ArticlesDefinition of subtypes of essential thrombocythaemia and relation to polycythaemia vera based on JAK2 V617F mutation status: a prospective study
Introduction
The human myeloproliferative disorders consist of three main diseases, essential thrombocythaemia, polycythaemia vera, and idiopathic myelofibrosis.1 The main clinical features of essential thrombocythaemia are arterial and venous thrombosis, although haemorrhage can also occur.2, 3, 4 In a few patients the disease can proceed to myelofibrosis, acute myeloid leukaemia, myelodysplasia, or polycythaemia vera. The idea that essential thrombocythaemia might be heterogeneous is lent support by studies of X chromosome inactivation patterns,5, 6 PRV1 mRNA expression,7, 8 myeloproliferative leukaemia expression,9, 10 histological features,11 and the presence of erythropoietin-independent erythroid colonies.8 However, where assessed, the concordance between these features is variable,8 and definition of biologically or pathogenetically distinct subgroups of essential thrombocythaemia has proved difficult.
Recently, a single somatic mutation of the Janus kinase 2 (JAK2) gene was reported in most patients with polycythaemia vera, but in only some patients with essential thrombocythaemia or idiopathic myelofibrosis.12, 13, 14, 15 The V617F mutation lies in the auto-inhibitory JH2 domain, and therefore increases JAK2 kinase activity, confers cytokine-independent growth on cell lines, and is associated with erythropoietin-independent growth of primary cells. Transplantation of bone marrow cells with mutant JAK2 results in erythrocytosis in vivo.13 By use of mutation-specific PCR, the JAK2 mutation was detected in peripheral blood granulocytes from around half of essential thrombocythaemia patients,12 but whether mutation-bearing patients are biologically distinct from those lacking the mutation is not known, or why the same mutation is associated with different diseases. To address these questions, we have analysed samples from patients enrolled in three large prospective studies of high-risk, intermediate-risk, and low-risk essential thrombocythaemia.
Section snippets
Study population
Newly diagnosed and previously treated patients, aged 18 years or over, who met the Polycythemia Vera Study Group (PVSG) criteria16 for essential thrombocythaemia, were recruited into one of three multicentre studies: the Medical Research Council PT-1 trial,17 in which high-risk patients were randomly assigned to either hydroxyurea plus aspirin or to anagrelide plus aspirin; the National Cancer Research Institute intermediate risk study, a randomisation between aspirin alone or hydroxyurea plus
Procedures
Samples of peripheral blood were requested at trial entry from all patients, and 776 samples were received from the 1022 patients entered. Whole-blood genomic DNA was extracted commercially (Whatman International, Ely, UK). Allele-specific PCR and BsaXI digestion were done as described previously.12 For platelet purification, blood was spun for 20 min up to three times, and the upper 50% of platelet-rich plasma used to extract RNA. Contaminating white cells were less than 1 per 106 platelets.
Results
The V617F mutation was present in over half of patients (table 1), giving an overall frequency of 53%. We considered the possibility that essential thrombocythaemia patients without the V617F mutation in peripheral blood leucocytes might nonetheless carry the mutation in the megakaryocyte lineage. To investigate this possibility, we used allele-specific PCR to detect the mutation in purified platelet cDNA from ten patients. The results were completely concordant with those obtained with
Discussion
Our analysis of patients with essential thrombocythaemia enrolled in three prospective studies has shown that the JAK2 V617F mutation unequivocally divides the disease into two subtypes, with the V617F-positive group showing phenotypic similarities to polycythaemia vera. The combined cohort provides a unique resource for studying essential thrombocythaemia, especially in view of its large size, centralised review of endpoints, and comprehensive follow-up. Moreover, the participation of a large
References (29)
Some speculations on the myeloproliferative syndromes
Blood
(1951)- et al.
Current opinion in essential thrombocythemia: pathogenesis, diagnosis, and management
Blood Rev
(2001) - et al.
Essential thrombocythemia
Hematol Oncol Clin North Am
(2003) - et al.
A large proportion of patients with a diagnosis of essential thrombocythemia do not have a clonal disorder and may be at lower risk of thrombotic complications
Blood
(1999) - et al.
Clonality analysis of hematopoiesis in essential thrombocythemia: advantages of studying T lymphocytes and platelets
Blood
(1997) - et al.
Comparison of molecular markers in a cohort of patients with chronic myeloproliferative disorders
Blood
(2003) - et al.
The expression pattern of c-mpl in megakaryocytes correlates with thrombotic risk in essential thrombocythemia
Blood
(2002) - et al.
Acquired mutation of the tyrosine kinase JAK2 in human myeloproliferative disorders
Lancet
(2005) - et al.
Activating mutation in the tyrosine kinase JAK2 in polycythemia vera, essential thrombocythemia, and myeloid metaplasia with myelofibrosis
Cancer Cell
(2005) Evaluation of diagnostic criteria in polycythemia vera
Semin Hematol
(2001)
The V617F JAK2 mutation is uncommon in cancers and in myeloid malignancies other than the myeloproliferative disorders
Blood
Polycythemia vera: myths, mechanisms, and management
Blood
Life expectancy and prognostic factors for survival in patients with polycythemia vera and essential thrombocythemia
Am J Med
Multiplicity in randomised trials II: subgroup and interim analyses
Lancet
Cited by (614)
The role and mechanism of JAK2/STAT3 signaling pathway regulated by m6A methyltransferase KIAA1429 in osteosarcoma
2023, Journal of Bone OncologyThe roles of sex and genetics in the MPN
2022, International Review of Cell and Molecular Biology
- ‡
These authors contributed equally to this study