Biological evaluation of the activity of some benzimidazole-4,7-dione derivatives.

The study presented here is a follow up of the authors' interest in the approach to selective and cytotoxic bioreductive anticancer prodrugs. The current work is devoted to explore both the biological activity of some previously obtained compounds and the search for an explanation of their target(s) in hypoxic pathways. In this work the biological activity of some benzimidazole-4,7-diones was evaluated. These compounds were examined as potential bioreductive agents specific for the hypoxic environment found in tumor cells. The main aim was concerned with establishing their cytotoxic properties by using proliferation, apoptosis and DNA destruction tests on selected tumor cells. Their cytotoxic effects on two tumor cell lines (human lung adenocarcinoma A549 cells line and human malignant melanoma WM115) was compared by means of a WST-1 test. Next, the mode of cytotoxicity behind the selected tumor cells' death was determined by the caspase 3/7 test. The last point referred to the DNA destruction of A549 and WM115 cells and the in situ DNA Assay Kit test was applied. The cytotoxic tests confirmed their activity against the tumor cells and target hypoxia (compounds 2b, 2a, 2d). The screening test of the caspase-dependent apoptosis proved that the exposure of the tested tumor cells in hypoxia to these benzimidazole-4,7-diones promoted the apoptotic cell death. Additionally, the DNA damage test established that benzimidazole-4,7-diones can be potential hypoxia-selective agents for tumor cells, especially compound 2b. All results classify the tested benzimidazole-4,7-diones as promising, lead molecules and provide a rationale for further molecular studies to explain their usefulness as potential inhibitors of the hypoxia-inducible factor 1 (HIF1).