MPN driver mutations (JAK2, CALR, MPL) are somatically acquired also in familial cases, so a genetic predisposition to acquire one of the MPN driver mutations would be inherited, even though the causative germline mutations underlying familial MPN remain largely unknown.
The combination of laboratory testing for the detection of JAK2, CALR, and MPL mutations is necessary to improve the diagnosis and classification of BCR-ABL1-negative MPN.
Mice lacking the inhibitory adaptor protein Lnk display deregulation of thrombopoietin/thrombopoietin receptor signaling pathways and exhibit similar myeloproliferative characteristics to those found in MPN patients, suggesting a role for Lnk in the molecular pathogenesis of these diseases.
Discovery in 2006 of mutants of thrombopoietin receptor (TPO-R/MPL) and later on of mutants in negative regulators of JAK-STAT pathway led to the notion that persistent JAK2 activation is a hallmark of MPNs.
Genomic DNA from peripheral blood, bone marrow, and FFPE bone marrow clot preparations from 52 MPN specimens with known JAK2 and MPL mutation status and 29 non-MPN specimens was analyzed.
Overall, our data indicate that the JAK1/JAK2 selective inhibitor CYT387 has potential for efficacious treatment of MPN harboring mutated JAK2 and MPL alleles.
Considering these results, we propose that mutant CALR promotes myeloproliferative neoplasm development by activating c-MPL and its downstream pathway.
We found examples of both of these categories in published and previously unpublished MPL exon 10 sequencing data from MPN patients, demonstrating that some, if not all of the new mutations reported here represent likely drivers or modifiers of myeloproliferative disease.
This review first considers the factors that may influence phenotype in JAK2-mutated MPNs, especially polycythemia vera (PV) and essential thrombocythemia (ET), and then discusses the mutations implicated in JAK2-negative MPNs such as in MPL and epigenetic regulators.
The association between the <i>JAK2</i> haplotype<sup>GGCC_46/1</sup> and mutations in other genes, such as thrombopoietin receptor (<i>MPL</i>) and calreticulin (<i>CALR</i>), or the association with triple negative MPN, is still controversial.
Recently, germline mutations in Janus kinase 2 (JAK2) and MPL, two genes frequently mutated in sporadic MPD, have been shown to cause inherited thrombocytosis.
Somatic mutations of Janus kinase 2 (JAK2V617F), calreticulin (CALR), and myeloproliferative leukemia virus oncogene (MPL) are the major clonal molecules that drive the pathogenesis of myeloproliferative neoplasms (MPN).
This study explored the relationship between mutations in the Janus kinase 2 gene ( JAK2), MPL, and the calreticulin gene ( CALR) in Uygur and Han Chinese patients with BCR-ABL fusion gene-negative MPN and corresponding clinical features.
Important changes include (1) the change of nomenclature of myeloproliferative disorder to myeloproliferative neoplasm emphasizing the clonal nature of these disorders; (2) the classification of mast cell disease as an MPN; (3) the reorganization of the eosinophilic disorders into a molecularly defined category of PDGFRA, PDGFRB and FGFR1-associated myeloid and lymphoid neoplasms with eosinophilia and chronic eosinophilic leukemia, not otherwise specified; and (4) refinement of the diagnostic criteria for PV, ET and PMF incorporating recently described molecular markers, JAK2V617F, JAK2 exon 12 mutations and MPL mutations.
Primary myelofibrosis (PMF) is a myeloproliferative neoplasm (MPN) characterized by stem cell-derived clonal myeloproliferation that is often but not always accompanied by JAK2, CALR, or MPL mutations; additional disease features include bone marrow stromal reaction including reticulin fibrosis, abnormal cytokine expression, anemia, hepatosplenomegaly, extramedullary hematopoiesis (EMH), constitutional symptoms, cachexia, leukemic progression, and shortened survival.
These mutations include JAK2, CALR and MPL mutations as the main disease drivers, mutations driving clonal expansion, and mutations that contribute to progression of chronic MPNs to myelodysplasia and acute leukemia.
Expression of mutant CALR in murine or human haematopoietic cell lines was accompanied by myeloproliferative leukemia protein (MPL)-dependent activation of MAPK signalling, and MPN patients with CALR mutations showed increased MAPK activity in CD34 cells, platelets and megakaryocytes.
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).