The development of new anticancer drugs is of extraordinary importance for public health. Human DNA-topoisomerase II? is a target of a wide spectrum of anticancer active substances, which, due to specific expression, allows targeting of highly proliferative cancer cells. The catalytic cycle of DNA-topoisomerase II? consists of several steps and thus provides different approaches of enzyme inhibition. In clinical use there are many active substances (eg. topoisomerase poisons) with different mechanisms of action on the catalytic enzyme cycle, but with serious side effects as a result of the treatment. For this reason, we focused on development of new catalytic DNA topoisomerase II? inhibitors that bind to the ATP-binding site of the N-terminal part of the enzyme and consequently inhibit the catalytic activity.
In the experimental part of the master's thesis, we synthesized and evaluated a series of new ATP competitive DNA topoisomerase II?, which are of pyrrolamide structural type. Residual activities at inhibitor concentration of 100 µM and 10 µM were measured for eight compounds. Compounds 10, 19 and 23 possess a free carboxyl group in the structure and show inhibitory activity on the enzyme. In comparison with etoposide, which was used as a positive control, lower IC50 values were determined for compounds 10, 19 and 23, and thus a better inhibitory activity on the enzyme. Compounds of the series, which had a methyl ester group or a sulphonamide group in the structure instead of the carboxyl group, did not show an inhibitory activity on the enzyme. We also evaluated the cytotoxic activity of the compounds 10, 19 and 23 on the breast cancer cell line (MCF-7) and found that the tested compounds were inactive, which is contrary to the results of enzymatic testing. The cause for the absence of cytotoxic activity can be the compounds' inability to pass into the cells or active pumping of the compounds from the cell. Further research is necessary to find out which mechanism is responsible for the absence of cytotoxic activity.
In the future, it would be reasonable to design and develop compounds that, in addition to good inhibitor activity on the enzyme, also have appropriate physicochemical properties in order to successfully reach the target in the cells.
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