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The role of asparagine synthetase in leukemic cells
Šafrhansová, Lucie ; Starková, Júlia (advisor) ; Čuřík, Nikola (referee)
This thesis focuses on the detection of mutations in the enzyme asparagine synthetase on leukemia cell metabolism and the role of this enzyme in the context of L-asparaginase- based chemotherapy. The experimental part of the work is divided into two separate sections. Given the lack of asparagine synthetase gene sequencing data in leukemias, the first objective was to determine whether mutations are present in the leukemia cell line that could affect ASNS function and thus play a role in the resistance of leukemia cells to ASNase therapy. No mutations that could affect the activity of the enzyme were detected by next-generation sequencing. In the second part, a model of RS4;11 that expresses ASNS was established. The effect of ASNS on glycolysis was then studied to sensitize these cells to the effects of L-asparaginase and to the depletion of asparagine and glutamine. It was observed that ASNS expression increased the level of glycolysis and increased the resistance of these cells to asparagine and glutamine depletion and their resistance to asparaginase. Key words: ASNS, aspragine, leukemia, L-asparaginase, chemotherapy, drug resistance
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The clinical relevance of immunogenic cell death associated signalling and molecules in cancer therapy
Holíček, Peter ; Palich Fučíková, Jitka (advisor) ; Říhová, Blanka (referee) ; Starková, Júlia (referee)
The clinical relevance of immunogenic cell death-associated signaling and molecules in cancer therapy The capacity of cancer cells to induce anticancer immune responses relies on multiple factors, including the antigenic repertoire of cancer cells and their ability to provide adjuvant signals, as represented by danger-associated molecular patterns (DAMPs), which are exposed and released by malignant cells during immunogenic cell death (ICD). The release and secretion of DAMPs can orchestrate the activation of innate and adaptive tumor-targeting immunity, resulting in tumor regression. Various chemotherapies, radiation therapy, physical modalities, and targeted anticancer agents have been described as potent ICD inducers, which besides being directly cytotoxic, can activate clinically relevant anticancer immune responses. Therefore, patients whose tumor microenvironment (TME) is shows defective DAMP release or downstream DAMP-sensing signaling pathways do not fully benefit from ICD-inducing treatments, which can lead to overall therapeutic failure. My dissertation contributes to this field by exploring the impact of ICD on the development of innate anticancer immune responses, with a particular focus on natural killer (NK) cells, showing that surface-exposed calreticulin (ecto-CALR) positively impacts the...
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Cancer metabolism and its role in the sensitivity to ASNase of leukemic cells to L-asparaginase
Alquezar Artieda, Natividad ; Starková, Júlia (advisor) ; Procházka, Vít (referee) ; Truksa, Jaroslav (referee)
Cancer metabolism and its role in the sensitivity of leukemic cells to L- asparaginase ABSTRACT No ultimate treatment strategy exists for relapsed or non-responsive (15-20%) children with acute lymphoblastic leukemia (ALL). In this study, we aimed to elucidate the impact of metabolic rewiring in leukemic cells on poor therapy response and the emergence of resistance. This dissertation focuses on l-asparaginase (ASNase), a crucial chemotherapeutic agent and its effect on leukemia, using models of leukemic cell lines and primary cells of ALL patients. Cell metabolism was assessed by measuring metabolic pathways and nutrient influx using a Seahorse analyzer and stable isotope tracing. Main findings of the study demonstrated that the ASNase- therapy response was mitigated by the activity of the mechanistic target of rapamycin (mTOR)- regulated biosynthetic pathways. This phenomenon was induced by the bone marrow environment, which enabled the activation of the resistant mechanism in leukemic cells. We next found a correlation between the following metabolic features and lower sensitivity to ASNase: low ATP- linked respiration, high mitochondrial membrane potential and high glycolytic flux before therapy. The latter was shown to have prognostic implications. Moreover, high glycolytic flux was detected in T-ALL...
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The impact of nucleophosmin gene mutations on its interaction potential
Šašinková, Markéta ; Brodská, Barbora (advisor) ; Čáp, Michal (referee) ; Starková, Júlia (referee)
Nucleophosmin 1 (NPM1) is predominantly localized in the nucleolus and occurs mainly in oligomers formed through its N-terminal domain (NTD). As a transport facilitator and chaperone, NPM1 has a wide range of interacting partners including tumor suppressors p53 and p14Arf. Characteristic C-terminal mutations in NPM1 are reported in approximately 30 % of acute myeloid leukemia (AML) cases and cause aberrant cytoplasmic localization of mutated (mut) NPM1. As a result, many NPM1-interacting proteins, including wild type (wt) NPM1, are relocalized to the cytoplasm. In order to analyze interactions and the oligomeric state of NPM1, we have introduced and optimized several in vitro techniques - native and semi-native polyacrylamide gel electrophoresis and immunoprecipitation - as well as in vivo confocal microscopy and time-resolved fluorescence approaches. Using these methods, we revealed that mutations at the C-terminal domain of NPM1 prevent it from binding nucleolar protein nucleolin (NCL), which has previously been shown to interact with the central part of NPM1, and that drug-induced relocation of mutNPM1 to close proximity of NCL does not induce mutNPM1-NCL complex formation. We proved a lowered stability of mutNPM1-formed oligomers as compared to the wtNPM1 ones, which could be useful for NPM1...
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Metabolic alterations in cancer cells and their implications in the therapy of acute leukemias
Harárová, Alžbeta ; Starková, Júlia (advisor) ; Mrvová, Silvia (referee)
Cancer metabolism differs from that of the healthy cells in several aspects. Aerobic glycolysis (e.g. converting pyruvate to lactate under normoxic conditions) was the first described metabolic alteration of cancer cells. Metabolic alterations have since been described in the tricarboxylic acid cycle, oxidative phosphorylation, in the metabolism of amino acids (especially glutamine, asparagine and serine) and also in the metabolism of fatty acids and cholesterol. The common feature of these changes is the tendency to prefer anabolic pathways, thus enabling fast proliferation of cancer cells. The study of cancer metabolism is particularly important in the case of cancer cells that show resistance to treatment, as their aberrant metabolism is not only a potential diagnostic marker but also a potential therapeutic target. The majority of metabolic alterations have been described for the first time in solid tumors, whereas only recently has the metabolism of acute leukamias gained more attention. Asparaginase is an example of a chemotherapeutic agent that targets a metabolic alteration of leukemic cells. Distinct metabolic profile is also associated with the glucocorticoid resistance. Detailled study of the metabolic alterations of leukemic cells has elucitated the mechanisms of the asparaginase and...
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The role of HOXA9 gene in leukemogenesis
Rejlová, Kateřina ; Starková, Júlia (advisor) ; Fraiberk, Martin (referee)
The evolutionarily conserved family of homeobox genes plays an important role in the development of the anterior-posterior body axis of vertebrates. These genes significantly affect hematopoiesis, the development of blood cells. Extensive studies on homeobox genes in normal hematopoiesis confirmed their role also in leukemogenesis. Since the neoplastic transformation of blood cells, i.e. leukemia, is the most frequent malignancy in children, it has become a major subject of research for many scientists. Precisely in what stage of the malignant transformation the homeobox genes take part has not been shown yet. Neither is it known whether HOX genes are crucial in pathogenesis or whether their deregulation is only a side effect of leukemogenesis. The most studied homeobox gene in leukemogenesis is the HOXA9 gene, which showed correlation with the prognosis of patients with certain leukemias. Many studies describe the effect of HOXA9 in leukemic cell transformation, suggesting this gene could be a promising future target in leukemia therapy. This work is focused on the HOXA9 gene and its association with leukemic transformation of blood cells.
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The mechanism of action of L-asparaginase in childhood acute lymfoblastic leukemia
Heřmanová, Ivana ; Starková, Júlia (advisor) ; Šálek, Cyril (referee) ; Trbušek, Martin (referee)
Acute lymphoblastic leukemia (ALL) is the most frequent type of childhood cancer. The key component in the therapy, L-asparaginase (ASNase), hydrolyzes plasma asparagine and glutamine. Leukemic cells are sensitive to the depletion due to low activity of asparagine synthetase. Although the treatment is very effective, resistance and side effects remain a serious problem in some cases and its mechanism of action is not well understood. In this study, we wanted to elucidate the effect of ASNS expression level on the sensitivity of ALL cells to ASNase treatment. Our aim was also to clarify the intracellular consequences of the amino acid depletion to define the reason of different patients' response. We used four ALL cell lines (NALM-6, RS4;11, REH, and UOCB-6) and 30 diagnostic bone marrow samples of ALL patients to study the relationship between ASNS expression and sensitivity to ASNase using MTS proliferation assay. RNA interference was used to study the effect of a range of ASNS levels on the response to ASNase treatment. Using a cell line model with a gradually knocked-down ASNS gene, we defined a cutoff level below which ASNS gene expression does not correlate with sensitivity to ASNase. Importantly, ASNS gene expression in patients' ALL blasts is below this level. We confirmed that there was no...
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The role of ETV6-RUNX1 fusion protein in the sensitivity of leukemic cells to L-asparaginase
Staněk, Petr ; Starková, Júlia (advisor) ; Burjanivová, Tatiana (referee)
Translocation t(12;21) with the presence of the fusion gene ETV6-RUNX1 (TEL-AML1) is the most common chromosomal aberration found in acute lymphoblastic leukemia in childhood. The occurrence of the ETV6-RUNX1 is associated with excellent prognosis and high sensitivity to the treatment with the enzyme L-asparaginase (ASNase). Resistance to the drug aggravates the outlook of the patient and increases the risk of treatment failure, therefore, the CLIP working group has been for a long time involved in the identification of the mechanism of action of ASNase and the origin of the resistance to it. This thesis follows previous findings of the group and is devoted to the analysis of the importance of ETV6-RUNX1 and signalization and metabolic changes accompanying shifts in the L-asparaginase resistance. In the first part of the thesis, the knockout clones with stable increased resistance to ASNase have been established thanks to the CRISPR/Cas9 system, which created frameshift in the fusion gene. The accomplishment in this regard and removal of the fusion protein was confirmed on the level of DNA, mRNA a protein expression. The presence of other significant chromosomal aberrations affection the sensitivity to ASNase was ruled out by the means of SNP analysis. In the second part of the project, the signalization...
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Targeted cancer therapy based on altered metabolism of amino acids
Šafrhansová, Lucie ; Starková, Júlia (advisor) ; Zelenka, Jaroslav (referee)
The effects of targeted therapies in the treatment of cancer have been extensively researched and tested in many clinical trials. In contrast to conventional chemotherapy treatment, targeted therapy should act specifically on cancer cells with limited toxicity and lower risk of side effects. One type of targeted therapy exploits the Achilles heel of cancer - the specificity of tumour metabolism. With knowledge of the metabolic differences between tumor and normal cells, we can set up conditions that normal cells easily bridge, while tumor cells die as a result. This can be achieved by removing certain amino acids from the extracellular environment on which cancer cells depend. A well-known enzyme that has been used therapeutically for many years is asparaginase. However, asparaginase therapy is only successful in some cancers, so further development is needed, as well as the search for enzymes with similar effects. Over the years, four other enzymes that could become an integral part of the treatment of cancer patients in the future have been discovered - arginine deiminase, arginase, methioninase and cyst(e)inase. Past and current studies have investigated their effects on cancer cells in vitro and in vivo. Successful elimination of cancer cells often comes with limitations as immunogenicity and...
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