Water-Soluble Gold(III)-Metformin Complex Alters Mitochondrial Bioenergetics in Breast Cancer Cells

Carbon-phosphorus stapled Au(I) anticancer agents via bisphosphine induced reductive elimination

Towards the goal of generating new stabilized gold complexes as potent anticancer agents, we report here a novel class of Au(I) agents from Au(III)-mediated Caryl-P bond formation captured within the same complex by reacting a C^N cyclometalated Au(III) complex with bisphosphines. Cyclometalated Au(III) complexes of the type [Au(C^N)Cl2], where C^N represent different aryl pyridine framework reacted with bis(2-diphenylphosphino)phenyl ether in refluxing methanol to access an unsymmetrical gold complex featuring C-P coupling and Au(I)-phosphine. The complexes were characterized by 1H-NMR, 13C-NMR, and 31P-NMR and mass spectrometry. The structures of the complexes were characterized by X-ray crystallography and purity ascertained by HPLC and elemental analysis. The complexes demonstrate promising anticancer activity in a broad panel of cancer cell lines of different tumor origin. Mechanistically, the complexes induce apoptosis, generate mitochondrial ROS, depolarize mitochondrial membrane potential and modulate mitochondrial respiration in cancer cells. Overall, we developed a new structural class of Au(I) complexes with promising anticancer potential with potential utility in other applications.

A gold-based inhibitor of oxidative phosphorylation is effective against triple negative breast cancer

Triple-negative breast cancer (TNBC) is associated with metabolic heterogeneity and poor prognosis with limited treatment options. New treatment paradigms for TNBC remains an unmet need. Thus, therapeutics that target metabolism are particularly attractive approaches. We previously designed organometallic Au(III) compounds capable of modulating mitochondrial respiration by ligand tuning with high anticancer potency in vitro and in vivo. Here, we show that an efficacious Au(III) dithiocarbamate (AuDTC) compound induce mitochondrial dysfunction and oxidative damage in cancer cells. Efficacy of AuDTC in TNBC mouse models harboring mitochondrial oxidative phosphorylation (OXPHOS) dependence and metabolic heterogeneity establishes its therapeutic potential following systemic delivery. This provides evidence that AuDTC is an effective modulator of mitochondrial respiration worthy of clinical development in the context of TNBC. ONE SENTENCE SUMMARY: Metabolic-targeting of triple-negative breast cancer by gold anticancer agent may provide efficacious therapy.

Binuclear Biphenyl Organogold(III) Complexes: Synthesis, Photophysical and Theoretical Investigation, and Anticancer Activity

A series of four binuclear complexes of general formula [(C^C)Au(Cl)(L^L)(Cl)Au(C^C)], where C^C is 4,4'-diterbutylbiphenyl and L^L is either a bridging diphosphine or 4,4'-bipyridine, are synthetized with 52 to 72 % yield and structurally characterized by X-ray diffraction. The use of the chelating 1,2-diphenylphosphinoethane ligand in a 1 : 2 (P^P):Au stoichiometry leads to the near quantitative formation of a gold double-complex salt of general formula [(C^C)Au(P^P)][(C^C^)AuCl2 ]. The compounds display long-lived yellow-green phosphorescence with λem in the range of 525 to 585 nm in the solid state with photoluminescence quantum yields (PLQY) up to 10 %. These AuIII complexes are tested for their antiproliferative activity against lung adenocarcinoma cells A549 and results show that compounds 2 and 5 are the most promising candidates. The digold salt 5 shows anticancer activity between 66 and 200 nM on the tested cancer cell lines, whereas derivative 2 displays concentration values required to reduce by 50 % the cell viability (IC50 ) between 7 and 11 μM. Reactivity studies of compound 5 reveal that the [(C^C)Au(P^P)]+ cation is stable in the presence of relevant biomolecules including glutathione suggesting a structural mechanism of action.

A Conformationally Restricted Gold(III) Complex Elicits Antiproliferative Activity in Cancer Cells

Diamine ligands are effective structural scaffolds for tuning the reactivity of transition-metal complexes for catalytic, materials, and phosphorescent applications and have been leveraged for biological use. In this work, we report the synthesis and characterization of a novel class of cyclometalated [C^N] Au(III) complexes bearing secondary diamines including a norbornane backbone, (2R,3S)-N2,N3-dibenzylbicyclo[2.2.1]heptane-2,3-diamine, or a cyclohexane backbone, (1R,2R)-N1,N2-dibenzylcyclohexane-1,2-diamine. X-ray crystallography confirms the square-planar geometry and chirality at nitrogen. The electronic character of the conformationally restricted norbornane backbone influences the electrochemical behavior with redox potentials of -0.8 to -1.1 V, atypical for Au(III) complexes. These compounds demonstrate promising anticancer activity, particularly, complex 1, which bears a benzylpyridine organogold framework, and supported by the bicyclic conformationally restricted diaminonorbornane, shows good potency in A2780 cells. We further show that a cellular response to 1 evokes reactive oxygen species (ROS) production and does not induce mitochondrial dysfunction. This class of complexes provides significant stability and reactivity for different applications in protein modification, catalysis, and therapeutics.

An anti-glioblastoma gold(i)-NHC complex distorts mitochondrial morphology and bioenergetics to induce tumor growth inhibition

Glioblastoma multiforme (GBM) is the most lethal brain cancer subtype, often advanced by the time of initial diagnosis. Existing treatment modalities including surgery, chemotherapy and radiation have been stymied by recurrence, metastasis, drug resistance and brain targetability. Here, we report a geometrically distinct Au(i) complex ligated by N^N-bidentate ligands and supported by a N-heterocyclic ligand that modulates mitochondrial morphology to inhibit GBM in vitro and in vivo. This work benefits from the facile preparation of anti-GBM Au(i)-NHC complexes.

Next Generation Gold Drugs and Probes: Chemistry and Biomedical Applications

The gold drugs, gold sodium thiomalate (Myocrisin), aurothioglucose (Solganal), and the orally administered auranofin (Ridaura), are utilized in modern medicine for the treatment of inflammatory arthritis including rheumatoid and juvenile arthritis; however, new gold agents have been slow to enter the clinic. Repurposing of auranofin in different disease indications such as cancer, parasitic, and microbial infections in the clinic has provided impetus for the development of new gold complexes for biomedical applications based on unique mechanistic insights differentiated from auranofin. Various chemical methods for the preparation of physiologically stable gold complexes and associated mechanisms have been explored in biomedicine such as therapeutics or chemical probes. In this Review, we discuss the chemistry of next generation gold drugs, which encompasses oxidation states, geometry, ligands, coordination, and organometallic compounds for infectious diseases, cancer, inflammation, and as tools for chemical biology via gold-protein interactions. We will focus on the development of gold agents in biomedicine within the past decade. The Review provides readers with an accessible overview of the utility, development, and mechanism of action of gold-based small molecules to establish context and basis for the thriving resurgence of gold in medicine.

Au(III) Cyclometallated Compounds with 2-Arylpyridines and Their Derivatives or Analogues: 34 Years (1989–2022) of NMR and Single Crystal X-ray Studies

A review paper on Au(III) cyclometallated compounds with 2-arylpyridines (2-phenylpyridine, 2-benzylpyridine, 2-benzoylpyridine, 2-phenoxypyridine, 2-phenylsulfanylpyridine, 2-anilinopyridine, 2-(naphth-2-yl)pyridine, 2-(9,9-dialkylfluoren-2-yl)pyridines, 2-(dibenzofuran-4-yl)pyridine, and their derivatives) and their analogues (2-arylquinolines, 1- and 3-arylisoquinolines, 7,8-benzoquinoline), with 113 references. A total of 554 species, containing κ2-N(1),C(6′)*-Au(III), or analogous moiety (i.e., chelated by nitrogen of the pyridine-like ring and the deprotonated ortho- carbon of the phenyl-like ring) and, thus, possessing a character intermediate between metal complexes and organometallics, studied in the years 1989–2022 by NMR spectroscopy and/or single crystal X-ray diffraction (207 X-ray structures), are described. The compounds for which biological or catalytic activity and the luminescence properties were studied are also quoted.

Unraveling the Peculiar Features of Mitochondrial Metabolism and Dynamics in Prostate Cancer

Prostate cancer (PCa) is the second leading cause of cancer deaths among men in Western countries. Mitochondria, the "powerhouse" of cells, undergo distinctive metabolic and structural dynamics in different types of cancer. PCa cells experience peculiar metabolic changes during their progression from normal epithelial cells to early-stage and, progressively, to late-stage cancer cells. Specifically, healthy cells display a truncated tricarboxylic acid (TCA) cycle and inefficient oxidative phosphorylation (OXPHOS) due to the high accumulation of zinc that impairs the activity of m-aconitase, the enzyme of the TCA cycle responsible for the oxidation of citrate. During the early phase of cancer development, intracellular zinc levels decrease leading to the reactivation of m-aconitase, TCA cycle and OXPHOS. PCa cells change their metabolic features again when progressing to the late stage of cancer. In particular, the Warburg effect was consistently shown to be the main metabolic feature of late-stage PCa cells. However, accumulating evidence sustains that both the TCA cycle and the OXPHOS pathway are still present and active in these cells. The androgen receptor axis as well as mutations in mitochondrial genes involved in metabolic rewiring were shown to play a key role in PCa cell metabolic reprogramming. Mitochondrial structural dynamics, such as biogenesis, fusion/fission and mitophagy, were also observed in PCa cells. In this review, we focus on the mitochondrial metabolic and structural dynamics occurring in PCa during tumor development and progression; their role as effective molecular targets for novel therapeutic strategies in PCa patients is also discussed.

Mitochondria as a target of third row transition metal-based anticancer complexes

In pursuit of better treatment options for malignant tumors, metal-based complexes continue to show promise as attractive chemotherapeutics due to tunability, novel mechanisms, and potency exemplified by platinum agents. The metabolic character of tumors renders the mitochondria and other metabolism pathways fruitful targets for medicinal inorganic chemistry. Cumulative understanding of the role of mitochondria in tumorigenesis has ignited research in mitochondrial targeting metal-based complexes to overcome resistance and inhibit tumor growth with high potency and selectivity. Here, we discuss recent progress made in third row transition metal-based mitochondrial targeting agents with the goal of stimulating an active field of research toward new clinical anticancer agents and the elucidation of novel mechanisms of action.

Biological Properties of Transition Metal Complexes with Metformin and Its Analogues

Metformin is a widely prescribed medication for the treatment and management of type 2 diabetes. It belongs to a class of biguanides, which are characterized by a wide range of diverse biological properties, including anticancer, antimicrobial, antimalarial, cardioprotective and other activities. It is known that biguanides serve as excellent N-donor bidentate ligands and readily form complexes with virtually all transition metals. Recent evidence suggests that the mechanism of action of metformin and its analogues is linked to their metal-binding properties. These findings prompted us to summarize the existing data on the synthetic strategies and biological properties of various metal complexes with metformin and its analogues. We demonstrated that coordination of biologically active biguanides to various metal centers often resulted in an improved pharmacological profile, including reduced drug resistance as well as a wider spectrum of activity. In addition, coordination to the redox-active metal centers, such as Au(III), allowed for various activatable strategies, leading to the selective activation of the prodrugs and reduced off-target toxicity.

A Green Synthesis of Carbene-Metal-Amides (CMAs) and Carboline-Derived CMAs with Potent in vitro and ex vivo Anticancer Activity

The modularity and ease of synthesis of carbene-metal-amide (CMA) complexes based on the coinage metals (Au, Ag, Cu) and N-heterocyclic carbenes (NHCs) as ancillary ligands pave the way for the expansion of their applications beyond photochemistry and catalysis. Herein, we further improve the synthesis of such compounds by circumventing the use of toxic organic solvents which were previously required for their purification, and we expand their scope to include complexes incorporating carbolines as the amido fragments. The novel complexes are screened both in vitro and ex vivo, against several cancer cell lines and high-grade serous ovarian cancer (HGSOC) tumoroids, respectively. Excellent cytotoxicity values are obtained for most complexes, while the structural variety of the CMA library screened thus far, provides promising leads for future developments. Variations of all three components (NHC, metal, amido ligand), enable the establishment of trends regarding cytotoxicity and selectivity towards cancerous over normal cells.