A biophysical study of the interactions of palladium(II), platinum(II) and gold(III) complexes of aminopyridyl-2,2'-bipyridine ligands with RNAs and other nucleic acid structures

Metal compounds form an attractive class of ligands for a variety of nucleic acids. Five metal complexes bearing aminopyridyl-2,2'-bipyridine tetradentate ligands and possessing a quasi-planar geometry were challenged toward different types of nucleic acid molecules including RNA polynucleotides in the duplex or triplex form, an RNA Holliday four-way junction, natural double helix DNA and a DNA G-quadruplex. The binding process was monitored comparatively using different spectroscopic and melting methods. The binding preferences that emerge from our analysis are discussed in relation to the structural features of the metal complexes.

[(C C)Au(N N)]+ Complexes as a New Family of Anticancer Candidates: Synthesis, Characterization and Exploration of the Antiproliferative Properties

A library of eleven cationic gold(III) complexes of the general formula [(C C)Au(N N)]⁺ when C C is either biphenyl or 4,4'-ditertbutyldiphenyl and N N is a bipyridine, phenanthroline or dipyridylamine derivative have been synthesized and characterized. Contrasting effects on the viability of the triple negative breast cancer cells MDA-MB-231 was observed from a preliminary screening. The antiproliferative activity of the seven most active complexes were further assayed on a larger panel of human cancer cells as well as on non-cancerous cells for comparison. Two complexes stood out for being either highly active or highly selective. Eventually, reactivity studies with biologically meaningful amino acids, glutathione, higher order DNA structures and thioredoxin reductase (TrxR) revealed a markedly different behavior from that of the well-known coordinatively isomeric [(C N C)Au(NHC)]⁺ structure. This makes the [(C C)Au(N N)]⁺ complexes a new class of organogold compounds with an original mode of action.

Antitumor activity of tridentate pincer and related metal complexes

Pincer complexes featuring tunable tridentate ligand frameworks are one of the most actively studied classes of metal-based complexes. Currently, growing attention is devoted to the cytotoxicity of pincer and related metal complexes. The antiproliferative activity of numerous pincer complexes has been reported. Pincer tridentate ligand scaffolds show different coordination modes and offer multiple options for directed structural modifications. This review summarizes the significant progress in the research studies of the antitumor activity of pincer and related platinum(ii), gold(iii), palladium(ii), copper(ii), iron(iii), ruthenium(ii), nickel(ii) and some other metal complexes, in order to provide a reference for designing novel metal coordination drug candidates with promising antitumor activity.

Synthesis, Molecular Docking and Cytotoxic Activity Evaluation of Organometallic Thiolated Gold(I) Complexes

The complex [(PhCH₂NC)AuCl], 1, was prepared by the reaction of [(Me₂S)AuCl], A, with an equimolar amount of benzyl isocyanide (PhCH₂NC) ligand. Through a salt metathesis reaction, the chloride ligand in 1 was replaced by potassium benzothiazole-2-thiolate (Kbt) and potassium benzoimidazole-2-thiolate (Kbi) to afford complexes (PhCH₂NC)Au(κ¹-S-bt)], 2a and (PhCH₂NC)Au(κ¹-S-bi)], 2b, respectively, which were characterized by NMR spectroscopy. The cytotoxic activities of 2a and 2b were evaluated against three human cancer cell lines, including A549 (lung), SKOV3 (ovary), and MCF-7 (breast). Our results indicated that 2a exhibited comparable cytotoxicity on investigated cell lines with cisplatin. It showed a good anti-proliferative activity with IC₅₀ of 19.46, 11.76 and 13.27 μM against A549, SKOV3 and MCF-7 cell lines, respectively. The effects of these complexes on the proliferation of the non-tumorigenic epithelial breast cell line (MCF-10A) showed their good selectivity between the tumorigenic and non-tumorigenic cell lines. Molecular docking simulation studies were also conducted to determine the specific binding site and binding mode of the synthesized gold complexes to DNA and thioredoxinreductase (TrxR) as their proposed targets.

Pt(II) and Au(III) complexes containing Schiff-base ligands: A promising source for antitumor treatment

The effective application of cisplatin in the clinic as an antitumor treatment has stimulated widespread interest in inorganic metal drugs. In particular, complexes containing the transition metals platinum and gold have attracted considerable attention due to their antitumor effects. The Pt(II) and Au(III) Schiff-base complexes are potential antitumor agents because of their remarkable biological activities and good stability, lipophilicity, and electroluminescent properties. These complexes act via various antitumor mechanisms that are unlike those of the classic platinum drugs, providing a feasible solution for improving the serious side effects caused by metal chemotherapy. In this review, promising antitumor agents based on Pt(II) and Au(III) complexes containing Schiff-base ligands, and their biological targets, including G-quadruplex DNA and thioredoxin reductase, are comprehensively summarized.

Conjugation of a gold(iii) complex with vitamin B1 and chlorambucil derivatives: anticancer evaluation and mechanistic insights

A gold(iii) complex containing vitamin B1 and chlorambucil derivatives was investigated for mechanistic insights in colon and breast cancer treatment.

Cyclometallated Au(iii) dithiocarbamate complexes: synthesis, anticancer evaluation and mechanistic studies

A series of cationic mixed cyclometallated (C^N)Au(iii) dithiocarbamate complexes has been synthesized in good yields [HC^N = 2-(p-t-butylphenyl)pyridine]. The crystal structure of [(C^N)AuS2CNEt2]PF6 (3) has been determined. The cytotoxic properties of the new complexes have been evaluated in vitro against a panel of human cancer cell lines and healthy cells and compared with a neutral mixed (C^C)Au(iii) dithiocarbamate complex (C^C = 4,4'-di-t-butylbiphenyl-2,2'-diyl). The complexes appeared to be susceptible to reduction by glutathione but were stable in the presence of N-acetyl cysteine. The potential mechanism of action of this class of compounds has been investigated by measuring the intracellular uptake of some selected complexes, by determining their interactions with higher order DNA structures, and by assessing the ability to inhibit thioredoxin reductase. The complexes proved unable to induce the formation of reactive oxygen species. The investigations add to the picture of the possible mode of action of this class of complexes.

Potent In Vitro and In Vivo Anticancer Activity of New Bipyridine and Bipyrimidine Gold (III) Dithiocarbamate Derivatives

We synthesized eight new bipyridine and bipyrimidine gold (III) dithiocarbamate-containing complexes (C1-C8) and tested them in a panel of human cancer cell lines. We used osteosarcoma (MG-63), lung (A549), prostate (PC3 and DU145), breast (MCF-7), ovarian (A2780 and A2780cis, cisplatin- and doxorubicin-resistant), and cervical (ME-180 and R-ME-180, cisplatin resistant) cancer cell lines. We found that C2, C3, C6, and C7 were more cytotoxic than cisplatin in all cell lines tested and overcame cisplatin and doxorubicin resistance in A2780cis and R-ME-180 cells. In the PC3 prostate cancer cell line, the gold (III) complex C6 ([Au₂(BPM)(DMDTC)₂]Cl₄) induced apoptosis and double-stranded DNA breaks, modified cell cycle phases, increased Reactive Oxigen Species (ROS) generation, and reduced thioredoxin reductase and proteasome activities. It inhibited PC3 cell migration and was more cytotoxic against PC3 cells than normal human adipose-derived stromal cells. In mice bearing PC3 tumor xenografts, C6 reduced tumor growth by more than 70% without causing weight loss. Altogether, our results demonstrate the anticancer activity of these new gold (III) complexes and support the potential of C6 as a new agent for prostate cancer treatment.

Interaction of a gold(i) dicarbene anticancer drug with human telomeric DNA G-quadruplex: solution and computationally aided X-ray diffraction analysis

Solution and solid-state data give a quite clear picture for a bis carbene gold(i) complex having perspective anticancer properties.

Cytotoxicity of Pyrazine-Based Cyclometalated (C^Npz^C)Au(III) Carbene Complexes: Impact of the Nature of the Ancillary Ligand on the Biological Properties

The synthesis of a series of cyclometalated gold(III) complexes supported by pyrazine-based (C^N^C)-type pincer ligands is reported, including the crystal structure of a cationic example. The compounds provide a new platform for the study of antiproliferative properties of gold(III) complexes. Seven complexes were tested: the neutral series (C^N^pz^C)AuX [X = Cl (1), 6-thioguanine (4), C≡CPh (5), SPh (6)] and an ionic series that included the N-methyl complex [(C^N^pzMe^C)AuCl]BF₄ (7) and the N-heterocyclic carbene complexes [(C^N^pz^C)AuL]⁺ with L = 1,3-dimethylbenzimidazol-2-ylidene (2) or 1,3,7,9-tetramethylxanthin-8-ylidene (3). Tests against human leukemia cells identified 1, 2, 3, and 4 as particularly promising, whereas protecting the noncoordinated N atom on the pyrazine ring by methylation (as in 7) reduced the cytotoxicity. Complex 2 proved to be the most effective of the entire series against the HL60 leukemia, MCF-7 breast cancer, and A549 lung cancer cell lines, with IC₅₀ values down to submicromolar levels, associated with a lower toxicity toward healthy human lung fibroblast cells. The benzimidazolylidene complex 2 accumulated more effectively in human lung cancer cells than its caffeine-based analogue 3 and the gold(III) chloride 1. Compound 2 proved to be unaffected by glutathione under physiological conditions for periods of up to 6 days and stabilizes the DNA G-quadruplex and i-motif structures; the latter is the first such report for gold compounds. We also show the first evidence of inhibition of MDM2–p53 protein–protein interactions by a gold-based compound and identified the binding mode of the compound with MDM2 using saturation transfer difference NMR spectroscopy combined with docking calculations.

We synthesized three new (C^N^pz^C)Au(III) complexes and screened them along with four other complexes as potential anticancer agents against leukemia cells. We tested the cellular uptake, the interaction with G4 and i-motif DNA structures, and the interaction with MDM2 protein. We highlight the very different biological behaviors of the compounds due to the different ancillary ligands.

(C^Npz^C)AuIII complexes of acyclic carbene ligands: synthesis and anticancer properties

Synthesis of amino ester conjugated (C^N^pz^C)Au acyclic carbene complexes with low micromolar cytotoxicity on human cancer cells.