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Myeloid lineage involvement in BCR/ABL-positive acute lymphoblastic leukaemia
Hovorková, Lenka ; Zuna, Jan (advisor) ; Mikyšková, Romana (referee)
The Philadelphia chromosome has been discovered in 1960. This chromosomal aberration was mistakenly associated only with chronic myeloid leukaemia (CML) for decade. However, this type of translocation including chromosomes 9 and 22 was found in patients with different type of neoplasia - acute lymphoblastic leukaemia (ALL). Different lineage involvement has been found in these two types of leukaemia. Whereas in Ph-positive ALL, the Philadelphia chromosome is restricted to the lymphoid lineage, in CML patients mostly myeloid cells are those being Ph-positive. Hence it seems quite trivial to distinguish between ALL and CML. But there is a phase of CML called lymphoid blast crisis which is indistinguishable from ALL. The possibility of distinguishing between CML in lymphoid blast crisis and ALL would inhere in determining myeloid lineage involvement. Actually it had been shown that some patients with Ph+ ALL have involved also a myeloid lineage. Different types of treating protocols are used in CML and ALL. In addition, prognoses for both types of leukaemia are different. Thus it is crucial to distinguish between this two disorders and revealing of any difference can impact the treatment outcome of above mentioned malignancies. Detection of minimal residual disease according to involvement of myeloid or CD34+...
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The Function of the Adaptor Molecules in Leukaemogenesis
Švojgr, Karel ; Zuna, Jan (advisor) ; Filipp, Dominik (referee) ; Zemanová, Zuzana (referee)
Acute lymphoblastic leukaemia is the most common malignancy in childhood. Various acquired and congenital factors are involved in leukemogenesis including aberrant cell signaling. Transmembrane adaptor molecules could play an important role in development and propagation of leukemia. In a first part of our study, we analyzed an expression of adaptor molecules PAG, LAT and NTAL in physiological lymphocyte precursors and in diagnostic samples of different subtypes of childhood acute lymphoblastic leukemia (ALL). In physiological lymphocyte development the expression of adaptor molecules has significant dynamics (increase of LAT and decrease of NTAL in T-lymphocyte development; decrease of PAG in B- lymphocyte development). Similarly, in subtypes of childhood ALL the expression of adaptor molecules is very different. Especially, TAL/AML1 positive acute lymphoblastic leukemia has a unique expression profile of adaptor molecules (high expression of PAG and LAT, low expression of molecule NTAL). In T-cell acute lymphoblastic leukemia the expression of NTAL molecule identifies two groups of patients - those, who respond favourably to initial prednisone treatment, have higher level of NTAL comparing to patients, who respond to prednisone unfavourably. Those patients have low level of NTAL molecule expression. In a...
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Leukaemias with BCR/ABL fusion gene.
Hovorková, Lenka ; Zuna, Jan (advisor) ; Zemanová, Karla (referee)
Philadelphia (Ph) chromosome, as a result of reciprocal translocation, is in majority of cases connected to two types of leukaemia - chronic myelogenous (CML) and acute lymphoblastic (ALL). The translocation occurs within large intronic sequences of BCR and ABL genes. The breakpoints are specific for individual patient and may be used as a target for monitoring of leukemic burden (MRD, minimal residual disease) during the treatment. In general, MRD is an important prognostic factor, which influences the treatment intensity. Two standardized methods are currently used for its monitoring. The first one is based on the detection of clonal specific Immunoglobulin and/or T-cell receptor genes rearrangements (and thus cannot be used for CML cases) at the DNA level, the second one utilizes detection of the BCR/ABL fusion gene at the mRNA level. Our aim was to optimize and standardize the process to find individual patient breakpoints on Ph chromosome and to use it for MRD quantification. We found the breakpoint in 80 % cases. The MRD data from 15 patients obtained by our method were compared to the levels obtained by standard methods (Ig/TCR and BCR/ABL transcript quantification). In all but 1 patient we found significant discrepancies, raising the questions about leukemic origin and the most accurate method for...
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Mechanisms of resistance to tyrosin kinase inhibitors in treatment of patients with chronic myeloid leukemia
Polívková, Václava ; Machová Poláková, Kateřina (advisor) ; Zuna, Jan (referee) ; Bělohlávková, Petra (referee)
Mechanisms of resistance to tyrosin kinase inhibitors in treatment of patients with chronic myeloid leukemia The introduction of tyrosine kinase inhibitor (TKI) therapy represented a breakthrough in the treatment of patients with chronic myeloid leukemia (CML). Despite a high success rate of the TKI therapy, 20-30 % of patients develop resistance to the treatment. The aim of this work was to study the mechanisms, related to the mutation development in BCR-ABL1 kinase domain (KD) or in the other genes responsible for TKI resistance, using the in vitro CML models. Furthermore, the effect of interferon alpha (IFN-α) and TKI sequential therapy on the presence of clones with multidrug-resistant mutations and a role of activation the immune response in achieving the treatment response were followed. Lastly, we studied the possibility of using the measurement of gene expression of hOCT1 and ABCB1 transporters at the time of diagnosis in CML patients as a predictive marker of the imatinib treatment response. KCL-22 CML cell line cells exposed to imatinib were repeatedly able to develop BCR-ABL1 kinase domain mutations. We demonstrated the existence of de novo mutagenesis in clones derived from the KCL-22 cell line. In four clones, which can proliferate in 4µM imatinib, mutations in BCR-ABL1 KD or KRAS were...
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Pathogenesis of childhood leukemia
Hovorková, Lenka ; Zuna, Jan (advisor) ; Kolenová, Alexandra (referee) ; Jarošová, Marie (referee)
BCR-ABL1 fusion gene is a hallmark of chronic myeloid leukaemia (CML), but can be found also in patients with acute lymphoblastic leukaemia (ALL). In BCR-ABL1-positive ALL, two principal approaches for treatment response and minimal residual disease (MRD) monitoring are routinely used - quantification of genomic clonal rearrangements of immunoglobulin/T-cell receptor genes (Ig/TCR) and BCR-ABL1 expression. We established methods for determination of BCR-ABL1 genomic fusion and used the intronic breakpoints to measure MRD levels also at the BCR-ABL1 DNA level. Comparison of MRD based on Ig/TCR and genomic BCR-ABL1 in 47 consecutive childhood patients showed poor correlation in about 25 % cases with significantly higher BCR-ABL1 levels. In those patients, we found the BCR-ABL1 not only in ALL-blasts, but also in other cell subtypes (T-cells, myeloid cells) negative for clonal Ig/TCR rearrangements. For the similarity with CML we assigned this new leukaemia subtype with multilineage BCR- ABL1 involvement "CML-like" leukaemia. Our ongoing study is focused on the prognostic implications of discordant MRD results. As we characterized the genomic BCR-ABL1 fusion in 428 patients (which is to our knowledge the largest cohort described so far), we also analysed the origin of the breakpoints. Our data suggest...
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Delineating aggressiveness of acute myeloid leukemia in a mouse model carrying mutations of Spil (PU.1) and Trp53.
Bašová, Petra ; Stopka, Tomáš (advisor) ; Machová Poláková, Kateřina (referee) ; Zuna, Jan (referee)
PU.1 downregulation within haematopoietic stem and progenitor cells (HSPCs) is the primary mechanism for the development of acute myeloid leukaemia (AML) in mice with homozygous deletion of the upstream regulatory element (URE) of PU.1 gene. p53 is a well known tumor suppressor that is often mutated in human haematologic malignancies including AML and adds to their aggressiveness; however its genetic deletion does not cause AML in mouse. Deletion of p53 in the PU.1ure/ure mice (PU.1ure/ure p53-/- ) results in more aggressive AML with shortened overall survival. PU.1ure/ure p53-/- progenitors express significantly lower PU.1 levels. In addition to URE deletion we searched for other mechanisms that in absence of p53 contribute to decreased PU.1 levels in PU.1ure/ure p53-/- mice. We found involvement of Myb and miR-155 in downregulation of PU.1 in aggressive murine AML. Upon inhibition of either Myb or miR-155 in vitro the AML progenitors restore PU.1 levels and lose leukaemic cell growth similarly to PU.1 rescue. The MYB/miR-155/PU.1 axis is a target of p53 and is activated early after p53 loss as indicated by transient p53 knockdown. Furthermore, deregulation of both MYB and miR-155 coupled with PU.1 downregulation was observed in human AML, suggesting that MYB/miR-155/PU.1 mechanism may be involved...
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