Unexplored features of Ru(ii) polypyridyl complexes - towards combined cytotoxic and antimetastatic activity

Design of an anticancer organoruthenium complex as the guest and polydiacetylene-coated fluorogenic nanocarrier as the host: engineering nanocarrier using ene-yne conjugation for sustained guest release, enhanced anticancer activity and reduced in vivo toxicity

Despite the enormous efforts made over the past two decades to develop metallodrugs and nanocarriers for metallodrug delivery, there are still few precise strategies that aim to optimize the design of both metallodrugs and metallodrug carriers jointly in a concerted effort. In this work, three half-sandwich ruthenium(II) complexes with pyridylimidazo[1,5-a]pyridine ligand functionalized with polycyclic aromatic moiety (Ru(nap), Ru(ant), Ru(pyr)) are evaluated as possible anticancer candidates and polydiacetylene (PDA)-coated amino-functionalized mesoporous silica nanoparticles (AMSNs) are designed as a functional nanocarrier for drug delivery. Ru(pyr) exhibits higher cytotoxicity in HT-29 colorectal cancer cells compared to other complexes and cis-platin, but it does not exhibit better cellular uptake. Ru(pyr) is found to be preferentially accumulated in plasma, mitochondria, and ER-Golgi membrane. The complex induces cell cycle arrest in the G0/G1 phase, while higher concentrations cause programmed cell death via apoptosis. Ru(pyr) influences cancer cell adhesion property and acts as an antioxidant in HT-29 cells. In order to modulate the anticancer potency of Ru(pyr), AMSNs are used to encapsulate the complex, and then diacetylene self-assembly is allowed to deposit on the surface of the nanoparticles. Subsequently, the nanoparticles undergo topopolymerization, which results in π-conjugated PDA-Ru(pyr)@AMSNs. Owing to the ene-yne polymeric skeleton in the backbone, the non-fluorescent AMSNs turn into red-emissive particles, which are exploited for cell imaging applications. The release profile analysis reveals that such a π-conjugated polymer prevents the premature release of the complex from porous silica nanoparticles with the accelerated release of the complex in an acidic medium compared to physiological conditions. The PDA gatekeepers have also been proven to enhance the cellular internalization of Ru(pyr) with slow continuous release from the nanoformulation. Zebrafish embryo toxicity analysis suggests that the PDA-coated nanocarriers could be suitable candidates for in vivo investigations.

Exploration of the Pharmacophore for Cytoskeletal Targeting Ruthenium Polypyridyl Complexes

Ruthenium(II) trisdiimine complexes of the formula, [Ru(dip)n (L-L)3-n ]2+ , where n=0-3; dip=4,7-diphenyl-1,10-phenanthroline; L-L=2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen) were prepared and tested for cytotoxicity in two cell lines (H358, MCF7). Cellular uptake and subcellular localization were determined by harvesting treated cells and determining the ruthenium concentration in whole or fractionated cells (cytosolic, nuclear, mitochondrial/ ER/Golgi, and cytoskeletal proteins) by Ru ICP-MS. The logP values for the chloride salts of these complexes were measured and the data were analyzed to determine the role of lipophilicity versus structure in the various biological assays. Cellular uptake increased with lipophilicity but shows the biggest jump when the complex contains two or more dip ligands. Significantly, preferential cytoskeletal localization is also correlated with increased cytotoxicity. All of the RPCs promote tubulin polymerization in vitro, but [Ru(dip)2 phen]2+ and [Ru(dip)3 ]2+ show the strongest activity. Analysis of the pellet formed by centrifugation of MTs formed in the presence of [Ru(dip)2 phen]2+ establish a binding stoichiometry of one RPC per tubulin heterodimer. Complexes of the general formula [Ru(dip)2 (L-L)]2+ possess the necessary characteristics to target the cytoskeleton in live cells and increase cytotoxicity, however the nature of the L-L ligand does influence the extent of the effect.

Carbohydrate effect of novel arene Ru(II) phenanthroline-glycoconjugates on metastatic biological processes

Novel water-soluble half-sandwich ruthenium(II) polypyridyl-glycoconjugates [Ru(p-cymene)Cl{N-(1,10-phenanthroline-5-yl)-β-glycopyranosylamine}][Cl] (glycopyranosyl = d-glucopyranosyl (1), D-mannopyranosyl (2), L-rhamnopyranosyl (3) and l-xylopyranosyl (4)) have been synthesized and fully characterized. Their behaviour in water under physiological conditions has been studied by nuclear magnetic resonance spectroscopy, revealing their hydrolytic stability. Interactions of the novel compounds with duplex-deoxiribonucleic acid (dsDNA) were investigated by different techniques and the results indicate that, under physiological pH and saline conditions, the metal glycoconjugates bind DNA in the minor groove and/or through external, electrostatic interactions, and by a non-classical, partial intercalation mechanism in non-saline phosphate buffered solution. Effects of compounds 1-4 on cell viability have been assessed in vitro against two human cell lines (androgen-independent prostate cancer PC-3 and non-tumorigenic prostate RWPE-1), showing moderate cytotoxicities, with IC50 values higher than those found for free ligands [N-(1,10-phenanthroline-5-yl)-β-glycopyranosylamine] (glycopyranosyl = d-glucopyranosyl (a), D-mannopyranosyl (b), L-rhamnopyranosyl (c) and l-xylopyranosyl (d)) or corresponding metal-aglycone. Cell viability was assayed in the presence and absence of the glucose transporters (GLUTs) inhibitor [N4-{1-(4-cyanobenzyl)-5-methyl-3-(trifluoromethyl)-1H-pyrazol-4-yl}-7-fluoroquinoline-2,4-dicarboxamide] (BAY-876), and the results point to a negligible impact of the inhibition of GLUTs on the cytotoxicity caused by Ru(II) compounds 1-4. Remarkably, glycoconjugates 1-4 potently affect the migration pattern of PC-3 cells, and the wound healing assay evidence that the presence of the carbohydrate and the Ru(II) center is a requisite for the anti-migratory activity observed in these novel derivatives. In addition, derivatives 1-4 strongly affect the matrix metalloproteinase MMP-9 activities of PC-3 cells, while proMMP-2 and especially proMMP-9 were influenced to a much lesser extent.

New ruthenium(II) complexes with cyclic thio- and semicarbazone: evaluation of cytotoxicity and effects on cell migration and apoptosis of lung cancer cells

We describe the synthesis, physicochemical characterization, and in vitro antitumor assays of four novel analogous ruthenium(II) complexes with general formula cis-[Ru^II(N-L)(P-P)₂]PF₆, where P-P = bis(diphenylphosphine)methane (dppm, in complexes 1 and 2) or bis(diphenylphosphine)ethane (dppe, in complexes 3 and 4) and N-L = 5,6-diphenyl-4,5-dihydro-2H-[1,2,4]triazine-3-thione (Btsc, in complexes 1 and 3) or 5,6-diphenyltriazine-3-one (Bsc, in complexes 2 and 4). The data were consistent with cis arrangement of the biphosphine ligands. For the Btsc and Bsc ligands, the data pointed to monoanionic bidentate coordination to ruthenium(II) through N,S and N,O, respectively. Single-crystal X-ray diffraction showed that complex 1 crystallized in the monoclinic system, space group P2₁/c. Determination of the cytotoxicity profiles of complexes 1-4 gave SI values ranging from 1.19 to 3.50 against the human lung adenocarcinoma cell line A549 and the non-tumor lung cell line MRC-5. Although the molecular docking studies suggested that the interaction between DNA and complex 4 was energetically favorable, the experimental results showed that they interacted weakly. Overall, our results demonstrated that these novel ruthenium(II) complexes have interesting in vitro antitumor potential and this study may contribute to further studies in medicinal inorganic chemistry.

Cytotoxicity and mechanism of action of metal complexes: An overview

After the discovery of cisplatin, many metal compounds were investigated for the therapy of diseases, especially cancer. The high therapeutic potential of metal-based compounds is related to the special properties of these compounds, such as their redox activity and ability to target vital biological sites. The overproduction of ROS and the consequent destruction of the membrane potential of mitochondria and/or the DNA helix is one of the known pathways leading to the induction of apoptosis by metal complexes. The apoptosis process can occur via the death receptor pathway and/or the mitochondrial pathway. The expression of Bcl2 proteins and the caspase family play critical roles in these pathways. In addition to apoptosis, autophagy is another process that regulates the suppression or promotion of various cancers through a dual action. On the other hand, the ability to interact with DNA is an important property found in several metal complexes with potent antiproliferative effects against cancer cells. These interactions were classified into two important categories: covalent/coordinated or subtle, and non-coordinated interactions. The anticancer activity of metal complexes is sometimes achieved by the simultaneous combination of several mechanisms. In this review, the anticancer effect of metal complexes is mechanistically discussed by different pathways, and some effective agents on their antiproliferative properties are explained.

Metal Complexes as Promising Matrix Metalloproteinases Regulators

Nowadays, cancers and dementia, such as Alzheimer's disease, are the most fatal causes of death. Many studies tried to understand the pathogenesis of those diseases clearly and develop a promising way to treat the diseases. Matrix metalloproteinases (MMPs) have been reported to be involved in the pathology of cancers and AD through tumor cell movement and amyloid degradation. Therefore, control of the levels and actions of MMPs, especially MMP-2 and MMP-9, is necessary to care for and/or cure cancer and AD. Various molecules have been examined for their potential application as regulators of MMPs expression and activity. Among the molecules, multiple metal complexes have shown advantages, including simple synthesis, less toxicity and specificity toward MMPs in cancer cells or in the brain. In this review, we summarize the recent studies and knowledge of metal complexes (e.g., Pt-, Ru-, Au-, Fe-, Cu-, Ni-, Zn-, and Sn-complexes) targeting MMPs and their potentials for treating and/or caring the most fatal human diseases, cancers and AD.

Ruthenium(II) Polypyridyl Complexes Containing Simple Dioxo Ligands: a Structure-Activity Relationship Study Shows the Importance of the Charge

Cancer is one of the main causes of death worldwide. Platinum complexes (i. e., cisplatin, carboplatin, and others) are currently heavily used for the treatment of different types of cancer, but unwanted effects occur. Ruthenium complexes have been shown to be potential promising alternatives to these metal-based drugs. In this work, we performed a structure-activity relationship (SAR) study on two small series of Ru(II) polypyridyl complexes of the type [Ru(L1)₂ (O^O)]Cl_n (3-8), where L1 is 4,7-diphenyl-1,10-phenantroline (DIP) or 1,10-phenantroline (phen), and O^O is a symmetrical anionic dioxo ligand: oxalate (ox, n=0), malonate (mal, n=0), or acetylacetonate (acac, n=1). These two self-consistent series of compounds allowed us to perform a systematic investigation for establishing how the nature of the ligands and the charge affect the anticancer properties of the complexes. Cytotoxicity tests on different cell lines demonstrated that some of the six compounds 3-8 have a promising anticancer activity. More specifically, the cationic complex [Ru(DIP)₂ (η² -acac)]Cl (4) has IC₅₀ values in the mid-nanomolar concentration range, lower than those of cisplatin on the same cell lines. Interestingly, [Ru(DIP)₂ (η² -acac)]Cl was found to localize mainly in the mitochondria, whereas a smaller fraction was detected in the nucleus. Overall, our SAR investigation demonstrates the importance of combining the positive charge of the complex with the highly lipophilic diimine ligand DIP.

Inhibition of Metastasis by Polypyridyl Ru(II) Complexes through Modification of Cancer Cell Adhesion - In Vitro Functional and Molecular Studies

The effect of polypyridyl Ru(II) complexes on the ability of cancer cells to migrate and invade, two features important in the formation of metastases, is evaluated. In vitro studies are carried out on breast cancer cell lines, MDA-MB-231 and MCF-7, as well as melanoma cell lines A2058 and A375. Three Ru(II) complexes comprising two 4,7-diphenyl-1,10-phenanthroline (dip) ligands and as a third ligand 2,2′-bipyridine (bpy), or its derivative with either 4-[3-(2-nitro-1H-imidazol-1-yl)propyl] (bpy-NitroIm), or 5-(4-{4′-methyl-[2,2′-bipyridine]-4-yl}but-1-yn-1-yl)pyridine-2-carbaldehyde semicarbazone (bpy-SC) moiety attached are examined. The low sub-toxic doses of the studied compounds greatly affected the cancer cells by inhibiting cell detachment, migration, invasion, transmigration, and re-adhesion, as well as increasing cell elasticity. The molecular studies revealed that the Ru(II) polypyridyl complexes impact the activity of the selected integrins and upregulate the expression of focal adhesion components such as vinculin and paxillin, leading to an increased number of focal adhesion contacts.

Impact of Polypyridyl Ru Complexes on Angiogenesis—Contribution to Their Antimetastatic Activity

The use of polypyridyl Ru complexes to inhibit metastasis is a novel approach, and recent studies have shown promising results. We have reported recently that Ru (II) complexes gathering two 4,7-diphenyl-1,10-phenanthroline (dip) ligands and the one being 2,2′-bipyridine (bpy) or its derivative with a 4-[3-(2-nitro-1H-imidazol-1-yl)propyl (bpy-NitroIm) or 5-(4-{4′-methyl-[2,2′-bipyridine]-4-yl}but-1-yn-1-yl)pyridine-2-carbaldehyde semicarbazone (bpy-SC) moieties can alter the metastatic cascade, among others, by modulating cell adhesion properties. In this work, we show further studies of this group of complexes by evaluating their effect on HMEC-1 endothelial cells. While all the tested complexes significantly inhibited the endothelial cell migration, Ru-bpy additionally interrupted the pseudovessels formation. Functional changes in endothelial cells might arise from the impact of the studied compounds on cell elasticity and expression of proteins (vinculin and paxillin) involved in focal adhesions. Furthermore, molecular studies showed that complexes modulate the expression of cell adhesion molecules, which has been suggested to be one of the factors that mediate the activation of angiogenesis. Based on the performed studies, we can conclude that the investigated polypyridyl Ru (II) complexes can deregulate the functionality of endothelial cells which may lead to the inhibition of angiogenesis.

Relevance of the electron transfer pathway in photodynamic activity of Ru(II) polypyridyl complexes containing 4,7-diphenyl-1,10-phenanthroline ligands under normoxic and hypoxic conditions

The purpose of this study was to investigate the correlation between the spectroscopic and photophysical properties of Ru(II) polypyridyl complexes and their photodynamic activity in vitro. A series of Ru(II) polypyridyl complexes with 4,7-diphenyl-1,10-phenanthroline (dip) and 2,3-bis(2-pyridyl)quinoxaline (dpq) and its derivatives were synthesized and characterized regarding their photophysical, biological, and photodynamic properties. The complexes were evaluated not only in the context of ¹O₂ generation but also regarding other types of reactive oxygen species (ROS) to assess the possibility of Ru(II) complexes to induce phototoxicity via various ROS using fluorescence and EPR spectroscopy. The compounds were found to be moderately cytotoxic with IC₅₀ values ranging from 1 to 35 μM and retained their cytotoxic activity under hypoxic conditions. The unraveled phototoxic activity is based mainly on the generation of H₂O₂ and ¹O₂, highlighting the importance of electron-transfer processes in the observed photodynamic activity of Ru polypyridyl complexes. A combination of photodynamic activity with cytotoxicity under decreased dioxygen concentrations may help overcome the current photodynamic therapy (PDT) limitation. The findings highlight the need for broadening the scope of tested Ru-based photosensitizers.

Ruthenium(ii)-arene complexes as anti-metastatic agents, and related techniques

With the discovery of cisplatin, a vast area of applications of metallodrugs in cancer treatment was opened but due to the side effects caused by the cisplatin complexes, researchers began to look for alternatives with similar anticancer properties but fewer side effects. Ruthenium was found to be a promising candidate, considering its significant anticancer properties and low side effects. Several ruthenium complexes, viz. NAMI-A, KP1019, KP1339, and TLD1433, have entered clinical trials. Some other arene ruthenium complexes such as RM175 and RAPTA-C have also entered clinical trials but very few of them have shown anti-metastatic properties. Herein, we provide information and probable mechanistic pathways for ruthenium(ii)-arene complexes that have been studied, so far, for their anti-metastatic activities. Also, we discuss the techniques and their significance for determining the anti-metastatic effects of the complexes.

Moving Ru polypyridyl complexes beyond cytotoxic activity towards metastasis inhibition

In recent years, Ru polypyridyl complexes have been intensively studied for their anticancer activity. The vast majority of research focuses on assessing their cytotoxic activity, as well as targeting cancer cells with them. Since the formation of metastases poses a greater risk than primary tumors, scientists recently began evaluating these compounds as potential metastasis inhibitors. This review highlights the latest achievements in this field with particular attention to the identification of the target proteins responsible for such activity. Cell migration, invasion, and adhesion are key components of metastasis, therefore understanding how they are affected by Ru polypyridyl complexes is of great importance. KEYWORDS: Ruthenium polypyridyl complexes Antimetastatic Migration Invasion Adhesion Metalloproteinases.

Inhibition of Matrix Metalloproteinases and Cancer Cell Detachment by Ru(II) Polypyridyl Complexes Containing 4,7-Diphenyl-1,10-phenanthroline Ligands-New Candidates for Antimetastatic Agents

Primary tumor targeting is the dominant approach in drug development, while metastasis is the leading cause of cancer death. Therefore, in addition to the cytotoxic activity of a series of Ru(II) polypyridyl complexes of the type [Ru(dip)₂L]²⁺ (dip: 4,7-diphenyl-1,10-phenanthroline while L = dip; bpy: 2,2′-bipyridine; bpy-SC: bipyridine derivative bearing a semicarbazone 2-formylopyridine moiety; dpq, dpq(CH₃)₂, dpb: quinoxaline derivatives) their ability to inhibit cell detachment was investigated. In vitro studies performed on lung cancer A549 cells showed that they accumulate in cells very well and exhibit moderate cytotoxicity with IC₅₀ ranging from 4 to 13 µM. Three of the studied compounds that have dip, bpy-SC, or dpb ligands after treatment of the cells with a non-toxic dose (<¹/₂IC₅₀) enhanced their adhesion properties demonstrated by lower detachment in the trypsin resistance assay. The same complexes inhibited both MMP-2 and MMP-9 enzyme activities with IC₅₀ ranging from 2 to 12 µM; however, the MMP-9 inhibition was stronger. More detailed studies for [Ru(dip)₂(bpy-SC)]²⁺, which induced the greatest increase in cell adhesion, revealed that it is predominately accumulated in the cytoskeletal fraction of A549 cells. Moreover, cells treated with this compound showed the localization of MMP-9 to a greater extent also in the cytoskeleton. Taken together, our results indicate the possibility of a reduction of metastatic cells escaping from the primary lesion to the surrounding tissue by prevention of their detachment and by influencing the activity of MMP-2 and MMP-9.

Ruthenium Complexes as Promising Candidates against Lung Cancer

Lung cancer is one of the most common malignancies with the highest mortality rate and the second-highest incidence rate after breast cancer, posing a serious threat to human health. The accidental discovery of the antitumor properties of cisplatin in the early 1960s aroused a growing interest in metal-based compounds for cancer treatment. However, the clinical application of cisplatin is limited by serious side effects and drug resistance. Therefore, other transition metal complexes have been developed for the treatment of different malignant cancers. Among them, Ru(II/III)-based complexes have emerged as promising anticancer drug candidates due to their potential anticancer properties and selective cytotoxic activity. In this review, we summarized the latest developments of Ru(II/III) complexes against lung cancer, focusing mainly on the mechanisms of their biological activities, including induction of apoptosis, necroptosis, autophagy, cell cycle arrest, inhibition of cell proliferation, and invasion and metastasis of lung cancer cells.

Bifunctional ruthenium(ii) polypyridyl complexes of curcumin as potential anticancer agents

Ru(ii)-polypyridyl complexes have been widely studied and well established for their antitumor properties. Modifications of the coordination environment around the Ru atom through a proper choice of the ligand can lead to different modes of action and result in greatly improved anticancer efficacy. Herein, two Ru(ii)-polypyridyl complexes of curcumin were synthesized and characterized as potential anticancer agents. In vitro tests indicated that complexes 1 and 2 displayed excellent antiproliferative activity against the tested cancer cell lines, especially complex 2, which exhibited superior cytotoxicity compared to curcumin and cisplatin. Further biological evaluations demonstrated that complexes 1 and 2 can cause cell apoptosis via DNA interaction and MEK/ERK signaling pathway, which is the first example of a Ru(ii)-polypyridyl complex inhibiting the MEK/ERK signaling pathway and DNA intercalation. Overall, this work suggests that coordination with bioactive agents may endow Ru(ii)-polypyridyl complexes with improved pharmaceutical properties and synergistic effects for cancer therapy.