A gold(III) porphyrin complex as an anti-cancer candidate to inhibit growth of cancer-stem cells

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.

Geometry and UV-Vis Spectra of Au3+ Complexes with Hydrazones Derived from Pyridoxal 5'-Phosphate: A DFT Study

Gold(III) complexes with different ligands can provide researchers with a measure against pathogenic microorganisms with antibiotic resistance. We reported in our previous paper that the UV-Vis spectra of different protonated species of complexes formed by gold(III) and five hydrazones derived from pyridoxal 5'-phosphate are similar to each other and to the spectra of free protonated hydrazones. The present paper focuses on the reasons of the noted similarity in electron absorption spectra. The geometry of different protonated species of complexes of gold(III) and hydrazones (15 structures in total) was optimized using the density functional theory (DFT). The coordination polyhedron of gold(III) bond critical points were further studied to identify the symmetry of the gold coordination sphere and the type of interactions that hold the complex together. The UV-Vis spectra were calculated using TD DFT methods. The molecular orbitals were analyzed to interpret the calculated spectra.

The anti-breast cancer stem cell properties of gold(i)-non-steroidal anti-inflammatory drug complexes

The anti-breast cancer stem cell (CSC) properties of a series of gold(i) complexes comprising various non-steroidal anti-inflammatory drugs (NSAIDs) and triphenylphosphine 1-8 are reported. The most effective gold(i)-NSAID complex 1, containing indomethacin, exhibits greater potency for breast CSCs than bulk breast cancer cells (up to 80-fold). Furthermore, 1 reduces mammosphere viability to a better extent than a panel of clinically used breast cancer drugs and salinomycin, an established anti-breast CSC agent. Mechanistic studies suggest 1-induced breast CSC death results from breast CSC entry, cytoplasm localisation, an increase in intracellular reactive oxygen species levels, cyclooxygenase-2 downregulation and inhibition, and apoptosis. Remarkably, 1 also significantly inhibits tumour growth in a murine metastatic triple-negative breast cancer model. To the best of our knowledge, 1 is the first gold complex of any geometry or oxidation state to demonstrate anti-breast CSC properties.

Porphyrin/Chlorin Derivatives as Promising Molecules for Therapy of Colorectal Cancer

Colorectal cancer (CRC) is a leading cause of cancer-related death. The demand for new therapeutic approaches has increased attention paid toward therapies with high targeting efficiency, improved selectivity and few side effects. Porphyrins are powerful molecules with exceptional properties and multifunctional uses, and their special affinity to cancer cells makes them the ligands par excellence for anticancer drugs. Porphyrin derivatives are used as the most important photosensitizers (PSs) for photodynamic therapy (PDT), which is a promising approach for anticancer treatment. Nevertheless, the lack of solubility and selectivity of the large majority of these macrocycles led to the development of different photosensitizer complexes. In addition, targeting agents or nanoparticles were used to increase the efficiency of these macrocycles for PDT applications. On the other hand, gold tetrapyrrolic macrocycles alone showed very interesting chemotherapeutic activity without PDT. In this review, we discuss the most important porphyrin derivatives, alone or associated with other drugs, which have been found effective against CRC, as we describe their modifications and developments through substitutions and delivery systems.

Anticancer Activity and Apoptosis Induction of Gold(III) Complexes Containing 2,2'-Bipyridine-3,3'-dicarboxylic Acid and Dithiocarbamates

Three novel gold(III) complexes (1–3) of general composition [Au(Bipydc)(S₂CNR₂)]Cl₂ (Bipydc = 2,2′-bipyridine-3,3′-dicarboxylic acid and R = methyl for dimethyldithiocarbamate (DMDTC), ethyl for diethyldithiocarbamate (DEDTC), and benzyl for dibenzyldithiocarbamate (DBDTC)) have been synthesized and characterized by elemental analysis, FTIR and NMR spectroscopic techniques. The spectral results confirmed the presence of both the Bipydc and dithiocarbamate ligands in the complexes. The in vitro cytotoxic studies demonstrated that compounds 1–3 were highly cytotoxic to A549, HeLa, MDA-231, and MCF-7 cancer cells with activities much higher (about 25-fold) than cisplatin. In order to know the possible mode of cell death complex 2, [Au(Bipydc)(DEDTC)]Cl₂ was further tested for induction of apoptosis towards the MCF-7 cells. The results indicated that complex 2 induces cell death through apoptosis.

Dinuclear orthometallated gold(I)-gold(III) anticancer complexes with potent in vivo activity through an ROS-dependent mechanism

Increasingly explored over the last decade, gold complexes have shown great promise in the field of cancer therapeutics. A major obstacle to their clinical progression has been their lack of in vivo stability, particularly for gold(III) complexes, which often undergo a facile reduction in the presence of biomolecules such as glutathione. Herein, we report a new class of promising anticancer gold(I)-gold(III) complexes with the general formula [XAuI(μ-2-C6F4PPh2)(κ2-2-C6F4PPh2)AuIIIX] [X = Cl (1), Br (2), NO3 (3)] which feature two gold atoms in different oxidation states (I and III) in a single molecule. Interestingly, gold(I)-gold(III) complexes (1-3) are stable against glutathione reduction under physiological-like conditions. In addition, complexes 1-3 exhibit significant cytotoxicity (276-fold greater than cisplatin) toward the tested cancer cells compared to the noncancerous cells. Moreover, the gold(I)-gold(III) complexes do not interact with DNA-like cisplatin but target cellular thioredoxin reductase, an enzyme linked to the development of cisplatin drug resistance. Complexes 1-3 also showed potential to inhibit cancer and endothelial cell migration, as well as tube formation during angiogenesis. In vivo studies in a murine HeLa xenograft model further showed the gold compounds may inhibit tumor growth on par clinically used cisplatin, supporting the significant potential this new compound class has for further development as cancer therapeutic.

A Comprehensive Overview of Colon Cancer- A Grim Reaper of the 21st Century

A few decades ago, the incidence of colorectal cancer (CRC) was low and is now the fourth in the list of deadly cancers producing nearly a million deaths annually. A population that is aging along with risk factors such as smoking, obesity, sedentary lifestyle with little or no physical activity, and non-healthy food habits of developed countries can increase the risk of colorectal cancer. The balance in gut microbiota and the metabolites produced during bacterial fermentation within the host plays a significant role in regulating intestinal diseases as well as colorectal cancer development. Recent progress in the understanding of illness resulted in multiple treatment options such as surgery, radiation, and chemotherapy, including targeted therapy and multitherapies. The treatment plan for CRC depends on the location, stage and grade of cancer as well as genomic biomarker tests. Despite all the advancements made in the genetic and molecular aspects of the disease, the knowledge seems inadequate as the drug action as well as the wide variation in drug response did not appear strongly correlated with the individual molecular and genetic characteristics, which suggests the requirement of comprehensive molecular understanding of this complex heterogeneous disease. Furthermore, multitherapies or a broad spectrum approach, which is an amalgamation of the various promising as well as effective therapeutic strategies that can tackle heterogeneity and act on several targets of the disease, need to be validated in clinical studies. The latest treatment options have significantly increased the survival of up to three years in the case of advanced disease. The fact that colorectal cancer is developed from a polypoid precursor, as well as the symptoms of the disease that occur at an advanced stage, underlines how screening programs can help early detection and decrease mortality as well as morbidity from CRC.

Rollover Cyclometalation vs Nitrogen Coordination in Tetrapyridyl Anticancer Gold(III) Complexes: Effect on Protein Interaction and Toxicity

In this work, a pair of gold(III) complexes derived from the analogous tetrapyridyl ligands H₂biqbpy1 and H₂biqbpy2 was prepared: the rollover, bis-cyclometalated [Au(biqbpy1)Cl ([1]Cl) and its isomer [Au(biqbpy2)Cl ([2]Cl). In [1]⁺, two pyridyl rings coordinate to the metal via a Au-C bond (C^∧N^∧N^∧C coordination) and the two noncoordinated amine bridges of the ligand remain protonated, while in [2]⁺ all four pyridyl rings of the ligand coordinate to the metal via a Au-N bond (N^∧N^∧N^∧N coordination), but both amine bridges are deprotonated. As a result, both complexes are monocationic, which allowed comparison of the sole effect of cyclometalation on the chemistry, protein interaction, and anticancer properties of the gold(III) compounds. Due to their identical monocationic charge and similar molecular shape, both complexes [1]Cl and [2]Cl displaced reference radioligand [³H]dofetilide equally well from cell membranes expressing the K_v11.1 (hERG) potassium channel, and more so than the tetrapyridyl ligands H₂biqbpy1 and H₂biqbpy2. By contrast, cyclometalation rendered [1]Cl coordinatively stable in the presence of biological thiols, while [2]Cl was reduced by a millimolar concentration of glutathione into metastable Au(I) species releasing the free ligand H₂biqbpy2 and TrxR-inhibiting Au⁺ ions. The redox stability of [1]Cl dramatically decreased its thioredoxin reductase (TrxR) inhibition properties, compared to [2]Cl. On the other hand, unlike [2]Cl, [1]Cl aggregated into nanoparticles in FCS-containing medium, which resulted in much more efficient gold cellular uptake. [1]Cl had much more selective anticancer properties than [2]Cl and cisplatin, as it was almost 10 times more cytotoxic to human cancer cells (A549, A431, A375, and MCF7) than to noncancerous cells (MRC5). Mechanistic studies highlight the strikingly different mode of action of the two compounds: while for [1]Cl high gold cellular uptake, nuclear DNA damage, and interaction with hERG may contribute to cell killing, for [2]Cl extracellular reduction released TrxR-inhibiting Au⁺ ions that were taken up in minute amounts in the cytosol, and a toxic tetrapyridyl ligand also capable of binding to hERG. These results demonstrate that bis-cyclometalation is an appealing method to improve the redox stability of Au(III) compounds and to develop gold-based cytotoxic compounds that do not rely on TrxR inhibition to kill cancer cells.

Role of the Enzymatic Environment in the Reactivity of the AuIII-C^N^C Anticancer Complexes

The action mechanism of anticancer gold(III) complexes is a multi-step process and depends on their redox stability. First, the gold(III) complex undergoes a ligand exchange reaction in the presence of cellular thiols, such as those available in the active site of the enzyme TrxR, and then, the Au^III → Au^I reduction occurs. Most experimental and theoretical studies describe these processes under chemical conditions without considering the enzyme structure effect. In the present study, molecular models are proposed for the [Au^III(C^N^C)(SHCys-R)]⁺ adduct, with the [Au^III(C^N^C)]⁺ moiety bonded to the Cys498 residue in the C-terminal arm of the TrxR. This one represents the product of the first ligand exchange reaction. Overall, our results suggest that the exchange of the auxiliary ligand (for instance, Cl^- to S-R) plays a primary role in increasing the reduction potential, with the enzyme structure having a small effect. The parent compound [Au^III(C^N^C)Cl] has E° = -1.20 V, which enlarges to -0.72 V for [Au^III(C^N^C)CH₃SH]⁺ and to -0.65 V for the largest model studied, Au-trx. In addition to the effect of the enzyme structure on the redox stability, we also analyze the Au transfer to the enzyme using a small peptide model (a tetramer). This reaction is dependent on the Cys497 protonation state. Thermodynamics and kinetic analysis suggests that the C^N^C ligand substitution by Cys497 is an exergonic process, with an energy barrier estimated at 20.2 kcal mol^-1. The complete transfer of the Au ion to the enzyme's active site would lead to a total loss of enzyme activity, generating oxidative damage and, consequently, cancer cell death.

Mononuclear gold(iii) complexes with diazanaphthalenes: the influence of the position of nitrogen atoms in the aromatic rings on the complex crystalline properties

A series of mononuclear gold(iii) complexes of the general formula [AuCl3(diazanaphthalene)], where diazanaphthalene is quinazoline (qz, 1), phthalazine (phtz, 2), 1,5-naphthyridine (1,5-naph, 3), 1,6-naphthyridine (1,6-naph, 4) or 1,8-naphthyridine (1,8-naph, 5), were prepared and fully characterized. The complexes 1-5 consist of discrete monomeric species with the Au(iii) cation in a square planar coordination geometry surrounded by three chloride anions and one diazanaphthalene ligand. Crystallographic studies indicate the presence of an extended 4 + 1 or 4 + 2 geometry around the square planar [AuCl3(diazanaphthalene)] center due to Au⋯Cl and Au⋯N interactions. The crystal structures of these complexes are controlled by a variety of intermolecular interactions that utilize the amphiphilic properties of the coordinated chloride anions and involve C-H groups, π-electrons, and an uncoordinated nitrogen atom of the diazanaphthalene ligand. The usual offset π-stacking between the N-heteroaromatic ligands appears to be completely hindered between the 1,5-naph fragments and significantly weakened between the 1,6-naph and 1,8-naph in their respective complexes 3, 4 and 5, for which the average molecular polarizability (α) values are the lowest in the series. It is remarkable that the [AuCl3(benzodiazine)] complexes 1 and 2 form centrosymmetric crystals, but the [AuCl3(naphthyridine)] complexes 3-5 assemble into non-centrosymmetric aggregates, making them potential alternatives to the previously studied systems for application in various fields by taking advantage of their polarity.

Anticancer Gold(III) Compounds With Porphyrin or N-heterocyclic Carbene Ligands

The use of gold in medicine has a long history. Recent clinical applications include anti-inflammatory agents for the treatment of rheumatoid arthritis (chrysotherapy), and is currently being developed as potential anticancer chemotherapeutics. Gold(III), being isoelectronic to platinum(II) as in cisplatin, is of great interest but it is inherently unstable and redox-reactive under physiological conditions. Coordination ligands containing C and/or N donor atom(s) such as porphyrin, pincer-type cyclometalated and/or N-heterocyclic carbene (NHC) can be employed to stabilize gold(III) ion for the preparation of anticancer active compounds. In this review, we described our recent work on the anticancer properties of gold(III) compounds and the identification of molecular targets involved in the mechanisms of action. We also summarized the chemical formulation strategies that have been adopted for the delivery of cytotoxic gold compounds, and for ameliorating the in vivo toxicity.

Multifunctional Microparticles Incorporating Gold Compound Inhibit Human Lung Cancer Xenograft

PURPOSE

Gold porphyrin (AuP) is a complex that has been shown to be potent against various tumors. A biocompatible interpenetrating network (IPN) system comprised of polyethyleneglycol diacrylate (PEGdA) and chemically-modified gelatin has been shown to be an effective implantable drug depot to deliver AuP locally. Here we designed IPN microparticles complexed with AuP to facilitate intravenous administration and to diminish systemic toxicity.

METHODS

We have synthesized and optimized an IPN microparticle formulation complexed with AuP. Tumor cell cytotoxicity, antitumor activity, and survival rate in lung cancer bearing nude mice were analyzed.

RESULTS

IPN microparticles maintained AuP bioactivity against lung cancer cells (NCI-H460). In vivo study showed no observable systemic toxicity in nude mice bearing NCI-H460 xenografts after intravenous injection of 6 mg/kg AuP formulated with IPN microparticles. An anti-tumor activity level comparable to free AuP was maintained. Mice treated with 6 mg/kg AuP in IPN microparticles showed 100% survival rate while the survival rate of mice treated with free AuP was much less. Furthermore, microparticle-formulated AuP significantly reduced the intratumoral microvasculature when compared with the control.

CONCLUSION

AuP in IPN microparticles can reduce the systemic toxicity of AuP without compromising its antitumor activity. This work highlighted the potential application of AuP in IPN microparticles for anticancer chemotherapy.

Studies of the stability, nucleophilic substitution reactions, DNA/BSA interactions, cytotoxic activity, DFT and molecular docking of some tetra- and penta-coordinated gold(iii) complexes

The stability in water and at pH = 7.2, substitution reactions with Tu, 5’-GMP, GSH and l-Met, DNA/BSA interactions, cytotoxicity, DFT and molecular docking of gold(iii) complexes with phenanthroline derivatives as inert ligands were studied.

Biological Activity of Au(III) Complexes

The earliest therapy use of gold compounds dated in 2500 AD. In 1960s gold compounds were used in the treatment of rheumatoid arthritis, discoid lupus erythematosus, etc. Although the compounds of Au(I) are well-known and used in the modern medicine, new complexes of Au(III) and ligands with different donor atoms are synthetized and examined for their biological (antitumor, antimicrobial) activity. So far conducted studies show that complexes with Au(III) as central metal ions have greater activity compared with free ligands. Future syntheses should be based on the increase of biological activity with complexes that have necessary stability under physiological conditions.

Identification of two mitochondrial-targeting cyclometalated iridium(III) complexes as potent anti-glioma stem cells agents

Glioma stem cells (GSCs) are thought to be responsible for the recurrence and invasion of glioblastoma multiform (GBM), which have been evaluated and exploited as the therapeutic target for GBM. Cyclometalated iridium(III) complexes have been demonstrated as the potential anticancer agents, however, their antitumor efficacies against GSCs are still unknown. Herein, we investigated the antitumor activity of two cyclometalated iridium(III) complexes [Ir(ppy)₂L](PF₆) (Ir1) and [Ir(thpy)₂L](PF₆) (Ir2) (ppy = 2-phenylpyridine, thpy = 2-(2-thienyl)pyridine and L = 4,4'-Bis(hydroxymethyl)-2,2'-bipyridine) against GSCs. The results clearly indicate that Ir1 and Ir2 kill GSCs selectively with IC₅₀ values ranging from 5.26-9.05 μM. Further mechanism research display that Ir1 and Ir2 can suppress the proliferation of GSCs, penetrate into GSCs efficiently, localize to mitochondria, and induce mitochondria-mediated apoptosis, including the loss of mitochondrial membrane (MMP), elevation of intracellular reactive oxygen species (ROS) and caspases activation. Moreover, Ir1 and Ir2 can destroy the GSCs self-renewal and unlimited proliferation capacity by affecting the GSCs colony formation. According our knowledge, this is the first study to investigate the anti-GSCs properties of cyclometalated iridium(III) complexes.

Mitochondria-Targeting Anticancer Metal Complexes

Background:

Since the serendipitous discovery of the antitumor activity of cisplatin there has been a continuous surge in studies aimed at the development of new cytotoxic metal complexes. While the majority of these complexes have been designed to interact with nuclear DNA, other targets for anticancer metallodrugs attract increasing interest. In cancer cells the mitochondrial metabolism is deregulated. Impaired apoptosis, insensitivity to antigrowth signals and unlimited proliferation have been linked to mitochondrial dysfunction. It is therefore not surprising that mitochondria have emerged as a major target for cancer therapy. Mitochondria-targeting agents are able to bypass resistance mechanisms and to (re-) activate cell-death programs.

Methods:

Web-based literature searching tools such as SciFinder were used to search for reports on cytotoxic metal complexes that are taken up by the mitochondria and interact with mitochondrial DNA or mitochondrial proteins, disrupt the mitochondrial membrane potential, facilitate mitochondrial membrane permeabilization or activate mitochondria-dependent celldeath signaling by unbalancing the cellular redox state. Included in the search were publications investigating strategies to selectively accumulate metallodrugs in the mitochondria.

Results:

This review includes 241 references on antimitochondrial metal complexes, the use of mitochondria-targeting carrier ligands and the formation of lipophilic cationic complexes.

Conclusion:

Recent developments in the design, cytotoxic potency, and mechanistic understanding of antimitochondrial metal complexes, in particular of cyclometalated Au, Ru, Ir and Pt complexes, Ru polypyridine complexes and Au-N-heterocyclic carbene and phosphine complexes are summarized and discussed.

In vitro and in vivo anti-tumor activity of two gold(III) complexes with isoquinoline derivatives as ligands

Two gold(III) complexes of isoquinoline derivatives: [Au(L¹)Cl₂] (Au1) and [Au(L²)Cl₂] (Au2) have been prepared and characterized. Au1 and Au2 exhibited greater cytotoxicity than their corresponding ligands and cisplatin against T-24 cells. Both complexes arrested cell cycle at S-phase by upregulation of p53, p27, and p21, and downregulation of cyclin A and cyclin E. The depolarization of the mitochondrial membrane potential, generation of ROS, and stimulated Ca²⁺ release activated the caspase cascade and ultimately caused apoptosis by increasing the levels of Bax and Bak, and decreasing the levels of Bcl-2 and Bcl-xl. Cell apoptosis was achieved via mitochondria mediated pathways. The in vivo studies of Au1 and Au2 demonstrated that they were safer than cisplatin and could effectively inhibit tumor growth.

The Next Generation of Anticancer Metallopharmaceuticals: Cancer Stem Cell-Active Inorganics

Cancer stem cells (CSCs) are heavily linked to fatal incidences of cancer relapse and metastasis. Conventional cancer therapies such as surgery, chemotherapy and radiation are largely futile against CSCs. Therefore, highly original approaches are needed to overcome CSCs and to provide durable, long-term clinical outcomes. Many academia- and pharmaceutical-led studies aimed at developing chemical or biological anti-CSC agents are ongoing; however, the application of inorganic compounds is rare. In this minireview, we discuss how the chemical diversity and versatility offered by metals has been harnessed to develop an unprecedented, emerging class of metallopharmaceuticals: CSC-active inorganics. A detailed account of their mechanism(s) of action is provided, and possible future directions for exploration are also put forward.

Porphyrins as ligands for 64copper: background and trends

Porphyrins and 64Cu have emerged as a novel synergic option for applications in PET molecular imaging. Both the characteristics and photophysical properties of macrocyclic porphyrins and the relatively long half-life of the copper isotope, in addition to the increased tumor-specific uptake of porphyrins compared to normal cells, make this complex an attractive option not only for diagnosis but also for therapeutic applications. Herein, we present an overview of the latest results on the development of PET agents based on porphyrins and 64Cu, including methods used to improve the selectivity of these macrocycles when conjugated with biological units such as monoclonal antibodies, peptides or proteins.

Diflunisal-adjoined cobalt(iii)-polypyridyl complexes as anti-cancer stem cell agents

We report a novel series of cobalt(iii)-polypridyl complexes that can selectively release diflunisal, a nonsteroidal anti-inflammatory drug, under reducing conditions.

Cancer Stem Cell and Bulk Cancer Cell Active Copper(II) Complexes with Vanillin Schiff Base Derivatives and Naproxen

Four copper(II) complexes, 1-4 containing regioisomeric vanillin Schiff base derivatives and the nonsteroidal anti-inflammatory drug (NSAID), naproxen, were synthesised and characterised. All complexes effectively cleave DNA in cell-free systems, with 4 displaying the highest nuclease activity. DNA binding studies suggest that 4 binds to DNA via the grooves prior to inducing oxidative DNA cleavage. Three of the complexes (1, 3, and 4) indiscriminately kill cancer stem cell (CSC)-enriched cells (HMLER-shEcad) and bulk cancer cells (HMLER) at micromolar concentrations. The most effective complex, 4 also reduced the formation and size of mammospheres to a similar extent as salinomycin, a well-established CSC-potent agent. Mechanistic studies show that 4 is readily taken up by CSCs, elevates intracellular reactive oxygen species (ROS) levels, causes DNA damage, and induces caspase-dependent apoptosis. Furthermore, 4 inhibits cyclooxygenase-2 (COX-2) expression and causes COX-2-dependent CSC death. The advantage of 4 over bulk cancer cell- or CSC-selective agents is that it has the potential to remove whole tumor populations (bulk cancer cells and CSCs) with a single dose.

Induction of Necroptosis in Cancer Stem Cells using a Nickel(II)-Dithiocarbamate Phenanthroline Complex

The cytotoxic properties of a series of nickel(II)-dithiocarbamate phenanthroline complexes is reported. The complexes 1-6 kill bulk cancer cells and cancer stem cells (CSCs) with micromolar potency. Two of the complexes, 2 and 6, kill twice as many breast cancer stem cell (CSC)-enriched HMLER-shEcad cells as compared to breast CSC-depleted HMLER cells. Complex 2 inhibits mammosphere formation to a similar extent as salinomycin (a CSC-specific toxin). Detailed mechanistic studies suggest that 2 induces CSC death by necroptosis, a programmed form of necrosis. Specifically, 2 triggers MLKL phosphorylation, oligomerization, and translocation to the cell membrane. Additionally, 2 induces necrosome-mediated propidium iodide (PI) uptake and mitochondrial membrane depolarisation, as well as morphological changes consistent with necroptotosis. Strikingly, 2 does not evoke necroptosis by intracellular reactive oxygen species (ROS) production or poly(ADP) ribose polymerase (PARP-1) activation.

Colorectal Carcinoma: A General Overview and Future Perspectives in Colorectal Cancer

Colorectal cancer (CRC) is the third most common cancer and the fourth most common cause of cancer-related death. Most cases of CRC are detected in Western countries, with its incidence increasing year by year. The probability of suffering from colorectal cancer is about 4%–5% and the risk for developing CRC is associated with personal features or habits such as age, chronic disease history and lifestyle. In this context, the gut microbiota has a relevant role, and dysbiosis situations can induce colonic carcinogenesis through a chronic inflammation mechanism. Some of the bacteria responsible for this multiphase process include Fusobacterium spp, Bacteroides fragilis and enteropathogenic Escherichia coli. CRC is caused by mutations that target oncogenes, tumour suppressor genes and genes related to DNA repair mechanisms. Depending on the origin of the mutation, colorectal carcinomas can be classified as sporadic (70%); inherited (5%) and familial (25%). The pathogenic mechanisms leading to this situation can be included in three types, namely chromosomal instability (CIN), microsatellite instability (MSI) and CpG island methylator phenotype (CIMP). Within these types of CRC, common mutations, chromosomal changes and translocations have been reported to affect important pathways (WNT, MAPK/PI3K, TGF-β, TP53), and mutations; in particular, genes such as c-MYC, KRAS, BRAF, PIK3CA, PTEN, SMAD2 and SMAD4 can be used as predictive markers for patient outcome. In addition to gene mutations, alterations in ncRNAs, such as lncRNA or miRNA, can also contribute to different steps of the carcinogenesis process and have a predictive value when used as biomarkers. In consequence, different panels of genes and mRNA are being developed to improve prognosis and treatment selection. The choice of first-line treatment in CRC follows a multimodal approach based on tumour-related characteristics and usually comprises surgical resection followed by chemotherapy combined with monoclonal antibodies or proteins against vascular endothelial growth factor (VEGF) and epidermal growth receptor (EGFR). Besides traditional chemotherapy, alternative therapies (such as agarose tumour macrobeads, anti-inflammatory drugs, probiotics, and gold-based drugs) are currently being studied to increase treatment effectiveness and reduce side effects.

A reactive oxygen species-generating, cyclooxygenase-2 inhibiting, cancer stem cell-potent tetranuclear copper(ii) cluster

Tetranuclear copper(ii) complexes containing multiple diclofenac and Schiff base moieties,1–4, are shown to kill bulk cancer cells and cancer stem cells (CSCs) with low micromolar potency.

Gold Tris(carboxyphenyl)corroles as Multifunctional Materials: Room Temperature Near-IR Phosphorescence and Applications to Photodynamic Therapy and Dye-Sensitized Solar Cells

Two amphiphilic corroles-5,10,15-tris(3-carboxyphenyl)corrole (H3[mTCPC]) and 5,10,15-tris(4-carboxyphenyl)corrole (H3[pTCPC])-and their gold complexes have been synthesized, and their photophysical properties and photovoltaic behavior have been investigated. Like other nonpolar gold corroles, Au[mTCPC] and Au[pTCPC] were both found to exhibit room temperature phosphorescence in deoxygenated solutions with quantum yields of ∼0.3% and triplet lifetimes of ∼75 μs. Both compounds exhibited significant activity as dyes in photodynamic therapy experiments and in dye-sensitized solar cells. Upon irradiation at 435 nm, both Au corroles exhibited significant phototoxicity against AY27 rat bladder cancer cells while the free-base corroles proved inactive. Dye-sensitized solar cells constructed using the free bases H3[mTCPC] and H3[pTCPC] exhibited low efficiencies (≪1%), well under that obtained with 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin, H2[pTCPP] (1.9%, cf. N719 9.5%). Likewise, Au[pTCPC] proved inefficient, with an efficiency of ∼0.2%. By contrast, Au[mTCPC] proved remarkably effective, exhibiting an open-circuit voltage (Voc) of 0.56 V, a short-circuit current of 8.7 mA cm(-2), a fill factor of 0.72, and an efficiency of 3.5%.

Synthesis, structural characterization and biological evaluation of dinuclear gold(iii) complexes with aromatic nitrogen-containing ligands: antimicrobial activity in relation to the complex nuclearity

Dinuclear Au(iii) complexes with N-heterocycles have been synthesized and biologically evaluated.

A macromolecular cyclometalated gold(iii) amphiphile displays long-lived emissive excited state in water: self-assembly and in vitro photo-toxicity

A cyclometalated gold(iii) amphiphile self-assembles into nano-sized micelles in water, displaying a long-lived emissive excited state andin vitrophoto-toxicity.

Synthesis, structural characterization, electrochemical behavior and anticancer activity of gold(iii) complexes of meso-1,2-di(1-naphthyl)-1,2-diaminoethane and tetraphenylporphyrin

Gold(iii) complexes were tested for in vitro antiproliferative activity against three human tumor cell lines. All complexes exhibited remarkable cytotoxicity.

The breast cancer stem cell potency of copper(ii) complexes bearing nonsteroidal anti-inflammatory drugs and their encapsulation using polymeric nanoparticles

This is the first report to demonstrate that polymeric nanoparticles can be used to effectively deliver CSC-potent metal complexes into CSCs.

Dinuclear Gold(I) Pyrrolidinedithiocarbamato Complex: Cytotoxic and Antimigratory Activities on Cancer Cells and the Use of Metal-Organic Framework

A dinuclear gold(I) pyrrolidinedithiocarbamato complex (1) with a bidentate carbene ligand has been constructed and shows potent in vitro cytotoxic activities towards cisplatin-resistant ovarian cancer cells A2780cis. Its rigid scaffold enables a zinc(II)-based metal-organic framework (Zn-MOF) to be used as a carrier in facilitating the uptake and release of 1 in solutions. Instead of using a conventional dialysis approach for the drug-release testing, in this study, a set of transwell assay-based experiments have been designed and employed to examine the cytotoxic and antimigratory activities of 1@Zn-MOF towards A2780cis.

Chemical biology of anticancer gold(iii) and gold(i) complexes

Anticancer gold complexes, including their mechanisms of action and the approaches adopted to improve the anticancer efficiency are described.

A breast cancer stem cell-selective, mammospheres-potent osmium(VI) nitrido complex

The effect of a newly developed osmium(VI) nitrido complex, 1, on breast cancer stem cells (CSCs) is reported. The complex displays selective toxicity for HMLER breast cancer cells enriched with CD44-positive, CSC-like cells over the same cells having reduced CSC character. Remarkably, 1 also reduces the proportion of CSCs within a heterogeneous breast cancer cell population and irreversibly inhibits the formation of free-floating mammospheres to an extent similar to that of salinomycin, a natural product that targets CSCs. Detailed mechanistic studies reveal that in breast cancer cells 1 induces DNA damage and endoplasmic reticulum stress, the latter being responsible for the CSC selectivity. The anti-CSC properties of 1 provide a strong impetus for the development of new metal-based compounds to target CSCs and to treat chemotherapy-resistant and relapsed tumors.

A cytotoxic and cytostatic gold(iii) corrole

The bis-sulfonated Au(iii) corrole (1-Au) was found to be much more cytotoxic and cytostatic than its Ga(iii) analog 1-Ga, which might be attributed to the lower affinity of 1-Au to serum albumin.