston-Bell NJ, Forconi F, Kluin-Nelemans HC, Sahota SS
Variant B cell receptor isotype functions differ in hairy cell leukemia with mutated BRAF and IGHV genes.
PLoS One. 2014; 9(1):e86556 [PubMed] Free Access to Full Article Related Publications
A functional B-cell receptor (BCR) is critical for survival of normal B-cells, but whether it plays a comparable role in B-cell malignancy is as yet not fully delineated. Typical Hairy Cell Leukemia (HCL) is a rare B-cell tumor, and unique in expressing multiple surface immunoglobulin (sIg) isotypes on individual tumor cells (mult-HCL), to raise questions as to their functional relevance. Typical mult-HCL also displays a mutated BRAF V(600)E lesion. Since wild type BRAF is a primary conduit for transducing normal BCR signals, as revealed by deletion modelling studies, it is as yet not apparent if mutated BRAF alters BCR signal transduction in mult-HCL. To address these questions, we examined BCR signalling in mult-HCL cases uniformly displaying mutated BRAF and IGHV genes. Two apparent functional sets were delineated by IgD co-expression. In sIgD(+ve) mult-HCL, IgD mediated persistent Ca(2+) flux, also evident via >1 sIgH isotype, linked to increased ERK activation and BCR endocytosis. In sIgD(-ve) mult-HCL however, BCR-mediated signals and downstream effects were restricted to a single sIgH isotype, with sIgM notably dysfunctional and remaining immobilised on the cell surface. These observations reveal discordance between expression and function of individual isotypes in mult-HCL. In dual sIgL expressing cases, only a single sIgL was fully functional. We examined effects of anti-BCR stimuli on mult-HCL survival ex-vivo. Significantly, all functional non-IgD isotypes increased ERK1/2 phosphorylation but triggered apoptosis of tumor cells, in both subsets. IgD stimuli, in marked contrast retained tumor viability. Despite mutant BRAF, BCR signals augment ERK1/2 phosphorylation, but isotype dictates functional downstream outcomes. In mult-HCL, sIgD retains a potential to transduce BCR signals for tumor survival in-vivo. The BCR in mult-HCL emerges as subject to complex regulation, with apparent conflicting signalling by individual isotypes when co-expressed with sIgD. This suggests the possibility that mutant BRAF by-passes BCR constraints in mult-HCL.

Tschernitz S, Flossbach L, Bonengel M, et al.
Alternative BRAF mutations in BRAF V600E-negative hairy cell leukaemias.
Br J Haematol. 2014; 165(4):529-33 [PubMed] Related Publications
The BRAF V600E mutation in exon 15 is considered the disease-defining mutation in hairy cell leukaemia (HCL), but single HCL cases lacking this mutation have been described. In 24 HCL, as well as in 194 various mature B- and T-cell neoplasms, we extended the search for BRAF mutations to exon 11. Two V600E-negative HCL contained novel, potentially functionally relevant mutations in exon 11 (F468C and D449E), while one other HCL was BRAF wild-type in exons 2-17. All non-HCL lymphomas lacked BRAF mutations. We therefore suggest screening of BRAF V600E-negative HCL for alternative exon 11 mutations in the diagnostic setting.

Waterfall JJ, Arons E, Walker RL, et al.
High prevalence of MAP2K1 mutations in variant and IGHV4-34-expressing hairy-cell leukemias.
Nat Genet. 2014; 46(1):8-10 [PubMed] Free Access to Full Article Related Publications
To understand the genetic mechanisms driving variant and IGHV4-34-expressing hairy-cell leukemias, we performed whole-exome sequencing of leukemia samples from ten affected individuals, including six with matched normal samples. We identified activating mutations in the MAP2K1 gene (encoding MEK1) in 5 of these 10 samples and in 10 of 21 samples in a validation set (overall frequency of 15/31), suggesting potential new strategies for treating individuals with these diseases.

Balsat M, Cornillon J
[Molecular and therapeutic advances in Hairy cell leukemia].
Bull Cancer. 2013; 100(10):1043-7 [PubMed] Related Publications
Hairy cell leukemia is a rare chronic lymphoproliferative disorder. Its diagnosis remains difficult due to different variant forms and differential diagnosis that are splenic marginal zone lymphoma and b-prolymphocytic leukemia. The prognosis of this malignancy has been transformed by purine nucleoside analogs, interferon, monoclonal antibodies and recombinant immunotoxins usually used in refractory or relapsed disease. The discovery of BRAF V600E mutation has become the milestone in the disease's history since it was uniformly identified in a HCL series in 2011. This mutation, commonly identified in melanoma, involves the protooncogene BRAF, a MAP3Kinase belonging to the RAF-MEK-ERK signaling pathway, which is the central key in several oncogenic processes. This mutation suggests disease-specific oncogene dependence. The detection of this mutation provides an additional diagnosis marker (because not found in variant forms), a best for monitoring minimal residual disease and a therapeutic target with the BRAF inhibitors in specific subgroups of patients, already tested in melanoma. This review aims to summarize the clinical and biological aspects and treatment of hairy cell leukemia and discusses the perspectives provided by the discovery of BRAF mutation in this disease.

Sári E, Nagy Z, Demeter J
[Recurrent somatic mutation in hairy cell leukemia].
Orv Hetil. 2013; 154(4):123-7 [PubMed] Related Publications
Hairy cell leukemia is a mature B-cell non-Hogkin lymphoma characterized by unique clinical, morphological and immunhistochemical features. Patients with hairy cell leukemia usually present with splenomegaly, progressive pancytopenia and a relative indolent clinical course. The diagnosis does not always indicate immediate treatment, as treatment depends on the clinical stage of the leukemia. Asymptomatic disease without progression requires a watchful waiting policy, while other categories usually need treatment. The treatment of choice is purine nucleoside analogues (pentostatin, cladribine) which can achieve complete remission even for decades. Interferon and monoclonal CD20 antibodies can also significantly prolong event-free survival. Unfortunately, only the latter two therapies are easily available in Hungary. Splenectomy, which was suggested as first line treatment before the era of purine nucleoside analogues, is only recommended as a last resort. Although hairy cell leukemia is a well-defined lymphoproliferative disease, sometimes it is difficult to differentiate it from other similar entities such as hairy cell leukema variant, splenic marginal zone lymphoma, small lymphocytic lymphoma etc. Making the correct diagnosis is of utmost importance because of the great difference in treatment modalities. Recently, a somatic mutation was found in all analysed hairy cell leukemia samples, but not in other splenic B-cell lymphomas. This article reviews the significance of this observation and presents the different types of methods for the detection of this mutation.

Recurrent Structural Abnormalities

Selected list of common recurrent structural abnormalities

Abnormality Type Gene(s)
Trisomy 12 in Hairy Cell LeukemiaTrisomy

This is a highly selective list aiming to capture structural abnormalies which are frequesnt and/or significant in relation to diagnosis, prognosis, and/or characterising specific cancers. For a much more extensive list see the Mitelman Database of Chromosome Aberrations and Gene Fusions in Cancer.

Trisomy 12 in Hairy Cell Leukemia

Vallianatou K, Brito-Babapulle V, Matutes E, et al.
p53 gene deletion and trisomy 12 in hairy cell leukemia and its variant.
Leuk Res. 1999; 23(11):1041-5 [PubMed] Related Publications
The deletion or mutation of the p53 tumour suppressor gene on chromosome 17p13 is known to be associated with aggressive disease in several B-cell malignancies. The present study describes the p53 gene status in 20 cases of hairy cell leukemia (HCL) and in 12 cases of its morphological variant (HCL-V) by fluorescence in situ hybridization (FISH). A high incidence of p53 deletion was found in both diseases (75-100% of cases). However, a significant difference was observed between the proportion of cells with p53 deletion in HCL-V cases (mean 31%) and HCL cases (mean 12%) P value < 0.01. The observed difference correlates with the well known tendency for transformation and poor response to therapy in HCL-V and seven cases of HCL-V with greater than 22% of cells with p53 deletion showed features of disease progression and transformation. Trisomy 12 was present in 8.5% of the cells in one case of HCL-V and in 6-8% of cells in three cases of HCL.

Cuneo A, Bigoni R, Balboni M, et al.
Trisomy 12 in chronic lymphocytic leukemia and hairy cell leukemia: a cytogenetic and interphase cytogenetic study.
Leuk Lymphoma. 1994; 15(1-2):167-72 [PubMed] Related Publications
Fluorescent in situ hybridization (FISH) with a chromosome 12-specific pericentromeric probe was performed in 42 patients with B-cell chronic lymphocytic leukemia (CLL) and in 10 patients with hairy cell leukemia (HCL). In all cases, a normal karyotype in more than 10 metaphase cells was obtained by conventional chromosome study. FISH documented that 6/42 patients with CLL in fact had trisomy 12 in 15-49% interphase cells. Sequential FISH studies were performed in 2 cases, showing an increase of percentage of trisomic cells over a 2-month to 4-year period. Two out of 10 patients with HCL, one of whom had morphologic features consistent with a diagnosis of HCL variant, showed 5.5 and 10% interphase nuclei with three fluorescent signals, a finding suggestive of the presence of trisomy 12. Combined immunophenotyping and FISH staining in these patients with HCL documented that trisomic cells were CD11c-positive, CD13-negative, and CD2-negative. We conclude that FISH is a sensitive technique allowing for the detection of trisomy 12 in a fraction of cytogenetically normal patients affected with CLL and HCL.

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