54P The combination of copper oxide nanoparticles and N-acetyl-L-cysteine triggers rapid oxidative burst and death of wild-type and multidrug-resistant tumour cells

Abstract

Overcoming drug resistance is a major problem in cancer therapy. Tumor cells are vulnerable to reactive oxygen species (ROS). The oxygen burst can be evoked by metal oxide nanoparticles (NPs) alone and/or together with conventional or novel compounds. We investigated the antitumor potential of the combination of copper oxide NPs and N-acetyl-L-cysteine (NAC) against various human tumor cell lines. CuO NPs (80±20 nm as determined by dynamic light scattering) were synthesized by the precipitation method. Intracellular accumulation of CuO NPs was measured by atomic absorption spectroscopy. The panel of cell lines included HCT116 colon and MDA-MB-231 triple-negative breast carcinomas as well as K562 (CML) cell line and its multidrug-resistant K562/4 subline. The cytotoxicity of CuO NPs, NAC and their combination were determined in MTT assays. Flow cytometry was used to analyze the mechanisms of cell response. Caspase-3 and poly(ADPribose) polymerase (PARP) were detected by immunoblotting. CuO NPs showed a slight toxicity for all tested cell lines after 72 h, while in combination with the non-toxic NAC a rapid (within 2 h) ROS generation and cell death by 8 h were detected. CuO NPs weakly accumulated in the cells, so ROS generation is likely to occur mainly outside the cells. The IC50 of the combination was 2-3 orders of magnitude smaller compared to NPs alone. Death associated events differed between the cell lines but generally caspase-independent apoptosis was followed by irreversible damage of the plasma membrane. Importantly, the combination of CuO NPs with NAC was equally potent for K562 cells and the multidrug-resistant K562/4 subline. Reduction of Cu2+ to Cu+ upon interaction with the thiol group in NAC can trigger ROS formation. The combination of CuO NPs and NAC killed human tumor cell lines including the multidrug-resistant variant. Rapid ROS generation can be promising in situations where tumor cells acquire multidrug resistance during treatment. Also, engineering of supramolecular systems will allow to guide copper to critical cysteine residues in specific proteins for their oxidative destruction.