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Antigenome defines a selection of mutated tumor peptides driving tumor-specific T-cell response
Hadlová, Petra ; Drbal, Karel (advisor) ; Dibus, Michal (referee)
T cells, as an essential part of the adaptive immune system, play crucial role in eradication of tumor growth. T cells target, interact with and eventually annihilate the tumor cells in antigen- specific (Ag) manner. T cells interact with tumor cells via short epitopes bound to the major histocompatibility complex (MHC) molecules on the tumor cell surface. Tumor specific neoepitopes arise from random somatic mutations and constitute a part of the tumor antigenome. Antigenome comprises of two classes of antigens, tumor specific antigens (TSA) and tumor associated antigens (TAA). TSA are neoantigens carrying neoepitopes unique to each tumor. TAA are self-antigens presented by both tumor cells and non-transformed cells. Each tumor cell is able to develop numerous ways to evade the immune system consisting of T cells, NK cells, macrophages and other mechanisms employed. Despite that immunotherapy has shown a great potential in personalized medicine. The stratification of responsive patients is essential for effective and durable management of therapy in clinical practice. Methods are employed, which study existing reactive T cell clones, somatic mutations present in each patient, role of somatic mutations in tumor development and present neoepitopes. All these patient- specific features facilitate...
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Use of cucurbitacin D for cancer treatment
Malátová, Iva ; Šírová, Milada (advisor) ; Dibus, Michal (referee)
Cucurbitacins are highly oxidized triterpenoids commonly found in plants, especially in the family Cucurbitaceae. There are seventeen types of cucurbitacins and each of them has its derivatives. Cucurbitacins with the most prominent antitumor activity are B, D, E and I. Of these, cucurbitacin B and D are the most common in plants. This work focuses mainly on cucurbitacin D. Cucurbitacin D often induces apoptosis in tumor cells, cell cycle arrest and thereby stops cell proliferation. Indicators of these processes are reduced levels of Bcl-xL, Bcl-2, p21, p27 and cyclins A and B proteins. The main effect of cucurbitacin D on tumor cells is the inhibition of the STAT3 signaling pathway. Whether this pathway is affected at the level of phosphorylation, dimerization, or STAT3 translocation into the nukleus, the result is blocking transcription of genes, which are activated thanks to STAT3 pathway. These are primarily genes that affect tumor growth, angiogenesis, cell invasion, and immune escape. Cucurbitacin D also affects other cell components and processes, such as the NF-κB transcription factor, the enzyme complex of proteasome and inflammasome. However, current knowledge of cucurbitacin D and its mechanism of action is not yet sufficient for its use as an antitumor drug, although the results of its testing...
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Regulatory mechanisms of CD47 surface expression
Jakubec, Martin ; Drbal, Karel (advisor) ; Dibus, Michal (referee)
CD47 glycoprotein can be found on the surface of all healthy cells in our body. The interaction of CD47 with inhibitory receptor SIRPα on the macrophage leads to the inhibition of phagocytosis. This makes CD47 irreplaceable for the safe recognition of own cells and removal of aged or apoptotic cells. Apart from this, CD47 plays a major role in several essential signalling pathways, such as cell adhesion and motility or calcium homeostasis. The level of CD47 expression and its presence on the cell membrane depends not only on the type of tissue, but also on the age of a cell. An increased expression of CD47 protein has also been observed in the cells undergoing tumorigenic transformation, allowing them to escape from tumour immunosurveillance. Spontaneous regulation of the CD47 gene expression is achieved via regulatory transcription factors, such as NF-κB or HIF-1. Another mechanism of CD47 regulation includes the 3'UTR of CD47 mRNA, which serves as a binding site for either regulatory proteins, such as HuR, or miRNAs. CD47 expression can thus be regulated on both transcriptional, as well as translational level. However, appropriate topological CD47 localization within the cell and on the cell surface has also an important effect of its physiological function. Our in depth understanding of key regulatory...
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Identification of novel substrates of PKN3 kinase and characterization of the role of phosphorylation in the regulation of Rho GAP activity
Dibus, Michal
Protein phosphorylation represents one of the most important posttranslational modifications in signal transduction and plays a crucial role in regulation of most of the cellular processes including cell cycle, communication with extracellular environment, cell migration or apoptosis. Phosphorylation is mediated by protein kinases, deregulation of which often negatively affects development and overall homeostasis and leads to development of several diseases, including cancer. In the first part of this work we focused on identification of new substrates of PKN3 kinase, which is a known player in regulation of cytoskeletal organization and pro-malignant tumor growth. Using an analog-sensitive mutant of PKN3 we performed a phosphoproteomic screen and identified 281 proteins that could potentially be phosphorylated by PKN3. Among these, we selected ARHGAP18, a protein from Rho GAP family, for further study. We confirmed PKN3 is able to phosphorylate ARHGAP18 on Thr154, Ser156 and Thr158 and that the two proteins are able to interact with one another in an ARHGAP18 isoform-specific manner. We further showed that substitution of the three candidate sites for phosphomimicking aspartate led to the activation of ARHGAP18 GAP domain which resulted in decreased levels of active RhoA, suggesting the existence...
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Identification of novel substrates of PKN3 kinase and characterization of the role of phosphorylation in the regulation of Rho GAP activity
Dibus, Michal ; Rösel, Daniel (advisor) ; Vomastek, Tomáš (referee) ; Petrák, Jiří (referee)
Protein phosphorylation represents one of the most important posttranslational modifications in signal transduction and plays a crucial role in regulation of most of the cellular processes including cell cycle, communication with extracellular environment, cell migration or apoptosis. Phosphorylation is mediated by protein kinases, deregulation of which often negatively affects development and overall homeostasis and leads to development of several diseases, including cancer. In the first part of this work we focused on identification of new substrates of PKN3 kinase, which is a known player in regulation of cytoskeletal organization and pro-malignant tumor growth. Using an analog-sensitive mutant of PKN3 we performed a phosphoproteomic screen and identified 281 proteins that could potentially be phosphorylated by PKN3. Among these, we selected ARHGAP18, a protein from Rho GAP family, for further study. We confirmed PKN3 is able to phosphorylate ARHGAP18 on Thr154, Ser156 and Thr158 and that the two proteins are able to interact with one another in an ARHGAP18 isoform-specific manner. We further showed that substitution of the three candidate sites for phosphomimicking aspartate led to the activation of ARHGAP18 GAP domain which resulted in decreased levels of active RhoA, suggesting the existence...
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Dual effect of mesenchymal stem cells on cancer: its suppression or progression?
Matsakyanová, Victoria ; Hubálek Kalbáčová, Marie (advisor) ; Dibus, Michal (referee)
Mesenchymal stem cells (MSCs) are multipotent non-hematopoietic cells, capable of differentiation into osteogenic, adipogenic and chondrogenic cell types and can be isolated from bone marrow, adipose tissue or umbilical cord. Due to their differentiation, trophic and immunomodulatory properties, and also their ability to migrate spontaneously to the site of inflammation, damaged tissue or tumor microenvironment, MSCs bring a great potential to become not only a tool to support tissue repair and regeneration, but also for anticancer therapy. Their potential can be also supported by genetic manipulations, which may enhance their antitumor effect. However, in the context of tumor growth, the effect of MSCs in not so clear. While in some cases, MSCs play antitumorigenic role, in other cases they contribute to the development of tumor growth. This dual effect of MSCs on tumor growth is the result of many factors, which modulate the interaction between MSCs and tumor cells. This thesis summarizes the current knowledge of the dual effect of MSC on tumor cells and demonstrates the most promising factors that play the role in the dual effect of MSC. Key words: mesenchymal stem cells, cancer, tumor tropism, cancer suppression, cancer progression
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Role of estrogen signaling in breast carcinoma: implications for cell metabolism
Urbančoková, Alexandra ; Smolková, Katarína (advisor) ; Dibus, Michal (referee)
Cellular transformation leads to rapid cell proliferation that causes a global disease called cancer. Breast cancer is the second most frequent group that affects primarily women. Disease progression is stimulated by the female sex hormone estrogen. This hormone affects cells via estrogen receptor signalization, for example, by changes in proliferation, angiogenesis, apoptosis, and differentiation. The estrogen signaling pathway also alters breast cancer cell metabolism. The inhibition of estrogen signalization is commonly used in cancer treatment. Nonetheless, some tumors show resistance to the treatment and increase the need for new targets of therapy which can be found among the changes in breast cancer cells metabolism. This thesis introduces more closely the topic of breast cancer and the effect of estrogen receptors.
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Neoangiogenesis as a target for tumor therapy
Vondráčková, Michaela ; Sivák, Ladislav (advisor) ; Dibus, Michal (referee)
Neoangiogenesis associated with tumours is formation of new blood vessels from pre-existing quiescent vessels in surrounding tumour tissue and it results from pathological employment of normal angiogenesis. Neoangiogenesis became a promising target for cancer treatment in spite of its complexity and many pro-angiogenic and anti-angiogenic factors involved in this process. Anti-angiogenic strategies are based on neutralization of angiogenic ligands, their receptors or inhibition of signalling pathways employed by such receptors. Other potential strategies include upregulation or delivery of endogenous inhibitors, inhibition of endothelial cell proliferation, stabilization of basement membrane and direct disruption of tumour vasculature. Many anti-angiogenic agents have been identified in past several decades but only a few of them were approved for clinical use. Anti-VEGF-A monoclonal antibody bevacizumab (Avastin® ), soluble decoy VEGF receptor aflibercept (Zaltrap® ), monoclonal antibody directed against VEGFR-2 ramucirumab (Cyramza® ) and tyrosin kinase VEGFR inhibitors sunitinib (Sutent® ) and sorafenib (Nexavar® ) belong among approved agents. Key words: angiogenesis, neoangiogenesis, anti-angiogenic therapy, HIF-1, VEGF, bevacizumab
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Use of cucurbitacin D for cancer treatment
Malátová, Iva ; Šírová, Milada (advisor) ; Dibus, Michal (referee)
Cucurbitacins are highly oxidized triterpenoids commonly found in plants, especially in the family Cucurbitaceae. There are seventeen types of cucurbitacins and each of them has its derivatives. Cucurbitacins with the most prominent antitumor activity are B, D, E and I. Of these, cucurbitacin B and D are the most common in plants. This work focuses mainly on cucurbitacin D. Cucurbitacin D often induces apoptosis in tumor cells, cell cycle arrest and thereby stops cell proliferation. Indicators of these processes are reduced levels of Bcl-xL, Bcl-2, p21, p27 and cyclins A and B proteins. The main effect of cucurbitacin D on tumor cells is the inhibition of the STAT3 signaling pathway. Whether this pathway is affected at the level of phosphorylation, dimerization, or STAT3 translocation into the nukleus, the result is blocking transcription of genes, which are activated thanks to STAT3 pathway. These are primarily genes that affect tumor growth, angiogenesis, cell invasion, and immune escape. Cucurbitacin D also affects other cell components and processes, such as the NF-κB transcription factor, the enzyme complex of proteasome and inflammasome. However, current knowledge of cucurbitacin D and its mechanism of action is not yet sufficient for its use as an antitumor drug, although the results of its testing...
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