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MPLW515L is a novel somatic activating mutation in myelofibrosis with myeloid metaplasia

Yana Pikman1, Benjamin H Lee, Thomas Mercher

  • 1Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America.

Plos Medicine
|July 13, 2006
PubMed
Abstract

Insights

Activating mutations in the MPL receptor (MPLW515L) drive myeloproliferative disorders in JAK2V617F-negative myelofibrosis. This MPLW515L mutation leads to JAK-STAT pathway activation and disease development.

Area of Science:

  • Hematology
  • Molecular Biology
  • Oncology

Background:

  • The JAK2V617F mutation is implicated in myeloproliferative neoplasms (MPNs) like polycythemia vera (PV), essential thrombocytosis (ET), and myelofibrosis (MF).
  • Constitutive activation of the JAK-STAT pathway is a key pathogenetic event in MPNs.
  • A subset of ET and MF patients are negative for the JAK2V617F mutation, suggesting alternative activation mechanisms.

Purpose of the Study:

  • To investigate activating mutations in hematopoietic cytokine receptors (EPOR, MPL, GCSFR) as a cause of JAK-STAT pathway activation in JAK2V617F-negative MPNs.
  • To characterize the functional consequences of identified mutations in vitro and in vivo.

Main Methods:

  • DNA sequencing of EPOR, MPL, and GCSFR in JAK2V617F-negative MF patients.
  • Expression of mutant MPL (MPLW515L) in hematopoietic cell lines (32D, UT7, Ba/F3).
  • JAK-STAT signaling analysis and in vitro JAK kinase inhibition assays.
  • Murine bone marrow transplant models to assess in vivoMPLW515L pathogenicity.

Main Results:

  • A somatic activating mutation, MPLW515L, was identified in 9% of JAK2V617F-negative MF patients.
  • MPLW515L expression induced cytokine-independent growth, thrombopoietin hypersensitivity, and constitutive phosphorylation of JAK-STAT, AKT, and ERK signaling pathways.
  • Inhibition of JAK kinase suppressed MPLW515L-mediated proliferation and signaling.
  • MPLW515L expression in mice caused a myeloproliferative disorder with thrombocytosis, splenomegaly, and myelofibrosis.

Conclusions:

  • Activation of JAK-STAT signaling through MPLW515L is a significant pathogenetic mechanism in JAK2V617F-negative myelofibrosis.
  • The MPLW515L murine model recapitulates key features of human MF, including extramedullary hematopoiesis and splenomegaly.
  • Further research into JAK-STAT pathway regulators is crucial for understanding and treating JAK2V617F-negative MPDs.

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