The role of bioreductive activation of antitumour anthracycline drugs in cytotoxic activity against sensitive and multidrug resistant leukaemia HL60 cells

Effect of the FE2+ chelation by 2,2'-dipyridyl in the doxorubicin-induced lethality in breast tumor cell lines

Breast cancer cells may exhibit changes in iron homeostasis, which results in increased labile iron pool (LIP) levels. Several studies highlight the crucial role of high LIP levels in the maintenance of tumor cell physiology. Iron chelators have been tested in anticancer therapy in combination with chemotherapeutic agents, to improve drug efficacy. Thus, the aim of this study was to evaluate the effect of 2,2'-dipyridyl (DIP), a Fe²⁺ chelator, in combination with doxorubicin (DOX) in breast tumor cells. The maximum concentration of DIP that did not significantly reduce the viability of MDA-MB-231 cells was 10μM and for MCF-7 cells was 50μM. We observed that MCF-7 had higher LIP levels than MDA-MB-231 cells. DIP alone increased ROS generation in MCF-7 cells, and DIP pretreatment reduced ROS generation induced by DOX treatment. In conclusion, the increase in MCF-7 cell viability induced by DIP pretreatment in DOX-treated cells seems to be related to an increase in the cellular antioxidant capacity and the iron chelator did not improve drug efficacy in the two breast tumor cell lines analyzed.

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/DOX₅₀₀ (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 IC₉₀ 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/DOX₅₀₀ cells. However, no changes were observed in the percentage of TUNEL-positive and DSB-positive cells for MCF7 as well as MCF7/DOX₅₀₀ 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/DOX₅₀₀ 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).