Ruthenium versus platinum: interactions of anticancer metallodrugs with duplex oligonucleotides characterised by electrospray ionisation mass spectrometry

Anticancer Activity of Metallodrugs and Metallizing Host Defense Peptides-Current Developments in Structure-Activity Relationship

This article provides an overview of the development, structure and activity of various metal complexes with anti-cancer activity. Chemical researchers continue to work on the development and synthesis of new molecules that could act as anti-tumor drugs to achieve more favorable therapies. It is therefore important to have information about the various chemotherapeutic substances and their mode of action. This review focuses on metallodrugs that contain a metal as a key structural fragment, with cisplatin paving the way for their chemotherapeutic application. The text also looks at ruthenium complexes, including the therapeutic applications of phosphorescent ruthenium(II) complexes, emphasizing their dual role in therapy and diagnostics. In addition, the antitumor activities of titanium and gold derivatives, their side effects, and ongoing research to improve their efficacy and reduce adverse effects are discussed. Metallization of host defense peptides (HDPs) with various metal ions is also highlighted as a strategy that significantly enhances their anticancer activity by broadening their mechanisms of action.

Selective Targeting of Regulated Rhabdomyosarcoma Cells by Trinuclear Ruthenium(II)-Arene Complexes

The use of benzimidazole-based trinuclear ruthenium(II)-arene complexes (1-3) to selectively target the rare cancer rhabdomyosarcoma is reported. Preliminary cytotoxic evaluations of the ruthenium complexes in an eight-cancer cell line panel revealed enhanced, selective cytotoxicity toward rhabdomyosarcoma cells (RMS). The trinuclear complex 1 was noted to show superior short- and long-term cytotoxicity in RMS cell lines and enhanced selectivity relative to cisplatin. Remarkably, 1 inhibits the migration of metastatic RMS cells and maintains superior activity in a 3D multicellular spheroid model in comparison to that of the clinically used cisplatin. Mechanistic insights reveal that 1 effectively induces genomic DNA damage, initiates autophagy, and prompts the intrinsic and extrinsic apoptotic pathways in RMS cells. To the best of our knowledge, 1 is the first trinuclear ruthenium(II) arene complex to selectively kill RMS cells in 2D and 3D cell cultures.

Dichloro Ru(II)-p-cymene-1,3,5-triaza-7-phosphaadamantane (RAPTA-C): A Case Study

The use of organometallic compounds to treat various phenotypes of cancer has attracted increased interest in recent decades. Organometallic compounds, which are transitional between conventional inorganic and organic materials, have outstanding and one-of-a-kind features that offer fresh insight into the development of inorganic medicinal chemistry. The therapeutic potential of ruthenium(II)-arene RAPTA-type compounds is being thoroughly investigated, specifically owing to the excellent antimetastatic property of the initial candidate RAPTA-C. This review gives a thorough analysis of this complex and its evolution as a potential anticancer drug candidate. The numerous mechanistic investigations of RAPTA-C are discussed, and they are connected to the macroscopic biological characteristics that have been found. The "multitargeted" complex described here target enzymes, peptides, and intracellular proteins in addition to DNA that allow it to specifically target cancer cells. Understanding these may allow researchers to find specific targets and tune a new-generation organometallic complex accordingly.

A split β-lactamase sensor for the detection of DNA modification by cisplatin and ruthenium-based chemotherapeutic drugs

Here we present a split-enzyme sensor approach for the sequence-specific detection of metal-based drug adducts of DNA. Split β-lactamase reporters were constructed using domain A of the High Mobility Group Box 1 protein (HMGB1a) in conjunction with zinc finger DNA-binding domains. As a proof of concept, the sensors were characterized with the well-known drug cisplatin, which forms 1,2-intrastrand crosslinks with DNA that are recognized by HMGB1a. After promising results with cisplatin, five ruthenium-based drugs were studied, four of which produced significant signal over background. These results highlight the utility of our approach for rapid screening of novel metal-based chemotherapeutic drug candidates and provide evidence that HMGB1a likely binds to DNA adducts formed by NAMI-A (imidazolium trans-tetrachlorodimethylsulfoxideimidazoleruthenate(III)), KP1019 (indazolium trans-tetrachlorodiindazoleruthenate(III)), KP418 (imidazolium trans-tetrachlorodiimidazoleruthenate(III)), and RAPTA-C (dichloro(η⁶-p-cymene)(1,3,5-triaza-7-phosphaadamantane)ruthenium(II)). These results thus imply a potential biologically relevant mode of action for the ruthenium-based drugs investigated herein.

Reactions of Ru(III)-drugs KP1019 and KP418 with guanine, 2'-deoxyguanosine and guanosine: a DFT study

Ruthenium (Ru)-based anticancer drugs are considered to be novel alternatives of platinum-based drugs. They exhibit potent cytotoxicity against the cancer cells and hence are useful for the treatment of cancer. Herein, the density functional theory calculations in the gas phase and aqueous media are carried out to study the reactions of two Ru(III)-based drugs such as KP1019 and KP418 with the N7 site of guanine (G), 2'-deoxyguanosine (dGua), and guanosine (Gua) to understand their reactivity against the DNA and RNA. All the reactions are found to be exothermic. The activation free energies and rate constants of these reactions indicate that KP1019 and KP418 would react with the dGua more readily than Gua. Hence, the binding of these drugs with the DNA would be more preferred as compared to RNA. It is further found that among these drugs, KP1019 would be more reactive than KP418 in agreement with the experimental observation. Thus, this study is expected to aid in the future development of potent anticancer drugs.

Determination of Relative Stabilities of Metal-Peptide Bonds in the Gas Phase

Understanding binding site preferences in biological systems as well as affinities to binding partners is a crucial aspect in metallodrug development. We here present a mass spectrometry‐based method to compare relative stabilities of metal‐peptide adducts in the gas phase. Angiotensin 1 and substance P were used as model peptides. Incubation with isostructural N‐heterocyclic carbene (NHC) complexes of Ru^II, Os^II, Rh^III, and Ir^III led to the formation of various adducts, which were subsequently studied by energy‐resolved fragmentation experiments. The gas‐phase stability of the metal‐peptide bonds depended on the metal and the binding partner. Of the four complexes used, the Os^II derivative bound strongest to Met, while Ru^II formed the most stable coordination bond with His. Rh^III was identified as the weakest peptide binder and Ir^III formed peptide adducts with intermediate stability. Probing these intrinsic gas‐phase properties can help in the interpretation of biological activities and the design of site‐specific protein binding metal complexes.

Ruthenium Complexes as Anticancer Agents: A Brief History and Perspectives

Platinum (Pt)-based anticancer drugs such as cisplatin have been used to treat various cancers. However, they have some limitations including poor selectivity and toxicity towards normal cells and increasing chemoresistance. Therefore, there is a need for novel metallo-anticancers, which has not been met for decades. Since the initial introduction of ruthenium (Ru) polypyridyl complex, a number of attempts at structural evolution have been conducted to improve efficacy. Among them, half-sandwich Ru-arene complexes have been the most prominent as an anticancer platform. Such complexes have clearly shown superior anticancer profiles such as increased selectivity toward cancer cells and ameliorating toxicity against normal cells compared to existing Pt-based anticancers. Currently, several Ru complexes are under human clinical trials. For improvement in selectivity and toxicity associated with chemotherapy, Ru complexes as photodynamic therapy (PDT), and photoactivated chemotherapy (PACT), which can selectively activate prodrug moieties in a specific region, have also been investigated. With all these studies on these interesting entities, new metallo-anticancer drugs to at least partially replace existing Pt-based anticancers are anticipated. This review covers a brief description of Ru-based anticancer complexes and perspectives.

Ruthenium(IV) Complexes as Potential Inhibitors of Bacterial Biofilm Formation

With increasing antimicrobial resistance there is an urgent need for new strategies to control harmful biofilms. In this study, we have investigated the possibility of utilizing ruthenium(IV) complexes (H₃O)₂(HL1)₂[RuCl₆]·2Cl·2EtOH (1) and [RuCl₄(CH₃CN)₂](L³2)·H₂O (2) (where L1-2-hydroxymethylbenzimadazole, L³2-1,4-dihydroquinoxaline-2,3-dione) as effective inhibitors for biofilms formation. The biological activities of the compounds were explored using E. coli, S. aureus, P. aeruginosa PAO1, and P. aeruginosa LES B58. The new chloride ruthenium complexes were characterized by single-crystal X-ray diffraction analysis, Hirshfeld surface analysis, FT-IR, UV-Vis, magnetic and electrochemical (CV, DPV) measurements, and solution conductivity. In the obtained complexes, the ruthenium(IV) ions possess an octahedral environment. The intermolecular classical and rare weak hydrogen bonds, and π···π stacking interactions significantly contribute to structure stabilization, leading to the formation of a supramolecular assembly. The microbiological tests have shown complex 1 exhibited a slightly higher anti-biofilm activity than that of compound 2. Interestingly, electrochemical studies have allowed us to determine the relationship between the oxidizing properties of complexes and their biological activity. Probably the mechanism of action of 1 and 2 is associated with generating a cellular response similar to oxidative stress in bacterial cells.

Top-down mass spectrometry reveals multiple interactions of an acetylsalicylic acid bearing Zeise's salt derivative with peptides

Synergistic effects and promising anticancer activities encourage the combination of non-steroidal anti-inflammatory drugs with metallodrugs. Here, we discuss the interactions of an organometallic complex consisting of an acetylsalicylic acid (ASA) moiety attached to a PtII center via an alkenol linker in a Zeise's salt-type coordination (ASA-buten-PtCl3) with model peptides angiotensin 1 (AT), substance P (Sub P), and ubiquitin (UQ). Top-down mass spectrometry experiments show that the amino acid involved in the initial binding to the metal complex controls the coordination sphere of PtII in the adducts. The strong trans labilizing effect of the coordinating sulfur atom in Met causes fast release of the organic moiety and leads to the formation of dimers and oligomers in the case of Sub P. In contrast, interactions with nitrogen donors in AT result in stable adducts containing the intact ASA-buten-PtII complex. UQ forms two sets of PtII adducts, only one of them retains the ASA moiety, which is presumably the result of an unexpected binding geometry. Importantly, UQ is additionally acetylated at various Ser and Lys residues by the ASA-buten-PtCl3 complex. Control experiments with ASA are negative. This is the first example of concomitant platination and acetylation of a peptide with an ASA metal complex.

NAMI-A and KP1019/1339, Two Iconic Ruthenium Anticancer Drug Candidates Face-to-Face: A Case Story in Medicinal Inorganic Chemistry

NAMI-A ((ImH)[trans-RuCl₄(dmso-S)(Im)], Im = imidazole) and KP1019/1339 (KP1019 = (IndH)[trans-RuCl₄(Ind)₂], Ind = indazole; KP1339 = Na[trans-RuCl₄(Ind)₂]) are two structurally related ruthenium(III) coordination compounds that have attracted a lot of attention in the medicinal inorganic chemistry scientific community as promising anticancer drug candidates. This has led to a considerable amount of studies on their respective chemico-biological features and to the eventual admission of both to clinical trials. The encouraging pharmacological performances qualified KP1019 mainly as a cytotoxic agent for the treatment of platinum-resistant colorectal cancers, whereas the non-cytotoxic NAMI-A has gained the reputation of being a very effective antimetastatic drug. A critical and strictly comparative analysis of the studies conducted so far on NAMI-A and KP1019 allows us to define the state of the art of these experimental ruthenium drugs in terms of the respective pharmacological profiles and potential clinical applications, and to gain some insight into the inherent molecular mechanisms. Despite their evident structural relatedness, deeply distinct biological and pharmacological profiles do emerge. Overall, these two iconic ruthenium complexes form an exemplary and unique case in the field of medicinal inorganic chemistry.

Selective binding of an organoruthenium complex to G-rich human telomeric sequence by tandem mass spectrometry

RATIONALE

Human telomeric DNA is reported to be a potential target for anticancer organometallic ruthenium(II) complexes, however, the interaction sites were not clearly discriminated and identified.

METHODS

In the current study, tandem mass spectrometry (MS/MS) using collision-induced dissociation (CID) was firstly introduced to identify the interaction sites of an organometallic ruthenium(II) complex [(η⁶ -biphenyl)Ru(en)Cl][PF₆ ] (1; en = ethylenediamine) with 5'-T₁ T₂ A₃ G₄ G₅ G₆ -3' (I), the repeating unit of human telomeric DNA, in both positive- and negative-ion mode at a low reaction molar ratio (1/I = 0.2) which was applied to preserve the site selectivity.

RESULTS

Mass spectrometric results showed that mono-ruthenated I was the main product under the conditions. In positive-ion mode, MS/MS results indicated that ruthenium complex 1 binds to T₂ or G₆ in strand I. However, in negative-ion mode, no efficient information was obtained for exact identification of ruthenation sites which may be attributed to losses of fragment ions due to charge neutralization by the coordination of the positively charged ruthenium complex to the short MS/MS fragments.

CONCLUSIONS

This is the first report of using top-down MS to characterize the interactions of organometallic ruthenium(II) complexes and human telomeric DNA. Thymine can be thermodynamically competitive with guanine for binding to ruthenium complexes even at low reaction molar ratio, which inspired us to explore in greater depth the significance of thymine binding.

Zeise's salt as powerful platinating agent for proteins investigated by top-down-mass spectrometry

Metallodrugs have become an integral part of modern medicinal chemistry with platinum drugs as anti-cancer agents being well-known examples. The historically interesting compound Zeise's salt, potassium trichlorido(ethene)platinate(II) has scarcely been investigated in this context yet. This study is geared towards shedding light on the biological reactivity of this platinum complex. Mass Spectrometry tools were used to obtain a deeper understanding of its interactions with biomolecules on the molecular level. Angiotensin I and Ubiquitin were chosen as model systems. Comparison to Cisplatin show that Zeise's salt is more reactive towards nucleophilic sites in proteins. Our data indicate that the ethylene ligand remains on the platinum when coordinated to a nitrogen donor in the biomolecule and therefore offers a linkage for the introduction of further functionality. When attached to sulfur donors in the biomolecule, platinum(II) provides a site for the formation of crosslinks and loops in the biomolecules by losing all four of its initial ligands.

Computational Approach to Unravel the Role of Hydrogen Bonding in the Interaction of NAMI-A with DNA Nucleobases and Nucleotides

Density functional theory method in combination with a continuum solvation model is used to understand the role of hydrogen bonding in the interactions of tertiary nitrogen centers of guanine and adenine with monoaqua and diaqua NAMI-A. In the case of adenine, the interaction of N3 with monoaqua NAMI-A is preferred over that of N7 and N1 whereas, N7 site is the most preferred site over N3 and N1 in the diaqua ruthenium-adenine interaction. In the monoaqua and diaqua NAMI-A-guanine interactions, the N7 site is the most preferred site over the N3 site. Here, the strength and number of H-bonds play important roles in stabilizing intermediates and transition states involved in the interaction of NAMI-A and purine bases. Atoms in molecules and Becke surface analysis confirm that the interactions between monoaqua and diaqua NAMI-A with the base pairs of GC and AT dinucleotides leads to the structural deformation in the geometry of the base pairs of dinucleotides. The diaqua NAMI-A adducts induce more disruption in the base pairs as compared to monoaqua NAMI-A adducts. which suggests that diaqua NAMI-A could be a better anticancer agent than monoaqua NAMI-A. This study can be extended to envisage the potential applications of computational studies in the development of new drugs and targeted drug delivery systems.

Sequence-dependent attack on peptides by photoactivated platinum anticancer complexes

Octahedral platinum(iv) complexes such as trans,trans,trans-[Pt(N3)2(OH)2(pyridine)2] (1) are stable in the dark, but potently cytotoxic to a range of cancer cells when activated by UVA or visible light, and active in vivo. Photoactivation causes the reduction of the complex and leads to the formation of unusual Pt(ii) lesions on DNA. However, radicals are also generated in the excited state resulting from photoactivation (J. S. Butler, J. A. Woods, N. J. Farrer, M. E. Newton and P. J. Sadler, J. Am. Chem. Soc., 2012, 134, 16508-16511). Here we show that once photoactivated, 1 also can interact with peptides, and therefore proteins are potential targets of this candidate drug. High resolution FT-ICR MS studies show that reactions of 1 activated by visible light with two neuropeptides Substance P, RPKPQQFFGLM-NH2 (SubP) and [Lys]3-Bombesin, pEQKLGNQWAVGHLM-NH2 (K3-Bom) give rise to unexpected products, in the form of both oxidised and platinated peptides. Further MS/MS analysis using electron-capture dissociation (ECD) dissociation pathways (enabling retention of the Pt complex during fragmentation), and EPR experiments using the spin-trap DEPMPO, show that the products generated during the photoactivation of 1 depend on the amino acid composition of the peptide. This work reveals the multi-targeting nature of excited state platinum anticancer complexes. Not only can they target DNA, but also peptides (and proteins) by sequence dependent platination and radical mechanisms.

Ruthenium complex exerts antineoplastic effects that are mediated by oxidative stress without inducing toxicity in Walker-256 tumor-bearing rats

The present study evaluated the in vivo antitumor effects and toxicity of a new Ru(II) compound, cis-(Ru[phen]₂[ImH]₂)²⁺ (also called RuphenImH [RuC]), against Walker-256 carcinosarcoma in rats. After subcutaneous inoculation of Walker-256 cells in the right pelvic limb, male Wistar rats received 5 or 10mgkg^-1 RuC orally or intraperitoneally (i.p.) every 3 days for 13 days. A positive control group (2mgkg^-1 cisplatin) and negative control group (vehicle) were also used. Tumor progression was checked daily. After treatment, tumor weight, plasma biochemistry, hematology, oxidative stress, histology, and tumor cell respiration were evaluated. RuC was effective against tumors when administered i.p. but not orally. The highest i.p. dose of RuC (10mgkg^-1) significantly reduced tumor volume and weight, induced oxidative stress in tumor tissue, reduced the respiration of tumor cells, and induced necrosis but did not induce apoptosis in the tumor. No clinical signs of toxicity or death were observed in tumor-bearing or healthy rats that were treated with RuC. These results suggest that RuC has antitumor activity through the modulation of oxidative stress and impairment of oxidative phosphorylation, thus promoting Walker-256 cell death without causing systemic toxicity. These effects make RuC a promising anticancer drug for clinical evaluation.

Antimetastatic activity of novel ruthenium (III) pyridine complexes

Ruthenium‐based complexes have emerged as promising anticancer, especially antimetastatic agents. Among them, NAMI‐A (trans‐[Ru(III)Cl₄ (DMSO)(Im)][ImH], Im = imidazole, DMSO = dimethyl sulfoxide) was well studied. In this study, we studied the antimetastatic activities of two novel NAMI‐A derivatives containing pyridine, G26b and G94a, using cultured cells and tumor‐bearing mice. Same to NAMI‐A, these two complexes displayed little direct cytotoxicity to the cancer cells in vitro and in vivo, but they, especially G26b, significantly reduced the occurrence and development of lung metastases in mice bearing the 4T1 mammary carcinoma. In vitro, these two complexes displayed significant suppressive effect on invasion and migration of cells and tube formation of human umbilical vein endothelial cell, to the same extent of NAMI‐A. The transcription of important molecules involved in metastasis, matrix metalloproteinase 2 and 9 (MMP‐2 and ‐9), and vascular endothelial growth factor, was suppressed by the two complexes, as well as NAMI‐A. Plasma atomic emission spectrometer showed G26b had a longer Ru‐elimination time in lung, which may be a reason for better antimetastatic effect of G26b than NAMI‐A. Our results have demonstrated that G26b is a more effective antimetastatic agent than NAMI‐A.

Interaction of anticancer Ru(III) complexes with single stranded and duplex DNA model systems

The interaction of the anticancer Ru(iii) complex AziRu - in comparison with its analogue NAMI-A, currently in advanced clinical trials as an antimetastatic agent - with DNA model systems, both single stranded and duplex oligonucleotides, was investigated using a combined approach, including absorption UV-vis spectroscopy, circular dichroism (CD) and electrospray mass spectrometry (ESI-MS) techniques. UV-vis absorption spectra of the Ru complexes were recorded at different times in a pseudo-physiological solution, to monitor the ligand exchange processes in the absence and in the presence of the examined oligonucleotides. CD experiments provided information on the overall conformational changes of the DNA model systems induced by these metal complexes. UV- and CD-monitored thermal denaturation studies were performed to analyse the effects of AziRu and NAMI-A on the stability of the duplex structures. ESI-MS experiments, carried out on the oligonucleotide/metal complex mixtures under investigation, allowed us to detect the formation of stable adducts between the guanine-containing oligomers and the ruthenium complexes. These data unambiguously demonstrate that both AziRu and NAMI-A can interact with the DNA model systems. Although very similar in their structures, the two metal compounds manifest a markedly different reactivity with the examined sequences, respectively, with either a naked Ru(3+) ion or a Ru(Im)(3+) (Im = imidazole) fragment being incorporated into the oligonucleotide structure via stable linkages.

Alteration of steric hindrance modulates glutathione resistance and cytotoxicity of three structurally related RuII-p-cymene complexes

Three structurally related Ru^II-p-cymene complexes of imidazole based Schiff bases show steric hindrance influences, hypoxia reactivity, cell cycle arrest and resistance to glutathione. The complexes show anti-metastatic and anti-angiogenic effects.

Structural analysis of ruthenium–arene complexes using ion mobility mass spectrometry, collision-induced dissociation, and DFT

Electrospray ionization of [RuCl₂(p-cymeme)(PTA)] afforded a mixture of two molecular ions resulting from an in source oxidation of Ru^II into Ru^III or from protonation of the 1,3,5-triaza-7-phosphaadamantane (PTA) ligand.

Mechanisms of reactions of Ru(iii)-based drug NAMI-A and its aquated products with DNA purine bases: a DFT study

The mechanism of reaction of NAMI-A with guanine has been investigated theoretically using density functional theory.

Identification and discrimination of binding sites of an organoruthenium anticancer complex to single-stranded oligonucleotides by mass spectrometry

We here report the identification of the binding sites of an organometallic ruthenium anticancer complex [(η(6)-biphenyl)Ru(en)Cl](+) (1) to single-stranded oligodeoxynucleotides (ODNs) 5'-CCCA4G5C6CC-3' (I) and 5'-CCC3G4A5CCC-3' (II) by mass spectrometry. The MS analysis of exonuclease ladders demonstrated that the 5'-exonuclease bovine spleen phosphodiesterase digestion of I and II mono-ruthenated by complex 1 was arrested solely at A4 and partially at C3 and G4, respectively, and that the 3'-exonuclease snake venom phosphodiesterase digestion of the ruthenated ODNs was arrested solely at G5 and G4, respectively, due to the ruthenation. These results did not allow unambiguous identification of ruthenation sites on the metallated ODNs. In contrast, tandem mass spectrometry analysis with CID fragmentation of the mono-ruthenated ODNs provided sequential and complementary [a(i) - B]/wi fragments, leading to unambiguous identification of G5 in I and G4 in II as the ruthenation sites on the ODN adducts, which is in line with the high selectivity of the complex towards guanine base as reported previously. These findings suggest that caution should be raised with regard to the identification of the binding sites of metal complexes, in particular complexes with bulky ligands, like biphenyl in complex 1, to DNA by MS analysis of exonuclease ladders of the metallated adducts, because the bulky ligands may adopt such an orientation that they block the exonuclease cleavage of the 5'- or 3'-side phosphodiester bonds adjacent to the binding sites, leading to digestion stalling at the nucleotides before the binding sites.

Cationic liposomes as efficient nanocarriers for the drug delivery of an anticancer cholesterol-based ruthenium complex

Cationic nanovectors loaded with Ru-based nucleolipids exert a high growth-inhibitory activity against human cancer cells (MCF-7 (A), WiDr (B), and HeLa (C)).

Luminescent ruthenium complexes for theranostic applications

The water-soluble and visible luminescent complexes cis-[Ru(L-L)2(L)2](2+) where L-L = 2,2-bipyridine and 1,10-phenanthroline and L= imidazole, 1-methylimidazole, and histamine have been synthesized and characterized by spectroscopic techniques. Spectroscopic (circular dichroism, saturation transfer difference NMR, and diffusion ordered spectroscopy NMR) and isothermal titration calorimetry studies indicate binding of cis-[Ru(phen)2(ImH)2](2+) and human serum albumin occurs via noncovalent interactions with K(b) = 9.8 × 10(4) mol(-1) L, ΔH = -11.5 ± 0.1 kcal mol(-1), and TΔS = -4.46 ± 0.3 kcal mol(-1). High uptake of the complex into HCT116 cells was detected by luminescent confocal microscopy. Cytotoxicity of cis-[Ru(phen)2(ImH)2](2+) against proliferation of HCT116p53(+/+) and HCT116p53(-/-) shows IC50 values of 0.1 and 0.7 μmol L(-1). Flow cytometry and western blot indicate RuphenImH mediates cell cycle arrest in the G1 phase in both cells and is more prominent in p53(+/+). The complex activates proapoptotic PARP in p53(-/-), but not in p53(+/+). A cytostatic mechanism based on quantification of the number of cells during the time period of incubation is suggested.

Insights into the binding sites of organometallic ruthenium anticancer compounds on peptides using ultra-high resolution mass spectrometry

The binding sites of two ruthenium(II) organometallic complexes of the form [(η(6)-arene)Ru(N,N)Cl](+), where arene/N,N = biphenyl (bip)/bipyridine (bipy) for complex AH076, and biphenyl (bip)/o-phenylenediamine (o-pda) for complex AH078, on the peptides angiotensin and bombesin have been investigated using Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. Fragmentation was performed using collisionally activated dissociation (CAD), with, in some cases, additional data being provided by electron capture dissociation (ECD). The primary binding sites were identified as methionine and histidine, with further coordination to phenylalanine, potentially through a π-stacking interaction, which has been observed here for the first time. This initial peptide study was expanded to investigate protein binding through reaction with insulin, on which the binding sites proposed are histidine, glutamic acid, and tyrosine. Further reaction of the ruthenium complexes with the oxidized B chain of insulin, in which two cysteine residues are oxidized to cysteine sulfonic acid (Cys-SO3H), and glutathione, which had been oxidized with hydrogen peroxide to convert the cysteine to cysteine sulfonic acid, provided further support for histidine and glutamic acid binding, respectively.

Application of mass spectrometric techniques to delineate the modes-of-action of anticancer metallodrugs

Mass spectrometry (MS) has emerged as an important tool for studying anticancer metallodrugs in complex biological samples and for characterising their interactions with biomolecules and potential targets on a molecular level. The exact modes-of-action of these coordination compounds and especially of next generation drug candidates have not been fully elucidated. Due to the fact that DNA is considered a crucial target for platinum chemotherapeutics, metallodrug-DNA binding studies dominated the field for a long time. However, more recently, alternative targets were considered, including enzymes and proteins that may play a role in the overall pharmacological and toxicological profile of metallodrugs. This review focuses on MS-based techniques for studying anticancer metallodrugs in vivo, in vitro and in situ to delineate their modes-of-action.