Antitumoral synergism between a copper(II) complex and cisplatin improves in vitro and in vivo anticancer activity against melanoma, lung and breast cancer cells.

Background: Intrinsic resistance of cancer cells is a major concern for the success of chemotherapy, and this undesirable feature stimulates further research into the design of new compounds and/or alternative multiple drug chemotherapy protocols.

Methods: In this study, we investigated the antitumoral potential of the coordination compounds [Cu(HPClNOL)Cl]Cl (1), [Fe(HPClNOL)Cl]NO(2) and [Mn(HPClNOL)Cl] (3). Using the human, MCF-7 and A549, and the murine melanoma, B16-F10, cell lines, we determined the cytotoxicity, DCFH oxidation, disruption of mitochondrial membrane potential (ΔΨm), Sub-G1 and TUNEL positive cells, and caspase 8 and 9 activities. Fractional inhibitory concentration (FIC) and xenograft models were also assessed to evaluate the efficacy of antitumoral potential.

Results: We observed that only complex 1 was cytotoxic. The treatment of cancer cells with complex 1 triggered ROS generation and promoted the disruption of ΔΨm. Complex 1 increased the number of Sub-G1 and TUNEL positive cells, and the measurement of caspase 8 and 9 activity confirmed that apoptosis was triggered by the intrinsic pathway. FIC demonstrated that the combination of complex 1 with cisplatin was additive for the A549 cells whilst it was synergic for MCF-7 and B16-F10. Treatment with complex 1, either alone or combined with cisplatin, reduced tumor growth on xenograft models.

Conclusions: The present study brings new clues regarding the mechanism of action of [Cu(HPClNOL)Cl]Cl, either alone or in combination with cisplatin.

General Significance: These results indicate that complex 1, administered either singly or in combination with current drugs, has real potential for use in cancer therapy.