EVI1-mediated down regulation of MIR449A is essential for the survival of EVI1 positive leukaemic cells.

in British Journal of Haematology (2011), 154(3), 337-48

Chromosomal rearrangements involving the MECOM (MDS1 and EVI1 complex) locus are recurrent genetic events in myeloid leukaemia and are associated with poor prognosis. In this study, we assessed the role ... [more ▼]

Chromosomal rearrangements involving the MECOM (MDS1 and EVI1 complex) locus are recurrent genetic events in myeloid leukaemia and are associated with poor prognosis. In this study, we assessed the role of MECOM locus protein EVI1 in the transcriptional regulation of microRNAs (miRNAs) involved in the leukaemic phenotype. For this, we profiled expression of 366 miRNAs in 38 MECOM-rearranged patient samples, normal bone marrow controls and MECOM (EVI1) knock down/re-expression models. Cross-comparison of these miRNA expression profiling data showed that MECOM rearranged leukaemias are characterized by down regulation of MIR449A. Reconstitution of MIR449A expression in MECOM-rearranged cell line models induced apoptosis resulting in a strong decrease in cell viability. These effects might be mediated in part by MIR449A regulation of NOTCH1 and BCL2, which are shown here to be bona fide MIR449A targets. Finally, we confirmed that MIR449A repression is mediated through direct promoter occupation of the EVI1 transcriptional repressor. In conclusion, this study reveals MIR449A as a crucial direct target of the MECOM locus protein EVI1 involved in the pathogenesis of MECOM-rearranged leukaemias and unravels NOTCH1 and BCL2 as important novel targets of MIR449A. This EVI1-MIR449A-NOTCH1/BCL2 regulatory axis might open new possibilities for the development of therapeutic strategies in this poor prognostic leukaemia subgroup. [less ▲]

EVI1-mediated down regulation of MIR449A is essential for the survival of EVI1 positive leukaemic cells.

in British Journal of Haematology (2011), 154(3), 337-48

Chromosomal rearrangements involving the MECOM (MDS1 and EVI1 complex) locus are recurrent genetic events in myeloid leukaemia and are associated with poor prognosis. In this study, we assessed the role ... [more ▼]

Chromosomal rearrangements involving the MECOM (MDS1 and EVI1 complex) locus are recurrent genetic events in myeloid leukaemia and are associated with poor prognosis. In this study, we assessed the role of MECOM locus protein EVI1 in the transcriptional regulation of microRNAs (miRNAs) involved in the leukaemic phenotype. For this, we profiled expression of 366 miRNAs in 38 MECOM-rearranged patient samples, normal bone marrow controls and MECOM (EVI1) knock down/re-expression models. Cross-comparison of these miRNA expression profiling data showed that MECOM rearranged leukaemias are characterized by down regulation of MIR449A. Reconstitution of MIR449A expression in MECOM-rearranged cell line models induced apoptosis resulting in a strong decrease in cell viability. These effects might be mediated in part by MIR449A regulation of NOTCH1 and BCL2, which are shown here to be bona fide MIR449A targets. Finally, we confirmed that MIR449A repression is mediated through direct promoter occupation of the EVI1 transcriptional repressor. In conclusion, this study reveals MIR449A as a crucial direct target of the MECOM locus protein EVI1 involved in the pathogenesis of MECOM-rearranged leukaemias and unravels NOTCH1 and BCL2 as important novel targets of MIR449A. This EVI1-MIR449A-NOTCH1/BCL2 regulatory axis might open new possibilities for the development of therapeutic strategies in this poor prognostic leukaemia subgroup. [less ▲]

CyclinD1-negative mantle cell lymphoma with cryptic t(12;14)(p13;q32) and cyclin D2 overexpression

in Blood (2008), 111(3), 1745-1746

Consultations in molecular diagnostics - A case of FIP1L1-PDGFRA-positive chronic eosinophilic leukemia with a rare FIP1L1 breakpoint

in Journal of Molecular Diagnostics (2007), 9(3), 414-419

The idiopathic hypereosinophilic syndrome (HES) has remained for a long time a diagnosis of exclusion. Differential diagnosis between the HES and the related chronic eosinophilic leukemia (CEL) relied on ... [more ▼]

The idiopathic hypereosinophilic syndrome (HES) has remained for a long time a diagnosis of exclusion. Differential diagnosis between the HES and the related chronic eosinophilic leukemia (CEL) relied on the identification of signs of clonality that allowed, when present, the reclassification of patients as CEL. Recently, a new acquired mutation was described in approximately 50% of the HES/CEL patients: a cryptic deletion on chromosome band 4q12 generating a FIP1IL1-PDGFRA fusion gene. According to the World Health Organization classification, this clonal abnormality has been proposed as a new surrogate marker for chronic eosinophilic leukemia diagnosis. Fluorescence in situ hybridization and reverse transcriptase-polymerase chain reaction protocols were developed for an accurate del(4)(q12q12) and FIP1L1-PDGFRA fusion gene detection. Here, we report a patient with a rare FIP1L1 intron 16 breakpoint located outside of the reported FIP1L1 breakpoint region (ie, from FIP1L1 introns 9 to 13). This case illustrates the risk of false-negative results with diagnostic procedures that do not take into account the occurrence of rare FIP1L1 breakpoints. As targeted therapy with tyrosine kinase inhibitors has dramatically changed the prognosis of FIP1L1-PDGFRA (+) CEL, false-negative results could hamper accurate diagnosis and treatment. [less ▲]

Duplication of the MYB oncogene in T cell acute lymphoblastic leukemia

in Nature Genetics (2007), 39(5), 593-595

We identified a duplication of the MYB oncogene in 8.4% of individuals with T cell acute lymphoblastic leukemia (T-ALL) and in five T-ALL cell lines. The duplication is associated with a threefold ... [more ▼]

We identified a duplication of the MYB oncogene in 8.4% of individuals with T cell acute lymphoblastic leukemia (T-ALL) and in five T-ALL cell lines. The duplication is associated with a threefold increase in MYB expression, and knockdown of MYB expression initiates T cell differentiation. Our results identify duplication of MYB as an oncogenic event and suggest that MYB could be a therapeutic target in human T-ALL. [less ▲]

Array-CGH analysis of T-ALL patients and cell lines

in Blood (2006, November 16), 108(11, Part 2), 195-196

Rational use of the EAC real-time quantitative PCR protocol in chronic myelogenous leukemia: report of three false-negative cases at diagnosis

in Leukemia (2006), 20(5), 886-888

A quantitative study of peripheral blood stem cell contamination in diffuse large-cell non-Hodgkin's lymphoma: one-half of patients significantly mobilize malignant cells.

in British Journal of Haematology (2000), 110(3), 631-7

Autologous transplantation using peripheral blood stem cells (PBSCs) collected after chemotherapy, followed by growth factor administration (ASCT), is increasingly used in the treatment of non-Hodgkin's ... [more ▼]

Autologous transplantation using peripheral blood stem cells (PBSCs) collected after chemotherapy, followed by growth factor administration (ASCT), is increasingly used in the treatment of non-Hodgkin's lymphoma (NHL). However, quantitative data regarding contaminating malignant cells in the harvests are still scarce. We prospectively investigated 37 diffuse large-cell lymphomas (DLCLs) in complete remission (CR) that were treated according to multicentric protocols at our centre. DNA was extracted from the diagnostic lymph node. The complementarity-determining region (CDR) III was sequenced and a patient-specific oligomer synthesized. Contamination was evaluated semiquantitatively by polymerase chain reaction (PCR) and was confirmed by a limiting dilution analysis. PBSCs collected at regeneration after administration of granulocyte colony-stimulating factor (G-CSF), steady-state bone marrow (BM) and peripheral blood samples at CR were compared. DNA was available in 37 patients, from which 22 rearrangements could be sequenced. Patients (n = 15) who had both the required follow-up samples and a suitable clonal marker were investigated. In two cases, the patient-specific PCR assay set up at diagnosis later gave false-negative results in samples in which clonal DNA was still detectable by other sets of primers. PBSC contamination was highly variable: 7 out of 15 patients showed a PBSC/BM ratio of NHL cells greater than 1 log, whereas 8 out of 15 patients showed no difference and could vary from one apheresis to another. Eight ASCTs were performed, five of which used highly contaminated PBSCs: four patients relapsed early, three with disseminated lymphoma. Thus, 50% of DLCLs in CR seem to mobilize significantly malignant cells at regeneration under G-CSF. Considering the higher numbers of cells reinfused, this translates into a much higher number of lymphoma cells reinfused when compared with autologous bone marrow transplantation (ABMT). However, their clonogenic potential remains unknown and, despite concerning observations in certain cases, it is still unclear whether this has an impact upon the outcome of ASCT. [less ▲]

The taste approach : general implicit solutions in MCQs, confidence marking, open books exams and interactive testing

in Leclercq, Dieudonné (Ed.) Item banking, self-assessment and interactive testing : actes du NATO ARW Conférence de Liège, novembre 1992 (1993)