Pancreatic cancer is one of the most aggressive malignancies and is characterized by a strongly immunosuppressive tumor microenvironment and poor response to treatment. Gemcitabine remains an important therapeutic option, but in addition to its direct cytotoxic effect on tumor cells, it may also influence their communication with immune cells. The aim of this master’s thesis was to investigate whether conditioned medium from pancreatic cancer cells previously treated with gemcitabine indirectly affects the phenotypic and functional characteristics of natural killer cells. In this study, the pancreatic cancer cell lines PANC-1 and CAPAN-2 were treated with gemcitabine, after which conditioned medium was prepared from their secreted factors. The conditioned medium was then applied to the NK-92 natural killer cell line and to primary natural killer cells isolated from two healthy donors. The expression of molecules involved in granule-mediated cytotoxicity was analyzed by western blotting, while the expression of surface markers related to activation, inhibition and adhesion was evaluated by flow cytometry. The results showed that conditioned medium from tumor cells affects natural killer cells, although the effect was not uniform. The most pronounced immunomodulatory effect was observed with the PANC-1 cell line, where under certain conditions increased expression of cathepsin C, perforin and granzyme B was detected, suggesting an enhanced cytotoxic potential of natural killer cells. In the CAPAN-2 cell line, the effects were weaker, more time-dependent and more often associated with changes in the regulatory molecule cystatin F. Analysis of surface markers did not reveal a uniform shift toward a clearly activated phenotype, but rather a complex adaptation depending on the tumor cell line, exposure time and the natural killer cell model used. An important finding of this study was also the difference between the NK-92 cell line and primary natural killer cells. The NK-92 cell line showed a more reproducible response, whereas primary cells displayed marked donor-dependent variability. Overall, the results indicate that gemcitabine can indirectly alter communication between tumor and immune cells, but this effect depends on tumor cell properties, response dynamics and the biological variability of immune cells.
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