Gold(I) complexes with alkylated PTA (1,3,5-triaza-7-phosphaadamantane) phosphanes as anticancer metallodrugs

Heteronuclear Complexes with Promising Anticancer Activity against Colon Cancer

This study investigates the activity of novel gold(I) and copper(I)/zinc(II) heteronuclear complexes against colon cancer. The synthesised heteronuclear Au(I)-Cu(I) and Au(I)-Zn(II) complexes were characterised and evaluated for their anticancer activity using human colon cancer cell lines (Caco-2). The complexes exhibited potent cytotoxicity, with IC50 values in the low micromolar range, and effectively induced apoptosis in cancer cells. In the case of complex [Cu{Au(Spy)(PTA)}2]PF6 (2), its cytotoxicity is ×10 higher than its mononuclear precursor, while showing low cytotoxicity towards differentiated healthy cells. Mechanistic studies revealed that complex 2 inhibits the activity of thioredoxin reductase, a key enzyme involved in redox regulation, leading to an increase in reactive oxygen species (ROS) levels and oxidative stress, in addition to an alteration in DNA's tertiary structure. Furthermore, the complexes demonstrated a strong binding affinity to bovine serum albumin (BSA), suggesting the potential for effective drug delivery and bioavailability. Collectively, these findings highlight the potential of the investigated heteronuclear Au(I)-Cu(I) and Au(I)-Zn(II) complexes as promising anticancer agents, particularly against colon cancer, through their ability to disrupt redox homeostasis and induce oxidative stress-mediated cell death.

Gold(I) Complexes Bearing Alkylated 1,3,5-Triaza-7-phosphaadamantane Ligands as Thermoresponsive Anticancer Agents in Human Colon Cells

Overheating can affect solubility or lipophilicity, among other properties, of some anticancer drugs. These temperature-dependent changes can improve efficiency and selectivity of the drugs, since they may affect their bioavailability, diffusion through cell membrane or activity. One recent approach to create thermosensitive molecules is the incorporation of fluorine atoms in the chemical structure, since fluor can tune some chemical properties such as binding affinity. Herein we report the anticancer effect of gold derivatives with phosphanes derived from 1,3,5-triaza-7-phosphaadamantane (PTA) with long hydrocarbon chains and the homologous fluorinated chains. Besides, we analysed the influence of temperature in the cytotoxic effect. The studied gold(I) complexes with phosphanes derived from PTA showed antiproliferative effect on human colon carcinoma cells (Caco-2/TC7 cell line), probably by inhibiting cellular TrxR causing a dysfunction in the intracellular redox state. In addition, the cell cycle was altered by the activation of p53, and the complexes produce apoptosis through mitochondrial depolarization and the consequent activation of caspase-3. Furthermore, the results suggest that this cytotoxic effect is enhanced by hyperthermia and the presence of polyfluorinated chains.

Potential of Gold Candidates against Human Colon Cancer

Development of novel metallodrugs with pharmacological profile plays a significant role in modern medicinal chemistry and drug design. Metal complexes have shown remarkable clinical results in current cancer therapy. Gold complexes have attained attention due to their high antiproliferative potential. Gold-based drugs are used for the treatment of rheumatoid arthritis. Gold-containing compounds with selective and specific targets are capable to assuage the symptoms of a range of human diseases. Gold (I) species with labile ligands (such as Cl in TEPAuCl) interact with isolated DNA; therefore, this biomolecule has been considered as a target for gold drugs. Gold (I) has a high affinity towards sulfur and selenium. Due to this, gold (I) drugs readily interact with cysteine or selenocysteine residue of the enzyme to form protein-gold(I) thiolate or protein-gold (I) selenolate complexes that lead to inhibition of the enzyme activity. Au(III) compounds due to their square-planner geometriesthe same as found in cisplatin, represent a good source for the development of anti-tumor agents. This article aims to review the most important applications of gold products in the treatment of human colon cancer and to analyze the complex interplay between gold and the human body.

Selective cytotoxicity of cyclometalated gold(III) complexes on Caco-2 cells is mediated by G2/M cell cycle arrest

New cyclometalated gold(III) complexes with a general structure [Au(C^N)(SR)2] or [Au(C^N)Cl(SR)], where C^N is a biphenyl ligand such as 2-(p-tolyl)pyridinate (tpy), 2-phenylpyridinate (ppy) and 2-benzylpyridinate (bzp) (SR = Spym, S(Me)2pym, 2-thiouracil (2-TU) and thiourea), and also with ethynyl moieties of the type [Au(C^N)(C≡C-Ar)2] (Ar = p-toluene and 2-pyridine) have been synthesized. All of them have been characterized, including X-ray studies of complex [Au(bzp)Cl(Spym)], and these studies have permitted to elucidate that leaving chloride ligand is trans located to CAr atom. After the full characterization, physicochemical properties were measured by evaluating drug-like water solubility and cell permeability (partition coefficient). All these experiments pointed that our complexes present adequate properties to be used as anticancer drugs. Although not all the complexes showed antiproliferative effects on Caco-2 cells, those that did were more cytotoxic than cisplatin; and complex [Au(tpy)Cl(2-TU)] is even more active than auranofin. In addition to this effectiveness, no evidence of cytotoxic effects was observed on considered normal cells (with the exception of [Au(bzp)Cl(2-TU)]. Further action mechanisms studies were performed using these selective complexes, showing cell cycle arrest on the G2/M phase, a proapoptotic behaviour and also the modification of some genes involved in tumorigenesis. Thus, as a result of this investigation, we present a new family of 17 cyclometalated complexes, 6 of them being selective and possible candidates to be used against colon cancer.

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.

New selective thiolate gold(i) complexes inhibit the proliferation of different human cancer cells and induce apoptosis in primary cultures of mouse colon tumors

New thiolate gold(i) complexes with P(NMe₂)₃ (HMPT) as phosphane group have been developed as proapoptotic and selective anticancer drugs.

Alkynyl Gold(I) complexes derived from 3-hydroxyflavones as multi-targeted drugs against colon cancer

The design of multi-targeted drugs has gained considerable interest in the last decade thanks to their advantages in the treatment of different diseases, including cancer. The simultaneous inhibition of selected targets from cancerous cells to induce their death represents an attractive objective for the medicinal chemist in order to enhance the efficiency of chemotherapy. In the present work, several alkynyl gold(I) phosphane complexes derived from 3-hydroxyflavones active against three human cancer cell lines, colorectal adenocarcinoma Caco-2/TC7, breast adenocarcinoma MCF-7 and hepatocellular carcinoma HepG2, have been synthesized and characterized. Moreover, these compounds display high selective index values towards differentiated Caco-2 cells, which are considered as a model of non-cancerous cells. The antiproliferative effect of the most active complexes [Au(L2b)PPh₃] (3b) and [Au(L2c)PTA] (4c) on Caco-2 cells, seems to be mediated by the inhibition of the enzyme cyclooxygenase-1/2 and alteration of the activities of the redox enzymes thioredoxin reductase and glutathione reductase. Both complexes triggered cell death by apoptosis, alterations in cell cycle progression and increased of ROS production. These results provide support for the suggestion that multi-targeting approach involving the interaction with cyclooxygenase-1/2 and the redox enzymes that increases ROS production, enhances cell death in vitro. All these results indicate that complexes [Au(L2b)PPh₃] and [Au(L2c)PTA] are promising antiproliferative agents for further anticancer drug development.

Gold as a Possible Alternative to Platinum-Based Chemotherapy for Colon Cancer Treatment

Due to the increasing incidence and high mortality associated with colorectal cancer (CRC), novel therapeutic strategies are urgently needed. Classic chemotherapy against CRC is based on oxaliplatin and other cisplatin analogues; however, platinum-based therapy lacks selectivity to cancer cells and leads to deleterious side effects. In addition, tumor resistance to oxaliplatin is related to chemotherapy failure. Gold(I) derivatives are a promising alternative to platinum complexes, since instead of interacting with DNA, they target proteins overexpressed on tumor cells, thus leading to less side effects than, but a comparable antitumor effect to, platinum derivatives. Moreover, given the huge potential of gold nanoparticles, the role of gold in CRC chemotherapy is not limited to gold(I) complexes. Gold nanoparticles have been found to be able to overcome multidrug resistance along with reduced side effects due to a more efficient uptake of classic drugs. Moreover, the use of gold nanoparticles has enhanced the effect of traditional therapies such as radiotherapy, photothermal therapy, or photodynamic therapy, and has displayed a potential role in diagnosis as a consequence of their optic properties. Herein, we have reviewed the most recent advances in the use of gold(I) derivatives and gold nanoparticles in CRC therapy.

Synthesis and biological evaluation of thiolate gold(i) complexes as thioredoxin reductase (TrxR) and glutathione reductase (GR) inhibitors

Au(i) complexes with PPh₂py and thiolate ligands are prepared. The complexes are shown considerable cytotoxic activities and those efficiently inhibit the TrxRs and GR.

Gold-Based Medicine: A Paradigm Shift in Anti-Cancer Therapy?

A new era of metal-based drugs started in the 1960s, heralded by the discovery of potent platinum-based complexes, commencing with cisplatin [(H₃N)₂PtCl₂], which are effective anti-cancer chemotherapeutic drugs. While clinical applications of gold-based drugs largely relate to the treatment of rheumatoid arthritis, attention has turned to the investigation of the efficacy of gold(I) and gold(III) compounds for anti-cancer applications. This review article provides an account of the latest research conducted during the last decade or so on the development of gold compounds and their potential activities against several cancers as well as a summary of possible mechanisms of action/biological targets. The promising activities and increasing knowledge of gold-based drug metabolism ensures that continued efforts will be made to develop gold-based anti-cancer agents.

Benzothiazole-Based Cycloplatinated Chromophores: Synthetic, Optical, and Biological Studies

Cycloplatinated complexes based on 2-(4-substituted)benzothiazole ligands of type [Pt(R-PBT-κC,N)Cl(L)] (PBT=2-phenylbenzothiazole; R=Br (1), Me₂ N (2); L=dimethyl sulfoxide (DMSO; a), 1,3,5- triaza-7-phosphaadamantane (PTA; b), triphenylphosphine 3,3',3''-trisulfonate (TPPTS; c)) and [Pt(Br-PBT-κC)Cl(PTA)₂ ] (3) are presented. On the basis of the photophysical data and time-dependent (TD)-DFT calculations (1 a and 2 a), the low-lying transitions (absorption and emission) were associated with ligand-center (LC) charge transfer, with minor metal-to-ligand charge transfer (MLCT), and intraligand charge transfer (ILCT) [Me₂ N-PBT→PBT] excited states, respectively. Simultaneous fluorescence/phosphorescence bands were found in fluid solutions (and also in the solid state for 2 a), which become dominated by triplet emission bands in rigid media at 77 K. The effect of the concentration on emissive behavior of 2 a, b indicated the occurrence of aggregation-induced luminescence properties related to the occurrence of metal-metal and π⋅⋅⋅π interactions, which are more enhanced in 2 a because of the less bulky DMSO ligand. The behavior of 2 a toward para-toluenesulfonic acid (PTSA) in aerated acetonitrile and to hydrogen chloride gas in the solid state has been evaluated, thus showing a clear reversible change between the ¹ ILCT and ³ LC/³ MLCT states due to protonation of the NMe₂ group (theoretical calculations on 2 a-H⁺ ). Solid 2 a undergoes a surprising oxidation of the Pt^II center to Pt^IV with concomitant deoxygenation of DMSO, under prolonged reaction with hydrogen chloride gas to afford the Pt^IV /dimethyl sulfide complex (mer-[Pt(Me₂ N-PBT-κC,N)Cl₃ (SMe₂ )]; mer-4), which evolves in solution to fac-4, as confirmed by X-ray studies. Cytotoxic activity studies on A549 and HeLa cell lines indicated cytotoxic activity of 1 b and 2 a, b. In addition, fluorescent cell microscopy revealed cytoplasmic staining, more visible in perinuclear areas. Inhibition of tubulin polymerization by 1 b in both cells is presented as a preliminary mechanism of its cytotoxic action.

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.

The anticancer effect related to disturbances in redox balance on Caco-2 cells caused by an alkynyl gold(I) complex

The alkynyl gold(I) derivative [Au(C≡CPh)(PTA)] (PTA=1,3,5-triaza-7-phosphaadamantane) induces apoptosis in colorectal carcinoma tumour cells (Caco-2) without affecting to normal enterocytes. [Au(C≡CPh)(PTA)] is a slight lipophilic drug, stable in PBS (Phosphate Buffered Saline) and able to bind BSA (Bovin Serum Albumin) by hydrophobic interactions. Once inside the cell, [Au(C≡CPh)(PTA)] targets seleno proteins such as Thioredoxin Reductase 1, increasing ROS (Reactive Oxygen Species) levels, reducing cell viability and proliferation and inducing mitochondrial apoptotic pathway, pro-apoptotic and anti-apoptotic protein imbalance, loss of mitochondrial membrane potential, cytochrome c release and activation of caspases 9 and 3. Moreover, unlike other metal-based drugs such as cisplatin, [Au(C≡CPh)(PTA)] does not target nucleic acid, reducing the risk of side mutation in the DNA. In consequence, our results predict a promising future for [Au(C≡CPh)(PTA)] as a chemotherapeutic agent for colorectal carcinoma.

Novel antitumor adamantane-azole gold(I) complexes as potential inhibitors of thioredoxin reductase

Gold complexes that could act as antitumor agents have attracted great attention. Heterocyclic compounds and their metal complexes display a broad spectrum of pharmacological properties. The present study reports the preparation and characterization of four novel gold(I) complexes containing tertiary phosphine and new ligands 5-adamantyl-1,3-thiazolidine-2-thione, 3-methyladamantane-1,3,4-oxadiazole-2-thione. Spectroscopic data suggest that gold is coordinated to the exocyclic sulfur atom in all cases, as confirmed by X-ray crystallographic data obtained for complex (1) and supported by quantum-mechanical calculations. The cytotoxicity of the compounds has been evaluated in comparison to cisplatin and auranofin in three different tumor cell lines, colon cancer (CT26WT), metastatic skin melanoma (B16F10), mammary adenocarcinoma (4T1) and kidney normal cell (BHK-21). The gold complexes were more active than their respective free ligands and able to inhibit the thioredoxin reductase (TrxR) enzyme, even in the presence of albumin. Molecular modeling studies were carried out to understand the interaction between the compounds and the TrxR enzyme, considered as a potential target for new compounds in cancer treatment. The docking results show that the adamantane ring is essential to stabilize the ligand-enzyme complex prior the formation of covalent bond with gold center. The structure of the new gold compounds was established on the basis of spectroscopic data, DFT calculations and X-ray diffraction. TrxR inhibition was evaluated and the results correlated with the assays in tumor cells, suggesting the TrxR as possible target for these compounds.

In vitro and in vivo evaluation of organometallic gold(I) derivatives as anticancer agents

Alkyne gold(I) derivatives with the water soluble phosphanes PTA (1,3,5-triaza-7-phosphaadamantane) and DAPTA (3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane) were described and their anticancer potential against the colon cancer cell line Caco-2 (PD7 and TC7 clones) was studied. Strong antiproliferative effects are found, for all the new complexes, to be even more pronounced than for the reference drug cisplatin, and similar to auranofin. The interaction of these derivatives with bovine serum albumin (BSA) was studied by fluorescence spectroscopy. The types of quenching and binding constants were determined by a fluorescence quenching method. Moderate values of the binding constants are calculated for the tested derivatives indicating that these complexes can be stored and carried easily by this protein in the body. The study of the thermodynamic parameters in the case of [Au(C[triple bond, length as m-dash]CCH2Spyridine)(PTA)] points out to the presence of van der Waals interactions or hydrogen bonding between the metallic complex and the protein. In addition, the complex [Au(C[triple bond, length as m-dash]CCH2Spyridine)(PTA)] has shown inhibition in colon cancer proliferation of HTC-116-luc2 cell lines via the apoptotic pathway and S-phase arrest of the cell cycle. Intraperitoneal injection of this derivative in athymic nude mice inoculated with HTC-116-luc2 cells prolonged their survival and displayed moderate inhibition of the tumour growth with no subsequent organ (kidney and liver) damage after treatment.

Lipid-based nanoparticles containing cationic derivatives of PTA (1,3,5-triaza-7-phosphaadamantane) as innovative vehicle for Pt complexes: Production, characterization and in vitro studies

The aliphatic phosphine PTA (1,3,5-triaza-7-phosphaadamantane) is a promising ligand for metal complexes designed and developed as innovative inorganic drugs. In the present paper, an N-alkylated derivative of PTA, (PTAC16H33)X (X=I, C1, or X=PF6, C2) and its platinum coordination complex cis-[PtCl2(PTAC16H33)2](PF6)2, C3, were considered as components of cationic lipid nanoparticles (CLNs). Particularly, CLN1, CLN2 and CLN3 were obtained by adding derivatives C1, C2 or C3 during nanoparticles preparation, while CLN2-Pt were obtained by treating preformed CLN2 with Pt(II). It was demonstrated that CLN1, CLN2 and CLN3 can be produced with technological conventional methods. However, among the two here proposed protocols, the one based on the treatment of preformed nanoparticles appears more advantageous as compared to the other since it allows a quantitative association yield of Pt. As determined by ICP-OES, a content of P and Pt 2.2-fold and 2.5-fold higher in CLN2-Pt than in CLN3 was evidenced. For the first time was demonstrated that properly functionalized preformed nanoparticles can be efficiently used to obtain a post production Pt(II) complex while maintaining a cytotoxic activity toward cultured cells. In fact, the antiproliferative activity shown by CLN3, CLN2-Pt on the three model cancer cell lines was substantially similar and comparable to that of complex C3 in dmso solution. Thus N-alkylated-PTA derivatives in CLNs could be proposed as innovative biocompatible and water dispersible nanoparticles carrying lipophilic Pt complexes becoming an interesting and improved system with respect to dmso solution.

Copper(I) targeting in the Alzheimer's disease context: a first example using the biocompatible PTA ligand

Copper(I) coordinating ligands in the Alzheimer's disease context have remained unexplored, despite the biological relevance of this redox state of the copper ion. Here, we show that the PTA ligand can remove copper from Aβ, prevent reactive oxygen species production and oligomer formation, two deleterious events in the disease's etiology.