Cathepsin X is a cysteine peptidase involved in the development of various diseases. Physiologically, it is located almost exclusively in the cells of the immune system, but has also been detected in the lungs and the central nervous system. During its excessive expression and proteolytic activity, with cleavage of its molecular targets, influence on the signalisation and the modulation of the immune system, cathepsin X strongly affects the course and the prognosis of malignancies, as well as inflammatory or non-inflammatory neurodegenerative diseases. Due to the ineffectiveness of endogenous inhibitors, the research now focuses on exogenous inhibitors. These compounds are either irreversible with low selectivity or reversible with higher selectivity, but insufficient effectiveness.
In this thesis, we tested five triazole-based cathepsin X inhibitors: CX24, CX26, CX32, CX38, and CX14 F2-8. These were synthesized based on the structure of inhibitor Z9 and have comparable 〖IC〗_50 values. First, we used the MTS assay to analyse their influence on cell viability on the PC-3 prostate cancer cell line after 24- and 48-hour incubation. After both time periods, two inhibitors, CX24 and CX14 F2-8, displayed weak cytotoxic effects in the 10 M concentration. The viability of CX24 was 87 % after 24 and 90 % after 48 hours. With CX14 F2-8, 93 % of cells survived the 24- and 91 % the 48-hour period. CX32 and CX38 were marked as non-cytotoxic based on no statistically significant difference in cell survival between the tested compounds and positive control. In spite of the 96 % viability rate, we calculated a statistically significant decrease for inhibitor CX26. Due to these results and its slightly inferior 〖IC〗_(50 )value to that of the parent compound Z9, only CX32 and CX38 were included in further testing. Using the same concentration as before, we tested their influence on cell migration with the xCELLigence system, uninterruptedly for 72 hours. Contrary to expectations, the compounds did not inhibit, but increased the migration.
In the thesis, we proved the compounds to be either non-cytotoxic or to have weak cytotoxic effects on PC-3 prostate cancer cell line. However, they did not lower their migration rate. Their structure could be useful for further development of compounds suitable for cathepsin X inhibition. Because of its impact on inflammatory and non-inflammatory neurodegeneration, we would suggest testing of new specific inhibitors in this area as well.
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