Among patients with essential thrombocythemia or primary myelofibrosis with nonmutated JAK2 or MPL, CALR mutations were detected in 67% of those with essential thrombocythemia and 88% of those with primary myelofibrosis.
The molecular diagnostic gap in JAK2/MPL-unmutated ET/PMF is now partially addressed by the recent discovery of calreticulin (CALR) mutations in the majority of such cases.
These observations signify immediate clinical relevance and warrant i) CALR and ASXL1 mutation determination in all patients with PMF and ii) molecular revision of DIPSS-plus.
We show that this antibody specifically recognized patients harboring different types of CALR mutation with no staining in healthy controls and JAK2- or MPL-mutated ET and PMF.
The recent discovery of mutations of the gene calreticulin has allowed raising the proportion of patients with essential thrombocythemia and primary myelofibrosis with known mutational abnormality up to 85-90%.
Patients with JAK2 V617F-positive MPN have a heterogeneous histology while CALR-positive ET is associated with megakaryocyte abnormalities and prefibrotic PMF.
We studied the impact of driver mutations of JAK2, CALR, (calreticulin gene) or MPL on clinical course, leukemic transformation, and survival of patients with primary myelofibrosis (PMF).
Calreticulin (CALR) mutations were recently identified in patients with essential thrombocythemia (ET) and primary myelofibrosis (PMF) devoid of JAK2 and MPL mutations.
In PMF (n = 428), but not in ET (n = 576), survival and blast transformation (BT) were significantly affected by mutational status; outcome was best in CALR-mutated and worst in triple-negative patients: median survival, 16 vs 2.3 years (HR, 5.1; 95% CI, 3.2-8.0) and BT, 6.5% vs 25% (HR, 7.6; 95% CI, 2.8-20.2), respectively.
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).
Four main molecular types of clonal MPN can be distinguished: JAK2(V617F)-positive ET and PV; JAK2 wild-type ET carrying the MPL(515); mutations in the calreticulin (CALR) gene in JAK2/MPL wild-type ET and MF, and a small proportion of JAK2/MPL/CALR wild-type ET and MF patients.
The in vitro treatment of splenic and peripheral blood MF CD34(+) cells with the JAK1/2/3 inhibitor, AZD1480, reduced the absolute number of CD34(+), CD34(+)CD90(+), and CD34(+)CXCR4(+) cells as well as assayable hematopoietic progenitor cells (HPCs) irrespective of the JAK2 and calreticulin mutational status.
Calreticulin (CALR) mutations have been reported in Janus kinase 2 (JAK2)- and myeloproliferative leukemia (MPL)-negative essential thrombocythemia and primary myelofibrosis.