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The role of iron in the regulation of proteins connected with tamoxifen-resistance
Potomová, Petra ; Truksa, Jaroslav (advisor) ; Balušíková, Kamila (referee)
Cancer cells are highly dependent on nutrient uptake to sustain their increased proliferation, one of these nutrients being iron. In recent years, a heightened dependency on iron was observed in cancer cells, allowing for the proper function of numerous enzymes, DNA synthesis and mitochondrial respiration. Here, we further delve into the iron metabolism of malignant cells, attempting to understand the differences between tamoxifen-sensitive and resistant (Tam5R) ones using two breast cancer cell lines of luminal A origin, MCF7 and T47D. These cells show numerous changes in iron homeostasis and iron-dependent mechanisms. Based on alterations in proteomes of Tam5R cell lines, we focused on iron regulation of proteins that are deregulated in tamoxifen resistance - assessing their regulation on transcriptional (mRNA) and post-transcriptional level (protein) as well as comparing their responsiveness to their sensitive parental cell line. We assessed two main types of regulation - iron-responsive element interaction with iron-regulatory proteins (IRE-IRP pathway) and tristetraprolin (TTP) driven mRNA degradation via AU-rich elements (ARE). Using iron loading and chelation, we challenged the cells - confirming the known IRE-IRP regulation of ferritin heavy chain (FTH), transferrin receptor 1 (TfR1),...
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Study of mechanism of action of anticancer drug tamoxifen and its toxic side effects
Kylarová, Salome ; Stiborová, Marie (advisor) ; Moserová, Michaela (referee)
Anti-estrogen therapy is used for treatment of hormone (estrogen) receptor positive breast cancer. The rise of this type of cancer is associated with a prolonged exposure to these hormones throughout life. Tamoxifen is one of the most used hormonal drugs, which blocks the effects of these hormones in breast cancer tissue by competitive binding to hormonal receptors. The affinity of tamoxifen to these receptors is not sufficient, therefore it has to be activated to metabolites having greater affinity, namely 4-hydroxytamoxifen and endoxifen. The formation of these intermediates is catalysed by cytochromes P450. In the second phase of its biotransformation hydroxylated metabolites of tamoxifen are primarily sulphated by sulphotransferases and eliminated from the body. In addition to these active intermediates, which inhibit the growth of breast tumor tissue, there are metabolites causing negative effects in the others. The most important metabolite is α-hydroxytamoxifen, which forms covalent DNA adducts in liver tissue of rats and endometrium of females. Tamoxifen therapy is associated with numerous side effects, but the greatest attention is focused to formation of endometrial cancer and induction of tumor's resistance to this therapy. Effects of tamoxifen therapy are dependent on the activity of...
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Pharmacogenetic prediction of tamoxifen efficiacy and adverse effects in hormonal dependent breast karcinoma patients.
Argalácsová, Soňa ; Slanař, Ondřej (advisor) ; Vrána, David (referee) ; Paluch, Zoltán (referee)
ABSTRACT/SUMMARY Background: The clinical efficacy of tamoxifen therapy may be modified by the drug-metabolizing enzymes and transporting molecules involved into the pharmacokinetics of tamoxifen. The aim of this study was to evaluate the association of CYP2D6, ABCB1 polymorhisms and comedication with efficacy and safety of tamoxifen treatment. Methods: Totally 258 women with hormonal positive breast carcinoma were retrospectively evaluated in relation to CYP2D6, ABCB1 polymorphisms and comedication. Results: CYP2D6 polymorphisms or co-medication affecting CYP2D6 activity demonstrated no statistically significant effect on the efficacy of tamoxifen therapy or adverse event incidence; there was only a trend towards shortening the time to event (TTE) in CYP2D6 poor metabolizers. ABCB1 polymorphism rs2032582 was not associated with clinical outcomes, while a trend towards an increase of TTE in variant allele carriers was noted. The ABCB1 polymorphism rs1045642 demonstrated statistical significance in premenopausal patients (p = 0.0012, HR 0.69 (95% CI 0.21 to 2.31), and its significant association was noted with gynaecological /vasomotor adverse events (p = 0.0221, HR = 1.0588), with no evidence of the influence on the incidence and onset of venous complications. Conclusions: Although this work did not show...
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Pharmacogenetic prediction of tamoxifen efficiacy and adverse effects in hormonal dependent breast karcinoma patients.
Argalácsová, Soňa ; Slanař, Ondřej (advisor) ; Vrána, David (referee) ; Paluch, Zoltán (referee)
ABSTRACT/SUMMARY Background: The clinical efficacy of tamoxifen therapy may be modified by the drug-metabolizing enzymes and transporting molecules involved into the pharmacokinetics of tamoxifen. The aim of this study was to evaluate the association of CYP2D6, ABCB1 polymorhisms and comedication with efficacy and safety of tamoxifen treatment. Methods: Totally 258 women with hormonal positive breast carcinoma were retrospectively evaluated in relation to CYP2D6, ABCB1 polymorphisms and comedication. Results: CYP2D6 polymorphisms or co-medication affecting CYP2D6 activity demonstrated no statistically significant effect on the efficacy of tamoxifen therapy or adverse event incidence; there was only a trend towards shortening the time to event (TTE) in CYP2D6 poor metabolizers. ABCB1 polymorphism rs2032582 was not associated with clinical outcomes, while a trend towards an increase of TTE in variant allele carriers was noted. The ABCB1 polymorphism rs1045642 demonstrated statistical significance in premenopausal patients (p = 0.0012, HR 0.69 (95% CI 0.21 to 2.31), and its significant association was noted with gynaecological /vasomotor adverse events (p = 0.0221, HR = 1.0588), with no evidence of the influence on the incidence and onset of venous complications. Conclusions: Although this work did not show...
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Expression and regulation of the ABC transporters in tumour cells
Tomková, Veronika ; Truksa, Jaroslav (advisor) ; Němcová, Vlasta (referee)
Estrogen signalling pathway plays crucial role in carcinogenesis of breast cancer. Estrogen receptor (ER) is a prototypical hormone receptor that upon binding its ligand, estradiol, translocates into the nucleus and turns on target genes related to cellular proliferation and survival. Although estrogen signalling physiologically supports normal breast tissue development, deregulations of this pathway contribute to development of breast tumours that are estrogen receptor dependent. One of the main obstacles in breast cancer treatment is acquired resistance to common anticancer drugs also known as multidrug resistance (MDR). The switch between chemotherapy responsive to chemotherapy resistant cell phenotype is usually accompanied by increased expression of ABC transporters, special membrane proteins responsible for export of various kinds of commonly used anticancer drugs from the intracellular to extracellular space and is also linked to the existence of cancer stem cells (CSCs). ABC transporters can not only export chemotherapeutic drugs but may modulate tumour microenvironment through the transport of endogenous intracellular substrates such as leukotrienes (LTs), sphingolipids and prostaglandins PGs). This function may also play important role in carcinogenesis. The aim of the thesis was to...
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Study of mechanism of action of anticancer drug tamoxifen and its toxic side effects
Kylarová, Salome ; Stiborová, Marie (advisor) ; Moserová, Michaela (referee)
Anti-estrogen therapy is used for treatment of hormone (estrogen) receptor positive breast cancer. The rise of this type of cancer is associated with a prolonged exposure to these hormones throughout life. Tamoxifen is one of the most used hormonal drugs, which blocks the effects of these hormones in breast cancer tissue by competitive binding to hormonal receptors. The affinity of tamoxifen to these receptors is not sufficient, therefore it has to be activated to metabolites having greater affinity, namely 4-hydroxytamoxifen and endoxifen. The formation of these intermediates is catalysed by cytochromes P450. In the second phase of its biotransformation hydroxylated metabolites of tamoxifen are primarily sulphated by sulphotransferases and eliminated from the body. In addition to these active intermediates, which inhibit the growth of breast tumor tissue, there are metabolites causing negative effects in the others. The most important metabolite is α-hydroxytamoxifen, which forms covalent DNA adducts in liver tissue of rats and endometrium of females. Tamoxifen therapy is associated with numerous side effects, but the greatest attention is focused to formation of endometrial cancer and induction of tumor's resistance to this therapy. Effects of tamoxifen therapy are dependent on the activity of...
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Study of alternatively spliced variants of estrogen receptor alpha in breast cancer cell lines
Lhota, Filip ; Kleibl, Zdeněk (advisor) ; Souček, Pavel (referee)
Filip Lhota: Study of alternatively spliced variants of estrogen receptor alpha in breast cancer cell lines Abstract: Estrogen receptor α (ER-α) is a transcription factor responsible for mediation of the activities of its natural ligand 17-β-estradiol (E2), the hormone that together with progesterone belongs to the key regulators of mammary epithelial as well as breast cancer cells proliferation. Except to the major gene product consisting of all eight coding exons of ER-α, numerous qualitatively and quantitatively different spliced variants originated from primary transcript by activity of alternative splicing is expressed. Despite that some of these spliced variants have been functionally characterized, their precise role on final ER-α cellular activity remains to be elucidated. The functional characterization of individual alternative forms of ER-α and description of its participation on the overall ER-α activity is important for our understanding of their biogenesis and is also critical for the delineation of molecular bases for ER-α regulation during anti cancer chemotherapy. This work aimed to study the influence of alternatively spliced ER-α variants on the growth characteristics of clones constructed from stable mammary tissue cell lines in regulation to cultivation conditions and cellular...
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