Evaluation of apoptotic activity of new condensed pyrazole derivatives

Cyclic pyrazoles exhibit cytotoxicity to human cancer cells through apoptosis induction. We investigated the proapoptotic activities of two novel synthetic pyrazoles: 5-(p-toluenesulfonyl)pyrazolo[4,3-f]quinoline (tospyrquin) and 5-chloro-3-(p-toluenesulfonyl)indazole (tosind) in HT29 colon cancer cells which are characterised by point mutation (G/A in codon 273) in the p53 gene, which causes the lack of functionality of the p53 protein. Cell viability was evaluated in the MTT assay, cell morphology was assessed by DAPI staining, flow cytometry was used to study the cell cycle, Western blot techniques were applied for measurements of the Bax, Bcl-2, caspase-8, caspase-9 and PARP-1 proteins and DNA damage was evaluated in the Comet assay. Tospyrquin or tosind in a concentration range of 2.5 μM-15 μM caused an approximately 20% diminishment in cell growth, but in higher concentrations (25-100 μM) the observed effect depended on the pyrazole structure and time of treatment. In cell cycle analysis, tosind caused 23.7% of apoptotic death and tospyrquin - 14.9%. These data were supported by an increased level of the pro-apoptotic protein Bax, a decreased level of the anti-apoptotic Bcl-2 and enhanced caspase-8, caspase-9, PARP-1 cleavage. DNA damage was dose-dependent for both tested compounds. The results suggest that the pro-apoptotic activity of tospyrquin and tosind is probably regulated by the extrinsic and the intrinsic pathways.