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Hairy cell leukemia: update and current therapeutic approach.

ABSTRACT: In this review, we discuss the pathogenesis and standard therapeutic approach to hairy cell leukaemia (HCL) as well as newer targeted therapies under investigation showing promising end-points in treating HCL.HCL is an indolent B-cell leukaemia. Historically, HCL patients have achieved excellent response to purine nucleoside analogues and single purine analogue treatment with pentostatin or cladribine is currently the standard of care for initial treatment. Most patients achieve complete remission with this form of therapy. However, long-term follow-up has demonstrated that a large number of patients eventually develop relapsed disease. Relapse disease tends to be more difficult to treat and refractory to the same purine analogues. Development of relapsing and refractory disease after initially achieving complete remission with purine analogue treatment has generated a need for alternative therapies.Identification of the BRAFV600E mutation in nearly 100% of HCL patients has provided rationale for inclusion of BRAF inhibitors into the therapeutic armamentarium to treat HCL. Clinical trials are currently underway measuring efficacy of vemurafenib in achieving clinical response in relapsed/refractory HCL and also toxicity. Other novel therapies with monoclonal and immunotoxin-conjugated antibodies have also shown promising response in recent investigational studies.

SUBMITTER: Salam L

PROVIDER: S-EPMC6051354 | biostudies-literature | 2015 Jul

REPOSITORIES: biostudies-literature

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Hairy cell leukemia: update and current therapeutic approach.

Salam Latif L Abdel-Wahab Omar O

Current opinion in hematology 20150701 4

<h4>Purpose of review</h4>In this review, we discuss the pathogenesis and standard therapeutic approach to hairy cell leukaemia (HCL) as well as newer targeted therapies under investigation showing promising end-points in treating HCL.<h4>Recent findings</h4>HCL is an indolent B-cell leukaemia. Historically, HCL patients have achieved excellent response to purine nucleoside analogues and single purine analogue treatment with pentostatin or cladribine is currently the standard of care for initial ...[more]

PMID: 26049757

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Project description: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).

Project description:In the category of mature B-cell neoplasms, splenic B-cell lymphoma and leukemia were clearly identified and include four distinct entities: hairy cell leukemia (HCL), splenic marginal zone lymphoma (SMZL), splenic diffuse red pulp lymphoma (SDRPL) and the new entity named splenic B-cell lymphoma/leukemia with prominent nucleoli (SBLPN). The BRAFV600E mutation is detected in nearly all HCL cases and offers a possibility of targeted therapy. BRAF inhibitors (BRAFi) represent effective and promising therapeutic approaches in patients with relapsed/refractory HCL. Vemurafenib and dabrafenib were assessed in clinical trials. The BRAFV600E mutation is missing in SDRPL and SBLPN: mitogen-activated protein kinase 1 (MAP2K1) mutations were found in 40% of SBLPN and VH4-34+ HCL patients, making possible to use MEK inhibitors (MEKi) such as trametinib, cobimetinib or binimetinib in monotherapy or associated with BRAFi. Other mutations may be associated and other signaling pathways involved, including the B-cell receptor signaling (BCR), cell cycle, epigenetic regulation and/or chromatin remodeling. In SDRPL, cyclin D3 (CCND3) mutations were found in 24% of patients, offering the possibility of using cell cycle inhibitors. Even if new emerging drugs, particularly those involved in the epigenetic regulation, have recently been added to the therapeutic armamentarium in HCL and HCL-like disorders, purine nucleoside analogs more and more associated with anti-CD20 monoclonal antibodies, are still used in the frontline setting. Thanks to the recent discoveries in genetics and signaling pathways in HCL and HCL-like disorders, new targeted therapies have been developed, have proven their efficacy and safety in several clinical trials and become essential in real life: BRAFi, MEKi, Bruton Tyrosine Kinase inhibitors (BTKi) and anti-CD22 immunotoxins. New other drugs emerged and have to be assessed in the future. In this article, we will discuss the main mutations identified in HCL and HCL-like disorders and the signaling pathways potentially involved in the pathogenesis of the different hairy cell disorders. We will discuss the results of the recent clinical trials, which will help us to propose an algorithm useful in clinical practice and we will highlight the different new drugs that may be used in the near future.

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Hairy cell leukemia: update and current therapeutic approach.

Publications

Hairy cell leukemia: update and current therapeutic approach.

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