We developed a time-dependent assay to mimic ruxolitinib withdrawal in primary JAK2<sup>V617F</sup> and CALR mutant myelofibrosis patient samples and observed notable activation of spontaneous STAT signaling in JAK2<sup>V617F</sup> samples after drug washout.
In conclusion, the size of the mutated clone in chronic phase MPN is different according to genotype with CALR-mutated ET showing a pattern similar to that observed in MF.
Key differences from the 2011 diagnostic recommendations included: lower threshold values for hemoglobin and hematocrit and bone marrow examination for diagnosis of polycythemia vera (PV), according to the revised WHO criteria; the search for complementary clonal markers, such as ASXL1, EZH2, IDH1/IDH2, and SRSF2 for the diagnosis of myelofibrosis (MF) in patients who test negative for JAK2V617, CALR or MPL driver mutations.
The classical Philadelphia chromosome-negative myeloproliferative neoplasms (MPN), which include essential thrombocythemia, polycythemia vera, and myelofibrosis (MF), are in a new era of molecular diagnosis, ushered in by the identification of the JAK2(V617F) and cMPL mutations in 2005 and 2006, respectively, and the CALR mutations in 2013.
The objective of the current study was to examine the impact of CALR mutation variant stratified driver mutational status on overall (OS), myelofibrosis-free (MFFS), thrombosis-free, and leukemia-free survival (LFS) in ET; 495 patients (median age 58 years; 61% females) with ET were fully annotated for the their driver mutational status: 321 (65%) harbored JAK2, 109 (22%) CALR, and 12 (2%) MPL mutations and 11% were triple-negative.
One-hundred Mayo Clinic patients with high/intermediate-risk myelofibrosis (MF) received momelotinib (MMB; JAK1/2 inhibitor) between 2009 and 2010, as part of a phase 1/2 trial (NCT00935987); 73% harbored JAK2 mutations, 16% CALR, 7% MPL, 44% ASXL1, and 18% SRSF2.
Recently, novel calreticulin (CALR) mutations were discovered in Janus kinase 2 (JAK2) non-mutated myelofibrosis (PMF) and essential thrombocythemia (ET) cases, with a frequency of 60-80%.
Finally, we tested the combined effect of busulfan and veliparib on CD34<sup>+</sup> cells obtained from the bone marrow or peripheral blood of 5 patients with JAK2<sup>V617F</sup>-mutated and 2 patients with CALR-mutated MF.
Collectively, our studies demonstrate that occasional patients with CALR mutation-positive ET or MF carry other MPN-initiating genetic mutations (including JAK2 V617F), acquire "secondary mutations" before or after the CALR mutation, or evolve over time to being CALR mutation-homozygous.
ABSTRACT: Background The BCR-ABL-negative myeloproliferative neoplasms, i.e., polycythemia vera, essential thrombocythemia (ET), and myelofibrosis (MF), are characterized by mutations in JAK2, CALR, or MPL.
This study revealed that CALR mutant essential thrombocythemia is associated with younger age, higher platelet counts, lower erythrocyte counts, leukocyte counts, hemoglobin, and hematocrit, and increased risk of progression to myelofibrosis in comparison with JAK2 V617F-positive essential thrombocythemia.
We screened 136 patients with myelofibrosis and a median age of 58 years who underwent allogeneic stem cell transplantation (AHSCT) for molecular residual disease for JAKV617F (n=101), thrombopoietin receptor gene (MPL) (n=4) or calreticulin (CALR) (n=31) mutation in peripheral blood on day +100 and +180 after AHSCT.
Type 1 CALR mutations were found to be more common in myelofibrosis, associated with a higher frequency and number of additional mutations and a higher mutant allelic burden as compared to type 2 CALR mutations.
AML transformation occurred faster in SMF than in PMF and patients who transformed to AML were more SRSF2-mutated and less CALR-mutated at MF sampling.
As such, CALR first, followed by MPL if CALRis absent, mutation screening is appropriate in the diagnostic work-up of JAK2-unmutated ET but does not replace the need for BM morphologic examination in (1) confirming the diagnosis in triple-negative ET and (2) distinguishing ET from other myeloproliferative neoplasms that share the same mutations, including masked PV and early/prefibrotic myelofibrosis.
Patients with CALR-mutated ET appear to be more likely to develop myelofibrosis compared with patients with wt CALRUpon completion of this activity you will be able to: describe morphologic features that are associated with CALR-mutated myeloproliferative neoplasms.examine cases of essential thrombocythemia and primary myelofibrosis and predict which cases are more likely to be CALR-mutated based on histopathologic features.initiate CALR mutation testing for cases likely to have mutations.
Effect of CALR and JAK2 mutations on the clinical and hematological phenotypes of the disease in patients with myelofibrosis - long-term experience from a single center.
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.