JAK2 in myeloproliferative disorders is not just another kinase.
Myeloproliferative disorders (MPD) represent a subcategory of hematological malignancies and are characterized by a stem cell-derived clonal proliferation of myeloid cells including erythrocytes, platelets, and leucocytes. Traditionally, the term 'MPD' included chronic myeloid leukemia (CML), polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis with myeloid metaplasia (MMM). At present, these four disorders are referred to as 'classic' MPD and are distinguished from a spectrum of other MPD-like clinicopathologic entities that are operationally classified as 'atypical' MPD. The oncogenic mutations(s) in classic MPD are unknown except for CML, which is associated with an activating mutation (Bcr/Abl) of the gene encoding for the Abl cytoplasmic protein kinase (PTK). In the last 3 months, a somatic point mutation of JAK2 (JAK2(V617F)), the gene encoding for another cytoplasmic PTK was reported in the majority of patients with PV and approximately half of those with either ET or MMM. The same mutation was also found in a small number of patients with either atypical MPD or the myelodysplastic syndrome but not in normal controls, germline tissue including T lymphocytes, and patients with secondary erythrocytosis. In vitro, JAK2(V617F) was associated with constitutive phosphorylation of JAK2 and its downstream effectors as well as induction of erythropoietin hypersensitivity in cell lines. In vivo, murine bone marrow transduced with a retrovirus containing JAK2(V617F) induced erythrocytosis in the transplanted mice. Taken together, these observations suggest that JAK2(V617F) is an acquired myeloid lineage-specific mutation that engenders a pathogenetic relevance for the PV phenotype in MPD.
Tefferi
Ayalew
A
Division of Hematology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA. tefferi.ayalew@mayo.edu
Gilliland
D Gary
DG
D000483:Alleles; D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology; D019070:Cell Lineage; D049109:Cell Proliferation; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA / Q000737:chemistry; D004252:DNA Mutational Analysis; D004912:Erythrocytes / Q000378:metabolism; D004921:Erythropoietin / Q000737:chemistry; D006720:Homozygote; D006801:Humans; D053614:Janus Kinase 2; D051379:Mice; D009154:Mutation; D009190:Myelodysplastic Syndromes / Q000378:metabolism; D009196:Myeloproliferative Disorders / Q000201:enzymology*; D010641:Phenotype; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism; D017354:Point Mutation; D011086:Polycythemia; D011505:Protein-Tyrosine Kinases / Q000378:metabolism / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism / Q000502:physiology*; D017422:Sequence Analysis, DNA; D013601:T-Lymphocytes / Q000378:metabolism; D014443:Tyrosine / Q000737:chemistry; D015854:Up-Regulation
D011518:Proto-Oncogene Proteins; D004921:Erythropoietin; D014443:Tyrosine; D004247:DNA; D010770:Phosphotransferases; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2