Studies on the mechanism of action of antitumor bis(aminophenolate) ruthenium(III) complexes

• Published in: Journal of inorganic biochemistry 2017-03, Vol.168, p.27-37
• Main Authors: Dömötör, Orsolya, de Almeida, Rodrigo F.M., Côrte-Real, Leonor, Matos, Cristina P., Marques, Fernanda, Matos, António, Real, Carla, Kiss, Tamás, Enyedy, Éva Anna, Helena Garcia, M., Tomaz, Ana Isabel
• Format: Article
• Language: English
• Subjects: Aminophenols - chemistry; Aminophenols - pharmacology; Antineoplastic Agents - chemical synthesis; Antineoplastic Agents - chemistry; Antineoplastic Agents - pharmacology; Antitumor; Apoptosis; Apoptosis - drug effects; Cell Cycle - drug effects; Cell cycle arrest; Cell Line, Tumor; Cell morphology; Coordination Complexes - chemical synthesis; Coordination Complexes - chemistry; Coordination Complexes - pharmacology; DNA - chemistry; DNA binding constants; Drug Screening Assays, Antitumor; Humans; Microscopy, Electron, Transmission; Models, Molecular; Ru(III)-bis(aminophenolate) complexes; Ru(III)-salan complexes; Ruthenium - chemistry; Ruthenium - pharmacology
• ISSN: 0162-0134; 1873-3344
• DOI: 10.1016/j.jinorgbio.2016.12.008

Two recently published Ru(III) complexes bearing (N2O2) tetradentate bis(aminophenolate) ligands, formulated as [Ru(III)(salan)(PPh3)Cl] (salan is the tetradentate ligand 6,6′-(1S,2S)-cyclohexane-1,2-diylbis(azanediyl)bis(methylene)bis(3-methoxyphenol) in complex 1, or 2,2′-(1S,2S)-cyclohexane-1,2-diylbis(azanediyl)bis(methylene)bis(4-methoxyphenol) in complex 2; PPh3 is triphenylphosphane) and found very active against ovarian and breast adenocarcinoma human cells were studied to outline their antitumor mode of action. The human cisplatin-sensitive ovarian adenocarcinoma line A2780 was used herein as the cell model. At a 24h challenge (similarly as found before for 72h) both complexes are active, their cytotoxicity being comparable to that of cisplatin in the same conditions. As a possible target in the cell for their action, the interaction of 1 and 2 with DNA was assessed through displacement of well-established DNA fluorescent probes (ethidium bromide, EB, and 4′,6-diamidino-2-phenylindole, DAPI) through steady-state and time-resolved fluorescence spectroscopy. The whole emission spectra were analyzed globally for the binary DNA–probe and ternary DNA–probe–Ru(III) complex systems. Both Ru(III) complexes can displace EB and bind to DNA with similar and moderate strong affinity with conditional stability constants of logK’=(5.05±0.01) for 1 and logK’=(4.79±0.01) for 2. The analysis of time-domain fluorescence intensity decays confirmed both qualitatively and quantitatively the model used to describe the binding and competition processes. Cell studies indicated that apoptosis is the major mechanism of cell death for both complexes, with 2 (the more active complex) promoting that process more efficiently than 1. Transmission electron micrographs revealed clear alterations on intracellular organization consistent with the induction of programmed cell death processes. Mechanisms underlying the anti-tumor effect of two [Ru(III)-bis(aminophenolate)] complexes are investigated. A novel fully quantitative approach to DNA–[complex] binding is applied and quantitatively validated with time-resolved fluorescence spectroscopy. These complexes induce different programmed cell death routes and exert a different effect on the cell cycle despite their structural resemblance. [Display omitted] •Metal complexes with bis(aminophenolate) ligands are also known as salan-complexes.•Two anti-tumor Ru(III)-salan-complexes induce apoptotic processes in cancer cells.•A novel quan