Disulfide bridges play a significant role in protein-folding as well as en- zyme activity and thus regulate many intra- and extracellular processes. Sulfhydryl oxidase QSOX1 forms S-S bridges de novo, modulating the activity of its substrates and thus directly or indirectly influences vital cel- lular processes. The first part of this thesis focuses on characterization of the role of QSOX1 in cancerogenesis, using breast cancer cell lines (MCF7, MDA-MB-231) and pancreatic cancer cell line (Panc-1), while the second part emphasizes the regulation of QSOX1 expression by different oxygen concentrations. To study the effect of QSOX1 on proliferation of triple-negative cancer cells MDA-MB-231, two genetically modified cell lines - QSOX1-overexpressing and QSOX1 knockout cell lines - were constructed. While increased QSOX1 protein levels do not have a significant effect, the absence of QSOX1 leads to a decreased cellular growth. Lack of QSOX1 also results in visible change in cellular morphology. QSOX1 knockout cells can be mostly characterized as more round-shaped with less noticeable or completely missing lamellipo- dia. This finding is with agreement with to-date literature suggesting that QSOX1 is important not only for cellular proliferation but also for migration and invasiveness. While authenticating the theory of...

Disulfide bridges play a significant role in protein-folding as well as en- zyme activity and thus regulate many intra- and extracellular processes. Sulfhydryl oxidase QSOX1 forms S-S bridges de novo, modulating the activity of its substrates and thus directly or indirectly influences vital cel- lular processes. The first part of this thesis focuses on characterization of the role of QSOX1 in cancerogenesis, using breast cancer cell lines (MCF7, MDA-MB-231) and pancreatic cancer cell line (Panc-1), while the second part emphasizes the regulation of QSOX1 expression by different oxygen concentrations. To study the effect of QSOX1 on proliferation of triple-negative cancer cells MDA-MB-231, two genetically modified cell lines - QSOX1-overexpressing and QSOX1 knockout cell lines - were constructed. While increased QSOX1 protein levels do not have a significant effect, the absence of QSOX1 leads to a decreased cellular growth. Lack of QSOX1 also results in visible change in cellular morphology. QSOX1 knockout cells can be mostly characterized as more round-shaped with less noticeable or completely missing lamellipo- dia. This finding is with agreement with to-date literature suggesting that QSOX1 is important not only for cellular proliferation but also for migration and invasiveness. While authenticating the theory of...

7 Abstract Protein kinase C alpha (PKCα) is a serine/threonine protein kinase. PKCα is an important protein regulating cell polarity, protein secretion, apoptosis, cell proliferation and differentiation and tumorogenesis. Previous research has shown a role of PKCα also in a cancer cell migration and cancer cell invasion. The aim of this study was to investigate the role of protein kinase C alpha (PKCα) played in amoeboid mode of cancer cell invasion. We showed that higher expression of PKCα resulted in mesenchymal-amoeboid transition of K2 and MDA mesenchymal cancer cell lines, which was accompanied with decreased cancer cell invasive capability in 3D collage matrix. PKCα overexpression had no effect on the cell morphology of A375m2, however, the results showed a trend in increased invasive potential of A375m2 cells. Conversely, the expression of dominant-negative PKCα resulted in amoeboid-mesenchymal transition of A375m2 cells, and it was associated with decreased invasive potential of K2 and MDA cell lines. Furthermore, a linkage between PKCα and phosphatidylinositol 3-kinase (PI3K) was tested. The results revealed that increased activity of PKCα was accompanied with decreased level of active Akt in K2 cell line. To summarize, our results suggest a probable role of PKCα in regulation of amoeboid...