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The role of WT1 and its isoforms in normal haematopoiesis and leukaemogenesis
Kramarzová, Karolina ; Trka, Jan (advisor) ; Pospíšilová, Dagmar (referee) ; Živný, Jan (referee)
61 Summary Wilms' tumor gene 1 (WT1) is highly expressed in acute leukemia and other hematological malignancies. It has been therefore suggested as a potential universal marker of minimal residual disease (MRD), particularly in patients with acute myeloid leukemia (AML). Due to controversial results of some of the studies, the role of WT1 in MRD follow-up and WT1 prognostic significance remain unclear. WT1 protein is produced in more than 36 different isoforms. These variants have distinct, partially overlapping functions and their ratio is supposed to influence the final effect of WT1. However, despite the increasing number of studies, the clinical impact of WT1 and its isoforms in acute leukemia have not yet been elucidated. We established a unique qPCR method to assess the expression pattern of the main 4 WT1 isoforms. Using this method, we determined the ratio of WT1 variants in the samples of patients with AML, myelodysplastic syndrome (MDS) and healthy controls. Our data showed that this pattern can distinguish among particular hematological malignancies, but lacks a prognostic significance. Within our international study group we determined the prognostic significance of total WT1 expression in childhood AML. Based on our results of a large cohort of patients we can conclude that WT1 expression at...
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Molecular mechanisms of Diamond-Blackfan anemia
Handrková, Helena ; Petrák, Jiří (advisor) ; Šebela, Marek (referee) ; Trka, Jan (referee)
Diamond-Blackfan anemia (DBA) is a rare congenital syndrome that presents with ane- mia and selective deficiency of erythroid precursors, while other blood lineages are usu- ally unaffected. Approximately half of the patients display additional somatic anoma- lies and growth retardation. The therapy is mostly symptomatic and is dominated by corticosteroids, other modalities include regular blood transfusions or hematopoietic stem cell transplantation. At the beginning of this work, only two DBA causal genes were known, RPS19 and RPS24, being mutated in approximately 1/4 of all DBA patients. The goals of this work were to study the consequences of the known DBA causal mutations on cellular level and to find novel DBA causal genes. To date, over a half of DBA patients have been reported to carry a mutation in one of nine known DBA causal genes, including RPS17, RPL11 and RPL5, that are reported in this dissertation. All confirmed DBA causal genes encode for ribosomal proteins (RPs) that were essential for ribosome assembly. We further hypothesized a non- ribosomal protein participating in this process might be involved in DBA pathogenesis, too. In one DBA patient, we identified a rare sequence variant in one such candidate, a protein arginine methyltransferase 3 (PRMT3). We reported that the patient PRMT3...
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Regulatory mechanisms of WNT signalling
Pospíchalová, Vendula ; Kořínek, Vladimír (advisor) ; Trka, Jan (referee) ; Bryja, Josef (referee)
AB T mu hom dise β sign mu liga stab tran sign T the focu disc cate of t cell targ the inte con sec I sign BSTRACT The Wnt si lticellular o meostasis. A eases, most β-catenin is nalling). In ltiprotein c ands when t bilized and nscription f nalling is tig This thesis knowledge uses on seq cusses the enin signall the Wnt pa ls of intest geted mous thesis des eraction wit nditional Hi retory cell t In conclusi nalling path T ignalling pa organisms Accordingly notably can s a central m n unstimula complex and they engage d transloca factors and ghtly regula is based on e of the reg quential po positive ro ling outcom athway whic tinal epithe e strains th scribes unp th members ic1 deletion types and en ion, our fin hway in dev athway is o ensuring s y, mutations ncer. mediator of ated cells d degraded e their recep tes to the to drive th ated at vario n four origin gulation of sttranslation ole of nucle me. The third ch reduces lium. Final at enable st ublished da s of the Wn n in the inte nhanced tum ndings contr velopment an one of the m successful s in the pat f canonical W β-catenin d in the pro ptors, degrad nucleus t he transcrip ous levels b nal articles f the Wnt s nal process ear protein d study repo the levels o lly, the las tudying the ata on the nt pathway, estinal epith mourigenesi ributed to t...
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Transcription factor PU.1 is a target of 5-azacitidine during differentiation therapy of myelodysplastic syndrome
Čuřík, Nikola ; Stopka, Tomáš (advisor) ; Kleibl, Zdeněk (referee) ; Trka, Jan (referee)
PU.1 is a key hematopoietic transcription factor. Knock-out of PU.1 in mouse is embryonic lethal due to complete depletion or several disruption of differentiation of multiple blood cell lineages. Low level of PU.1 and the disruption of its regulation are associated in vivo with acute myeloid leukemia and other hematologic malignancies. Myelodysplastic syndrome (MDS) is hematopoietic stem cell disorder with extremely heterogeneous features and outcome. It is characterized by improper differentiation of blood cells resulting in loss of function, dysplasia and blasts accumulation in bone marrow. About one third of MDS cases transforms into AML. MDS is also characterized by silencing of gene expression caused by aberrant DNA hypermethylation. Using DNA Methyltransferase inhibitors (DNMTi) such as 5-azacitidine (AZA) has good clinical results for the MDS patients with higher risk of disease. Indeed, AZA became standard therapy of high risk MDS in recent years. Nonetheless, our understanding of molecular mechanisms of AZA remains incomplete. This PhD thesis reports about the role of transcription factor PU.1 in MDS. We found that significant subset of high risk MDS patients express low level of PU.1 due to DNA hypermethylation of PU.1 upstream regulatory element (URE). We also found significant...
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Analysis of TRAIL-induced apoptosis in acute myeloid leukemia cells
Klener, Pavel ; Nečas, Emanuel (advisor) ; Herget, Jan (referee) ; Trka, Jan (referee)
Advanced tumors, including leukemia, represent heterogeneous cell populations evolved from original malignant clones. Chemotherapy of leukemia is often associated with selection of drug-resistant cells followed by progression/relapse of the disease. Implementation of molecules that specifically target leukemia cells with minimal toxicity to normal tissues might significantly improve outcome of leukemia treatment. TRAIL belongs to the tumor necrosis factor (TNF) ligand family of cytokines. TRAIL triggers apoptosis in target cells via the receptor-mediated apoptotic pathway. Receptors for TRAIL can be divided into death receptors, TRAILR1/ DR4 , TRAIL-R2/DR5, and decoy receptors, TRAIL-R3/DcR1, TRAIL-R4/DcR2, osteoprotegerin/OPG/TRAIL-R5, based on their ability to transduce apoptotic signal. While normal tissues, including hematopoietic progenitor cells, are resistant to TRAIL-induced apoptosis, TRAIL induces programmed death in many tumor cell lines and primary cells. Various malignant cell lines and primary tumor cells, however, show resistance to TRAIL-induced apoptosis. TRAIL-resistance could represent important limitation for the potential TRAIL anti-tumor therapy. Combined in vitro application of TRAIL with other anti-cancer agents often increased sensitivity or overcame resistance of the tumor cells to...
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The Role of Dipeptidyl Peptidase-IV in Glioma Cell Growth
Bušek, Petr ; Šedo, Aleksi (advisor) ; Trka, Jan (referee) ; Konvalinka, Jan (referee)
Dipeptidyl peptidase-IV (DPP-IV, CD26, EC 3.4.14.5) is a widely expressed serine protease that by limited proteolysis regulates a number of biologically active peptides including a number of mitogenic peptides involved in cancer development. Deranged DPP-IV expression and/or enzymatic activity has been reported in a number of tumors, and could lead to altered signaling and biological function of its substrates. Changes in DPP-IV expression were observed in glioma cell lines in association with differentiation, and recently also in malignant gliomas in vivo. In addition, DPP-IV substrates substance P (SP) and stromal cell derived factor-1 (SDF-1) that trigger growth promoting intracellular signaling cascades in glioma cells have strongly been implicated in the pathogenesis of gliomas. The aim of this study was (i) to investigate the effects of DPP-IV on the signaling of its biologically active substrates that promote the malignant phenotype of glioma cells, and (ii) to assess the effects of DPP-IV on the growth, migration and adhesion of human glioma cells. Using transfected glioma cell lines (U373CD26, T98GCD26, U87CD26) with mifepristone-inducible DPP-IV expression, we demonstrate that DPP-IV overexpressing T98GCD26 cells can cleave SP and thus abrogate its ability to trigger calcium signaling in U373...
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TEL/AML1, BCR/ABL and TEL/ABL Fusion genes in childhood acute lymphoblastic leukemia
Žaliová, Markéta ; Trka, Jan (advisor) ; Machová Poláková, Kateřina (referee) ; Pospíšilová, Dagmar (referee)
Acute lymphoblastic leukemia (ALL) is the most common malignancy in childhood. It represents a group of clinically and biologically heterogenous malignancies that can be subclasified into several subtypes according to the presence of recurrent genetic aberrations. The typical genetic aberrations in childhood ALL are chromosomal translocation, that often result in creation of fusion genes encoding either chimeric kinases or chimeric transcription factors. These recurrent genetic aberations are aquired lesions, they are supposed to be the initial hits (that may arise even prenataly) with a causal role in the process of leukemogenesis, which is, however, in the majority of them not yet fully understood. They further represent specific markes used for the detection of leukemic cells and some of them have also prognostic significance and belong among the factors used for risk group stratification in treatment protocols. Risk group stratification and subsequent risk-adapted therapy together with introduction of new therapeutic approaches (intensive chemotherapeutic regimens involving intrathecal application, hematopoetic stem cell transplantation (HSCT), supportive therapy) account for the significant improvement of the treatment outcomes of childhood ALL in the last decades. In addition to genotype, several...
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The alterations of MLL (mixed-lineage leukemia) gene and their clinical importance in pediatric patients with acute leukemia
Řezníčková, Leona ; Trka, Jan (advisor) ; Sedláček, Zdeněk (referee)
Presence of the MLL gene rearrangement at 11q23 is an important prognostic feature. Moreover, the rearrangements represent a suitable target for the minimal residual disease (MRD) monitoring in some subtypes of childhood acute leukaemias (AL). Currently more than 80 different translocations involving the MLL gene and more than 50 of those are characterised at the molecular leve\. Using multiplex-reverse transcriptase polymerase chain reaction (multiplex RT -PCR) and - in some cases - its combination with DNA analysis of the translocation breakpoint we examined a group of infants «1 year of age) diagnosed with acute lymphoblastic leukaemia (ALL), children with M4 and M5 subtypes of acute myeloid leukaemia (AML) and patients with secondary leukaemias. Moreover, we exaITŮned children with B-cell precursor fulfilling at least one of the ťollowing criteria: proB immunophenotype, cytogenetically confirmed MLL rearrangement and/or expression oťNG2 molecule shown by f10w cytometry. MultiplexRT PCR technique enables fast detection of the most frequent fusion partners of the :MLL gene (AF4, AF6, AF9, AFlO, ENL a ELL). We screened almost 80 patients diagnosed and treated in the Czech Republic between 1997 and 2007 and we found an MLL-fusion gene in 51 of them. Vast majority of rearrangements (92%) was detected by the...
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