📚 BiometalDB

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. Show less

Novel rhodium, iridium, and ruthenium half-sandwich complexes containing (N,N)-bound picolinamide ligands have been prepared for use as anticancer agents. The complexes show promising cytotoxicities, with the presence, position, and number of halides having a significant effect on the corresponding IC50 values. One ruthenium complex was found to be more cytotoxic than cisplatin on HT-29 and MCF-7 cells after 5 days and 1 h, respectively, and it remains active with MCF-7 cells even under hypoxic conditions, making it a promising candidate for in vivo studies. Show less

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. Show less

A novel water soluble organometallic compound, [RuCp(mTPPMSNa)(2,2'-bipy)][CF3SO3] (TM85, where Cp=η(5)-cyclopentadienyl, mTPPMS=diphenylphosphane-benzene-3-sulfonate and 2,2'-bipy=2,2'-bipyridine) is presented herein. Studies of interactions with relevant proteins were performed to understand the behavior and mode of action of this complex in the biological environment. Electrochemical and fluorescence studies showed that TM85 strongly binds to albumin. Studies carried out to study the formation of TM85 which adducts with ubiquitin and cytochrome c were performed by electrospray ionization mass spectrometry (ESI-MS). Antitumor activity was evaluated against a variety of human cancer cell lines, namely A2780, A2780cisR, MCF7, MDAMB231, HT29, PC3 and V79 non-tumorigenic cells and compared with the reference drug cisplatin. TM85 cytotoxic effect was reduced in the presence of endocytosis modulators at low temperatures, suggesting an energy-dependent mechanism consistent with endocytosis. Ultrastructural analysis by transmission electron microscopy (TEM) revealed that TM85 targets the endomembranar system disrupting the Golgi and also affects the mitochondria. Disruption of plasma membrane observed by flow cytometry could lead to cellular damage and cell death. On the whole, the biological activity evaluated herein combined with the water solubility property suggests that complex TM85 could be a promising anticancer agent. Show less

Ruthenium complexes hold great potential as alternatives to cisplatin in cancer chemotherapy. We present results on the in vitro antitumor activity of an organometallic 'Ru(II)Cp' complex, [Ru(II)Cp(bipy)(PPh(3))][CF(3)SO(3)], designated as TM34 (PPh(3) = triphenylphosphine; bipy = 2,2'-bipyridine), against a panel of human tumor cell lines with different responses to cisplatin treatment, namely ovarian (A2780/A2780cisR, cisplatin sensitive and resistant, respectively), breast (MCF7) and prostate (PC3) adenocarcinomas. TM34 is very active against all tumorigenic cell lines, its efficacy largely surpassing that of cisplatin (CisPt). The high activity of TM34 towards CisPt resistant cell lines possibly suggests a mechanism of action distinct from that of CisPt. The effect of TM34 on the activity of the enzyme poly(ADP-ribose) polymerase 1 (PARP-1) involved in DNA repair mechanisms and apoptotic pathways was also evaluated, and it was found to be a strong PARP-1 ruthenium inhibitor in the low micromolar range (IC(50)=1.0 ± 0.3 μM). TM34 quickly binds to human serum albumin forming a 1:1 complex with a conditional stability constant (log K'~4.0), comparable to that of the Ru(III) complex in clinical trial KP1019. This indicates that TM34 can be efficiently transported by this protein, possibly being involved in its distribution and delivery if the complex is introduced in the blood stream. Albumin binding does not affect TM34 activity, yielding an adduct that maintains cytotoxic properties (against A2780 and A2780cisR cells). Altogether, the properties herein evaluated suggest that TM34 could be an anticancer agent of highly relevant therapeutic value. Show less

We report herein a systematic study on interactions of organometallic ruthenium(II) anticancer complex [(η(6)-arene)Ru(en)Cl](+) (arene = p-cymene (1) or biphenyl (2), en = ethylenediamine) with human transferrin (hTf) and the effects of the hTf-ligation on the bioavailability of these complexes with cisplatin as a reference. Incubated with a 5-fold excess of complex 1, 2, or cisplatin, 1 mol of diferric hTf (holo-hTf) attached 0.62 mol of 1, 1.01 mol of 2, or 2.14 mol of cisplatin. Mass spectrometry revealed that both ruthenium complexes coordinated to N-donors His242, His273, His578, and His606, whereas cisplatin bound to O donors Tyr136 and Tyr317 and S-donor Met256 in addition to His273 and His578 on the surface of both apo- and holo-hTf. Moreover, cisplatin could bind to Thr457 within the C-lobe iron binding cleft of apo-hTf. Neither ruthenium nor platinum binding interfered with the recognition of holo-hTf by the transferrin receptor (TfR). The ruthenated/platinated holo-hTf complexes could be internalized via TfR-mediated endocytosis at a similar rate to that of holo-hTf itself. Moreover, the binding to holo-hTf well preserved the bioavailability of the ruthenium complexes, and the hTf-bound 1 and 2 showed a similar cytotoxicity toward the human breast cancer cell line MCF-7 to those of the complexes themselves. However, the conjugation with holo-hTf significantly reduced the cellular uptake of cisplatin and the amount of platinated DNA adducts formed intracellularly, leading to dramatic reduction of cisplatin cytotoxicity toward MCF-7. These findings suggest that hTf can serve as a mediator for the targeting delivery of Ru(arene) anticancer complexes while deactivating cisplatin. Show less

Continuing the study of the physicochemical and biological properties of ruthenium-quinolone adducts, four novel complexes with the general formula [Ru([9]aneS3)(dmso-κS)(quinolonato-κ(2)O,O)](PF6), containing the quinolones levofloxacin (1), nalidixic acid (2), oxolinic acid (3), and cinoxacin (4), were prepared and characterized in solid state as well as in solution. Contrary to their organoruthenium analogues, these complexes are generally relatively stable in aqueous solution as substitution of the dimethylsulfoxide (dmso) ligand is slow and not quantitative, and a minor release of the quinolonato ligand is observed only in the case of 4. The complexes bind to serum proteins displaying relatively high binding constants. DNA binding was studied using UV-vis spectroscopy, cyclic voltammetry, and performing viscosity measurements of CT DNA solutions in the presence of complexes 1-4. These experiments show that the ruthenium complexes interact with DNA via intercalation. Possible electrostatic interactions occur in the case of compound 4, which also shows the most pronounced rate of hydrolysis. Compounds 2 and 4 also exhibit a weak inhibition of cathepsins B and S, which are involved in the progression of a number of diseases, including cancer. Furthermore, complex 2 displayed moderate cytotoxicity when tested on the HeLa cell line. Show less

Three water-soluble ruthenium(II) complexes with chiral 4-(2,3-dihydroxypropyl)-formamide oxoaporphine (FOA) were synthesized and characterized. It was found that these ruthenium(II) complexes exhibited considerable in vitro anticancer activities and that they were the effective stabilizers of telomeric and G-quadruplex-DNA (G4-DNA) in promoter of c-myc, which acted as a telomerase inhibitor targeting G4-DNA and induced cell senescence and apoptosis. Interestingly, the in vitro anticancer activity of 6 (LC-003) was higher than those of 4 (LC-001) and 5 (LC-002), more selective for BEL-7404 cells than for normal HL-7702 cells, and preferred to activate caspases-3/9. The different biological behaviors of the ruthenium complexes could be correlated with the chiral nature of 4-(2,3-dihydroxypropyl)-formamide oxoaporphine. More significantly, 6 exhibited effective inhibitory on tumor growth in BEL-7402 xenograft mouse model and higher in vivo safety than cisplatin. These mechanistic insights indicate that 6 displays low toxicity and can be a novel anticancer drug candidate. Show less

Improving the selectivity of anticancer drugs towards cancer cells is one of the main goals of drug optimization; the prodrug strategy has been one of the most promising. A light-triggered prodrug strategy is presented as an efficient approach for controlling cytotoxicity of the substitutionally inert cytotoxic complex [Ru(dppz)2(CppH)](PF6)2(C1; CppH=2-(2-pyridyl)pyrimidine-4-carboxylic acid; dppz=dipyrido[3,2-a:2',3'-c]phenazine). Attachment of a photolabile 3-(4,5-dimethoxy-2-nitrophenyl)-2-butyl (DMNPB) ester ("photocaging") makes the otherwise active complex C1 innocuous to both cancerous (HeLa and U2OS) and non-cancerous (MRC-5) cells. The cytotoxic action can be successfully unleashed in living cells upon light illumination (350 nm), reaching similar level of activity as the parent cytotoxic compound C1. This is the first substitutionally inert cytotoxic metal complex to be used as a light-triggered prodrug candidate. Show less

Following the identification of [Ru(η(6)-p-cymene)Cl2(1H,1H,2H,2H-perfluorodecyl-3-(pyridin-3-yl)propanoate)], a ruthenium(II)-arene complex with a perfluoroalkyl-modified ligand that displays remarkable in vitro cancer cell selectivity, a series of structurally related compounds were designed. In the new derivatives, the p-cymene ring and/or the chloride ligands are substituted by other ligands to modulate the steric bulk or aquation kinetics. The new compounds were evaluated in both in vitro (cytotoxicity and migration assays) and in vivo (chicken chorioallantoic membrane) models and were found to exhibit potent antivascular effects. Show less

With the aim to develop more efficient, less toxic, target specific metal drugs and evaluate their anticancer properties in terms of oxidation state and co-ligand sphere, a sequence of Ru(II), Ru(III) complexes bearing 4-hydroxy-pyridine-2,6-dicarboxylic acid and PPh(3)/AsPh(3) were synthesized and structurally characterized. Biological studies such as DNA binding, antioxidant assays and cytotoxic activity were carried out and their anticancer activities were evaluated. Interactions of the complexes with calf thymus DNA revealed that the triphenylphosphine complexes could bind more strongly than the triphenylarsine complexes. The free radical scavenging ability, assessed by a series of in vitro antioxidant assays involving DPPH radical, hydroxyl radical, nitric oxide radical, superoxide anion radical, hydrogen peroxide and metal chelating assay, showed that the Ru(III) complexes possess excellent radical scavenging properties compared to those of Ru(II). Cytotoxicity studies using three cancer lines viz HeLa, HepG2, HEp-2 and a normal cell line NIH 3T3 showed that Ru(II) complexes exhibited substantial cytotoxic specificity towards cancer cells. Furthermore, the Ru(II) complexes were found to be superior to Ru(III) complexes in inhibiting the growth of cancer cells. Show less

To mimic the structural aspects of staurosporine, a potent but unspecific kinase inhibitor, several coordination compounds based on two readily available diimine ligands containing hydrogen bonding donor/acceptor sites (NH-CO fragment) have been designed and synthesized. These complexes are constructed around Ru(II) and Pt(II) metal centers. A total of 9 compounds, named Ru(1)-(5) and Pt(1)-(4), were obtained through straightforward synthetic approaches. The cytotoxicity of the compounds was evaluated on AGS gastric cancer cells (GC) through standard MTT assays. All ruthenium and platinum complexes with low toxicity, i.e.Ru(3), Ru(5), Pt(3) and Pt(4), were docked in the ATP binding pocket of two protein kinases (S6K1 and MST2). The docking scores highlighted a preferred affinity of Ru(5) for the MST2 binding pocket, whereas the platinum compounds are predicted to bind stronger to the S6K1 binding site. Inhibitory activity of the metal complexes on the MST2 and S6K1 signaling pathways was evaluated by analyzing via western blot experiments the phosphorylation state of YAP, a downstream component of the Hippo pathway and the protein expression of S6 and its phosphorylated analogue p-S6. A clear difference of behavior between the Pt(II) and the Ru(II) complexes depending on the type of kinase was observed. Show less

Abstract The first examples of Ru(II) η 6 ‐arene (benzene and p ‐cymene) complexes containing a bidentate triazolylidene‐triazolide ligand have been prepared and fully characterized. Their antiproliferative effect has been investigated against tumour cells A2780 (ovarian carcinoma), HCT116 (colorectal carcinoma), and HCT116dox (colorectal carcinoma resistant to doxorubicin), and in human dermal fibroblasts. The Ru complex bearing the p ‐cymene arene group exhibited a stronger antiproliferative effect across all tested cell lines, while the benzene‐containing complex displayed higher selectivity toward tumor cells. Both complexes induced apoptosis, likely through ROS production (in the benzene complex), and inhibited tumorigenic processes, including cell migration and angiogenesis. In zebrafish models, they showed strong selectivity for cancer cells with minimal toxicity to healthy cells, effectively reducing the proliferation of HCT116 colorectal cancer cells. This study provides the first in vivo evidence of the anticancer potential of Ru triazolylidenes in zebrafish models. Show less

Lung cancer is most terrible cause of cancer-related death throughout the world. This study focused on the synthesis and characterisation of novel flavokawain A ruthenium-p-cymene complex and to investigate the chemotherapeutic activity against lung carcinoma via in silico, in vitro and in vivo approaches. The complex was characterised via several spectroscopic techniques. In vitro study including cell viability, transwell migration, Western blot and flow cytometric analysis have been executed on both A549 and NCI-H460 cells. The toxicological assessment was performed and subsequently anticancer activity of complex was evaluated in benzo[α]pyrene persuaded lung carcinoma in mice. The molecular docking study demonstrated the compound has greater binding ability with β-catenin, Akt, HER2 and PARP. Followed by the complex treatment, the downregulation of β-catenin, PI3K, Akt, HER2 and PARP were investigated by Western blot analysis and cell cycle arrest was determined through flow cytometry. The outcomes of in vivo experimentation represented fruitful restoration of typical lung architecture after complex treatment. Immunohistochemical analysis demonstrated the downstream of β-catenin/m-TOR/Akt and upstream of caspase-3 and p53 expression, thereby initiating apoptosis. The complex exhibited a potent chemotherapeutic activity via the alteration of tumour microenvironment by modulating PI3K/Akt/β-catenin/HER2/PARP transduction in correlates with apoptotic events in lung carcinoma. Show less

A significant challenge in the treatment of melanoma with immune checkpoint blockades (ICBs) is the limited T cells response often observed in immunologically "cold" tumors. By leveraging the immunogenicity of immunogenic cell death (ICD), which increases the susceptibility of tumor cells to ICBs, this study investigated the potential of a nucleus-targeted ruthenium(II) complex (Ru1) as an inducer of ICD. Treatment with Ru1 induced DNA damage in melanoma cells, activating the cyclic GMP-AMP synthase-stimulator of the interferon genes (cGAS-STING) pathway. This triggered endoplasmic reticulum (ER) stress, leading to ICD. Ru1-treated dying melanoma cells exhibited characteristics such as cell exposure of calreticulin (CRT) on the cell surface, release of adenosine triphosphate (ATP), and secretion of high-mobility group box 1 (HMGB1). Vaccination with Ru1-treated, dying melanoma cells elicited robust antitumor immune responses, as evidenced by CD8⁺ T cells activation, reduced Foxp3⁺ T cells count, and the development of a memory immune response that protected mice from subsequent melanoma challenges. Combining Ru1 with anti-PD-1 therapy significantly promoted T cells infiltration, enhanced dendritic cell activation, and reduced tumor-associated immunosuppressive factors, indicating a reprogramming of the tumor microenvironment. These findings suggest that Ru1 is a promising therapeutic agent for treating "cold" tumors in cancer chemoimmunotherapy. Show less

Ruthenium-based metallodrugs have garnered attention as a promising alternative for anticancer therapy, aiming to overcome chemoresistance and severe side effects linked to platinum-based drugs. However, ruthenium complexes tested in clinical trials to date have yielded unsatisfactory results. This study synthesized a positively charged ruthenium complex (Ru-2) that effectively penetrated cancer cells and exhibited superior cytotoxicity to cisplatin in vitro against cancer cell lines and organoids. Ru-2 selectively targeted mitochondria, disrupting their function by depolarizing mitochondrial membrane potential, elevating reactive oxygen species production, and impairing both oxidative phosphorylation and the tricarboxylic acid cycle. Furthermore, Ru-2 triggered endoplasmic reticulum (ER) stress and apoptosis. Integrative transcriptomic and proteomic analyses, performed using RNA sequencing and mass spectrometry, identified key molecular changes in cancer cells treated with Ru-2. For enhanced in vivo application, we developed a transferrin-based nanomedicine formulation, TF/Ru-2, incorporating Ru-2 into transferrin. In vivo studies demonstrated that both Ru-2 and TF/Ru-2 exhibited superior antitumor efficacy and improved biosafety compared to cisplatin. This study presents a novel ruthenium complex and a transferrin-based drug delivery platform with significant potential for future cancer therapies. Show less

Background

Melanoma is the most aggressive and lethal skin cancer that affects thousands of people worldwide. Ruthenium complexes have shown promising results as cancer chemotherapeutics, offering several advantages over platinum drugs, such as potent efficacy, low toxicity, and less drug resistance. Additionally, anthraquinone derivatives have broad therapeutic applications, including melanoma.

Objectives

Thus, two new ruthenium complexes with 1-hydroxy-9,10-anthraquinone were obtained: trans-[Ru(HQ)(PPh₃)₂(bipy)]PF₆ (1) and cis-[RuCl₂(HQ)(dppb)] (2), where HQ = 1-hydroxy-9,10-anthraquinone, PPh₃ = triphenylphospine, bipy = 2,2'-bipyridine, PF₆ = hexafluorophosphate, and dppb = 1,4-bis(diphenylphosphine)butane.

Methods

The complexes were characterized by infrared (IR), UV-vis, ¹H, ¹³C{¹H}, and ³¹P{¹H} NMR spectroscopies, molar conductivity, cyclic voltammetry, and elemental analysis. Furthermore, density functional theory (DFT) calculations were performed.

Results

Compound (2) was determined by single-crystal X-ray diffraction, which confirms the bidentate coordination mode of HQ through the carbonyl and phenolate oxygens. Additionally, DNA-binding experiments yielded constants of 10⁵ M^-1 (Kb = 6.93 × 10⁵ for (1) and 1.60 × 10⁵ for (2)) and demonstrate that both complexes can interact with DNA through intercalation, electrostatic attraction, or hydrogen bonding.

Conclusions

The cytotoxicity profiles of the compounds were evaluated in human melanoma cell lines (SK-MEL-147, CHL-1, and WM1366), revealing greater cytotoxic activity for (1) on the CHL-1 cell line with an IC₅₀ of 14.50 ± 1.09 µM. Subsequent studies showed that (1) inhibits the proliferation of CHL-1 cells and induces apoptosis, associated at least in part with the pro-oxidant effect and cell cycle arrest at the G1/S transition. Show less

Hypoxia, a hallmark of many solid tumors, is linked to increased cancer aggressiveness, metastasis, and resistance to conventional therapies, leading to poor patient outcomes. This challenges the efficiency of photodynamic therapy (PDT), which relies on the generation of cytotoxic reactive oxygen species (ROS) through the irradiation of a photosensitizer (PS), a process partially dependent on oxygen levels. In this work, we introduce a novel family of potent PSs based on ruthenium(II) polypyridyl complexes with 2,2'-bipyridyl ligands derived from COUPY coumarins, termed COUBPYs. Ru-COUBPY complexes exhibit outstanding in vitro cytotoxicity against CT-26 cancer cells when irradiated with light within the phototherapeutic window, achieving nanomolar potency in both normoxic and hypoxic conditions while remaining nontoxic in the dark, leading to impressive phototoxic indices (>30,000). Their ability to generate both Type I and Type II ROS underpins their exceptional PDT efficiency. The lead compound of this study, SCV49, shows a favorable in vivo pharmacokinetic profile, excellent toxicological tolerability, and potent tumor growth inhibition in mice bearing subcutaneous CT-26 tumors at doses as low as 3 mg/kg upon irradiation with deep-red light (660 nm). These results allow us to propose SCV49 as a strong candidate for further preclinical development, particularly for treating large hypoxic solid tumors. Show less

As novel promising anticancer candidates, the piano-stool type complexes of ruthenium, [RuCl(η⁶-p-cymene)(N,S-L_n)]PF₆, K₁-₄, were synthesized from the reaction of the substituted benzo[b]thiophene based thiosemicarbazone ligands (L_1-4) with [{RuCl(η⁶-p-cymene)}₂(μ-Cl)₂]. All complexes were fully characterized using elemental analysis, and spectroscopic methods such as FT-IR and ¹H NMR. The molecular masses of the complexes were proved by MALDI-TOF analysis. Single crystal X-ray diffraction study was employed in the structural elucidation of complex K₁ which shows a distorted octahedral geometry around the Ru(II) ion. Furthermore, spectroscopic methods revealed that in all complexes the ligands are coordinated to the metal center in neutral thione form via N, S donors. In this study, the effect of all ligands, complexes and commercial drugs with a different concentration on the viability of OVCAR-3, A2780 and OSE cells were compared. In this comparison, the cytotoxicity of ruthenium (II) complexes on two ovarian cancer cell lines (human A2780 and human OVCAR-3) was evaluated. For this purpose, the resazurin assay was performed. Based on our studies, complex K₂ showed the highest toxicity against OVCAR-3 and A2780 cells. The cytotoxic effect of K₂ was found to be higher than that of the commercial anticancer agents Oxalpin and Carbodex, 1.8-34.7-fold for OVCAR-3 cells and 1.9-11.8-fold for A2780 cells, respectively. These results provide insight into the potential of ruthenium (II) complexes as a cytotoxic agent for the treatment of ovarian cancer, particularly for primary tumors. Show less

The synthesis, characterisation, and evaluation of the in vitro cytotoxicity of five maleonitriledithiolate-based ruthenium metal complexes bearing various phosphine ligands towards two ovarian cancer cell lines (A2780 and A2780cisR), one non-small-cell lung cancer cell line (H460) and one normal prostate cell line (PNT2) are presented herein. These 18-electron complexes were designed with four water-soluble phosphine ligands to increase the water-solubility character of the corresponding electron-deficient ruthenium complex which showed great in vitro promises, and triphenylphosphine for comparison. The complexes with triphenylphosphine-3,3',3''-trisulfonic acid and triphenylphosphine present similar cytotoxicity compared to the 16-electron precursor, with equal cytotoxicity to both A2780 and A2780cisR. Hints at the mechanism of action suggest an apoptotic pathway based on reactive oxygen species (ROS) production. No toxicity was observed in preliminary in vivo pilot studies for these two complexes in subcutaneous A2780 and A2780cisR xenograft models, with some evidence of tumour growth delay. Show less

New mononuclear and dinuclear Ru(II) coordination compounds with the 2,7-bisbenzoimidazolyl-naphthyridine ligand have been synthesized and characterized by UV-vis, NMR, and MALDI-TOF. The molecular structures for Ru(II) compounds were determined by single-crystal X-ray diffraction. With the expansion of ligand π-conjugation and the increase in the complexed Ru number, the maximum emission wavelength red-shifted from 696 to 786 nm. The binding mode between complexes and DNA was predicted by molecular docking, which is intercalations and π-π stacking interactions with the surrounding bases. The intercalation mode of DNA binding was then determined by DNA titration and ethidium bromide (EB) displacement experiments. The antigrowth effects of complexes RuY, RuY1, and RuY2 were tested in HaCat (normal cells), HeLa (cervical cancer), A549 (lung cancer), and A549/DDP (cisplatin-resistant lung cancer) through the MTT assay. The dinuclear complex RuY2 was superior to mononuclear complexes and cisplatin in the cisplatin-resistant cell line. Confocal imaging proved that the subcellular localization of Ru(II) complexes was mitochondria; moreover, apoptosis was detected by flow cytometry. All three complexes showed a dose-dependent manner in all four cell lines. All Ru(II) complexes were found to have reactive oxygen species (ROS). The finding indicated that these Ru(II) complexes caused cell death by both DNA disruption and ROS. This study helps to explore the potential of the polynuclear Ru(II) complexes for the combination of NIR imaging and Pt-resistant cancer therapy. Show less

Ruthenium compounds have been shown to be promising alternatives to platinum(II) drugs. However, their clinical success depends on achieving mechanisms of action that overcome Pt-resistance mechanisms. Electron-deficient organoruthenium complexes are an understudied class of compounds that exhibit unusual reactivity in solution and might offer novel anticancer mechanisms of action. Here, we evaluate the in vitro and in vivo anticancer properties of the electron-deficient organoruthenium complex [(p-cymene)Ru(maleonitriledithiolate)]. This compound is found to be highly cytotoxic: 5 to 60 times more potent than cisplatin towards ovarian (A2780 and A2780cisR), colon (HCT116 p53+/+ and HCT116 p53-/-), and non-small cell lung H460 cancer cell lines. It shows no cross-resistance and is equally cytotoxic to both A2780 and A2780cisR cell lines. Furthermore, unlike cisplatin, the remarkable in vitro antiproliferative activity of this compound appears to be p53-independent. In vivo evaluation in the hollow-fibre assay across a panel of cancer cell types and subcutaneous H460 non-small cell lung cancer xenograft model hints at the activity of the complex. Although the impressive in vitro data are not fully corroborated by the in vivo follow-up, this work is the first preclinical study of electron-deficient half-sandwich complexes and highlights their promise as anticancer drug candidates. Show less

The monocationic chloro complexes containing chelating N∩N ligands: [(η⁶-p-cymene)Ru(L1-4)Cl]⁺ (1-4), where L1 = 4-methyl-1,10-phenantroline, L2 = dipyrido[3,2-a:2',3'-c]phenazine, L3 = 11-chloro-dipyrido[3,2-a:2',3'-c]phenazine, L4 = 11-nitro-dipyrido[3,2-a:2',3'-c]phenazine; p-cymene = 1-methyl-4-isopropylbenzene) have been prepared and characterized as the hexafluorophosphate salts. The biological activity of 1-4 has been investigated in selected 2D monolayer cell cultures (A549, PANC-1, MDA-MB-231, MRC-5). All investigated ruthenium complexes showed similar or even better cytotoxicity to cisplatin. However, there was no significant reduction in growth of PANC-1 cells in a 3D cell culture of multicellular tumor spheroids (MCTS) after treatment with 2-4, while the cisplatin treatment induced retardation in MCTS growth. Flow cytometry analysis of the cell cycle of PANC-1 cells shows that 3 caused changes of cell cycle phase distribution characterized by slight accumulation of cells in the G2-M phase. Absence of the Sub-G1 phase in the cell cycle of the treated cells indicated that there was no fragmentation of DNA for the analyzed time intervals (48 and 72 h treatment). Fluorescent microscopy, after acridine orange/ethidium bromide staining, revealed that the investigated ruthenium complexes induced some characteristics of apoptotic morphology (shrinking and condensation of chromatin) with notably preserved integrity of the plasma membrane. Investigation of cellular uptake and DNA - fraction accumulation performed by inductively coupled plasma mass spectrometry in PANC-1 cells with equimolar concentrations (5 μM) of 2-4 and cisplatin showed more efficient cellular uptake and DNA - fraction accumulation of complex 3 compared to complexes 2 and 4. Show less

An organoruthenium(II) complex with pyrithione (2-mercaptopyridine N-oxide) 1 a has previously been identified by our group as a compound with promising anticancer potential without cytotoxicity towards non-cancerous cells. To expand the rather limited research on compounds of this type, an array of novel chlorido and 1,3,5-triaza-7-phosphaadamantane (pta) organoruthenium(II) complexes with methyl-substituted pyrithiones has been prepared. After thorough investigation of the aqueous stability of these complexes, their modes of action have been elucidated at the cellular level. Minor structural alterations in the ruthenium-pyrithionato compounds resulted in fine-tuning of their cytotoxicities. The best performing compounds, 1 b and 2 b, with a chlorido or pta ligand bound to ruthenium, respectively, and a methyl group at the 3-position of the pyrithione scaffold, have been further investigated. Both compounds trigger early apoptosis, induce the generation of reactive oxygen species and G1 arrest in A549 cancer cells, and show no strong interaction with DNA. However, only 1 b also inhibits thioredoxin reductase. Wound healing assays and mitochondrial function evaluation have revealed differences between these two compounds at the cellular level. Show less

In this study, five ruthenium arene complexes with fluorene-bearing N,N-(1) and N,O-(2) donor Schiff base ligands were synthesized and fully characterized. Cationic ruthenium complexes 3[X], ([Ru(η⁶-C₆H₆)(Cl)(fluorene-N[double bond, length as m-dash]CH-pyridine)][X] (where X = BF₄, PF₆, BPh₄), were obtained by reacting ligand 1 with [Ru(η⁶-C₆H₆)Cl₂]₂ in the presence of NH₄X salts, whereas neutral complex 4, Ru(η⁶-C₆H₆)(Cl)(fluorene-N[double bond, length as m-dash]CH-naphtholate), was isolated by reacting ligand 2 with the same precursor. It was possible to obtain a cationic version of the latter, 5[BF₄], by reacting 4 with AgBF₄ in the presence of pyridine. All compounds were fully characterized by NMR and HR-ESI-MS whereas some of them were also analyzed by single crystal X-ray analysis. Their in vitro antiproliferative activity was also assessed in human breast cancer cell lines, notably MCF-7 and T47D. Complex 4 and its cationic counterpart 5[BF₄] were found to be the most cytotoxic compounds of the series (IC₅₀ = 6.2-16.2 μM) and displayed higher antiproliferative activities than cisplatin in both cell lines. It was found that 5[BF₄] undergoes a ligand exchange reaction and readily converts to 4 in the presence of 0.1 M NaCl, explaining the similarity in their observed cytotoxicities. Whereas 3[BF₄] and 3[PF₆] were found inactive at the tested concentrations, 3[BPh₄] displayed a considerable cytotoxicity (IC₅₀ = 16.7-27.8 μM). Notably, 3[BPh₄], 4 (and 5[BF₄]) were active against T47D, a cisplatin resistant cell line. Interestingly, 4 (16.4 μM) was found to be less cytotoxic than 3[BPh₄] and cisplatin (6.6 and 7.9 μM, respectively) in breast healthy cells (MCF-12A). However, in comparison to 4 and cisplatin (at 10 μM), a lower in vivo toxicity was observed for complex 3[BPh₄] on the development of zebrafish (Danio rerio) embryos. Show less

Multidrug resistance mediated by the overexpression of ABC transporters is a major challenge in cancer chemotherapy. Here, we report the synthesis of an organoruthenium complex, RuF, that was designed to surmount multidrug resistance by combining ABCG2 inhibition and cancer cell cytotoxicity, yielding synergistic efficacy. Show less

Benzoylthiourea derivatives feature several donor atoms capable of coordinating to metal centers. We report here a series of Ru(η⁶ -p-cymene) complexes employing benzoylthiourea derivatives as ligands. Such ligands often coordinate to metal centers through their S and O donor atoms. We isolated complexes where the ligands were mono- or bidentately coordinated to Ru involving the S donor atom and surprisingly in bidentate coordination mode a deprotonated thiourea nitrogen resulting in a 4-membered ring structure around the metal center. DFT calculations were used to explain the differences in coordination behavior. These were complemented by stability studies and biological investigations of the compounds as anticancer agents. Several of the synthesized derivatives exhibited significant cell growth inhibitory activity, with the complexes featuring bidentate ligands being more potent than their monodentate counterparts. This can be explained by the higher stability of the former under the conditions employed in cell culture assays. Show less

Three new ruthenium(II)-arene complexes with pyrido[2',3':5,6]pyrazino[2,3-f][1, 10]phenanthroline (ppf) of general formula: C1 ([(ƞ⁶-benzene)Ru(ppf)Cl]PF₆, C2 ([(ƞ⁶-toluene)Ru(ppf)Cl]PF₆) and C3 ([(ƞ⁶-p-cymene)Ru(ppf)Cl]PF₆) have been synthesized. The structures of complexes were determined by elemental analysis, IR, ESI-MS, as well as with ¹H and ¹³C NMR spectroscopy. Cytotoxic activity has been evaluated in three different human neoplastic cell lines (A549, A375, LS 174T) and in one human non-tumor cell line (MRC-5), by the MTT assay. Complexes C1-C3 showed IC₅₀ values in the micromolar range below 100 µM. Complex C3, carrying ƞ⁶-p-cymene as the arene ligand, exhibited cytoselective activity toward human malignant melanoma A375 cells (IC₅₀ = 15.8 ± 2.7 µM), and has been selected for further analyses of its biological effects. Drug-accumulation study performed in the A375 cells disclosed that C3 possess lower ability of entering the cells compared to cisplatin and distributes approximately equally in the cytosol and membrane/organelle fraction of cells. Investigations in the 3D model of A375 cells, disclosed different effects of the complex C3 and cisplatin on growth of multicellular tumor spheroids (MCTSs). While the size of cisplatin-treated MCTSs decreased with time, MCTSs treated with C3 continued to growth. Differences in structural organization and biological activity of this type of ruthenium(II)-arene complexes versus cisplatin in A375 malignant melanoma cells pointed out their different modes of action, and necessity for further biological studies and optimizations for potential applications. Show less

In this study we report the synthesis, characterization and a thorough biological evaluation of twelve organoruthenium-8-hydroxyquinolinato (Ru-hq) complexes. The chosen hqH ligands bear various halogen atoms in different positions which enables to study effect of the substituents on physico-chemical and biological properties. The determined crystal structures of novel complexes expectedly show the cymene ring, a bidentately coordinated deprotonated hq and a halide ligand (chlorido or iodido) coordinated to the ruthenium central ion. In previous studies the anticancer potential of organoruthenium complex with 8-hydroxyquinoline ligand clioquinol was well established and we have decided to perform an extended biological evaluation (antibacterial and antitumor activity) of the whole series of halo-substituted analogs. Beside the cytotoxic potential of studied compounds also the effect of two selected complexes (9 and 10) on apoptosis induction in MG-63 and A549 cells was also studied via externalization of phosphatidylserine at the outer plasma membrane leaflet. Both selected complexes that gave best preliminary cytotoxicity results contain bromo substituted hq ligands. Apoptosis induction results are in agreement with the cell viability assays suggesting the higher and more selective anticancer activity of complex 10 in comparison to complex 9 on MG-63 cells. Show less

Ru^II(η⁶-arene) compounds carrying bioactive flavonol ligands have shown promising anticancer activity against tumor cells via a multitargeting mode of action, i.e., through interaction with DNA and inhibition of topoisomerase IIα. By introducing a novel arene ligand based on the amino acid l-phenylalanine (Phe), we aimed to alter the pharmacological properties of the complexes. We report here a series of novel Ru^II(η⁶-arene)Cl complexes with different substituents on the phenyl ring of the flavonol which should maintain the multitargeting capability of the parent η⁶- p-cymene (cym) complexes. Studies with selected examples revealed stability in aqueous solution after quickly forming aqua complexes but rapid decomposition in pure DMSO. The reactions with protein and DNA models proceeded quickly and resulted in cleavage of the flavonol or adduct formation, respectively. The compounds were found to be cytotoxic with significant antiproliferative activity in cancer cells with IC₅₀ values in the low μM range, while not following the same trends as observed for the cym analogues. Notably, the cellular accumulation of the new derivatives was significantly higher than for their respective cym complexes, and they induced DNA damage in a manner similar to that of cisplatin but to a lesser extent. Show less