Myeloproliferative neoplasms (MPNs) are a heterogeneous group of haematological stem cell malignancies characterised by proliferation of one or more cells of the myeloid lineage. The molecular investigation of MPN was revolutionized in 2005 by the finding that approximately 95% of cases with polycythaemia vera (PV) and 50-60% of cases of essential thrombocythaemia (ET) and primary myelofibrosis (PMF) are characterised by a single acquired mutation, JAK2 V617F. My study has focused on four principal areas: (i) Involvement of V617F in other myeloid disorders. After developing sensitive methods to detect and quantify V617F, this mutation was identified in 17% of cases of atypical chronic myeloid leukaemia (17/99) as well as other atypical MPN, thus demonstrating that it was more widely involved in myeloid disorders that initially thought. Homozygosity of V617F was shown to have arisen by acquired uniparental disomy (UPD) and examination of two cases with V617F plus either KIT D816V or BCR-ABL demonstrated that the mutations had arisen in independent clones. (ii) In vitro assays to predict imatinib sensitivity. Haemopoietic colony and liquid cultures were used to determine if peripheral blood or bone marrow cells from atypical MPN cases (n=200) were sensitive to imatinib. Of those that responded in one or both cultures (n=185) some had known abnormalities of PDGFRA or PDGFRB, but a significant minority proved negative for all molecular tests suggesting the presence of uncharacterised imatinib-sensitive mutations. (iii) V617F as a marker of response to therapy. JAK2 V617F was used as a molecular marker to monitor the response of PV patients (n=21) to therapy with imatinib and interferon-α. Neither therapy eradicated V617F but there was a modest reduction in %V617F which correlated with haematological response. By contrast, in those patients that did not respond (n=13) the %V617F marginally increased. (iv) Genetic predisposition to MPN. Whilst investigating the possible contribution of JAK2 single nucleotide polymorphisms to the phenotypic diversity associated with V617F, marked skewing of alleles associated with the mutation was observed. Further investigation revealed that V617Fassociated disease is strongly associated with a specific constitutional JAK2 haplotype, designated 46/1, in all three disease entities compared to healthy controls (PV, n=192, P=2.9x10-16; ET, n=78, P=8.2x10-9 and MF, n=41, P=8.0x10-5). Furthermore, allele-specific PCR demonstrated that V617F specifically arises on the 46/1 allele in most cases. The 46/1 JAK2 haplotype thus predisposes to the development of V617F associated MPNs (OR=3.7; 95% CI 3.1-4.3) and provides a model whereby a constitutional genetic factor is associated with an increased risk of acquiring a specific somatic mutation.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:518582 |
| Date | January 2010 |
| Creators | Jones, Amy Victoria |
| Contributors | Cross, Nicholas |
| Publisher | University of Southampton |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://eprints.soton.ac.uk/162665/ |
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