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Význam rostlinných proteinů z podrodiny ABCB pro transport auxinu
Kubeš, Martin ; Zažímalová, Eva (advisor) ; Hejátko, Jan (referee) ; Reinöhl, Vilém (referee)
Polar auxin transport provides essential directional and positional information for many developmental processes in plants. At the cellular level, it is realized by both passive diffusion and the active transport through the membrane proteins - AUX1/LAXes, PINs and ABCBs. The aim of this thesis was to characterize the role of ABCB1, ABCB4 and ABCB19 proteins in polar auxin transport using transformed tobacco BY-2 cell lines. It was shown that the plasma membrane (PM) localization of the ABCB1, 4 and 19 is not polar. The ABCB4 was also more stable on PM after the treatment with auxin influx inhibitors; making use of ABCB4-cell line helped to uncover new characteristics of markers of endocytosis - the FM- dyes. The induction of ABCB19 has led to a decrease in 3 H-NAA accumulation with characteristic auxin starvation phenotype, similar to PIN7 overexpressing cell line, that could be rescued in case of PIN7 cell line by application of the auxin efflux inhibitor NPA; however, the accumulation of auxin in ABCB19-overexpressing cell line was less sensitive to NPA and the rescue of the auxin starvation phenotype was ineffective. Importantly, unique property of the ABCB4 was demonstrated: It displayed dual, auxin-concentration-dependent auxin transport activity in Arabidopsis roots, tobacco BY-2 and yeast cells. The...
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Resistance mechanisms in therapy of acute myeloid leukemia
Suchá, Simona ; Čečková, Martina (advisor) ; Žák, Pavel (referee) ; Matoušková, Petra (referee)
IN ENGLISH LANGUAGE Candidate: Mgr. Simona Suchá Supervisor: Assoc. Prof. PharmDr. Martina Čečková, PhD. Title of the doctoral thesis: Resistance mechanisms in therapy of acute myeloid leukemia Acute myeloid leukemia (AML) is a hematologic cancer known for its extensive heterogeneity, poor treatment outcomes and high relapse rate. Therapy outcome is often compromised by highly resistant leukemic clones present at diagnosis, which evade chemotherapy and continue to spread the disease. Identification of their cellular features is, therefore, a key in successful targeting and eliminating of these resistant leukemic cells. AML cells can, however, develop drug resistance even overtime due to prolonged drug exposure. Extremely high adaptability of leukemic cells enables them to survive whenever therapeutic stress stimuli occur. Uncovering molecular mechanisms that cells utilize to activate their survival mode is crucial in selection of treatment leading to maximal efficacy. Based on these grounds, two main aims of this thesis were set. First, to determine clinical relevance of ABC efflux transporters in AML and to evaluate the effect of targeted agents on chemotherapy. The focus was put on agents belonging to either FLT3 inhibitors (midostaurin) or CDK4/6 inhibitors (abemaciclib, palbociclib,...
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Expression of ABC transporters in cell cultures of non-small cell lung cancer: effect of selected targeted drugs
Žofajová, Barbora ; Hofman, Jakub (advisor) ; Červený, Lukáš (referee)
Charles University Faculty of Pharmacy in Hradec Králové Department of Pharmacology & Toxicology Student: Barbora Žofajová Supervisor: doc. RNDr. Jakub Hofman, Ph.D. Title of diploma thesis: Expression of ABC transporters in non-small cell lung carcinoma cell cultures: effect of selected targeted drugs ABC transporters form a special family of transmembrane proteins, their function is the active efflux of substrates into the extracellular environment. These transporters are expressed in normal tissues and tumor cells. Thus, they influence drug pharmacokinetics and play a role in the development of multidrug resistance (MDR). Tyrosine kinases have essential functions ranging from proliferation to differentiation and cell death, their mutation can cause carcinogenesis. Finding, exploring, and inhibiting the functions of these targets is a promising strategy to treat cancer. This work aimed to determine whether the selected drugs are involved in pharmacokinetic interactions that are based on inductions of ABC efflux transporter genes and whether they have the potential to affect MDR phenotype of tumor cells. The drugs, which we studied, were three targeted anticancer drugs (capmatinib, pralsetinib, and tazemetostat) and two well- known chemotherapeutic drugs (pemetrexed and methotrexate). First, we...
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Resistance mechanisms in therapy of acute myeloid leukemia
Suchá, Simona ; Čečková, Martina (advisor) ; Žák, Pavel (referee) ; Matoušková, Petra (referee)
IN ENGLISH LANGUAGE Candidate: Mgr. Simona Suchá Supervisor: Assoc. Prof. PharmDr. Martina Čečková, PhD. Title of the doctoral thesis: Resistance mechanisms in therapy of acute myeloid leukemia Acute myeloid leukemia (AML) is a hematologic cancer known for its extensive heterogeneity, poor treatment outcomes and high relapse rate. Therapy outcome is often compromised by highly resistant leukemic clones present at diagnosis, which evade chemotherapy and continue to spread the disease. Identification of their cellular features is, therefore, a key in successful targeting and eliminating of these resistant leukemic cells. AML cells can, however, develop drug resistance even overtime due to prolonged drug exposure. Extremely high adaptability of leukemic cells enables them to survive whenever therapeutic stress stimuli occur. Uncovering molecular mechanisms that cells utilize to activate their survival mode is crucial in selection of treatment leading to maximal efficacy. Based on these grounds, two main aims of this thesis were set. First, to determine clinical relevance of ABC efflux transporters in AML and to evaluate the effect of targeted agents on chemotherapy. The focus was put on agents belonging to either FLT3 inhibitors (midostaurin) or CDK4/6 inhibitors (abemaciclib, palbociclib,...
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Critical sites determining the resistance phenotype of ABC proteins from the ARE subfamily and the molecular mechanism of their function
Lenart, Jakub
Vga(A) and Msr(A) are resistance proteins belonging to the ARE subfamily of ABC -F proteins. They confer resistance to inhibitors of the peptidyltransferase center. It has been proposed that the mechanism of resistance is based on interaction with a transmembrane partner that forms the functional transporter. Their ribosomal function has been described by cryoelectron microscopy of ribosome complexes with ABCF mutants unable to hydrolyze ATP. However, the exact mechanism of resistance is not yet known. We have produced the mutant proteins combining the four amino acid residues in Vga(A) and Vga(A)LC at the linker tip, and we were the first to describe the effects of substrate specificity of the single mutants. Amino acid positions 212 and 220 are important for resistance to lincosamides and pleuromutilins, respectively, while position 219 is responsible for resistance to streptogramin A. Each amino acid property plays a critical role in conferring antibiotic specificity, as confirmed by the fact that amino acid substitution at position K218T in the Vga(A) protein causes the shift in resistance from streptogramins to lincosamides and pleuromutilins. The mechanism of resistance conferred by Vga(A) is ribosomal protection. This is supported by the fact that the rate of [3H]-lincomycin accumulation in...
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The effect of aminoacid variability on the resistance phenotype in ARE subfamily of ABC proteins
Lenart, Jakub ; Balíková Novotná, Gabriela (advisor) ; Fišer, Radovan (referee)
ARE subfamily proteins belonging to ABC transporters confers a different degree of resistance to macrolides, linkosamides and streptogramins antibiotics. Among the most clinically ARE subfamily proteins in staphylococci is Vga(A) protein lead to the award resistance to streptogtramins A. In 2006, discovered the new variant called the Vga(A)LC, which in addition to streptogramins A resistance also confers linkosamides. Vga(A) and Vga(A)LC differ in only 7 amino acids, yet confer different resistance phenotypes. In previous experiments it was found that the central role in determining substrate specificity play a 4 amino acid differences that accumulate in the section of 15 amino acids within the linker connecting the two ABC domains (positions 212, 219, 220 and 226). The combination of amino acids LGAG Vga(A) increases resistance to streptogramins A while present in combination SVTS Vga(A)LC increased resistance to linkosamides. Although in this subfamily includes a large number of resistance proteins, the mechanism of resistance has not yet been established with certainty. The aim was to create a new Vga(A) variants that contain specific combinations of amino acids for Vga(A) and Vga(A)LC protein at positions 212, 219, 220 and 226 and compared their ability to grant resistance to linkosamides. We also...
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Critical sites determining the resistance phenotype of ABC proteins from the ARE subfamily and the molecular mechanism of their function
Lenart, Jakub ; Balíková Novotná, Gabriela (advisor) ; Melter, Oto (referee) ; Branny, Pavel (referee)
Vga(A) and Msr(A) are resistance proteins belonging to the ARE subfamily of ABC -F proteins. They confer resistance to inhibitors of the peptidyltransferase center. It has been proposed that the mechanism of resistance is based on interaction with a transmembrane partner that forms the functional transporter. Their ribosomal function has been described by cryoelectron microscopy of ribosome complexes with ABCF mutants unable to hydrolyze ATP. However, the exact mechanism of resistance is not yet known. We have produced the mutant proteins combining the four amino acid residues in Vga(A) and Vga(A)LC at the linker tip, and we were the first to describe the effects of substrate specificity of the single mutants. Amino acid positions 212 and 220 are important for resistance to lincosamides and pleuromutilins, respectively, while position 219 is responsible for resistance to streptogramin A. Each amino acid property plays a critical role in conferring antibiotic specificity, as confirmed by the fact that amino acid substitution at position K218T in the Vga(A) protein causes the shift in resistance from streptogramins to lincosamides and pleuromutilins. The mechanism of resistance conferred by Vga(A) is ribosomal protection. This is supported by the fact that the rate of [3H]-lincomycin accumulation in...
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Molecular mechanisms of tamoxifen resistance in breast cancer
Tomková, Veronika ; Truksa, Jaroslav (advisor) ; Brábek, Jan (referee) ; Mráček, Tomáš (referee)
The resistance to tamoxifen, a drug used in the adjuvant therapy for hormone sensitive breast cancer, represents a major clinical obstacle. Although various mechanisms leading to tamoxifen resistance have been described and intensively studied, a significant number of patients still become resistant to the treatment and eventually relapse. Tamoxifen therapy has been shown to enrich tumors with cancer stem cells (CSCs), which are naturally resistant, and have self-renewal ability and the potential to form secondary tumors. Metabolic rewiring, altered iron metabolism and upregulation of ATP-binding cassette (ABC) transporters have been shown to be important in the maintenance of CSC phenotype. Therefore, we investigated these mechanisms as possible contributors to tamoxifen resistance in vitro in two tamoxifen resistant (Tam5R) cell lines that we established. We show that Tam5R cells have dramatically disassembled and less active mitochondrial supercomplexes (SCs) and higher level of mitochondrial superoxide, together with a fragmented mitochondrial network. Such dysfunction of mitochondria results in the AMP-activated protein kinase (AMPK) activation and metabolic rewiring towards glycolysis. Importantly, cells lacking functional mitochondria are significantly more resistant to tamoxifen, supporting...
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The influence of xenobiotic metabolizing enzymes and transporters on the incidence of colorectal cancer and chemotherapy outcome
Krus, Ivona ; Souček, Pavel (advisor) ; Králíčková, Milena (referee) ; Hodis, Jiří (referee)
Introduction: Colorectal cancer (CRC) is one of the most frequent malignancies and affects approximately 5% of worldwide population. More than 75% of CRC cases represent sporadic forms. Susceptibility to nonhereditary CRC is significantly influenced by polymorphisms and mutations in low-penetrance genes. Variations in biotransformation and DNA repair genes may result in acumulation of toxins and DNA damage in cells leading to the development of cancer. Furthermore, different gene expression profiles of membrane transporters affecting the accumulation of anticancer drugs in tumour cells, e.g. ABC drug transporters, may largely influence inter-individual variability in drug response and chemotherapy outcome. The aim of this study was to evaluate the role of genetic and lifestyle factors in the risk of onset and progression of colorectal cancer. This study followed selected genetic alterations in xenobiotic-metabolizing enzymes (CYP1B1, GSTM1, GSTT1, GSTP1, NQO1 and EPHX1) and genes involved in response to DNA damage (CHEK2 and NBN), as potential CRC susceptibility factors. Another aim of this study was to investigate expression profile of all human ABC transporter genes to follow their prognostic and predictive potential in colorectal carcinoma. Materials and methods: The polymorphisms and other...
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Mechanisms of resistance and iron metabolism in cancer stem cells
Lettlová, Sandra
(EN) Analogously to normal stem cells within the tissues, cancer stem cells (CSCs) have been proposed to be responsible for maintenance and growth of tumours. CSCs represent a small fraction of cells within the tumour, which is characterised by self-renewal capacity and ability to give rise to a tumour when grafted into immunocompromised mice. Cells with increased stemness properties are believed to be responsible for tumour resistance, metastases formation and relapse after tumour treatment. The first part of this work concentrates on resistance of the tumours, which is often associated with increased expression of ATP-binding cassete (ABC) transporters pumping chemotherapeutics out of the cells. For the purposes of this study, we utilized an in vitro model of CSCs, based on cultivation of cells as 3D "spheres". Expression profiling demonstrates that our model of CSCs derived from breast and prostate cancer cell lines express higher mRNA level of ABC transporters, particularly ABCA1, ABCA3, ABCA5, ABCA12, ABCA13, ABCB7, ABCB9, ABCB10, ABCC1, ABCC2, ABCC3, ABCC5, ABCC8, ABCC10, ABCC11 and ABCG2 among the cell lines tested. The protein level of ABC transporters tested in breast CSCs showed higher expression of ABCB8, ABCC1, ABCC2, ABCC10 and ABCG2 but downregulation of ABCB10 and ABCF2 proteins....
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