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Cytochromes P450 are heme enzymes with very broad substrate specificity, they can oxidize tens to hundreds of different substrates including both eobiotics and xenobiotics, but with varying efficiencies and kinetics. They are responsible for the metabolic activation of many carcinogens resulting in formation of reactive intermediates, these reactive species participate in the formation of DNA adducts and also increase of oxidative stress. Eukaryotic cytochromes P450 are membrane bound enzymes found mostly in the endoplasmic reticulum. In vertebrates, they are expressed in a variety of tissues mostly in the liver, but also in kidney, lung, skin and others. The cytochrome P450 1B1 is an inducible enzyme which occurs mainly in the lung and skin. Its expression is induced predominantly by the presence of polycyclic aromatic hydrocarbons, dioxins and heterocyclic amines. The human cytochromes P450 are typically obtained using heterologous expression and isolated as a C-terminally modified hexa-histaq constructs using immobilized metal affinity chromatography. This thesis focuses on effect of C-terminal modifications on activity of human cytochrome P450 1B1. First, the two expression vectors encoding the human form of cytochrome P450 1B1 were prepared, one contained a classical C-terminal hexa-histaq...

Colorectal carcinoma (CRC) ranks high in mortality and morbidity in most developed countries. Following theses focus on specific aspects of colorectal carcinoma pathogenesis including the issue of screening. The goal of the first study was assessment of expression of epithelial markers of colorectal carcinogenesis p53, COX-2, bcl-2. The study included patients with active ulcerative colitis (UCA), ulcerative colitis in remission (UCR), primary sclerosing cholangitis with ulcerative colitis (PSC-UC) (PSC), patients after liver transplantation for PSC (OLT) and a control group (N). We found significantly increased expression of tumour suppressor gene p53 in non-dysplastic mucosae in PSC-UC compared with UCA, UCR, OLT, and N, which may indicate higher neoplastic potential of PSC. Statistically significant correlation was found between PSC incidence and p53 expression. Surprisingly, OLT showed no p53 expression in non-dysplastic mucosa compared with PSC-UC. This indicates that PSC may contribute to increased expression of p53 and p53-induced colorectal carcinogenesis. Furthermore, a correlation between expression of p53 and COX-2 together with the increased expression of bcl-2 in UCA compared to N can support the role of inflammation in colorectal carcinogenesis. The goal of the second study was...

Epigenetic changes represent chemical modifications of the DNA molecule and histone proteins by which gene expression is altered. Among them, DNA methylation is a known mechanism of silencing of tumor-suppressor and DNA repair genes, with an important role in carcinogenesis. Many studies have been done in order to identify the methylation signatures of these genes in different types of cancer. In our study, we investigated the methylation status of promoter regions of eight mismatch repair genes (MLH1, MSH2, MSH3, MLH3, PMS1, PMS2, MSH6 and EXO1) in 45 sporadic colorectal cancer cases and 12 head and neck cancer patients. Two out of eight genes, MLH1 and MLH3, exhibited promoter methylation. The results from both groups of patients were concordant. We summarize that the methylation profiles of MLH1 and MLH3 promoters could be potential candidates for epigenetic biomarkers in colorectal cancer, and eventually in head and neck cancer. Further investigations, which would confirm this theory, should be carried out.

Non-small cell lung cancer belongs to most frequent malignant tumours at all worldwide. Despite significant progress in knowledge about etiopathogenesis and targeted anticancer therapy, basic scientific research in this particular field and development of more effective treatment remains challenging. In case of its inadequate activation, the Hedgehog signaling pathway is involved in non-small cell cancer development. P53 is well known tumour suppressor gene, that serves as anticancer barrier. Its activity is mostly determined by the transcriptional activation of many pro-apoptotic genes, one of which is SIVA-1. Recently, it has been surprisingly shown, that SIVA-1 has also pro-oncogenic properties in a mouse model of non-small cell lung cancer. The aim of this study was to clarify the importance of Hedgehog signaling pathway and protein SIVA-1 and their potential relationship in development and progression of human non-small cell lung cancer. In selected cell lines of human non-small cell lung cancer, expression of each single component of Hedgehog signalign pathway was detected. In the tissue samples of tumour obtained from 39 patients that underwent surgery for non-small cell lung cancer and selected cell lines of the same tumour, expression of SIVA-1 protein was revealed. These findings indicate...

The dissertation deals with a cell response to genotoxic stress, specifically to anti-cancer treatments with a genotoxic mechanism of action. In principle, cells can respond to these perturbing stimuli in several ways: in case of severe DNA damage, they usually undergo apoptosis or enter senescence. In case of minor DNA damage, or upon defective checkpoint mechanisms, they may continue the cell cycle, either with successfully repaired DNA or with mutations of various kind. Thanks to selection pressure, the mutations that provide cells with a certain growth advantage under conditions of continuing genotoxic stress, gradually accumulate and render the tumor treatment-resistant. In my thesis, I focus on several aspects of this whole process. First, I participated in a characterization of a radioresistant and anoikis-resistant population of prostate cancer cells. This population was generated by irradiating cells 35 times by 2 Gy, a regime used in clinics. After this treatment, a population of low-adherent cells emerged that demonstrated increased expression of EMT- and stem cell markers. The low-adherent state of these cells was maintained by Snail signaling and their anoikis resistance by ERK1/2 signaling. Interestingly, after a protracted period of time, these cells were able to re-adhere and...