Background: Copper complex has been gaining much attention in anticancer research as targeted agent since cancer cells uptake more copper than non-cancerous cells. Our group has synthesised a ternary copper complex which is composed of 1,10-phenanthroline and tyrosine [Cu(phen)(L-tyr)Cl].3H20. These two payloads are designed to cleave DNA and inhibit protein degradation system (proteasome) concurrently in cancer cells, making this copper complex a dual-target compound. Objective: Current study was carried out to investigate the mode of cell death and role of autophagy induced by [Cu(phen)(L-tyr)Cl].3H20 in MCF-7 and MDA-MB-231 breast cancer cells. Methods: Growth inhibition of [Cu(phen)(L-tyr)Cl].3H20 towards MDA-MB-231 and human non-cancerous MCF10A breast cells was determined by MTT assay. Annexin-V-FITC/PI and cell cycle analysis were evaluated by flow cytometry. The expression of p53, Bax, caspase-9, caspase-7, caspase-3 and LC3 were determined using western blot analysis. The cells were then co-treated with hydroxychloroquine to ascertain the role of autophagy induced by [Cu(phen)(L-tyr)Cl].3H20. Results: [Cu(phen)(L-tyr)Cl].3H20 inhibited the growth of cancer cells dose-dependently with less toxicity towards MCF10A cells. Additionally, [Cu(phen)(L-tyr)Cl].3H20 induced apoptosis and cell cycle arrest towards MCF-7 and MDA-MB-231 breast cancer cells possibly via regulation of p53, Bax, caspase-9, caspase-3 and capase-7. The expression of LC3II was upregulated in both cancer cell lines upon treatment with [Cu(phen)(L-tyr) Cl].3H20, indicating the induction of autophagy. Co-treatment with autophagy inhibitor hydroxychloroquine significantly enhanced growth inhibition of both cell lines, suggesting that the autophagy induced by [Cu(phen)(L-tyr) Cl].3H20 in both breast cancer cells was promoting cell survival. Conclusion: [Cu(phen)(L-tyr)Cl].3H20 holds great potential to be developed for breast cancer treatment.

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