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Lineage plasticity of leukemic blasts. Importance for detection of minimal residual disease and study of hematopoesis
Vakrmanová, Barbora ; Mejstříková, Ester (advisor) ; Šálek, Cyril (referee) ; Klener, Pavel (referee)
Acute leukemia is the most common malignancy in children. According to the origin of the leukemic blasts, two types of leukemia are distinguished - lymphoid (ALL) and myeloid (AML). The focus of this thesis is lineage plasticity of the leukemic blasts. In about 2-5% of leukemias, blasts share immunophenotypic features of both lymphoid and myeloid lineages. In international retrospective study we showed superior overall survival in patients treated according to lymphoid type of protocol compared to patients treated to myeloid type of protocol, especially in cases with CD19 positivity on the blasts. Another type of the plasticity and diagnostic uncertainty in leukemia is ALL with early switch to monocytic lineage. About 8% of B cell precursor ALL underwent monocytic switch in our consecutive cohort. This phenomenon is more common among DUX4r, PAX5-P80R and ZNF384r leukemias. Discrepancy between minimal residual disease (MRD) measured by flow cytometry and quantitative assessment of immunoreceptor rearrangements method occurs because of the loss of B-lymphoid markers. We investigated transdifferentiation process by mass cytometry. By the multilabel panel we were able to determine the sequence of changes in proteins and transcription factors by new tviblindi algorithm. Targeted treatment, such as...
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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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Differentiation plasticity of hematopoietic cells
Polgárová, Kamila ; Stopka, Tomáš (advisor) ; Otáhal, Pavel (referee) ; Šálek, Cyril (referee)
Hematopoiesis has been for many years seen as a straightforward process based on sequential restriction of cell fate potential leading to production of mature blood cells. In the last decade, however, several works documented an unexpected plasticity of hematopoietic cells with expanded potential of myeloid development from lymphoid progenitors and vice versa. Under physiologic conditions hematopoiesis is tightly controlled and the definite cell fate is denominated by multiple factors that all lead to changes in regulatory networks that include transcription factors, epigenetic changes and post-transcriptional modulations. Any disruption of this strict regulation, caused by mutations or other events, affects the proliferation and lineage fidelity of hematopoietic precursors. This may lead to clonal growth of variable significance or leukemogenesis and may possibly affect the treatment sensitivity of the hematological malignancies. For better understanding of hematopoietic regulation we described gene expression changes during physiological development of lymphoid and myeloid lineages and in leukemic specimens using our own simplified real-time PCR based platform. We investigated expression of 95 genes connected with lymphoid and myeloid differentiation or with leukemogenesis in sorted hematopoietic...
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Genetic and epigenetic mechanisms (and their cooperation) in the leukemogenesis of acute myeloid leukemia in adults.
Šestáková, Šárka ; Šálek, Cyril (advisor) ; Vymetálková, Veronika (referee) ; Kubričanová Žaliová, Markéta (referee)
Acute myeloid leukemia (AML) is a hematopoietic malignancy characterized by great heterogeneity and clonal nature. In recent years, rapidly evolving next-generation sequencing methods provided a deep insight into the mutational background of AML. It was shown that ~ 44 % of AML patients harbor mutations in genes that regulate DNA methylation. So far, many researchers have tried to evaluate the prognostic significance of DNA methylation changes in AML, however, due to a great inconsistency in these studies, none of the reported markers were implemented into clinical practice. The aim of this work was to further investigate the DNA methylation changes in AML patients with specific mutations and their prognostic effect. Next, we wanted to develop a new approach for a complex evaluation of prognostically significant DNA methylation aberrations. In our first project, we assessed the overall DNA methylation, hydroxymethylation, and gene expression in AML patients with mutations in either DNMT3A or IDH1/2 or their combinations. We discovered that each genetic aberration is connected with a distinct pattern of DNA hydroxy-/methylation changes that are not entirely reflected in altered gene expression. Patients with mutations in both genes exhibited a mixed DNA methylation profile most similar to healthy...
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Genetic and epigenetic mechanisms (and their cooperation) in the leukemogenesis of acute myeloid leukemia in adults.
Šestáková, Šárka ; Šálek, Cyril (advisor) ; Vymetálková, Veronika (referee) ; Kubričanová Žaliová, Markéta (referee)
Acute myeloid leukemia (AML) is a hematopoietic malignancy characterized by great heterogeneity and clonal nature. In recent years, rapidly evolving next-generation sequencing methods provided a deep insight into the mutational background of AML. It was shown that ~ 44 % of AML patients harbor mutations in genes that regulate DNA methylation. So far, many researchers have tried to evaluate the prognostic significance of DNA methylation changes in AML, however, due to a great inconsistency in these studies, none of the reported markers were implemented into clinical practice. The aim of this work was to further investigate the DNA methylation changes in AML patients with specific mutations and their prognostic effect. Next, we wanted to develop a new approach for a complex evaluation of prognostically significant DNA methylation aberrations. In our first project, we assessed the overall DNA methylation, hydroxymethylation, and gene expression in AML patients with mutations in either DNMT3A or IDH1/2 or their combinations. We discovered that each genetic aberration is connected with a distinct pattern of DNA hydroxy-/methylation changes that are not entirely reflected in altered gene expression. Patients with mutations in both genes exhibited a mixed DNA methylation profile most similar to healthy...
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Differentiation plasticity of hematopoietic cells
Polgárová, Kamila ; Stopka, Tomáš (advisor) ; Otáhal, Pavel (referee) ; Šálek, Cyril (referee)
Hematopoiesis has been for many years seen as a straightforward process based on sequential restriction of cell fate potential leading to production of mature blood cells. In the last decade, however, several works documented an unexpected plasticity of hematopoietic cells with expanded potential of myeloid development from lymphoid progenitors and vice versa. Under physiologic conditions hematopoiesis is tightly controlled and the definite cell fate is denominated by multiple factors that all lead to changes in regulatory networks that include transcription factors, epigenetic changes and post-transcriptional modulations. Any disruption of this strict regulation, caused by mutations or other events, affects the proliferation and lineage fidelity of hematopoietic precursors. This may lead to clonal growth of variable significance or leukemogenesis and may possibly affect the treatment sensitivity of the hematological malignancies. For better understanding of hematopoietic regulation we described gene expression changes during physiological development of lymphoid and myeloid lineages and in leukemic specimens using our own simplified real-time PCR based platform. We investigated expression of 95 genes connected with lymphoid and myeloid differentiation or with leukemogenesis in sorted hematopoietic...
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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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Prognosis of childhood acute lymphoblastic leukemia according to novel clinical and biological risk factors
Volejníková, Jana ; Froňková, Eva (advisor) ; Šálek, Cyril (referee) ; Klener, Pavel (referee)
Great progress has been achieved in the diagnostics and therapy of childhood acute lymphoblastic leukemia (ALL) during the last few decades and the permanent cure rate for children and adolescents has risen to nearly 90%. The basic principle of ALL treatment is to split patients into several groups receiving treatment of different intensity according to exactly defined prognostic features. This is aimed at reducing both the risk of relapse and toxic complications of treatment. The development of new diagnostic methods, especially in the field of molecular genetics and flow cytometry, allowed further improvements in the risk stratification - the minimal residual disease (MRD) has become a crucial prognostic factor in modern treatment protocols for pediatric ALL as a sensitive marker of both response to therapy and subclinical leukemic involvement of various tissues of the organism. Nevertheless, there is still an intensive search for new markers that would enable even more precise characterization of the leukemic clone, and treatment strategies reflecting the biology of leukemic cells are being optimized. The first part of our study describes the monitoring and prognostic impact of MRD in peripheral blood of children with ALL with emphasis on very early time points of treatment. MRD was examined by the...
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