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Tracing intestinal tumorigenesis driven by BRAF V600E oncogene
Herrmannová, Terezie ; Hrčkulák, Dušan (advisor) ; Vomastek, Tomáš (referee)
Colorectal carcinoma is one of the most commonly diagnosed tumor diseases worldwide and is the cause of more than nine percent of deaths due to neoplasia. Colorectal cancer develops through different ways and one of them is the so-called serrated pathway, which is characterized by the presence of the BRAF V600E oncogenic mutation. Tumors arising through serrated pathway do not respond to classical therapy, and therefore are currently being studied at the molecular level. The oncogenic variant of the BRAF kinase activates MAPK signaling and is considered to be the main cause of serrated intestinal tumor formation. However, the mere presence of this oncogene is not sufficient for tumor development that requires further changes within the genome of the cell. In this thesis, we try to clarify what effect the BRAF V600E mutation has on the cells of the intestinal epithelium. In addition, we try to identify a possible cooperation between BRAF gene mutation and disruption of p53 and Wnt signaling, whose components are also frequently mutated in colorectal cancer. As a model for studying the processes associated with BRAF V600E activation, we use a mouse strain with conditional expression of a mutant variant of the Braf gene. We isolate intestinal organoids from these mice and subsequently perform in vitro...
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The role of TCF4 transcription factor in intestinal epithelial stem cells and tumors
Hrčkulák, Dušan ; Kořínek, Vladimír (advisor) ; Machoň, Ondřej (referee) ; Macůrková, Marie (referee)
For more than 20 years, T-cell specific factor 4 (Tcf4) is the most intensively studied member of the conserved Tcf/Lymphoid enhancer-binding factor (Lef) family of transcription factors. Together with β-catenin coactivator, Tcf4 represents the prominent nuclear effector of canonical Wnt signaling in the intestinal epithelium. Regulation of Wnt-β-catenin signaling in intestinal stem cells is crucial for tissue homeostasis and tumor formation initiation. Up to date, several mouse models were generated to manipulate Tcf4 abundance or activity in vivo and dissect its function. Moreover, mutational screens and expression profiling of human colorectal tumors were carried out to disclose a contribution of TCF4 to tumor progression. However, subsequent studies brought conflicting results in relation to the potential of Tcf4 to activate or repress Wnt target genes and drive or inhibit cell proliferation. Here in this study, we analyze publicly available datasets for global expression of TCF4 and its paralogs in human tissues and colorectal cancer (CRC) samples. Notably, we present newly generated Tcf4flox5 mouse with a conditional Tcf4 allele that can be used to eliminate expression of Tcf4 from two alternative promoters of the gene. Using this mouse strain we documented that Tcf4 loss led to the demise of...
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Function and regulation of ETV4 and MSX1 transcription factors in colon cancer progression
Hrčkulák, Dušan ; Kříž, Vítězslav (advisor) ; Libusová, Lenka (referee)
Colon cancer causes approximately seven percent of all cancer-related deaths in the world and presumably due to modern lifestyle, it is also one of the most frequently diagnosed cancers. The inefficiency of standard treatment indicates the need for intensive research of molecular mechanisms of cancer development. The canonical Wnt signaling pathway is essential for maintenance of the progenitor phenotype of stem cells in crypts of the intestine and controls repopulation of the epithelia, in physiological conditions. However, aberrant activation leads to tumor formation. Although Wnt signaling in cancer has been subjected to thorough investigation, there is still a lot of questions concerning further branching of the pathway. As a model of Wnt/β-catenin triggered colorectal cancer, we use mice with mutated APC, which is the tumor suppressor involved in this pathway. Previous expression profiling of the intestinal tumors from relevant mice revealed two transcription factors: ETV4 and MSX1 which are significantly overexpressed in cancer cells. In this project we elucidate whether the overexpression is really tumor restricted and Wnt dependent or there is a crosstalk with another signal transduction pathway. We investigate the function and regulation of these transcription factors by synthetic reporter assays,...
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Structural basis of cell invasion
Hrčkulák, Dušan ; Novotný, Marian (advisor) ; Hájková, Zuzana (referee)
Mezenchymal migration strategy is a mode of individual cell invasion, along with an ameboid migration strategy. It is dependent on cell adhesion structures formation and traction forces generation. This work is focused on integrin-mediated cell to extracellular matrix connections called focal adhesions. Focal adhesions are very complex and comprise of many proteins. The clusters of integrin dimers make up the focal adhesion core that binds extracellular matrix. Their intracellular domains indirectly interact with actin stress fibres throught plaque proteins talin and vinculin. Focal adhesion assembly is force dependent and its commponents turnover is also regulated by focal adhesion kinase and prolin-rich tyrosin kinase 2. These kinases are probably recruited to focal adhesions by paxillin and then linked to signaling complexes by adaptor proteins as p130Cas. The 3D structure is what defines the options of interaction among participating proteins. Therefore, this work summarizes 3D structures of six proteins of interest, deals with their interactions and impact on focal adhesions. PDB codes of all available structures of these six proteins are enclosed.
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