Constant activation of the RAF-MEK-ERK pathway as a diagnostic and therapeutic target in hairy cell leukemia

Enrico Tiacci, Gianluca Schiavoni, Maria Paola Martelli, Emanuela Boveri, Roberta Pacini, Alessia Tabarrini, Silvia Zibellini, Alessia Santi, Valentina Pettirossi, Elisabetta Fortini, Stefano Ascani, Luca Arcaini, Giorgio Inghirami, Marco Paulli, Brunangelo Falini

Research output: Contribution to journalArticlepeer-review

Abstract

The BRAF-V600E mutation defines genetically hairy cell leukemia among B-cell leukemias and lymphomas. In solid tumors, BRAF-V600E is known to aberrantly activate the oncogenic MEK-ERK pathway, and targeted BRAF and/or MEK inhibitors have shown remarkable efficacy in clinical trials in melanoma patients. However, the MEKERK pathway status in hairy cell leukemia has not been thoroughly investigated. We assessed phospho-ERK expression in 37 patients with hairy cell leukemia and 44 patients with neoplasms mimicking hairy cell leukemia (40 splenic marginal zone lymphoma, 2 hairy cell leukemia-variant and 2 splenic lymphoma/leukemia unclassifiable) using immunohistochemistry on routine biopsies and/or Western blotting on purified leukemic cells, and correlated the phospho-ERK status with the BRAF-V600E mutation status. Besides confirming the constant presence of BRAF-V600E in all patients with hairy cell leukemia, we observed ubiquitous phospho-ERK expression in this malignancy. Conversely, all 44 cases with neoplasms mimicking hairy cell leukemia were devoid of BRAF-V600E and none expressed phospho-ERK. Furthermore, the two exceptionally rare cases of non-hairy cell leukemia unclassifiable chronic B-cell neoplasms previously reported to be BRAF-V600E+ on allele-specific polymerase chain reaction lacked phospho-ERK expression as well, suggesting the presence of the mutation in only a small part of the leukemic clone in these cases. In conclusion, our findings support the use of phospho-ERK immunohistochemistry in the differential diagnosis between hairy cell leukemia and its mimics, and establish the MEK-ERK pathway as a rational therapeutic target in this malignancy.

Original languageEnglish
Pages (from-to)635-639
Number of pages5
JournalHaematologica
Volume98
Issue number4
DOIs
Publication statusPublished - Apr 2013

ASJC Scopus subject areas

  • Hematology

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