ABSTRACT
The novel NHC ligand precursor 1,4-bis(4-nitrobenzyl)-1H-1,2,4-triazol-4-ium bromide, [HTz((pNO2Bz)2)]Br, has been synthesized and used in the synthesis of the corresponding metal complexes M[Tz((pNO2Bz)2)]Br (M = Cu(I), Ag(I) or Au(I)). These compounds were characterized by several spectroscopic techniques including NMR and mass spectroscopy. The complete series of Au(I), Ag(I) and Cu(I) 1,2,4-triazole based NHC complexes has been synthesized aiming at a SAR study and at identifying the primary cellular targets accounting for their cytotoxic action. The cytotoxic properties of the NHC complexes have been assessed in various human cancer cell lines, including cisplatin sensitive and resistant cells, the most efficacious antiproliferative compound being Cu(I)-NHC, which was able to promote a growth inhibitory effect up to ten times higher than that promoted by cisplatin. A detailed analysis of molecular and cellular pharmacology allowed us to elucidate the role of the metallic core in determining the biological properties. In particular, gold(I) and silver(I) NHC complexes were found to be able to hamper mammalian thioredoxin reductase (TrxR) activity in human A431 cervical cancer cells, ultimately leading to a dramatic alteration of the cellular redox state and to the induction of cell death via apoptosis. Conversely, the copper NHC complex was found to be capable of inhibiting proteasome functionality thus determining the induction of a non-apoptotic cell death pathway.
Subject(s)
Coordination Complexes/chemistry , Heterocyclic Compounds/chemistry , Methane/analogs & derivatives , Triazoles/chemistry , Apoptosis/drug effects , Cell Line, Tumor , Cell Proliferation/drug effects , Coordination Complexes/chemical synthesis , Coordination Complexes/toxicity , Copper/chemistry , Gold/chemistry , Humans , Ligands , Methane/chemistry , Microscopy, Electron, Transmission , Oxidation-Reduction , Proteasome Endopeptidase Complex/chemistry , Proteasome Endopeptidase Complex/metabolism , Reactive Oxygen Species/metabolism , Silver/chemistry , Thioredoxin-Disulfide Reductase/antagonists & inhibitors , Thioredoxin-Disulfide Reductase/metabolismABSTRACT
BACKGROUND: A frequent mechanism of acquired multidrug resistance in human cancers is overexpression of ATP-binding cassette transporters such as the Multi-Drug Resistance Protein 1 (MDR-1). Nutlin-3, an MDM2-p53 antagonist, has previously been reported to be a competitive MDR-1 inhibitor. METHODS: This study assessed whether the structurally diverse MDM2-p53 antagonists, MI-63, NDD0005, and RG7388 are also able to modulate MDR-1 function, particularly in p53 mutant neuroblastoma cells, using XTT-based cell viability assays, western blotting, and liquid chromatography-mass spectrometry analysis. RESULTS: Verapamil and the MDM2-p53 antagonists potentiated vincristine-mediated growth inhibition in a concentration-dependent manner when used in combination with high MDR-1-expressing p53 mutant neuroblastoma cell lines at concentrations that did not affect the viability of cells when given alone. Liquid chromatography-mass spectrometry analyses showed that verapamil, Nutlin-3, MI-63 and NDD0005, but not RG7388, led to increased intracellular levels of vincristine in high MDR-1-expressing cell lines. CONCLUSIONS: These results show that in addition to Nutlin-3, other structurally unrelated MDM2-p53 antagonists can also act as MDR-1 inhibitors and reverse MDR-1-mediated multidrug resistance in neuroblastoma cell lines in a p53-independent manner. These findings are important for future clinical trial design with MDM2-p53 antagonists when used in combination with agents that are MDR-1 substrates.
