DNA damage induced by NADPH cytochrome P450 reductase-activated idarubicin in sensitive and multidrug resistant MCF7 breast cancer cells.

Background: Idarubicin (IDA) is one of clinically important anticancer drugs belonging to the anthracycline antibiotic family. The aim of this study was to examine DNA damage induced by NADPH cytochrome P450 reductase (CPR)-activated IDA in human sensitive MCF7 and multidrug resistant MCF7/DOX (overexpressing P-gp) breast adenocarcinoma cells.

Methods: The evaluation of DNA fragmentation caused by single strand breaks (SSB) and double strand breaks (DSB) was performed using terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) test. Additionally, DSB formation was examined using H2AX histone phosphorylation assays.

Results: It was found that IDA alone and CPR-activated used at IC caused a higher level of DNA strand breaks in sensitive MCF7 cells detected by TUNEL assessments (p=0.0011 for IDA alone and p=0.0109 for IDA reductively activated, Kruskal-Wallis test) and γ-H2AX-positive staining (p=0.0003 for IDA alone and p=0.0193 for IDA reductively activated, Kruskal-Wallis test) than in multidrug resistant MCF7/DOX cells. However, no changes were observed in the percentage of TUNEL-positive and DSB-positive cells for MCF7 as well as MCF7/DOX cells in the case of IDA alone and the drug pretreated in the presence of the activating system.

Conclusions: The obtained results suggest that CPR-activation of IDA does not significantly change the cellular DNA damage response of studied sensitive MCF7 and multidrug resistant MCF7/DOX breast cancer cells, even if the results concerning the interaction of IDA undergoing CPR activation with naked DNA showed the important differences in comparison with the drug alone (non-activated).