Role of the NHE1 exchanger in the antitumor effects of copper(II) complexes and phenanthroline derivatives

Abstract

Three copper(II) complexes containing 1,10-phenanthroline: [CuCl₂(phen)]·0.5H₂O (1), neocuproine [CuCl₂(neo)]·0.75 H₂O (2) and tetramethyl-phenanthroline [CuCl₂(tmp)]·H₂O (3) as the primary ligand and another three copper(II) complexes with L-Ala-Phe dipeptide as auxiliary ligand: [Cu(L-Ala-Phe)(phen)]·4H₂O (4), [Cu(L-Ala-Phe)(neo)]·3H₂O (5) and [Cu(L-Ala-Phe)(tmp)]·3H₂O (6), inhibited cell viability in the MCF-7 cell line, both in the monolayer and spheroid models. The pair with tmp displayed a better selectivity index than cisPt and non-cytotoxicity-related ROS induction and apoptosis in the monolayer model. Cell proliferation was affected by all compounds in a concentration-dependent manner. Cell viability on spheroids showed a reduction from 1 µM, with IC₅₀ values that were half those of cisplatin. All copper complexes, except for 1, showed DNA damage at a concentration below IC₅₀. Our study revealed that all compounds inhibited sodium-hydrogen exchanger (NHE1) activity in MCF-7 cells. However, only complexes containing the dipeptide could extend their effect on cell migration and metalloprotease MMP-9 activity. Western Blot analysis showed that metalloproteases MMP-2, MMP-9, and NHE1 expression was also affected when MCF-7 cells were treated with the six compounds. Overall, our results reveal an antitumor effect of all copper(II) complexes studied in breast cancer cells and a fundamental role of NHE1 in cell migration.