title: BRAF inhibitors reverse the unique molecular signature and phenotype of hairy cell leukemia and exert potent antileukemic activity.
abstract: 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.
authors.affiliation: Institute of Hematology, and.
authors.forename: Valentina
authors.initials: V
authors.lastname: Pettirossi
authors.affiliation: Institute of Hematology, and.
authors.forename: Alessia
authors.initials: A
authors.lastname: Santi
authors.affiliation: Institute of Hematology, and.
authors.forename: Elisa
authors.initials: E
authors.lastname: Imperi
authors.affiliation: Institute of Hematology, and.
authors.forename: Guido
authors.initials: G
authors.lastname: Russo
authors.affiliation: Institute of Hematology, and.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Pucciarini
authors.affiliation: Institute of Hematology, and.
authors.forename: Barbara
authors.initials: B
authors.lastname: Bigerna
authors.affiliation: Institute of Hematology, and.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Schiavoni
authors.affiliation: Institute of Hematology, and.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Fortini
authors.affiliation: Institute of Hematology, and.
authors.forename: Ariele
authors.initials: A
authors.lastname: Spanhol-Rosseto
authors.affiliation: Institute of Hematology, and.
authors.forename: Paolo
authors.initials: P
authors.lastname: Sportoletti
authors.affiliation: Institute of Internal Medicine and Oncologic Sciences, University of Perugia, Perugia, Italy; and.
authors.forename: Roberta
authors.initials: R
authors.lastname: Mannucci
authors.affiliation: Institute of Hematology, and.
authors.forename: Maria Paola
authors.initials: MP
authors.lastname: Martelli
authors.affiliation: Biochip Laboratory, Institute for Cell Biology-Tumor Research, University of Duisburg-Essen, Essen, Germany.
authors.forename: Ludger
authors.initials: L
authors.lastname: Klein-Hitpass
authors.affiliation: Institute of Hematology, and.
authors.forename: Brunangelo
authors.initials: B
authors.lastname: Falini
authors.affiliation: Institute of Hematology, and.
authors.forename: Enrico
authors.initials: E
authors.lastname: Tiacci
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology / Q000627:therapeutic use; D007211:Indoles / Q000494:pharmacology / Q000627:therapeutic use; D007943:Leukemia, Hairy Cell / Q000188:drug therapy* / Q000235:genetics*; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects; D010091:Oximes / Q000494:pharmacology / Q000627:therapeutic use; D010766:Phosphorylation / Q000187:drug effects; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors; D011728:Pyridones / Q000494:pharmacology / Q000627:therapeutic use; D011744:Pyrimidinones / Q000494:pharmacology / Q000627:therapeutic use; D013449:Sulfonamides / Q000494:pharmacology / Q000627:therapeutic use; D059467:Transcriptome / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D000077484:Vemurafenib
chemical_list: D000970:Antineoplastic Agents; D007093:Imidazoles; D007211:Indoles; D010091:Oximes; D011728:Pyridones; D011744:Pyrimidinones; D013449:Sulfonamides; D000077484:Vemurafenib; C560077:trametinib; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D020930:MAP Kinase Kinase Kinases; C561627:dabrafenib