👤 Dai W

Mitochondria-targeted compounds represent a promising approach to target tumors selectively and overcome resistance to current anticancer therapies. In this work, three cyclometalated iridium(III) complexes (1-3) containing bis-N-heterocyclic carbene (NHC) ligands have been explored as theranostic and photodynamic agents targeting mitochondria. These complexes display rich photophysical properties, which greatly facilitates the study of their intracellular fate. All three complexes are more cytotoxic than cisplatin against the cancer cells screened. 1-3 can penetrate into human cervical carcinoma (HeLa) cells quickly and efficiently, and they can carry out theranostic functions by simultaneously inducing and monitoring the morphological changes in mitochondria. Mechanism studies show that these complexes exert their anticancer efficacy by initiating a cascade of events related to mitochondrial dysfunction. Additionally, they display up to 3 orders of magnitude higher cytotoxicity upon irradiation at 365 nm, which is so far the highest photocytotoxic responses reported for iridium complexes. Show less

The reaction of the dimer [Rh(III)(pentamethylcyclopentadienyl)(μ-Cl)Cl]2 ([Rh(III)(Cp*)(μ-Cl)Cl]2) with the hydroxypyrone ligands maltol and allomaltol affords complexes of the general formula [Rh(III)(Cp*)(L)Cl] under standard and microwave conditions. The organometallic compounds were characterized by standard analytical methods and in the case of the allomaltol derivative in the solid state by single-crystal X-ray diffraction analysis. The complexes showed similar cytotoxicity profiles and were proved to be moderately active against various human cancer cell lines. The stoichiometry and stability of these complexes were determined in aqueous solution by pH-potentiometry, (1)H NMR spectroscopy and UV-visible spectrophotometry. Speciation was studied in the presence and in the absence of chloride ions. Hydrolysis of [Rh(III)(Cp*)(H2O)3](2+) gave dimeric mixed hydroxido species [(Rh(III)(Cp*))2(μ-OH)3](+) and [(Rh(III)(Cp*))2(μ-OH)2Z2] (Z=H2O/Cl(-)). Formation of the mononuclear complexes [Rh(III)(Cp*)(L)Z] of maltol and allomaltol with similar and moderate stability was found. These species predominate at physiological pH and decompose only partially at micromolar concentrations. In addition, hydrolysis of the aqua complex or a chlorido/hydroxido co-ligand exchange resulted in the formation of the mixed-hydroxido species [Rh(III)(Cp*)(L)(OH)] in the basic pH range. Replacement of the chlorido by an aqua ligand in the complex [Rh(III)(Cp*)(L)Cl] was monitored and with the help of the equilibrium constants the extent of aquation at various chloride concentrations of the extra- and intracellular milieu can be predicted. Complexation of these Rh(III) complexes was compared to analogous [Ru(II)(η(6)-p-cymene)] species and higher conditional stabilities were found in the case of the Rh(III) compounds at pH7.4. Show less

Cell lines are invaluable biomedical research tools, and recent literature has emphasized the importance of genotype authentication and characterization. In the present study, 24 out of 27 cell line identities were confirmed by short tandem repeat profiling. The molecular phenotypes of the 24 colon cancer cell lines were examined, and microsatellite instability (MSI) and CpG island methylator phenotype (CIMP) were determined, using the Bethesda panel mononucleotide repeat loci and two epimarker panels, respectively. Furthermore, the BRAF, KRAS and PIK3CA oncogenes were analyzed for mutations in known hotspots, while the entire coding sequences of the PTEN and TP53 tumor suppressors were investigated. Nine cell lines showed MSI. Thirteen and nine cell lines were found to be CIMP positive, using the Issa panel and the Weisenberger et al. panel, respectively. The latter was found to be superior for CIMP classification of colon cancer cell lines. Seventeen cell lines harbored disrupting TP53 mutations. Altogether, 20/24 cell lines had the mitogen-activated protein kinase pathway activating mutually exclusive KRAS or BRAF mutations. PIK3CA and PTEN mutations leading to hyperactivation of the phosphoinositide 3-kinase/AKT pathway were observed in 13/24 cell lines. Interestingly, in four cell lines there were no mutations in neither BRAF, KRAS, PIK3CA nor in PTEN. In conclusion, this study presents molecular features of a large number of colon cancer cell lines to aid the selection of suitable in vitro models for descriptive and functional research. Show less

Organometallic Ru(II), Os(II) and Rh(III) complexes of lapachol induce apoptosis in human tumour cell lines in the low μM range by a mode of action involving oxidative stress, especially in the case of the ruthenium compound. 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

KP1339 is a promising ruthenium-based anticancer compound in early clinical development. This study aimed to test the effects of KP1339 on the in vitro and in vivo activity of the multi-kinase inhibitor sorafenib, the current standard first-line therapy for advanced hepatoma. Anticancer activity of the parental compounds as compared to the drug combination was tested against a panel of cancer cell lines with a focus on hepatoma. Combination of KP1339 with sorafenib induced in the majority of all cases distinctly synergistic effects, comprising both sorafenib-resistant as well as sorafenib-responsive cell models. Several mechanisms were found to underlie these multifaceted synergistic activities. Firstly, co-exposure induced significantly enhanced accumulation levels of both drugs resulting in enhanced apoptosis induction. Secondly, sorafenib blocked KP1339-mediated activation of P38 signalling representing a protective response against the ruthenium drug. In addition, sorafenib treatment also abrogated KP1339-induced G2/M arrest but resulted in check point-independent DNA-synthesis block and a complete loss of the mitotic cell populations. The activity of the KP1339/sorafenib combination was evaluated in the Hep3B hepatoma xenograft. KP1339 monotherapy led to a 2.4-fold increase in life span and, thus, was superior to sorafenib, which induced a 1.9-fold prolonged survival. The combined therapy further enhanced the mean survival by 3.9-fold. Synergistic activity was also observed in the VM-1 melanoma xenograft harbouring an activating braf mutation. Together, our data indicate that the combination of KP1339 with sorafenib displays promising activity in vitro and in vivo especially against human hepatoma models. Show less

A series of ketone-N(4)-substituted thiosemicarbazone (TSC) compounds (L1-L9) and their corresponding [(η(6)-p-cymene)Ru(II)(TSC)Cl](+/0) complexes (1-9) were synthesized and characterized by NMR, IR, elemental analysis, and HR-ESI-mass spectrometry. The molecular structures of L4, L9, 1-6, and 9 were determined by single-crystal X-ray diffraction analysis. The compounds were further evaluated for their in vitro antiproliferative activities against the SGC-7901 human gastric cancer, BEL-7404 human liver cancer, and HEK-293T noncancerous cell lines. Furthermore, the interactions of the compounds with DNA were followed by electrophoretic mobility spectrometry studies. Show less

Organometallic Ru(arene)-peptide bioconjugates with potent in vitro anticancer activity are rare. We have prepared a conjugate of a Ru(arene) complex with the neuropeptide [Leu(5)]-enkephalin. [Chlorido(η(6)-p-cymene)(5-oxo-κO-2-{(4-[(N-tyrosinyl-glycinyl-glycinyl-phenylalanyl-leucinyl-NH2)propanamido]-1H-1,2,3-triazol-1-yl)methyl}-4H-pyronato-κO)ruthenium(II)] (8) shows antiproliferative activity in human ovarian carcinoma cells with an IC50 value as low as 13 μM, whereas the peptide or the Ru moiety alone are hardly cytotoxic. The conjugation strategy for linking the Ru(cym) (cym=η(6)-p-cymene) moiety to the peptide involved N-terminal modification of an alkyne-[Leu(5)]-enkephalin with a 2-(azidomethyl)-5-hydroxy-4H-pyran-4-one linker, using Cu(I)-catalyzed alkyne-azide cycloaddition (CuAAC), and subsequent metallation with the Ru(cym) moiety. The ruthenium-bioconjugate was characterized by high resolution top-down electrospray ionization mass spectrometry (ESI-MS) with regard to peptide sequence, linker modification and metallation site. Notably, complete sequence coverage was obtained and the Ru(cym) moiety was confirmed to be coordinated to the pyronato linker. The ruthenium-bioconjugate was analyzed with respect to cytotoxicity-determining constituents, and through the bioconjugate models [{2-(azidomethyl)-5-oxo-κO-4H-pyronato-κO}chloride (η(6)-p-cymene)ruthenium(II)] (5) and [chlorido(η(6)-p-cymene){5-oxo-κO-2-([(4-(phenoxymethyl)-1H-1,2,3-triazol-1-yl]methyl)-4H-pyronato-κO}ruthenium(II)] (6) the Ru(cym) fragment with a triazole-carrying pyronato ligand was identified as the minimal unit required to achieve in vitro anticancer activity. Show less

Six novel ruthenium(II)- and osmium(II)-arene complexes with three modified indolo[3,2-c]quinolines have been synthesized in situ starting from 2-aminoindoloquinolines and 2-pyridinecarboxaldehyde in the presence of [M(p-cymene)Cl(2)](2) (M = Ru, Os) in ethanol. All complexes have been characterized by elemental analysis, spectroscopic techniques ((1)H, (13)C NMR, IR, UV-vis), and ESI mass spectrometry, while four complexes were investigated by X-ray diffraction. The complexes have been tested for antiproliferative activity in vitro in A549 (non-small cell lung), SW480 (colon), and CH1 (ovarian) human cancer cell lines and showed IC(50) values between 1.3 and >80 μM. The effects of Ru vs Os and modifications of the lactam unit on intermolecular interactions, antiproliferative activity, and cell cycle are reported. One ruthenium complex and its osmium analogue have been studied for anticancer activity in vivo applied both intraperitoneally and orally against the murine colon carcinoma model CT-26. Interestingly, the osmium(II) complex displayed significant growth-inhibitory activity in contrast to its ruthenium counterpart, providing stimuli for further investigation of this class of compounds as potential antitumor drugs. Show less

Nanoparticle formulations offer besides the advantage of passive drug targeting also the opportunity to increase the stability of drugs. KP1019 is a lead ruthenium(III) compound which has been successfully tested in a clinical phase I trial. However, it is characterized by low stability in aqueous solution especially at physiological pH. To overcome this limitation, poly(lactic acid) (PLA) nanoparticles of KP1019 with two different surfactants (Pluronic F68 and Tween 80) were prepared by a single oil-in-water (o/w) emulsion. Cytotoxicity measurements comparing different aged Tween 80 nanoparticles revealed that the color change from brown to green was associated with an up to 20 fold increased activity compared to "free" KP1019. Further investigations suggested that this is based on the formation of enhanced intracellular reactive oxygen species levels. Additional studies revealed that the origin of the green color is a reaction between KP1019 and Tween 80. Kinetic studies of this reaction mixture using UV-Vis, ESI-MS and ESR spectroscopy indicated on the one hand a coordination of Tween 80 to KP1019, and on the other hand, the color change was found to correlate with a reduction of the Ru(III) center by the surfactant. Together, the results provide a first experimental approach to stabilize a biologically active Ru(II) species of KP1019 in aqueous solution, which probably can be also used to selectively generate this activated species in the tumor tissue via delivery of KP1019 using Tween 80 nanoparticles. Show less

Ruthenium complexes are widely recognized as one of the most promising DNA damaging chemotherapeutic drugs. The main goal of this study was to explore the anticancer activity and underlying mechanisms of [Ru(phen)(2)(p-BrPIP)](ClO(4))(2), a novel chemically synthesized ruthenium (Ru) complex. To this end, we employed MTT assays to determine the anticancer activity of the complex, and performed single-cell gel electrophoresis (SCGE) and Western blotting to evaluate DNA damage. Our results showed that the Ru(II)-poly complex caused severe DNA damage, possibly by downregulating key factors involved in DNA repair pathways, such as proliferating cell nuclear antigen (PCNA) and ring finger protein 8 (RNF8). In addition, this complex induced cell apoptosis by upregulating both p21 and p53. Taken together, our findings demonstrate that the Ru(II)-poly complex exhibits antitumour activity by inducing cell apoptosis, which results from the accumulation of large amounts of unrepaired DNA damage. Show less

Ru(II)(η(6)-arene) complexes, especially with bioactive ligands, are considered to be very promising compounds for anticancer drug design. We have shown recently that Ru(II)(η(6)-p-cymene) complexes with 3-hydroxyflavone ligands exhibit very high in vitro cytotoxic activities correlating with a strong inhibition of topoisomerase IIα. In order to expand our knowledge about the structure-activity relationships and to determine the impact of lipophilicity of the arene ligand and of the hydrolysis rate on anticancer activity, a series of novel 3-hydroxyflavone derived Ru(II)(η(6)-arene) complexes were synthesised. Furthermore, the impact of the heteroatom in the bioactive ligand backbone was studied by comparing the cytotoxic activity of Ru(II)(η(6)-p-cymene) complexes of 3-hydroxyquinolinone ligands with that of their 3-hydroxyflavone analogues. To better understand the behaviour of these Ru(II) complexes in aqueous solution, the stability constants and pK(a) values for complexes and the corresponding ligands were determined. Furthermore, the interaction with the DNA model 5'-GMP and with a series of amino acids was studied in order to identify potential biological target structures. Show less

The emission enhancement behavior and photocleavage activity of a ruthenium(II) arene complex, [(η(6)-p-cymene)Ru(dppn)(py)](2+) (1) (dppn = 4,5,9,16-tetraaza-dibenzo[a,c]naphthacene, py = pyridine), towards DNA were compared with [(η(6)-p-cymene)Ru(bpy)(py)](2+) (2), [Ru(bpy)2(dppz)](2+) (3) and [Ru(bpy)2(dppn)](2+) (4) (bpy = 2,2'-bipyridine, dppz = dipyrido-[3,2-a:2',3'-c]phenazine). It was found that 1 emits fluorescence from the dppn-based ligand-centered (LC) singlet excited state and generates singlet oxygen ((1)O2) from the dppn-based LC triplet excited state. As a result, 1 displays emission enhancement behavior and photocleavage activity towards DNA simultaneously. In contrast, 3 is the most classical DNA light switch but shows poor DNA photocleavage activity, while 4 is an efficient DNA photocleaver but cannot report DNA binding by luminescence enhancement. An increased cytotoxicity against human lung carcinoma cells A549 by about 10-fold was also observed for 1 upon visible light activation. These intriguing properties result from the unique combination of the Ru(II) arene and dppn subunits. Show less

The complexation with organoruthenium fragments confers 4-anilinoquinazoline pharmacophores with higher potential for inducing cellular apoptosis while the highly inhibitory activity of 4-anilinoquinazolines against EGFR and the reactivity of the ruthenium centre to 9-ethylguanine are well preserved. Show less

Five iridium(III) complexes with two N-heterocyclic carbene (NHC) ligands and an ancillary ligand have been designed and successfully synthesized. With multicolor photoluminescence and low toxicity, these carbene complexes were tested, for the first time, as living cell imaging reagents and showed promise for application beyond the OLED (organic light emitting diode) area. Show less

Oxaliplatin is successfully used in systemic cancer therapy. However, resistance development and severe adverse effects are limiting factors for curative cancer treatment with oxaliplatin. The purpose of this study was to comparatively investigate in vitro and in vivo anticancer properties as well as the adverse effects of two methyl-substituted enantiomerically pure oxaliplatin analogs [[(1R,2R,4R)-4-methyl-1,2-cyclohexanediamine] oxalatoplatinum(II) (KP1537), and [(1R,2R,4S)-4-methyl-1,2-cyclohexanediamine]oxalatoplatinum(II) (KP1691)] and to evaluate the impact of stereoisomerism. Although the novel oxaliplatin analogs demonstrated in multiple aspects activities comparable with those of the parental compound, several key differences were discovered. The analogs were characterized by reduced vulnerability to resistance mechanisms such as p53 mutations, reduced dependence on immunogenic cell death induction, and distinctly attenuated adverse effects including weight loss and cold hyperalgesia. Stereoisomerism of the substituted methyl group had a complex and in some aspects even contradictory impact on drug accumulation and anticancer activity both in vitro and in vivo. To summarize, methyl-substituted oxaliplatin analogs harbor improved therapeutic characteristics including significantly reduced adverse effects. Hence, they might be promising metal-based anticancer drug candidates for further (pre)clinical evaluation. Show less

The regulation of hydrogen ion concentration (pH) is fundamental to cell viability, metabolism, and enzymatic function. Within the nervous system, the control of pH is also involved in diverse and dynamic processes including development, synaptic transmission, and the control of network excitability. As pH affects neuronal activity, and can also itself be altered by neuronal activity, the existence of tools to accurately measure hydrogen ion fluctuations is important for understanding the role pH plays under physiological and pathological conditions. Outside of their use as a marker of synaptic release, genetically encoded pH sensors have not been utilized to study hydrogen ion fluxes associated with network activity. By combining whole-cell patch clamp with simultaneous two-photon or confocal imaging, we quantified the amplitude and time course of neuronal, intracellular, acidic transients evoked by epileptiform activity in two separate in vitro models of temporal lobe epilepsy. In doing so, we demonstrate the suitability of three genetically encoded pH sensors: deGFP4, E(2)GFP, and Cl-sensor for investigating activity-dependent pH changes at the level of single neurons. Show less

RuII(arene) complexes have been shown to be promising anticancer agents, capable of overcoming major drawbacks of currently used chemotherapeutics. We have synthesized RuII(η6-arene) compounds carrying bioactive flavonol ligands with the aim to obtain multitargeted anticancer agents. To validate this concept, studies on the mode of action of the complexes were conducted which indicated that they form covalent bonds to DNA, have only minor impact on the cell cycle, but inhibit CDK2 and topoisomerase IIα in vitro. The cytotoxic activity was determined in human cancer cell lines, resulting in very low IC50 values as compared to other RuII(arene) complexes and showing a structure-activity relationship dependent on the substitution pattern of the flavonol ligand. Furthermore, the inhibition of cell growth correlates well with the topoisomerase inhibitory activity. Compared to the flavonol ligands, the RuII(η6-p-cymene) complexes are more potent antiproliferative agents, which can be explained by potential multitargeted properties. Show less

A series of ruthenium(II) arene complexes with 3-(1H-benzimidazol-2-yl)-1H-quinoxalin-2-one, bearing pharmacophoric groups of known protein kinase inhibitors, and related benzoxazole and benzothiazole derivatives have been synthesized. In addition, the corresponding osmium complexes of the unsubstituted ligands have also been prepared. The compounds have been characterized by NMR, UV-vis, and IR spectroscopy, ESI mass spectrometry, elemental analysis, and by X-ray crystallography. Antiproliferative activity in three human cancer cell lines (A549, CH1, SW480) was determined by MTT assays, yielding IC(50) values of 6-60 μM for three unsubstituted metal-free ligands, whereas values for the metal complexes vary in a broad range from 0.3 to 140 μM. Complexation with osmium of quinoxalinone derivatives with benzimidazole or benzothiazole results in a more consistent increase in cytotoxicity than complexation with ruthenium. For selected compounds, the capacity to induce apoptosis was confirmed by fluorescence microscopy and flow-cytometric analysis, whereas cell cycle effects are only moderate. Show less

A one-pot synthesis of osmium(IV) complexes with two different tautomers of indazole, 1H-indazole and 2H-indazole, namely (H(2)ind)[Os(IV)Cl(5)(2H-ind)] (1) and (H(2)ind)[Os(IV)Cl(5)(1H-ind)] (2) is reported. Both compounds have been comprehensively characterized by NMR spectroscopy, ESI (electrospray ionization) mass spectrometry, electronic absorption spectroscopy, IR spectroscopy, cyclic voltammetry and tested for antiproliferative activity in vitro in three human cancer cell lines, CH1 (ovarian carcinoma), A549 (non-small cell lung cancer) and SW480 (colon carcinoma), as well as in vivo in a Hep3B SCID mouse xeno-transplantation model. 2H-Indazole tautomer stabilization in 1 has been confirmed by X-ray diffraction. Show less

With the aim of exploring the anticancer properties of organometallic compounds with bioactive ligands, Ru(arene) compounds of the antibacterial quinolones nalidixic acid (2) and cinoxacin (3) were synthesized, and their physicochemical properties were compared to those of chlorido(η(6)-p-cymene)(ofloxacinato-κ(2)O,O)ruthenium(II) (1). All compounds undergo a rapid ligand exchange reaction from chlorido to aqua species. 2 and 3 are significantly more stable than 1 and undergo minor conversion to an unreactive [(cym)Ru(μ-OH)(3)Ru(cym)](+) species (cym = η(6)-p-cymene). In the presence of human serum albumin 1-3 form adducts with this transport protein within 20 min of incubation. With guanosine 5'-monophosphate (5'-GMP; as a simple model for reactions with DNA) very rapid reactions yielding adducts via its N7 atom were observed, illustrating that DNA is a possible target for this compound class. A moderate capacity of inhibiting tumor cell proliferation in vitro was observed for 1 in CH1 ovarian cancer cells, whereas 2 and 3 turned out to be inactive. Show less

Three novel Ru(II) complexes of the general formula [Ru(N-N)(2)(Norharman)(2)](SO(3)CF(3))(2), where N-N = 2,2'-bipyridine (bpy, 1), 1,10-phenanthroline (phen, 2), 4,7-diphenyl-1,10-phenanthroline (DIP, 3) and Norharman (9H-pyrido[3,4-b]indole) is a naturally occurring β-carboline alkaloid, have been synthesized and characterized. The molecular structures of 1 and 2 have been determined by X-ray diffraction analysis. The cellular uptake efficiencies, in vitro cytotoxicities and apoptosis-inducing properties of these complexes have been extensively explored. Notably, 1-3 exhibit potent antiproliferative activities against a panel of human cancer cell lines with IC(50) values lower than those of cisplatin. Further studies show that 1-3 can cause cell cycle arrest in the G0/G1 phase and induce apoptosis through mitochondrial dysfunction and reactive oxygen species (ROS) generation. In vitro DNA binding studies have also been conducted to provide information about the possible mechanism of action. Show less

Ruthenium(II) methylimidazole complexes, with the general formula [Ru(MeIm)(4)(N⌢N)](2+) (N⌢N = tip (RMC1), iip (RMC2), dppz (RMC3), dpq (RMC4); MeIm = 1-methylimidazole, tip = 2-(thiophene-2-yl)-1H-imidazo [4,5-f] [1,10]phenanthroline, iip = 2-(1H-imidazol-4-yl)-1H-imidazo [4,5-f] [1,10]phenanthroline, dppz = dipyrido[3,2-a:2',3'-c]phenazine, dpq = pyrazino [2,3-f] [1,10]phenanthroline), were synthesized and characterized. As determined by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, these complexes displayed potent anti-proliferation activity against various cancer cells. RMC1 inhibited the growth of A549 (human lung adenocarcinoma) lung cells through induction of apoptotic cell death, as evidenced by the accumulation of cell population in sub-G1 phase. RMC1 also induced the depletion of mitochondrial membrane potential in A549 cells by regulating the expression of pro-survival and pro-apoptotic Bcl-2 family members. Another experiment showed that Bid protein was also activated by RMC1, which implied that RMC1 could existed two pathways crosstalk, namely, have exogenous death receptor signaling pathway. These results demonstrated that RMC1 induced cancer cell death by acting on both mitochondrial and death receptor apoptotic pathways, suggesting that RMC1 could be a candidate for further evaluation as a chemotherapeutic agent against human cancers. Show less

The ruthenium compound KP1019 has demonstrated promising anticancer activity in a pilot clinical trial. This study aims to evaluate the intracellular uptake/binding patterns of KP1019 and its sodium salt KP1339, which is currently in a phase I-IIa study. Although KP1339 tended to be moderately less cytotoxic than KP1019, IC(50) values in several cancer cell models revealed significant correlation of the cytotoxicity profiles, suggesting similar targets for the two drugs. Accordingly, both drugs activated apoptosis, indicated by caspase activation via comparable pathways. Drug uptake determined by inductively coupled plasma mass spectrometry (ICP-MS) was completed after 1 h, corresponding to full cytotoxicity as early as after 3 h of drug exposure. Surprisingly, the total cellular drug uptake did not correlate with cytotoxicity. However, distinct differences in intracellular distribution patterns suggested that the major targets for the two ruthenium drugs are cytosolic rather than nuclear. Consequently, drug-protein binding in cytosolic fractions of drug-treated cells was analyzed by native size-exclusion chromatography (SEC) coupled online with ICP-MS. Ruthenium-protein binding of KP1019- and KP1339-treated cells distinctly differed from the platinum binding pattern observed after cisplatin treatment. An adapted SEC-SEC-ICP-MS system identified large protein complexes/aggregates above 700 kDa as initial major binding partners in the cytosol, followed by ruthenium redistribution to the soluble protein weight fraction below 40 kDa. Taken together, our data indicate that KP1019 and KP1339 rapidly enter tumor cells, followed by binding to larger protein complexes/organelles. The different protein binding patterns as compared with those for cisplatin suggest specific protein targets and consequently a unique mode of action for the ruthenium drugs investigated. Show less

The role of autophagy in cancer development and response to cancer therapy has been a subject of debate. Here we demonstrate that a series of ruthenium(II) complexes containing a β-carboline alkaloid as ligand can simultaneously induce autophagy and apoptosis in tumor cells. These Ru(II) complexes are nuclear permeable and highly active against a panel of human cancer cell lines, with complex 3 displaying activities greater than those of cisplatin. The antiproliferative potentialities of 1-3 are in accordance with their relative lipophilicities, cell membrane penetration abilities, and in vitro DNA binding affinities. Complexes 1-3 trigger release of reactive oxygen species (ROS) and attenuation of ROS by scavengers reduced the sub-G1 population, suggesting ROS-dependent apoptosis. Inhibition of ROS generation also reduces autophagy, indicating that ROS triggers autophagy. Further studies show that suppression of autophagy using pharmacological inhibitors (3-methyladenine and chloroquine) enhances apoptotic cell death. Show less

The synthesis, characterization, reactivity and in vitro anticancer activity of a series of Ru(II)-arene complexes with carbohydrate-derived phosphite and biscarboxylato co-ligands are reported. The compounds were characterized by NMR spectroscopy and electrospray ionization (ESI) mass spectrometry, and the molecular structures of oxalato(η(6)-p-cymene)(3,5,6-bicyclophosphite-1,2-O-isopropylidene-α-D-glucofuranoside)ruthenium(II) and oxalato(η(6)-p-cymene)(3,5,6-bicyclophosphite-1,2-O-cyclohexylidene-α-D-glucofuranoside)ruthenium(II) were determined by X-ray diffraction analysis. In contrast to their dichlorido counterparts, the biscarboxylato complexes did not exhibit significant reactivity towards biomolecules, such as cysteine, methionine, ubiquitin or the DNA model 5'-GMP, and resist hydrolysis; no hydrolytic species were detected by (1)H and (31)P{(1)H} NMR spectroscopy over several days. These structural alterations led to a decrease in the tumor-inhibiting potency of the compounds in human cancer cell lines. Show less

The synthesis and in vitro anticancer activity of Os(II)-arene complexes with carbohydrate-derived phosphite co-ligands are reported. The compounds were characterized by standard methods and the molecular structure of dichlorido(eta(6)-p-cymene)(3,5,6-bicyclophosphite-1,2-O-isopropylidene-alpha-D-glucofuranoside)osmium(II) was determined by X-ray diffraction analysis. Complexes with chlorido leaving groups undergo hydrolysis by consecutive formation of aqua compounds, followed by cleavage of a P-O bond of sugar phosphite ligands, as demonstrated by NMR studies. These observations are similar to those of analogous Ru(II)-arene complexes; however the rate of hydrolysis is very slow for osmium compounds. The complexes with oxalato leaving groups resist hydrolysis; no hydrolytic species were detected by (31)P{(1)H} NMR spectroscopy over several days. Within this series of Os compounds, in vitro anticancer activity is highest for the most lipophilic chlorido complex dichlorido(eta(6)-p-cymene)(3,5,6-bicyclophosphite-1,2-O-cyclohexylidene-alpha-D-glucofuranoside)osmium(II). Show less

Organometallic ruthenium-arene compounds bearing a maltol ligand have been shown to be nearly inactive in in vitro anticancer assays, presumably due to the formation of dimeric Ru(II) species in aqueous solutions. In an attempt to stabilize such complexes, [Ru(eta(6)-p-cymene)(XY)Cl] (XY=pyrones or thiopyrones) complexes with different substitution pattern of the (thio)pyrone ligands have been synthesized, their structures characterized spectroscopically, and their aquation behavior investigated as well as their tumor-inhibiting potency. The aquation behavior of pyrone systems with electron-donating substituents and of thiopyrone complexes was found to be significantly different from that of the maltol-type complex reported previously. However, the formation of the dimer can be excluded as the primary reason for the inactivity of the complex because some of the stable compounds are not active in cancer cell lines either. In contrast, studies of their reactivity towards amino acids demonstrate different reactivities of the pyrone and thiopyrone complexes, and the higher stability of the latter probably renders them active against human tumor cells. Show less

A series of octahedral Ru(II) polypyridyl complexes, [Ru(phen)(2)L](2+) (L=R-PIP and PIP=2-phenylimidazo[4,5-f][1,10]phenanthroline) were synthesized and characterized by elementary analysis, (1)H NMR and ES-MS, as well as UV-visible spectra and emission spectra. The antitumor activities of these complexes and their corresponding ligands were investigated against mouse leukemia L1210 cells, human oral epidermoid carcinoma KB cells, human promyelocytic leukemia cells (HL-60) and Bel-7402 liver cancer cells by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. It was found that the complexes [Ru(phen)(2)L](2+) (L=R-PIP) exert rather potent activities against all of these cell lines, especially for the KB cells (IC(50)=4.7+/-1.3 microM). The binding affinities of these Ru(II) complexes to CT-DNA (calf thymus DNA), as well as the DNA-unwinding properties on supercoiled pBR322 DNA were also investigated. The results showed that these Ru(II) polypyridyl complexes not only had an excellent DNA-binding property but also possessed a highly effective DNA-photocleavage ability. The structure-activity relationships and antitumor mechanism were also carefully discussed. Show less