Induction of caspase 8 and reactive oxygen species by ruthenium-derived anticancer compounds with improved water solubility and cytotoxicity

The unfolded protein response-glutathione metabolism axis: A novel target of a cycloruthenated complexes bypassing tumor resistance mechanisms

Platinum-based drugs remain the reference treatment for gastric cancer (GC). However, the frequency of resistance, due to mutations in TP53 or alterations in the energy and redox metabolisms, impairs the efficacy of current treatments, highlighting the need for alternative therapeutic options. Here, we show that a cycloruthenated compound targeting the redox metabolism, RDC11, induces higher cytotoxicity than oxaliplatin in GC cells and is more potent in reducing tumor growth in vivo. Detailed investigations into the mode of action of RDC11 indicated that it targets the glutathione (GSH) metabolism, which is an important drug resistance mechanism. We demonstrate that cycloruthenated complexes regulate the expression of enzymes of the transsulfuration pathway via the Unfolded Protein Response (UPR) and its effector ATF4. Furthermore, RDC11 induces the expression of SLC7A11 encoding for the cystine/glutamate antiporter xCT. These effects lead to a lower cellular GSH content and elevated oxygen reactive species production, causing the activation of a caspase-independent apoptosis. Altogether, this study provides the first evidence that cycloruthenated complexes target the GSH metabolism, neutralizing thereby a major resistance mechanism towards platinum-based chemotherapies and anticancer immune response.

3D-Shaped Binders of Unfolded Proteins Inducing Cancer Cell-Specific Endoplasmic Reticulum Stress In Vitro and In Vivo

The amount of unfolded proteins is increased in cancer cells, leading to endoplasmic reticulum (ER) stress. Therefore, cancer cells are sensitive to drugs capable of further enhancing ER stress. Examples of such drugs include the clinically approved proteosome inhibitors bortezomib and carfilzomib. Unfortunately, the known ER stress inducers exhibit dose-limiting side effects that justify the search for better, more cancer-specific drugs of this type. Herein, we report on FeC 2, which binds to unfolded proteins prevents their further processing, thereby leading to ER stress and ROS increase in cancer cells, but not in normal cells. FeC 2 exhibits low micromolar toxicity toward human acute promyelocytic leukemia HL-60, Burkitt's lymphoma BL-2, T-cell leukemia Jurkat, ovarian carcinoma A2780, lung cancer SK-MES-1, and murine lung cancer LLC1 cells. Due to the cancer-specific mode of action, 2 is not toxic in vivo up to the dose of 147 mg/kg, does not affect normal blood and bone marrow cells at the therapeutically active dose, but strongly suppresses both primary tumor growth (confirmed in Nemeth-Kellner lymphoma and LLC1 lung cancer models of murine tumor) and spreading of metastases (LLC1).

Organometallic Ru, Os, Rh and Ir half-sandwich conjugates of ispinesib - impact of the organometallic group on the antimitotic activity

Antimitotic agents are among the most important drugs used in anticancer therapy. Kinesin spindle protein (KSP) was proposed as a promising target for new antimitotic drugs. Herein, we report the synthesis of Ru, Os, Rh, and Ir half-sandwich complexes with the KSP inhibitor ispinesib and its (S)-enantiomer. Conjugation of the organometallic moiety with ispinesib and its (S)-enantiomer resulted in a significantly increased cytotoxicity of up to 5.6-fold compared to the parent compounds, with IC50 values in the nanomolar range. The most active derivatives were the ispinesib Ru and Rh conjugates which were able to generate reactive oxygen species (ROS), which may at least partially explain their high cytotoxicity. At the same time, the Os and Ir derivatives acted as KSP inhibitors with no effects on ROS generation.

ER Stress Response and Induction of Apoptosis in Malignant Pleural Mesothelioma: The Achilles Heel Targeted by the Anticancer Ruthenium Drug BOLD-100

Simple Summary

Malignant mesothelioma is a rare cancer arising from the serosal surfaces of the body, mainly from the pleural layer. This cancer, strongly linked to asbestos exposure, shows a very inauspicious prognosis. In fact, there is no efficient therapeutic treatment for malignant pleural mesothelioma (MPM). Thus, there is an urgent need to develop novel therapeutic approaches to treat this form of cancer. Our previous study showed the importance of GRP78 in MPM survival. BOLD-100 is a specific modulator of GRP78 and we have observed that it shows cytotoxicity against MPM cells. In particular, we describe that BOLD-100 increases oxidative stress and deregulates the calcium homeostasis leading to cell stress and, ultimately, to cell death. Our in vitro data strongly suggest that BOLD-100 inhibits the growth of MPM cell lines, proposing the application as a single agent, or in combination with other standard-of-care drugs, to treat MPM.

Abstract

Malignant mesothelioma is a rare cancer arising from the serosal surfaces of the body, mainly from the pleural layer. This cancer is strongly related to asbestos exposure and shows a very inauspicious prognosis, because there are scarce therapeutic options for this rare disease. Thus, there is an urgent need to develop novel therapeutic approaches to treat this form of cancer. To explore the biology of malignant pleural mesothelioma (MPM), we previously observed that MPM cell lines show high expression of the GRP78 protein, which is a chaperone protein and the master regulator of the unfolded protein response (UPR) that resides in the endoplasmic reticulum (ER). Based on our previous studies showing the importance of GRP78 in MPM, we observed that BOLD-100, a specific modulator of GRP78 and the UPR, shows cytotoxicity against MPM cells. Our studies demonstrated that BOLD-100 increases ROS production and Ca²⁺ release from the ER, leading to ER stress activation and, ultimately, to cell death. Our in vitro data strongly suggest that BOLD-100 inhibits the growth of MPM cell lines, proposing the application as a single agent, or in combination with other standard-of-care drugs, to treat MPM.

Bypassing the Resistance Mechanisms of the Tumor Ecosystem by Targeting the Endoplasmic Reticulum Stress Pathway Using Ruthenium- and Osmium-Based Organometallic Compounds: An Exciting Long-Term Collaboration with Dr. Michel Pfeffer

Metal complexes have been used to treat cancer since the discovery of cisplatin and its interaction with DNA in the 1960’s. Facing the resistance mechanisms against platinum salts and their side effects, safer therapeutic approaches have been sought through other metals, including ruthenium. In the early 2000s, Michel Pfeffer and his collaborators started to investigate the biological activity of organo-ruthenium/osmium complexes, demonstrating their ability to interfere with the activity of purified redox enzymes. Then, they discovered that these organo-ruthenium/osmium complexes could act independently of DNA damage and bypass the requirement for the tumor suppressor gene TP53 to induce the endoplasmic reticulum (ER) stress pathway, which is an original cell death pathway. They showed that other types of ruthenium complexes—as well complexes with other metals (osmium, iron, platinum)—can induce this pathway as well. They also demonstrated that ruthenium complexes accumulate in the ER after entering the cell using passive and active mechanisms. These particular physico-chemical properties of the organometallic complexes designed by Dr. Pfeffer contribute to their ability to reduce tumor growth and angiogenesis. Taken together, the pioneering work of Dr. Michel Pfeffer over his career provides us with a legacy that we have yet to fully embrace.

Light activation of cyclometalated ruthenium complexes drives towards caspase 3 dependent apoptosis in gastric cancer cells

Polypyridyl ruthenium complexes have been intensively investigated for their remarkable antiproliferative properties and some are currently being tested in clinical trials. Here, we investigated the impact of illumination on the biological properties of a series of new cyclometalated ruthenium compounds with increased π-conjugation. We determined that various of these complexes display a bivalent biological activity as they are highly cytotoxic by themselves in absence of light while their cytotoxicity can significantly be elevated towards an IC₅₀ in the nanomolar range upon illumination. In particular, we showed that these complexes are particularly active (IC₅₀ < 1 μM) on two gastric cancer cell lines (AGS, KATO III) that are resistant towards cisplatin (IC₅₀ > 25 μM). As expected, light activation leads to increased production of singlet oxygen species in vitro and accumulation of reactive oxygen species in vivo. Importantly, we established that light exposure shifts the mode of action of the complexes towards activation of a caspase 3-dependent apoptosis that correlates with increased DNA damage. Altogether, this study characterizes novel ruthenium complexes with dual activity that can be tuned towards different mode of action in order to bypass cancer cell resistance mechanisms.

Photostable NIR emitting ruthenium(II) conjugates; uptake and biological activity in live cells

A photostable Ru(2,2-biquinoline)₂(3-(2-pyridyl)-5-(4-carboxyphenyl)-1,2,4-triazolate) (Ru(biq)₂(trzbenzCOOH)) complex that exhibits near-infrared (NIR) emission centred at 786 nm is reported. The parent complex was conjugated via amide coupling to a cell-penetrating peptide sequence octa-arginine (R8), and two signal peptide sequences; the nuclear localizing sequence (NLS) VQRKRQKLMP and the mitochondria penetrating peptide (MPP) FrFKFrFK(Ac) (r = D isomer of arginine, Ac = terminal lysine amine acetyl blocked). Notably, none of the peptide conjugates were cell-permeable as chloride salts but efficient and rapid membrane permeation was observed post ion exchange with perchlorate counterion. Also, surprisingly, all three peptide conjugates exhibited potent dark cytotoxicity in both CHO and HeLa cell lines. The peptide conjugates induce cell death through a caspase dependent apoptotic pathway. At the minimum concentration of dye (approx. 15 μM) required for cell imaging, only 20% of the cells were viable after a 24 h incubation period. To overcome cytotoxicity, the parent complex was PEGylated; this dramatically decreased cytotoxicity, where 50% of cells were viable even at 150 μM concentration after 24 h. Confocal luminescence microscopy indicated that all four bioconjugates, peptides in perchlorate form and polyethylene glycol (PEG) in chloride form, were rapidly internalized within the cell. However, interestingly the precise localisation by the signal peptides observed in related complexes was not observed here and the peptide conjugates were unsuitable as luminescent probes for cell microscopy due to their high cell toxicity. The poor targeting of signal peptides in this instance is attributed to the high lipophilicity of the metal centre.

Anticancer activity of ruthenium and osmium cyclometalated compounds: identification of ABCB1 and EGFR as resistance mechanisms

Switching from ruthenium to osmium reduces sensitivity towards ABCB1 resistance for cyclometalated anticancer drugs.

Endoplasmic reticulum stress: an arising target for metal-based anticancer agents

Metal anticancer agents are rapidly emerging as selective, potent therapeutics that exhibit anticancer activity by inducing endoplasmic reticulum stress.

HDAC4 Levels Control Sensibility toward Cisplatin in Gastric Cancer via the p53-p73/BIK Pathway

Gastric cancer (GC) remains a health issue due to the low efficiency of therapies, such as cisplatin. This unsatisfactory situation highlights the necessity of finding factors impacting GC sensibility to therapies. We analyzed the cisplatin pangenomic response in cancer cells and found HDAC4 as a major epigenetic regulator being inhibited. HDAC4 mRNA repression was partly mediated by the cisplatin-induced expression of miR-140. At a functional level, HDAC4 inhibition favored cisplatin cytotoxicity and reduced tumor growth. Inversely, overexpression of HDAC4 inhibits cisplatin cytotoxicity. Importantly, HDAC4 expression was found to be elevated in gastric tumors compared to healthy tissues, and in particular in specific molecular subgroups. Furthermore, mutations in HDAC4 correlate with good prognosis. Pathway analysis of genes whose expression in patients correlated strongly with HDAC4 highlighted DNA damage, p53 stabilization, and apoptosis as processes downregulated by HDAC4. This was further confirmed by silencing of HDAC4, which favored cisplatin-induced apoptosis characterized by cleavage of caspase 3 and induction of proapoptotic genes, such as BIK, in part via a p53-dependent mechanism. Altogether, these results reveal HDAC4 as a resistance factor for cisplatin in GC cells that impacts on patients' survival.

The Growing Development of DNA Nanostructures for Potential Healthcare-Related Applications

DNA self-assembly has proven to be a highly versatile tool for engineering complex and dynamic biocompatible nanostructures from the bottom up with a wide range of potential bioapplications currently being pursued. Primary among these is healthcare, with the goal of developing diagnostic, imaging, and drug delivery devices along with combinatorial theranostic devices. The path to understanding a role for DNA nanotechnology in biomedical sciences is being approached carefully and systematically, starting from analyzing the stability and immune-stimulatory properties of DNA nanostructures in physiological conditions, to estimating their accessibility and application inside cellular and model animal systems. Much remains to be uncovered but the field continues to show promising results toward developing useful biomedical devices. This review discusses some aspects of DNA nanotechnology that makes it a favorable ingredient for creating nanoscale research and biomedical devices and looks at experiments undertaken to determine its stability in vivo. This is presented in conjugation with examples of state-of-the-art developments in biomolecular sensing, imaging, and drug delivery. Finally, some of the major challenges that warrant the attention of the scientific community are highlighted, in order to advance the field into clinically relevant applications.

Anti-cancer organoruthenium(ii) complexes and their interactions with cysteine and its analogues. A mass-spectrometric study

The ruthenium complexes [Ru(CYM)(p-Cl-dkt)(Cl)] (1), [Ru(CYM)(pta)(p-Cl-dkt)]PF₆ (2), and [Ru(CYM)(pta)Cl₂] (3, RAPTA-C) (CYM = para-cymene, p-Cl-dkt = 1-(4-chlorophenyl)-4,4,4-trifluorobutane-1,3-dione, pta = 1,3,5-triaza-7-phosphaadamantane) are biologically active and show anti-cancer activities, albeit with different mechanisms. To further understand these mechanisms, we compared their speciation in aqueous solutions with an amino acid (cysteine), with an amino acid derivative (N-acetylcysteine) and with a tripeptide (glutathione) by Mass Spectrometry (MS). Here, we show that all ruthenium complexes have high selectivity for cysteine and cysteine-derived molecules. On one hand, [Ru(CYM)(p-Cl-dkt)(Cl)] undergoes solvolysis in water and forms [Ru₂(CYM)₂(OH)₃]⁺. Subsequently, all hydroxyl anions are exchanged by deprotonated cysteine. Infrared Photodissociation Spectroscopy (IRPD) showed that cysteine binds to the ruthenium atoms via the deprotonated thiol group and that sulfur bridges the ruthenium centers. On the other hand, the pta-bearing complexes remain monometallic and undergo only slow Cl or p-Cl-dkt exchange by deprotonated cysteine. Therefore, the pta ligand protects the ruthenium complexes from ligand exchange with water and from the formation of biruthenium clusters, possibly explaining why the mechanism of pta-bearing ruthenium complexes is not based on ROS production but on their reactivity as monometallic complexes.

ESI-MS study of ruthenium complexes shows their high selectivity toward thiol containing molecules and formation of larger thiolate-bound clusters in absence of a protecting ligand such as pta.

Induction of the Endoplasmic Reticulum Stress Pathway by Highly Cytotoxic Organoruthenium Schiff-Base Complexes

Current anticancer drug discovery efforts focus on the identification of first-in-class compounds with a mode-of-action distinct from conventional DNA-targeting agents for chemotherapy. An emerging trend is the identification of endoplasmic reticulum (ER) targeting compounds that induce ER stress in cancer cells, leading to cell death. However, a limited pool of such compounds has been identified to date, and there are limited studies done on such compounds to allow for the rational design of ER stress-inducing agents. In our present study, we present a series of highly cytotoxic, ER stress-inducing Ru(II)-arene Schiff-Base (RAS) complexes, bearing iminoquinoline chelate ligands. We demonstrate that by structural modification to the iminoquinoline ligand, we could tune its π-acidity and influence reactive oxygen species (ROS) induction, switching between a ROS-mediated ER stress pathway activation and one that is not mediated by ROS induction. Our current study adds to the available ER stress inducers and shows how structural tuning could be used as a means to modulate the mode-of-action of such compounds.

A ruthenium anticancer compound interacts with histones and impacts differently on epigenetic and death pathways compared to cisplatin

Ruthenium complexes are considered as potential replacements for platinum compounds in oncotherapy. Their clinical development is handicapped by a lack of consensus on their mode of action. In this study, we identify three histones (H3.1, H2A, H2B) as possible targets for an anticancer redox organoruthenium compound (RDC11). Using purified histones, we confirmed an interaction between the ruthenium complex and histones that impacted on histone complex formation. A comparative study of the ruthenium complex versus cisplatin showed differential epigenetic modifications on histone H3 that correlated with differential expression of histone deacetylase (HDAC) genes. We then characterized the impact of these epigenetic modifications on signaling pathways employing a transcriptomic approach. Clustering analyses showed gene expression signatures specific for cisplatin (42%) and for the ruthenium complex (30%). Signaling pathway analyses pointed to specificities distinguishing the ruthenium complex from cisplatin. For instance, cisplatin triggered preferentially p53 and folate biosynthesis while the ruthenium complex induced endoplasmic reticulum stress and trans-sulfuration pathways. To further understand the role of HDACs in these regulations, we used suberanilohydroxamic acid (SAHA) and showed that it synergized with cisplatin cytotoxicity while antagonizing the ruthenium complex activity. This study provides critical information for the characterization of signaling pathways differentiating both compounds, in particular, by the identification of a non-DNA direct target for an organoruthenium complex.

Sensitivity towards the GRP78 inhibitor KP1339/IT-139 is characterized by apoptosis induction via caspase 8 upon disruption of ER homeostasis

The ruthenium drug and GRP78 inhibitor KP1339/IT-139 has already demonstrated promising anticancer activity in a phase I clinical trial. This study aimed to identify mechanisms underlying increased sensitivity to KP1339 treatment. Based on a screen utilizing 23 cell lines, a small panel was selected to compare KP1339-sensitive and low-responsive models. KP1339 sensitivity was neither based on differences in ruthenium accumulation, nor sensitivity to oxidative stress or constituents of KP1339 (ruthenium chloride and indazole). Subsequently, the biochemical response to KP1339 was analyzed using whole genome expression arrays indicating that, while sensitive cell lines were characterized by "response to chemical stimuli" and "regulation of cell death", low-responsive cells preferentially activated pathways controlling cell cycle, DNA repair, and metabolism. Cell culture experiments confirmed that, while low-responsive cells executed cell cycle arrest in G2 phase, pronounced apoptosis induction via activation of caspase 8 was found in sensitive cells. Cell death induction is based on a unique disruption of the ER homeostasis by depletion of key cellular chaperones including GRP78 in combination with enhanced KP1339-mediated protein damage.

Recent developments in the nanostructured materials functionalized with ruthenium complexes for targeted drug delivery to tumors

In recent years, the field of metal-based drugs has been dominated by other existing precious metal drugs, and many researchers have focused their attention on the synthesis of various ruthenium (Ru) complexes due to their potential medical and pharmaceutical applications. The beneficial properties of Ru, which make it a highly promising therapeutic agent, include its variable oxidation states, low toxicity, high selectivity for diseased cells, ligand exchange properties, and the ability to mimic iron binding to biomolecules. In addition, Ru complexes have favorable adsorption properties, along with excellent photochemical and photophysical properties, which make them promising tools for photodynamic therapy. At present, nanostructured materials functionalized with Ru complexes have become an efficient way to administer Ru-based anticancer drugs for cancer treatment. In this review, the recent developments in the nanostructured materials functionalized with Ru complexes for targeted drug delivery to tumors are discussed. In addition, information on "traditional" (ie, non-nanostructured) Ru-based cancer therapies is included in a precise manner.

Impact of cyclometalated ruthenium(II) complexes on lactate dehydrogenase activity and cytotoxicity in gastric and colon cancer cells

Lactate dehydrogenase (LDH) is a redox enzyme often overexpressed in cancer cells allowing their survival in stressful metabolic tumor environment. Ruthenium(II) complexes have been shown to impact on the activity of purified horseradish peroxidase and glucose oxidase but the physiological relevance remains unclear. In this study we investigated how ruthenium complexes impact on the activity of LDH in vitro and in cancer cells and performed a comparative study using polypyridine ruthenium(II) complex [Ru(bpy)₃]²⁺ (1) and its structurally related cyclometalated 2-phenylpyridinato counterpart [Ru(phpy)(bpy)₂]⁺ (2) (bpy=2,2'-bipyridine, phpyH=2-phenylpyridine). We show that the cytotoxicity in gastric and colon cancer cells induced by 2 is significantly higher compared to 1. The kinetic inhibition mechanisms on purified LDH and the corresponding inhibition constants K_i or i_0.5 values were calculated. Though complexes 1 and 2 are structurally very similar (one Ru-C bond in 2 replaces one Ru-N bond in 1), their inhibition modes are different. Cyclometalated complex 2 behaves exclusively as a non-competitive inhibitor of LDH from rabbit muscle (LDH_rm), strongly suggesting that 2 does not interact with LDH in the vicinities of either lactate/pyruvate or NAD⁺/NADH binding sites. Sites of interaction of 1 and 2 with LDH_rm were revealed theoretically through computational molecular docking. Inhibition of LDH activity by 2 was confirmed in cancer cells. Altogether, these results revealed an inhibition of LDH activity by ruthenium complex through a direct interaction structurally tuned by a Ru-C bond.

Structural tuning of organoruthenium compounds allows oxidative switch to control ER stress pathways and bypass multidrug resistance

Multidrug resistance (MDR) is a major impediment to the success of chemotherapy in many cancer types. One particular MDR mechanism is the inherent or acquired adaptation of the cellular survival pathways that render malignant cells resistant to apoptotic cell death. Since most drugs act through apoptosis, compounds capable of inducing alternative forms of programmed cell death (PCD) can potentially be harnessed to bypass MDR. We investigated two organoruthenium complexes, RAS-1H and RAS-1T, and demonstrated that although they both induced non-apoptotic PCD through ER stress pathways, their modes-of-action were drastically different despite modest structural variations. RAS-1T acted through ROS-mediated ER stress while RAS-1H was ROS-independent. We further showed that they were more efficacious against apoptosis-resistant cells compared to clinical drugs including oxaliplatin. This work provides the basis for underpinning ER stress modulation using metal complexes to bypass apoptosis resistance.

A multifunctional DNA origami as carrier of metal complexes to achieve enhanced tumoral delivery and nullified systemic toxicity

The use of metal complexes in cancer treatment is hampered by the insufficient accumulation in tumor regions and observable systemic toxicity due to their nonspecificity in vivo. Herein we present a cancer-targeted DNA origami as biocompatible nanocarrier of metal complexes to achieve advanced antitumor effect. The formation of unique tetrahedral nanostructure of DNA cages effectively enhances the interaction between ruthenium polypyridyl complexes (RuPOP) and the cages, thus increasing the drug loading efficacy. Conjugation of biotin to the DNA-based nanosystem (Bio-cage@Ru) enhances its specific cellular uptake, drug retention and cytotoxicity against HepG2 cells. Different from free RuPOP and the cage itself, Bio-cage@Ru translocates to cell nucleus after internalization, where it undergoes self-immolative cleavage in response to DNases, leading to triggered drug release and induction of ROS-mediated cell apoptosis. Moreover, in the nude mice model, the nanosystem specifically accumulates in tumor sites, thus exhibits satisfactory in vivo antitumor efficacy, and alleviates the damage of liver, kidney, lung and heart function of nude mice induced by RuPOP and tumor xenografts. Collectively, this study demonstrates a strategy for construction of biocompatible and cancer-targeted DNA origami with enhanced anticancer efficacy and reduced toxicity for next-generation cancer therapy.

Structural Determinants of p53-Independence in Anticancer Ruthenium-Arene Schiff-Base Complexes

p53 is a key tumor suppressor gene involved in key cellular processes and implicated in cancer therapy. However, it is inactivated in more than 50% of all cancers due to mutation or overexpression of its negative regulators. This leads to drug resistance and poor chemotherapeutic outcome as most clinical drugs act via a p53-dependent mechanism of action. An attractive strategy to circumvent this resistance would be to identify new anticancer drugs that act via p53-independent mode of action. In the present study, we identified 9 Ru (II)-Arene Schiff-base (RAS) complexes able to induce p53-independent cytotoxicity and discuss structural features that are required for their p53-independent activity. Increasing hydrophobicity led to an increase in cellular accumulation in cells with a corresponding increase in efficacy. We further showed that all nine complexes demonstrated p53-independent activity. This was despite significant differences in their physicochemical properties, suggesting that the iminoquinoline ligand, a common structural feature for all the complexes, is required for the p53-independent activity.

Tracking antitumor metallodrugs: promising agents with the Ru(II)- and Fe(II)-cyclopentadienyl scaffolds

Research on the field of metal complexes for the treatment of cancer diseases has attracted increasing interest due to the urgency in finding more efficient and selective treatments. Owing to their wide structural diversity, organometallic complexes appear as potential alternatives to the design of new anticancer candidates. Herein, we review recent progress in our work toward the development of new drugs based on Ru(II)- and Fe(II)-cyclopentadienyl scaffolds. Their design and chemical properties are reviewed and correlated with their biological effects, in particular the key role that coligands play in the overall behavior of the complex.

Transcriptional activator TAp63 is upregulated in muscular atrophy during ALS and induces the pro-atrophic ubiquitin ligase Trim63

Mechanisms of muscle atrophy are complex and their understanding might help finding therapeutic solutions for pathologies such as amyotrophic lateral sclerosis (ALS). We meta-analyzed transcriptomic experiments of muscles of ALS patients and mouse models, uncovering a p53 deregulation as common denominator. We then characterized the induction of several p53 family members (p53, p63, p73) and a correlation between the levels of p53 family target genes and the severity of muscle atrophy in ALS patients and mice. In particular, we observed increased p63 protein levels in the fibers of atrophic muscles via denervation-dependent and -independent mechanisms. At a functional level, we demonstrated that TAp63 and p53 transactivate the promoter and increased the expression of Trim63 (MuRF1), an effector of muscle atrophy. Altogether, these results suggest a novel function for p63 as a contributor to muscular atrophic processes via the regulation of multiple genes, including the muscle atrophy gene Trim63.

Synthesis, characterization and biological evaluation of novel Ru(II)-arene complexes containing intercalating ligands

Three new ruthenium(II)-arene complexes, namely [(η(6)-p-cymene)Ru(Me2dppz)Cl]PF6 (1), [(η(6)-benzene)Ru(Me2dppz)Cl]PF6 (2) and [(η(6)-p-cymene)Ru(aip)Cl]PF6 (3) (Me2dppz=11,12-dimethyldipyrido[3,2-a:2',3'-c]phenazine; aip=2-(9-anthryl)-1H-imidazo[4,5-f] [1,10] phenanthroline) have been synthesized and characterized using different spectroscopic techniques including elemental analysis. The complexes were found to be well soluble and stable in DMSO. The biological activity of the three complexes was tested in three different human cancer cell lines (A549, MDA-MB-231 and HeLa) and in one human non-cancerous cell line (MRC-5). Complexes 1 and 3, carrying η(6)-p-cymene as the arene ligand, were shown to be toxic in all cell lines in the low micromolar/subnanomolar range, with complex 1 being the most cytotoxic complex of the series. Flow cytometry analysis revealed that complex 1 caused concentration- and time-dependent arrest of the cell cycle in G2-M and S phases in HeLa cells. This event is followed by the accumulation of the sub-G1 DNA content after 48h, in levels higher than cisplatin and in the absence of phosphatidylserine externalization. Fluorescent microscopy and acridine orange/ethidium bromide staining revealed that complex 1 induced both apoptotic and necrotic cell morphology characteristics. Drug-accumulation and DNA-binding studies performed by inductively coupled plasma mass spectrometry in HeLa cells showed that the total ruthenium uptake increased in a time- and concentration-dependent manner, and that complex 1 accumulated more efficiently than cisplatin at equimolar concentrations. The introduction of a Me2dppz ligand into the ruthenium(II)-p-cymene scaffold was found to allow the discovery of a strongly cytotoxic complex with significantly higher cellular uptake and DNA-binding properties than cisplatin.

Flexibility of short ds-DNA intercalated by a dipyridophenazine ligand

We use Förster Resonant Energy Transfer (FRET) in order to measure the increase of flexibility of short ds-DNA induced by the intercalation of dipyridophenazine (dppz) ligand in between DNA base pairs. By using a DNA double strand fluorescently labeled at its extremities, it is shown that the end-to-end length increase of DNA due to the intercalation of one dppz ligand is smaller than the DNA base pair interdistance. This may be explained either by a local bending of the DNA or by an increase of its flexibility. The persistence length of the formed DNA/ligand is evaluated. The described structure may have implications in the photophysical damages induced by the complexation of DNA by organometallic molecules.

Anticancer Activities of Mononuclear Ruthenium(II) Coordination Complexes

Ruthenium compounds are highly regarded as potential drug candidates. The compounds offer the potential of reduced toxicity and can be tolerated in vivo. The various oxidation states, different mechanism of action, and the ligand substitution kinetics of ruthenium compounds give them advantages over platinum-based complexes, thereby making them suitable for use in biological applications. Several studies have focused attention on the interaction between active ruthenium complexes and their possible biological targets. In this paper, we review several ruthenium compounds which reportedly possess promising cytotoxic profiles: from the discovery of highly active compounds imidazolium [trans-tetrachloro(dmso)(imidazole)ruthenate(III)] (NAMI-A), indazolium [trans-tetrachlorobis(1H-indazole)ruthenate(III)](KP1019), and sodium trans-[tetrachloridobis(1H-indazole)ruthenate(III)] (NKP-1339) to the recent work based on both inorganic and organometallic ruthenium(II) compounds. Half-sandwich organometallic ruthenium complexes offer the opportunity of derivatization at the arene moiety, while the three remaining coordination sites on the metal centre can be functionalised with various coordination groups of various monoligands. It is clear from the review that these mononuclear ruthenium(II) compounds represent a strongly emerging field of research that will soon culminate into several ruthenium based antitumor agents.

Gold-phosphine-porphyrin as potential metal-based theranostics

Two new gold-phosphine-porphyrin derivatives were synthesized and fully characterized, and their photophysical properties investigated along a water-soluble analog. The cytotoxicity of the compounds was tested on cancer cells (HCT116 and SW480), and their cell uptake was followed by fluorescence microscopy in vitro (on SW480). The proof that the water-soluble gold-phosphine-porphyrin is a biologically active compound that can be tracked in vitro was clearly established, especially concerning the water-soluble analog. Some preliminary photodynamic therapy (PDT) experiments were also performed. They highlight a dramatic increase of the cytotoxicity when the cells were illuminated for 30 min with white light.

Labile ruthenium(ii) complexes with extended phenyl-substituted terpyridyl ligands: synthesis, aquation and anticancer evaluation

The present study demonstrated that the anticancer activities of labile Ru(ii) complexes can be efficiently tuned by chelating with different phenyl-substituted terpyridyl ligands.

Comparison between polypyridyl and cyclometalated ruthenium(II) complexes: anticancer activities against 2D and 3D cancer models

The aim of this study was to illustrate the dramatically different anticancer activities between coordinatively saturated polypyridyl (1 a-4 a) and cyclometalated (1 b-4 b) ruthenium(II) complexes. The cyclometalated complexes 1 b-4 b function as DNA transcription inhibitors, exhibiting switch-on cytotoxicity against a 2D cancer cell monolayer, whereas the polypyridyl complexes 1 a-4 a are relatively inactive. Moreover, complexes 1 b-4 b exhibit excellent cytotoxicity against 3D multicellular tumor spheroids (MCTSs), which serve as an intermediate model between in vitro 2D cell monolayers and in vivo 3D solid tumors. The hydrophobicity, efficient cell uptake, and nucleus targeting ability, as well as the high DNA binding affinity of complexes 1 b-4 b, likely contribute to their enhanced anticancer activity. We surmise that cyclometalation could be a universal approach to significantly enhance the anticancer activity of substituted polypyridyl Ru(II) complexes. We also suggest that 3D MCTSs may be a more practical platform for anticancer drug screening than 2D cancer monolayer approaches.

Regulation of a Notch3-Hes1 pathway and protective effect by a tocopherol-omega alkanol chain derivative in muscle atrophy

Muscular atrophy, a physiopathologic process associated with severe human diseases such as amyotrophic lateral sclerosis (ALS) or cancer, has been linked to reactive oxygen species (ROS) production. The Notch pathway plays a role in muscle development and in muscle regeneration upon physical injury. In this study, we explored the possibility that the Notch pathway participates in the ROS-related muscular atrophy occurring in cancer-associated cachexia and ALS. We also tested whether hybrid compounds of tocopherol, harboring antioxidant activity, and the omega-alkanol chain, presenting cytoprotective activity, might reduce muscle atrophy and impact the Notch pathway. We identified one tocopherol-omega alkanol chain derivative, AGT251, protecting myoblastic cells against known cytotoxic agents. We showed that this compound presenting antioxidant activity counteracts the induction of the Notch pathway by cytotoxic stress, leading to a decrease of Notch1 and Notch3 expression. At the functional level, these regulations correlated with a repression of the Notch target gene Hes1 and the atrophy/remodeling gene MuRF1. Importantly, we also observed an induction of Notch3 and Hes1 expression in two murine models of muscle atrophy: a doxorubicin-induced cachexia model and an ALS murine model expressing mutated superoxide dismutase 1. In both models, the induction of Notch3 and Hes1 were partially opposed by AGT251, which correlated with ameliorations in body and muscle weight, reduction of muscular atrophy markers, and improved survival. Altogether, we identified a compound of the tocopherol family that protects against muscle atrophy in various models, possibly through the regulation of the Notch pathway.

Discovery and investigation of anticancer ruthenium-arene Schiff-base complexes via water-promoted combinatorial three-component assembly

The structural diversity of metal scaffolds makes them a viable alternative to traditional organic scaffolds for drug design. Combinatorial chemistry and multicomponent reactions, coupled with high-throughput screening, are useful techniques in drug discovery, but they are rarely used in metal-based drug design. We report the optimization and validation of a new combinatorial, metal-based, three-component assembly reaction for the synthesis of a library of 442 Ru-arene Schiff-base (RAS) complexes. These RAS complexes were synthesized in a one-pot, on-a-plate format using commercially available starting materials under aqueous conditions. The library was screened for their anticancer activity, and several cytotoxic lead compounds were identified. In particular, [(η6-1,3,5-triisopropylbenzene)RuCl(4-methoxy-N-(2-quinolinylmethylene)aniline)]Cl (4) displayed low micromolar IC50 values in ovarian cancers (A2780, A2780cisR), breast cancer (MCF7), and colorectal cancer (HCT116, SW480). The absence of p53 activation or changes in IC50 value between p53+/+ and p53-/- cells suggests that 4 and possibly the other lead compounds may act independently of the p53 tumor suppressor gene frequently mutated in cancer.

Development of anticancer agents: wizardry with osmium

Platinum compounds are one of the pillars of modern cancer chemotherapy. The apparent disadvantages of existing chemotherapeutics have led to the development of novel anticancer agents with alternative modes of action. Many complexes of the heavy metal osmium (Os) are potent growth inhibitors of human cancer cells and are active in vivo, often superior or comparable to cisplatin, as the benchmark metal-based anticancer agent, or clinically tested ruthenium (Ru) drug candidates. Depending on the choice of ligand system, osmium compounds exhibit diverse modes of action, including redox activation, DNA targeting or inhibition of protein kinases. In this review, we highlight recent advances in the development of osmium anticancer drug candidates and discuss their cellular mechanisms of action.

Inhibition of ectopic glioma tumor growth by a potent ferrocenyl drug loaded into stealth lipid nanocapsules

In this work, a novel ferrocenyl complex (ansa-FcdiOH) was assessed for brain tumor therapy through stealth lipid nanocapsules (LNCs). Stealth LNCs, prepared according to a one-step process, showed rapid uptake by cancer cells and extended blood circulation time. The ferrocenyl complex was successfully encapsulated into these LNCs measuring 40 nm with a high loading capacity (6.4%). In vitro studies showed a potent anticancer effect of ansa-FcdiOH on 9L cells with a low IC50 value (0.1 μM) associated with an oxidative stress and a dose-dependent alteration of the cell cycle. Repeated intravenous injections of stealth ansa-FcdiOH LNCs in ectopic glioma bearing rats induced a significant tumor growth inhibition, supported by a reduced number of proliferative cells in tumors compared to control group. Additionally, no liver damage was observed in treated animals. These results indicated that stealth ansa-FcdiOH LNCs might be considered as a potential new approach for cancer chemotherapy.

FROM THE CLINICAL EDITOR

In this study, a novel ferrocenyl complex was assessed for brain tumor therapy through stealth lipid nanocapsules, demonstrating no liver damage, and superior tumor volume reduction compared to saline and stealth lipid nanocapsules alone in an ectopic glioma model.

Subcellular localization and transport kinetics of ruthenium organometallic anticancer compounds in living cells: a dose-dependent role for amino acid and iron transporters

Ruthenium-based compounds are developed for anticancer treatment, but their mode of action including their import mechanism and subcellular localization remains elusive. Here, we used the intrinsic luminescent properties of cytotoxic organoruthenium (Ru(II)) compounds obtained with an anionic cyclometalated 2-phenylpyridine chelate and neutral aromatic chelating ligands (e.g., phenanthrolines) to follow their behavior in living cells. We established that the difference in sensitivity between cancer cells and noncancerous cells toward one of the compounds correlates with its import kinetics and follows a balance between active and passive transport. The active-transport mechanism involves iron and amino-acid transporters, which are transcriptionally regulated by the drug. We also demonstrated a correlation between the accumulation of these compounds in specific compartments (endoplasmic reticulum, nucleus, mitochondria) and the activation of specific cytotoxic mechanisms such as the mitochondrial stress pathway. Our study pinpoints a novel and complex mechanism of accumulation of ruthenium drugs in cancer cells.

Synthesis, characterization, and anticancer activity of ruthenium(II)-β-carboline complex

Four [Ru(tpy)(N-N)(L)] type complexes: [Ru(tpy)(bpy)(Nh)](2+) (Ru1, tpy = 2,2';6',2″-terpyridine, bpy = 2'2-bipyridine, Nh = Norharman), [Ru(tpy)(phen)(Nh)](2+) (Ru2, phen = 1,10-phenanthroline), [Ru(tpy)(dpa)(Nh)](2+) (Ru3, dpa = 2,2'-dipyridylamine) and [Ru(tpy)(dip)(Nh)](2+) (Ru4, dip = 4,7-diphenyl-1,10-phenanthroline) were presented as anticancer drugs. In vitro cytotoxicity assays indicated that these complexes showed anticancer activity against various cancer cells. Flow cytometry and signaling pathways analysis demonstrated that these complexes induced apoptosis via the mitochondrial pathway, as evidenced by the loss of mitochondrial membrane potential and the release of cytochrome c. The resulting accumulation of p53 proteins from phosphorylation at serine-15 and serine-392 was correlated with an increase in p21 and caspase activation. Taken together, these findings suggested that Ru1-Ru4 may contribute to the future development of improved chemotherapeutics against human cancers.