Polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF) are classical Philadelphia chromosome (Ph)-negative MPN that have a Janus Kinase 2 (JAK2) mutation, especially JAK2V617F in the majority of patients.
We investigated this question using conditional JAK2(V617F) knock-in mice with constitutive and inducible expression of JAK2(V617F) in hematopoietic cells, which develop a polycythemia vera (PV)-like disorder evolving into myelofibrosis.
The recent discovery of CALR mutations in essential thrombocythemia (ET) and primary myelofibrosis (PMF) patients without JAK2/MPL mutations has emerged as a relevant finding for the molecular diagnosis of these myeloproliferative neoplasms (MPN).
An acquired V617F mutation in JAK2 occurs in most patients with polycythaemia vera, but is seen in only half those with essential thrombocythaemia and idiopathic myelofibrosis.
Mutations in Janus Kinase-2 (JAK2), calreticulin (CALR) and myeloproliferative leukemia protein (MPL) genes have been recently associated to MF and they all activate the JAK/STAT signaling pathway.
When present in a heterozygous state the JAK2-V617F mutation preferentially stimulates megakaryopoiesis and in most cases manifests as essential thrombocythemia (ET), whereas homozygous JAK2-V617F reduces megakaryopoiesis in favor of increased erythropoiesis, resulting in polycythemia vera and/or myelofibrosis.
The JAK2 mutation was detected in 25 patients (46%); 12 of 26 patients with essential thrombocythemia (ET), 9 of 12 patients with polycyhtemia vera (PV), one of 7 patients with chronic idiopathic myelofibrosis (CIM) and one patient with unclassifiable MPD.
Primary Myelofibrosis (PMF) is a myeloproliferative disorder associated with JAK2V617F, Calreticulin (CALR) indels, and MPLW515L/K mutations activating the tyrosine kinase JAK2 and its downstream signaling pathway.
The mutational spectrum in myelofibrosis includes driver mutations in genes such as JAK2, calreticulin, and myeloproliferative leukemia virus oncogene.
A point mutation in exon 14 of the JAK2 gene resulting in the formation of the JAK2V617F transcript occurs in 95% of PV patients and around 50% of ET and PMF patients driving constitutive activation of the JAK/STAT pathway.
Given that the identical somatic activating mutation in the JAK2 tyrosine kinase gene (JAK2(V617F)) is observed in most individuals with polycythemia vera, essential thrombocythemia and primary myelofibrosis, there likely are additional genetic events that contribute to the pathogenesis of these phenotypically distinct disorders.
Three studies now report an amino acid substitution in the JAK2 kinase in most patients with polycythemia vera as well as in some cases of essential thrombocythemia and chronic idiopathic myelofibrosis.
The V617F mutation in the JAK2 gene on chromosome 9p24.1 was identified recently in peripheral blood leukocytes in the majority of patients with PV and in approximately half of patients with essential thrombocythemia and idiopathic myelofibrosis.
Strikingly, the JAK2(V617F) mutation is found in nearly all patients suffering from polycythemia vera and in roughly every second patient suffering from essential thrombocythemia and primary myelofibrosis.
The JAK2V617F mutation has been detected in patients with classical myeloproliferative disorders (MPD) including polycythemia vera and essential thrombocythemia and idiopathic myelofibrosis.
A somatic mutation (V617F) resulting in enhanced JAK2 kinase activity can be frequently found in patients with serious myeloproliferative neoplasms such as polycythemia vera, essential thrombocythemia and primary myelofibrosis.
Recently, a point mutation in the JAK2 gene, JAK2 (V617F) , was discovered in several myeloid proliferative neoplasms including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF).
Concerning myelofibrosis (MF), controversy remains on the relationship between the above JAK2 haplotype and the patients' clinicohematological features and survival.
In the current study, we have increased the number of informative cases from 130 to 414 (median age 63 years; 63% males), in order to revisit with the phenotypic and prognostic relevance of the JAK2 46/1 haplotype in PMF.