| 1. |
- Barbouti, Aikaterini
(författare)
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Characterization of Genetic Abnormalities at Disease Progression of Chronic Myeloid Leukemia
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Chronic myeloid leukemia (CML) is a myeloproliferative disorder associated with the translocation t(9;22)(q34;q11) and progresses from a relatively indolent chronic phase (CP) to an accelerated phase (AP) and finally to the more aggressive blast crisis (BC). The general aim of this thesis was to identify and characterize genetic abnormalities occurring at disease progression of CML using molecular cytogenetic, molecular genetic, and bioinformatic analyses. In the first study, multicolor fluorescent in situ hybridization (M-FISH) was used to identify possible cryptic genetic changes in CML BC and AP cases. Two novel and cytogenetically cryptic balanced translocations, t(7;17)(p15;q23) and t(7;17)(q32-34;q23), and an AML-associated translocation, t(9;11)(p21-22;q23), with concomitant rearrangement of the MLL gene, were detected, suggesting that balanced translocations are more common during CML progression than previously indicated by G-banding alone. In the second study, further characterization of the t(7;17)(p15;q23) and t(7;17)(q32-34;q23) showed rearrangement of a novel gene located in 17q23, Musashi-2 (MSI2), encoding a putative RNA-binding protein. In the case with the t(7;17)(p15;q23), a MSI2/HOXA9 fusion transcript was identified, harboring both RNA recognition motif domains of MSI2 and the homeobox domain of HOXA9, suggesting an important role in the disease progression of CML. In the third study, the mechanism of formation of ETV6/ABL1 rearrangement in CML BC, as well as the possible clinical and genetic effects of imatinib treatment, was investigated. FISH analysis revealed that a complex array of chromosomal rearrangements were required for the generation of ETV6/ABL1. Moreover, imatinib treatment resulted in a durable, albeit transient, hematologic and genetic response, lasting approximately three months. Upon disease relapse, no mutations were identified in the SH1 (kinase) domain of ABL1, but a decrease in the expression level of wild-type ETV6 was observed that may have been a contributory factor for the relapse. In the fourth and final study, a detailed mapping of the breakpoints of i(17q) - the most common structural rearrangement observed at disease progression in CML – was performed using locus-specific FISH. In silico analysis of the involved breakpoint region revealed a complex genomic architecture, characterized by large (~ 38-49 kb) palindromic, low-copy repeats (LCR), strongly suggestive of being a genomic feature implicated in the mechanism of formation of i(17q).
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| 2. |
- Barbouti, Aikaterini, et al.
(författare)
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Clinical and genetic studies of ETV6/ABL1-positive chronic myeloid leukaemia in blast crisis treated with imatinib mesylate.
- 2003
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Ingår i: British Journal of Haematology. - : Wiley. - 0007-1048. ; 122:1, s. 85-93
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Tidskriftsartikel (refereegranskat)abstract
- Most chronic myeloid leukaemia (CML) patients are genetically characterized by the t(9;22)(q34;q11), generating the BCR/ABL1 fusion gene. However, a few CML patients with rearrangements of 9q34 and 12p13, leading to ETV6/ABL1 chimaeras, have also been reported. Here we describe the clinical and genetic response to imatinib mesylate treatment of an ETV6/ABL1-positive CML patient diagnosed in blast crisis (BC). A chronic phase was achieved after acute myeloid leukaemia induction therapy. Then, treatment with imatinib mesylate (600 mg/d) was initiated and the effect was assessed clinically as well as genetically, including by repeated interphase fluorescence in situ hybridization studies. Until d 71 of imatinib mesylate therapy, stable improvements in the clinical and laboratory features were noted, and the frequency of ABL1-rearranged peripheral blood cells decreased from 56% to 11%. At d 92, an additional t(12;13)(p12;q13), with the 12p breakpoint proximal to ETV6, was found. The patient relapsed into BC 126 d after the start of the imatinib mesylate treatment and succumbed to the disease shortly afterwards. No mutations in the tyrosine kinase domain of ABL1 of the ETV6/ABL1 fusion were identified in the second BC. However, whereas the ETV6/ABL1 expression was seemingly the same at diagnosis and at second BC, the expression of ETV6 was markedly lower at the second BC. This decreased expression of wild-type ETV6 may have been a contributory factor for the relapse.
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| 3. |
- Barbouti, Aikaterini, et al.
(författare)
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Multicolor COBRA-FISH analysis of chronic myeloid leukemia reveals novel cryptic balanced translocations during disease progression.
- 2002
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Ingår i: Genes, Chromosomes and Cancer. - : Wiley. - 1045-2257. ; 35:2, s. 127-137
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Tidskriftsartikel (refereegranskat)abstract
- During the initial indolent chronic phase of chronic myeloid leukemia (CML), the t(9;22)(q34;q11), resulting in the Philadelphia chromosome (Ph), is usually the sole cytogenetic anomaly, but as the disease progresses into the accelerated phase (AP), and eventually into aggressive blast crisis (BC), secondary aberrations, mainly unbalanced changes such as +8, i(17q), and +Ph, are frequent. To date, molecular genetic studies of CML BC have mainly focused on alterations of well-known tumor-suppressor genes (e.g., TP53, CDKN2A, and RB1) and oncogenes (e.g., RAS and MYC), whereas limited knowledge is available about the molecular genetic correlates of the unbalanced chromosomal abnormalities. Balanced secondary changes are rare in CML AP/BC, but it is not known whether cryptic chromosomal translocations, generating fusion genes, may be responsible for disease progression in a subgroup of CML. To address this issue, we used multicolor combined binary ratio fluorescence in situ hybridization (FISH), which allows the simultaneous visualization of all 24 chromosomes in different colors, verified by locus-specific FISH in a series of 33 CML cases. Two cryptic balanced translocations, t(7;17)(q32-34;q23) and t(7;17)(p15;q23), were found in two of the five cases showing the t(9;22) as the only cytogenetic change. Using several BAC clones, the breakpoints at 17q23 in both cases were mapped within a 350-kb region. In the case with the 7p15 breakpoint, a BAC clone containing the HOXA gene cluster displayed a split signal, suggesting a possible creation of a fusion gene involving a member of the HOXA family. Furthermore, one case with a partially cryptic t(9;11)(p21-22;q23) and an MLL rearrangement as well as a previously unreported t(3;10)(p22;p12-13) were identified. Altogether, a refined karyotypic description was achieved in 12 (36%) of the 33 investigated cases, illustrating the value of using multicolor FISH for identifying pathogenetically important aberrations in CML AP/BC.
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