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PLoS Med DOI:10.1371/journal.pmed.0030270

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

Publication TypeJournal Article
Year of Publication2006
AuthorsPikman, Y, Lee, BH, Mercher, T, McDowell, E, Ebert, BL, Gozo, M, Cuker, A, Wernig, G, Moore, S, Galinsky, I, DeAngelo, DJ, Clark, JJ, Lee, SJ, Golub, TR, Wadleigh, M, D Gilliland, G, Levine, RL
JournalPLoS Med
Date Published2006 Jul
KeywordsAmino Acid Substitution, Animals, Bone Marrow Cells, Bone Marrow Transplantation, Cell Division, Cells, Cultured, Colony-Forming Units Assay, Cytokines, Disease Models, Animal, Gene Expression Regulation, Genetic Vectors, Hematologic Neoplasms, Hematopoiesis, Humans, Janus Kinases, Megakaryocytes, Mice, Mice, Inbred BALB C, mRNA Cleavage and Polyadenylation Factors, Mutation, Missense, Myeloid Cells, Myeloproliferative Disorders, Oncogene Proteins, Fusion, Phosphorylation, Point Mutation, Primary Myelofibrosis, Protein Kinase Inhibitors, Protein Processing, Post-Translational, Receptor, Platelet-Derived Growth Factor alpha, Receptors, Cytokine, Recombinant Fusion Proteins, Sequence Analysis, DNA, Signal Transduction, Spleen, STAT Transcription Factors, Thrombocytosis, Transcription, Genetic

BACKGROUND: The JAK2V617F allele has recently been identified in patients with polycythemia vera (PV), essential thrombocytosis (ET), and myelofibrosis with myeloid metaplasia (MF). Subsequent analysis has shown that constitutive activation of the JAK-STAT signal transduction pathway is an important pathogenetic event in these patients, and that enzymatic inhibition of JAK2V617F may be of therapeutic benefit in this context. However, a significant proportion of patients with ET or MF are JAK2V617F-negative. We hypothesized that activation of the JAK-STAT pathway might also occur as a consequence of activating mutations in certain hematopoietic-specific cytokine receptors, including the erythropoietin receptor (EPOR), the thrombopoietin receptor (MPL), or the granulocyte-colony stimulating factor receptor (GCSFR).

METHODS AND FINDINGS: DNA sequence analysis of the exons encoding the transmembrane and juxtamembrane domains of EPOR, MPL, and GCSFR, and comparison with germline DNA derived from buccal swabs, identified a somatic activating mutation in the transmembrane domain of MPL (W515L) in 9% (4/45) of JAKV617F-negative MF. Expression of MPLW515L in 32D, UT7, or Ba/F3 cells conferred cytokine-independent growth and thrombopoietin hypersensitivity, and resulted in constitutive phosphorylation of JAK2, STAT3, STAT5, AKT, and ERK. Furthermore, a small molecule JAK kinase inhibitor inhibited MPLW515L-mediated proliferation and JAK-STAT signaling in vitro. In a murine bone marrow transplant assay, expression of MPLW515L, but not wild-type MPL, resulted in a fully penetrant myeloproliferative disorder characterized by marked thrombocytosis (Plt count 1.9-4.0 x 10(12)/L), marked splenomegaly due to extramedullary hematopoiesis, and increased reticulin fibrosis.

CONCLUSIONS: Activation of JAK-STAT signaling via MPLW515L is an important pathogenetic event in patients with JAK2V617F-negative MF. The bone marrow transplant model of MPLW515L-mediated myeloproliferative disorders (MPD) exhibits certain features of human MF, including extramedullary hematopoiesis, splenomegaly, and megakaryocytic proliferation. Further analysis of positive and negative regulators of the JAK-STAT pathway is warranted in JAK2V617F-negative MPD.


Alternate JournalPLoS Med.
PubMed ID16834459
PubMed Central IDPMC1502153
Grant ListCA66996 / CA / NCI NIH HHS / United States
DK50654 / DK / NIDDK NIH HHS / United States
P01 CA066996 / CA / NCI NIH HHS / United States
T32 CA009172 / CA / NCI NIH HHS / United States
P01 DK050654 / DK / NIDDK NIH HHS / United States