👤 Honorato J

Description

Two new ruthenium(II) complexes containing guanidinium as ligands, [Ru(dip)2 (L1)]3+ (Ru1) and [Ru(dip)2(L2)]3+ (Ru2) (dip=4,7-diphenyl-1,10-phenanthroline; L1=1-(4-(1H-imidazo[4,5- f][1,10]phenanthrolin-2-yl)phenyl)guanidine cation; L2 = 1-(3-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl) phenyl)guanidine cation) have been synthesized and characterized. Both complexes display higher cytotoxicity against several cancer cell lines compared to cisplatin and are less cytotoxic on the nontumorigenic cell line LO2. Intracellular distribution studies show that these complexes are selectively localized in the cytoplasm.

Findings

Further analysis revealed that Ru1 and Ru2 had no obvious effects on the cell cycle and induced apoptosis in HeLa cells via the mitochondrial pathway, which involved reactive oxygen species (ROS) accumulation, mitochondrial dysfunction, and Bcl-2 family member activation. Taken together, the two complexes have the potential to be utilized as anticancer agents. Show less

In this study, Ru(II)-arene complexes with acylthiourea ligands of the type [Ru(η⁶‑p‑cymene)(PPh₃)(T)Cl]PF₆(1-5) and [Ru(η⁶‑p‑cymene)(PPh₃)(T)]PF₆(1a, 4a), where PPh₃ = triphenylphosphine and T = N‑acyl‑N'(monosubstituted)thiourea, were synthesized and characterized, and their cytotoxic properties were also evaluated. 1a and 4a were obtained from the hydrolysis reaction of 1 and 4. All complexes showed unusual coordination modes for acylthiourea ligands, which are coordinated in a monodentate fashion (S) in 1-5, while they found to be bidentate (S,N), in 1a and 4a. To the best of our knowledge, 1a and 4a are the first crystallographically reported ruthenium compounds with acylthiourea coordinated via S and N(amide) atoms. The cytotoxicity of the compounds was evaluated in human lung cells, A549 and MRC-5. The IC₅₀ values ranging from 0.25 to 0.61 μM after 48 h incubation in lung cancer cells indicate that the compounds showed high cytotoxicity with values significantly lower than the reference drug, cisplatin (11.84 μM). Interaction studies were carried out using human serum albumin (HSA) and DNA. All complexes showed similar cytotoxic activity, however complex 1a, which is the hydrolysis product of 1, presented the highest activity and selectivity among all seven compounds synthesized here. Complexes 1 and 1a inhibited the colony formation decreasing the colony size and inducing morphology changes in A549 cells. These complexes induced apoptosis cell death and promoted cell cycle arrest in the Sub-G1 phase with a decrease in the cell number at the S phase. Show less

As hypoxia is an important factor to limit chemotherapeutic efficacy in tumors, we herein report three ruthenium(II)-arene complexes containing a hypoxia inducible factor-1α inhibitor (YC-1), which endow the organometallic complexes with potential for hypoxia targeting. In vitro tests showed the resulting complexes had higher anticancer activities in hypoxia than in normoxia against the tested cancer cell lines. Western blot analysis revealed that complexes 1-3 blocked HIF-1α protein accumulation under hypoxic conditions. Moreover, these complexes displayed much less cytotoxicity toward the normal human umbilical vein endothelial cell line (HUVEC), indicating that complexes 1-3 may be selectively cytotoxic for human cancer cell lines. These findings proved that ligation with YC-1 endowed these organometallic ruthenium(II) complexes with potential for hypoxia targeting in addition to enhancing their anticancer activities. Show less

Three new bis(2,2'-bipyridine)-heteroleptic Ru(II) dyads incorporating thienyl groups (n = 1-3, compounds 1, 2 and 3, respectively) appended to 1,10-phenanthroline were synthesized and characterized to investigate the impact of n on the photophysical and photobiological properties within the series. All three complexes showed unstructured emission near 618 nm from a triplet metal-to-ligand charge transfer (³ MLCT) state with a lifetime (τ_em ) of approximately 1 μs. Transient absorption measurements revealed an additional excited state that was nonemissive and long-lived (τ_TA  = 43 μs for 2 and 27 μs for 3), assigned as a triplet intraligand (³ IL) state that was accessible only in 2 and 3. All three complexes were strong singlet oxygen (¹ O₂ ) sensitizers, with quantum yields (Φ_∆ ) for 2 and 3 being the largest (74-78%), and all three were photocytotoxic to cancer cells with visible light activation in the order: 3 > 2 > 1. Cell-free DNA photodamage followed the same trend, where potency increased with decreasing ³ IL energy. Compounds 2 and 3 also showed in vitro photobiological effects with red light (625 nm), where their molar absorptivities were <100 m^-1  cm^-1 . These findings highlight that Ru(II) dyads derived from α-oligothiophenes directly appended to 1,10-phenanthroline-namely 2 and 3-possess low-lying ³ IL states that are highly photosensitizing, and they may therefore be of interest for photobiological applications such as photodynamic therapy (PDT). Show less

The photophysical and photobiological properties of a new class of cyclometalated ruthenium(II) compounds incorporating π-extended benzo[ h]imidazo[4,5- f]quinoline (IBQ) cyclometalating ligands (C^N) bearing thienyl rings ( n = 1-4, compounds 1-4) were investigated. Their octanol-water partition coefficients (log P_o/w) were positive and increased with n. Their absorption and emission energies were red-shifted substantially compared to the analogous Ru(II) diimine (N^N) complexes. They displayed C^N-based intraligand (IL) fluorescence and triplet excited-state absorption that shifted to longer wavelengths with increasing n and N^N-based metal-to-ligand charge transfer (MLCT) phosphorescence that was independent of n. Their photoluminescence lifetimes (τ_em) ranged from 4-10 ns for ¹IL states and 12-18 ns for ³MLCT states. Transient absorption lifetimes (τ_TA) were 5-8 μs with 355 nm excitation, ascribed to ³IL states that became inaccessible for 1-3 with 532 nm excitation (1-3, τ_TA = 16-17 ns); the ³IL of 4 only was accessible by lower energy excitation, τ_TA = 3.8 μs. Complex 4 was nontoxic (EC₅₀ > 300 μM) to SK-MEL-28 melanoma cells and CCD1064-Sk normal skin fibroblasts in the dark, while 3 was selectively cytotoxic to melanoma (EC₅₀= 5.1 μM) only. Compounds 1 and 2 were selective for melanoma cells in the dark, with submicromolar potencies (EC₅₀ = 350-500 nM) and selectivity factors (SFs) around 50. The photocytotoxicities of compounds 1-4 toward melanoma cells were similar, but only compounds 3 and 4 displayed significant phototherapeutic indices (PIs; 3, 43; 4, >1100). The larger cytotoxicities for compounds 1 and 2 were attributed to increased cellular uptake and nuclear accumulation, and possibly related to the DNA-aggregating properties of all four compounds as demonstrated by cell-free gel mobility-shift assays. Together, these results demonstrate a new class of thiophene-containing Ru(II) cyclometalated compounds that contain both highly selective chemotherapeutic agents and extremely potent photocytotoxic agents. Show less

There is an urgent need to discover new, selective compounds to add to the limited arsenal of chemotherapeutics displaying selective toxicity for aggressive triple-negative breast cancer (TNBC) cells. The effect of two, recently developed metal-based half-sandwich complexes [Os(η6-pcym)(bphen)(dca)]PF6 (Os-dca) and [Ru(η6-pcym)(bphen)(dca)]PF6 (Ru-dca) [pcym = 1-methyl-4-(propan-2-yl)benzene (p-cymene); bphen = 4,7-diphenyl-1,10-phenanthroline (bathophenanthroline); dca = dichloroacetate] on triple-negative breast cancer cells MDA-MB-231 is reported. The complexes display selective toxicity in several tumor cells (at submicromolar concentrations), and a prominent effect is observed against highly progressive triple negative breast cancer MDA-MB-231 cells for Os-dca. The lower potency of Ru-dca in comparison with Os-dca is apparently connected with a relatively quick release of the dca ligand due to the hydrolysis of Ru-dca before this complex enters the cells. Remarkably, both Os-dca and Ru-dca reduce successfully metastasis-related properties of the triple-negative breast cancer cells such as migration, invasion, and re-adhesion. The anti-metastatic effects of Os-dca and Ru-dca are associated with their ability to suppress matrix metalloproteinase activity and/or production and reduce the expression of aquaporins. Further detailed mechanistic studies reveal that Os-dca reverses Warburg's effect and oncosis seems to be a prominent mode of cell death that predominates over apoptosis. As such, Os-dca can efficiently overcome the resistance of cancer cells to clinically-used apoptotic inducers cisplatin and carboplatin. The cytostatic and anti-metastatic properties of Os-dca in MDA-MB-231 provide a strong impetus for the development of new metal-based compounds to target hardly treatable human TNBC cells and displaying different modes of action compared to the antitumor metallodrugs in clinical use. Show less

Poor selectivity between cancer cells and normal cells is one of the major limitations of cancer chemotherapy. Lysosome-targeted ruthenium-based complexes target tumor cells selectively, only displaying rather weak cytotoxicity or inactivity toward normal cells. Confocal microscopy was employed for the first time to determine the cellular localization of the half-sandwich Ru complex. Show less

Six novel polypyridyl ruthenium complexes with (E)-2-styryl-1H- imidazo[4,5-f][1,10]phenanthroline ligand and its analogues have been designed to enhance the DNA intercalation ability of their model compound [Ru(bpy)₂(pip)]²⁺ (bpy = 2,2'-bipyridine, pip = 2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline). As shown in the optimized geometry of the complexes, the introduction of styryl group not only extended the conjugated area of the intercalative ligand, but also retained the excellent planarity. These two merits have been proven to be beneficial for their DNA intercalation, thus greatly improved their inhibition activity towards DNA transcription by RNA polymerase and DNA topoisomerase, two enzymes closely related to both DNA and tumor cell growth. The relationships between the substituent group structures and the biological activities have also been investigated from energetic and electronic aspects by quantum chemistry calculations. Results from cell cytotoxicity and apoptosis assay testified that the styryl substituted ruthenium complexes possessed higher antitumor activity than [Ru(bpy)₂(pip)]²⁺, as expected. As quantified in the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, the tumor cell death is caused mostly through apoptosis for Ru2 and Ru3, while non-apoptotic processes for Ru1, Ru4 and Ru5. In vitro fluorescence evaluation revealed that all complexes located mainly in cytoplasm, but the three complexes with high antiproliferative activity could enter nucleus. All complexes have shown apparent lower cytotoxicity towards normal human colon epithelial cell CCD-841-CON than the examined tumor cell lines. Show less

We report the synthesis and characterization of four neutral organometallic tethered complexes, [Ru(η⁶-Ph(CH₂)₃-ethylenediamine-N-R)Cl], where R = methanesulfonyl (Ms, 1), toluenesulfonyl (Ts, 2), 4-trifluoromethylbenzenesulfonyl (Tf, 3), and 4-nitrobenzenesulfonyl (Nb, 4), including their X-ray crystal structures. These complexes exhibit moderate antiproliferative activity toward human ovarian, lung, hepatocellular, and breast cancer cell lines. Complex 2 in particular exhibits a low cross-resistance with cisplatin. The complexes show potent catalytic activity in the transfer hydrogenation of NAD⁺ to NADH with formate as hydride donor in aqueous solution (310 K, pH 7). Substituents on the chelated ligand decreased the turnover frequency in the order Nb > Tf > Ts > Ms. An enhancement of antiproliferative activity (up to 22%) was observed on coadministration with nontoxic concentrations of sodium formate (0.5-2 mM). Complex 2 binds to nucleobase guanine (9-EtG), but DNA appears not to be the target, as little binding to calf thymus DNA or bacterial plasmid DNA was observed. In addition, complex 2 reacts rapidly with glutathione (GSH), which might hamper transfer hydrogenation reactions in cells. Complex 2 induced a dose-dependent G₁ cell cycle arrest after 24 h exposure in A2780 human ovarian cancer cells while promoting an increase in reactive oxygen species (ROS), which is likely to contribute to its antiproliferative activity. Show less

A series of neutral pseudo-octahedral RuII sulfonamidoethylenediamine complexes [(η6-p-cym)Ru(N,N')Cl] where N,N' is N-(2-(R1,R2-amino)ethyl)-4-toluenesulfonamide (TsEn(R1,R2)) R1,R2 = Me,H (1); Me,Me (2); Et,H (3); benzyl,H (Bz, 4); 4-fluorobenzyl,H (4-F-Bz, 5) or naphthalen-2-ylmethyl,H (Naph, 6), were synthesised and characterised including the X-ray crystal structure of 3. These complexes catalyse the reduction of NAD+ regioselectively to 1,4-NADH by using formate as the hydride source. The catalytic efficiency depends markedly on the steric and electronic effects of the N-substitutent, with turnover frequencies (TOFs) increasing in the order: 1 < 2 < 3, 6 < 4, 5, achieving a TOF of 7.7 h-1 for 4 with a 95% yield of 1,4-NADH. The reduction rate was highest between pH* (deuterated solvent) 6 and 7.5 and improved with an increase in formate concentration (TOF of 18.8 h-1, 140 mM formate). The calculations suggested initial substitution of an aqua ligand by formate, followed by hydride transfer to RuII and then to NAD+, and indicated specific interactions between the aqua complex and both NAD+ and NADH, the former allowing a preorganisation involving interaction between the aqua ligand, formate anion and the pyridine ring of NAD+. The complexes exhibited antiproliferative activity towards A2780 human ovarian cancer cells with IC50 values ranging from 1 to 31 μM, the most potent complex, [(η6-p-cym)Ru(TsEn(Bz,H))Cl] (4, IC50 = 1.0 ± 0.1 μM), having a potency similar to the anticancer drug cisplatin. Co-administration with sodium formate (2 mM), increased the potency of all complexes towards A2780 cells by 20-36%, with the greatest effect seen for complex 6. Show less

Here and for the first time, we show that the organometallic compound [Ru(η⁵-C₅H₅)(PPh₃)₂Cl] (RuCp) has potential to be used as a metallodrug in anticancer therapy, and further present a new approach for the cellular delivery of the [Ru(η⁵-C₅H₅)(PPh₃)₂]⁺ fragment via coordination on the periphery of low-generation poly(alkylidenimine) dendrimers through nitrile terminal groups. Importantly, both the RuCp and the dendrimers functionalized with [Ru(η⁵-C₅H₅)(PPh₃)₂]⁺ fragments present remarkable toxicity towards a wide set of cancer cells (Caco-2, MCF-7, CAL-72, and A2780 cells), including cisplatin-resistant human ovarian carcinoma cell lines (A2780cisR cells). Also, RuCp and the prepared metallodendrimers are active against human mesenchymal stem cells (hMSCs), which are often found in the tumor microenvironment where they seem to play a role in tumor progression and drug resistance. Show less

Ruthenium(II) complexes are currently considered a viable alternative to the widely used platinum complexes as efficient anticancer agents. We herein present the synthesis and characterization of half-sandwich ruthenium compounds with the general formula [Ru( p-cymene)(L-N,N)Cl][CF₃SO₃] (L = 3,6-di-2-pyridyl-1,2,4,5-tetrazine (1) 6,7-dimethyl-2,3-bis(pyridin-2-yl)quinoxaline (2)), which have been synthesized by substitution reactions from the precursor dimer [Ru( p-cymene)(Cl)(μ-Cl)]₂ and were characterized by elemental analysis, mass spectrometry, ¹H NMR, UV-vis, and IR spectroscopy, conductivity measurements, and cyclic voltammetry. The molecular structure for complex 2 was determined by single-crystal X-ray diffraction. The cytotoxic activity of these compounds was evaluated against human tumor cells, namely ovarian carcinoma A2780 and breast MCF7 and MDAMB231 adenocarcinoma cells, and against normal primary fibroblasts. Whereas the cytotoxic activity of 1 is moderate, IC₅₀ values found for 2 are among the lowest previously reported for Ru( p-cymene) complexes. Both compounds present no cytotoxic effect in normal human primary fibroblasts when they are used at the IC₅₀ concentration in A2780 and MCF7 cancer cells. Their antiproliferative capacity is associated with a combined mechanism of apoptosis and autophagy. A strong interaction with DNA was observed for both with a binding constant value of the same magnitude as that of the classical intercalator [Ru(phen)₂(dppz)]²⁺. Both complexes bind to human serum albumin with moderate to strong affinity, with conditional binding constants (log K_b) of 4.88 for complex 2 and 5.18 for complex 1 in 2% DMSO/10 mM Hepes pH7.0 medium. The acute toxicity was evaluated in zebrafish embryo model using the fish embryo acute toxicity test (FET). Remarkably, our results show that compounds 1 and 2 are not toxic/lethal even at extremely high concentrations. The novel compounds reported herein are highly relevant antitumor metallodrug candidates, given their in vitro cytotoxicity toward cancer cells and the lack of in vivo toxicity. Show less

The promise of the metal(arene) structure as an anticancer pharmacophore has prompted intensive exploration of this chemical space. While N-heterocyclic carbene (NHC) ligands are widely used in catalysis, they have only recently been considered in metal complexes for medicinal applications. Surprisingly, a comparatively small number of studies have been reported in which the NHC ligand was coordinated to the Ru^II(arene) pharmacophore and even less with an Os^II(arene) pharmacophore. Here, we present a systematic study in which we compared symmetrically substituted methyl and benzyl derivatives with the nonsymmetric methyl/benzyl analogues. Through variation of the metal center and the halido ligands, an in-depth study was conducted on ligand exchange properties of these complexes and their biomolecule binding, noting in particular the stability of the M-C_NHC bond. In addition, we demonstrated the ability of the complexes to inhibit the selenoenzyme thioredoxin reductase (TrxR), suggested as an important target for anticancer metal-NHC complexes, and their cytotoxicity in human tumor cells. It was found that the most potent TrxR inhibitor diiodido(1,3-dibenzylbenzimidazol-2-ylidene)(η⁶-p-cymene)ruthenium(II) 1b^I was also the most cytotoxic compound of the series, with the antiproliferative effects in general in the low to middle micromolar range. However, since there was no clear correlation between TrxR inhibition and antiproliferative potency across the compounds, TrxR inhibition is unlikely to be the main mode of action for the compound type and other target interactions must be considered in future. Show less

Series of half-sandwich Ir^IIIN-heterocyclic carbene (NHC) antitumor complexes [(η⁵-Cp*)Ir(C^C)Cl] have been synthesized and characterized (Cp* is pentamethyl cyclopentadienyl, and C^C are four NHC chelating ligands containing phenyl rings at different positions). Ir^III complexes showed potent antitumor activity with IC₅₀ values ranged from 3.9 to 11.8 μM against A549 cells by the MTT assay. Complexes can catalyze the conversion of the coenzyme NADH to NAD⁺ and induce the production of reactive oxygen species (ROS), and bonding to BSA by static quenching mode. Complexes can arrest the cell cycle in G₁ or S phase and reduce the mitochondrial membrane potential. Confocal microscopy test show complexes could target the lysosome and mitochondria in cells with the Pearson's colocalization coefficient of 0.82 and 0.21 after 12 h, respectively, and followed by an energy-dependent cellular uptake mechanism. Show less

A series of five kinetically inert bis-cyclometalated Ir^III complexes of general formula [Ir(C^N)₂ (N^N)][PF₆ ] [C^N=2-phenyl-1-[4-(trifluoromethyl)benzyl]-1H-benzo[d]imidazol-κN,C; N^N=1,10-phenanthroline (phen, 1), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq, 2), dipyrido[3,2-a:2',3'-c]phenazine (dppz, 3), benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (dppn, 4), and dipyrido[3,2-a:2',3'-c]phenazine-10,11-imidazolone (dppz-izdo, 5)] were designed and synthesized to explore the effect of the degree of π conjugation of the polypyridyl ligand on their toxicity in cancer cells. We show that less-lipophilic complexes 1 and 2 exhibit the highest toxicity [sub-micromolar inhibitory concentration (IC₅₀ ) values] in A2780, HeLa, and MCF-7 cancer cells, and they are markedly more efficient than clinically used platinum drugs. It is noteworthy that the investigated Ir agents display the capability to overcome acquired and inherent resistance to conventional cisplatin (in A2780cisR and MCF-7 cells, respectively). We demonstrate that the Ir complexes, unlike clinically used platinum antitumor drugs, do not kill cells through DNA-damage response. Rather, they kill cells by inhibiting protein translation by targeting preferentially the endoplasmic reticulum. Our findings also reveal that the toxic effect of the Ir complexes can be significantly potentiated by irradiation with visible light (by more than two orders of magnitude). The photopotentiation of the investigated Ir complexes can be attributed to a marked increase (≈10-30-fold) in intracellular reactive oxygen species. Collectively, these data highlight the functional diversity of antitumor metal-based drugs and the usefulness of a mechanism-based rationale for selecting candidate agents that are effective against chemoresistant tumors for further preclinical testing. Show less

Twelve novel half-sandwich IrIII-NHC complexes [(η5-Cpx)Ir(C^O)Cl] were synthesized and characterized. These complexes showed higher cytotoxic activity toward A549 cells and HeLa cells than cisplatin. An increase in the number of contained phenyl groups was related to better anticancer activity. The reaction of complexes with nucleobases 9-MeA, nucleobases 9-EtG, plasmid DNA and CT-DNA showed no significant effects. These complexes captured hydrogen from NADH and converted it to NAD+, which produced the reactive oxygen species (ROS). ROS led to a decrease in the mitochondrial membrane potential and lysosomal damage, finally inducing apoptosis. Show less

Precise quantitative measurement of viscosity at the subcellular level presents great challenges. Two-photon phosphorescence lifetime imaging microscopy (TPPLIM) can reflect micro-environmental changes of a chromophore in a quantitative manner. Phosphorescent iridium complexes are potential TPPLIM probes due to their rich photophysical properties including environment-sensitive long-lifetime emission and high two-photon absorption (TPA) properties. In this work, a series of iridium(iii) complexes containing rotatable groups are developed as mitochondria-targeting anticancer agents and quantitative viscosity probes. Among them, Ir6 ([Ir(ppy-CHO)₂(dppe)]PF₆; ppy-CHO: 4-(2-pyridyl)benzaldehyde; dppe: cis-1,2-bis(diphenylphosphino)ethene) shows satisfactory TPA properties and long lifetimes (up to 1 μs). The emission intensities and lifetimes of Ir6 are viscosity-dependent, which is mainly attributed to the configurational changes in the diphosphine ligand as proved by ¹H NMR spectra. Ir6 displays potent cytotoxicity, and mechanism investigations show that it can accumulate in mitochondria and induce apoptotic cell death. Moreover, Ir6 can induce mitochondrial dysfunction and monitor the changes in mitochondrial viscosity simultaneously in a real-time and quantitative manner via TPPLIM. Upon Ir6 treatment, a time-dependent increase in viscosity and heterogeneity is observed along with the loss of membrane potential in mitochondria. In summary, our work shows that multifunctional phosphorescent metal complexes can induce and precisely detect microenvironmental changes simultaneously at the subcellular level using TPPLIM, which may deepen the understanding of the cell death mechanisms induced by these metallocompounds. Show less

Organometallic half-sandwich Ir^III complexes of the type [(η⁵ -Cp^x )Ir(N^N)Cl]PF₆ (Cp^x : Cp* or its phenyl Cp^xph or biphenyl Cp^xbiph derivatives; N^N: triphenylamine (TPA)-substituted bipyridyl ligand groups) were synthesized and characterized. The complexes showed excellent bovine serum albumin (BSA) and DNA binding properties and were able to oxidize NADH to NAD⁺ (NAD=nicotinamide adenine dinucleotide) efficiently. The complexes induced apoptosis effectively and led to the emergence of reactive oxygen species (ROS) in cells. All complexes showed potent cytotoxicity with IC₅₀ values ranging from 1.5 to 7.1 μm toward A549 human lung cancer cells after 24 hours of drug exposure, which is up to 14 times more potent than cisplatin under the same conditions. Show less

The rational design of the ligands around transition metals has achieved success in the development of anticancer complexes. In this contribution, a series of organometallic half-sandwich iridium(iii) complexes with various corresponding counteranions have been prepared and characterized. The size and coordination ability of the counteranions exert a great influence on the chemical reactivity and anticancer activity of these complexes. The influence of the counteranions on the cell cycle, apoptosis, ROS and mitochondrial membrane potential is also discussed. This work has shown for the first time that the modification of counteranions can affect the anticancer activity of transition metal-based complexes. Show less

Oncosis is a non-apoptotic form of programmed cell death (PCD), which differs from apoptosis in both morphological changes and inner pathways, and might hold the key to defeating a major obstacle in cancer therapy - drug-resistance, which is often a result of the intrinsic apoptosis resistance of tumours. However, despite the fact that the term "oncosis" was coined and used much earlier than apoptosis, little effort has been made to discover new drugs which can initiate this form of cell death, in comparison to drugs inducing apoptosis or any other type of PCD. So herein, we present the synthesis of a series of mitochondria-targeting cyclometalated Ir(iii) complexes, which activated the oncosis-specific protein porimin and calpain in cisplatin-resistant cell line A549R, and determined their cytotoxicity against a wide range of drug-resistant cancer types. To the best of our knowledge, these complexes are the very first metallo-components to induce oncosis in drug-resistant cancer cells. Show less

Two novel rhodium(III) complexes, namely, [Rh^III(X)Cl₃] (X = 2 2,6-bis((4 S,7 R)-7,8,8-trimethyl-4,5,6,7-tetrahydro-1 H-4,7-methanoindazol-3-yl)pyridine or 2,6-bis((4 S,7 R)-1,7,8,8-tetramethyl-4,5,6,7-tetrahydro-1 H-4,7-methanoindazol-3-yl)pyridine), were synthesized from camphor derivatives of a bis(pyrazolylpyridine), tridentate nitrogen-donor chelate system, giving [Rh^III(H₂L*)Cl₃] (1a) and [Rh^III(Me₂L*)Cl₃] (1b). A rhodium(III) terpyridine (terpy) ligand complex, [Rh^III(terpy)Cl₃] (1c), was also synthesized. By single-crystal X-ray analysis, 1b crystallizes in an orthorhombic P2₁2₁2₁ system, with two molecules in the asymmetric unit. Tridentate coordination by the N,N,N-donor localizes the central nitrogen atom close to the rhodium(III) center. Compounds 1a and 1b were reactive toward l-methionine (l-Met), guanosine-5'-monophosphate (5'-GMP), and glutathione (GSH), with an order of reactivity of 5'-GMP > GSH > l-Met. The order of reactivity of the Rh^III complexes was: 1b> 1a > 1c. The Rh^III complexes showed affinity for calf thymus DNA and bovine serum albumin by UV-vis and emission spectral studies. Furthermore, 1b showed significant in vitro cytotoxicity against human epithelial colorectal carcinoma cells. Since the Rh^III complexes have similar coordination modes, stability differences were evaluated by density functional theory (DFT) calculations (B3LYP(CPCM)/LANL2DZp). With (H₂L*) and (terpy) as model ligands, DFT calculations suggest that both tridentate ligand systems have similar stability. In addition, molecular docking suggests that all test compounds have affinity for the minor groove of DNA, while 1b and 1c have potential for DNA intercalation. Show less

Loss of function mutations in Kelch-like ECH Associated Protein 1 (KEAP1), or gain-of-function mutations in nuclear factor erythroid 2-related factor 2 (NRF2), are common in non-small cell lung cancer (NSCLC) and associated with therapeutic resistance. To discover novel NRF2 inhibitors for targeted therapy, we conducted a quantitative high-throughput screen using a diverse set of ∼400 000 small molecules (Molecular Libraries Small Molecule Repository Library, MLSMR) at the National Center for Advancing Translational Sciences. We identified ML385 as a probe molecule that binds to NRF2 and inhibits its downstream target gene expression. Specifically, ML385 binds to Neh1, the Cap 'N' Collar Basic Leucine Zipper (CNC-bZIP) domain of NRF2, and interferes with the binding of the V-Maf Avian Musculoaponeurotic Fibrosarcoma Oncogene Homologue G (MAFG)-NRF2 protein complex to regulatory DNA binding sequences. In clonogenic assays, when used in combination with platinum-based drugs, doxorubicin or taxol, ML385 substantially enhances cytotoxicity in NSCLC cells, as compared to single agents. ML385 shows specificity and selectivity for NSCLC cells with KEAP1 mutation, leading to gain of NRF2 function. In preclinical models of NSCLC with gain of NRF2 function, ML385 in combination with carboplatin showed significant antitumor activity. We demonstrate the discovery and validation of ML385 as a novel and specific NRF2 inhibitor and conclude that targeting NRF2 may represent a promising strategy for the treatment of advanced NSCLC. Show less

Synergistic photodynamic therapy (PDT) that combines photosensitizers (PSs) to attack different key sites in cancer cells is very attractive. However, the use of multiple PSs may increase dark cytotoxicity. Additionally, realizing the multiple vein passage of several PSs through dosing could be a challenge in clinical treatment. To address these issues, a novel strategy that enables a single PS to ablate two key sites (i.e., cytomembranes on the outside and mitochondria on the inside) of cancer cells synergistically was proposed. Five new fluorinated ruthenium (II) complexes (Ru1-Ru5), which possessed excellent two-photon properties and good singlet oxygen quantum yields, were designed and synthesized. When incubated with HeLa cells, the complexes were observed on the cytomembranes at first. With an extension of the treatment time, both the cytomembranes and mitochondria were lit up by the complexes. Under two-photon laser irradiation, the mitochondria and cytomembranes were ablated simultaneously, and the HeLa cells were destroyed effectively by the complexes, whether the cells were in a monolayer or in multicellular spheroids. With the largest phototoxicity index under the two-photon laser, Ru4 was used for two-photon PDT of in vivo xenograft tumors and successfully inhibited the growth of the tumors. Our results emphasized that the strategy of attacking two key sites with a single PS is an efficient method for PDT. Show less

Two [Ru(phen)₂ dppz]²⁺ derivatives (phen=1,10-phenantroline, dppz=dipyrido[3,2-a:2',3'-c]phenazine) with different functional groups on the dppz ligand [dppz-7,8-(OMe)₂ (1), dppz-7,8-(OH)₂ (2)] have been synthesized, characterized and investigated as photosensitizers (PSs) for photodynamic therapy (PDT) against cancer. Both complexes showed intense red phosphorescence and promising singlet oxygen (¹ O₂ ) quantum yields of 75 % (1) and 54 % (2) in acetonitrile. Complex 1 (logP_o/w =-0.52, 2.4 nmol Ru per mg protein) was found to be more lipophilic, having also a higher cellular uptake efficiency compared to 2 (logP_o/w =-0.20, 0.9 nmol Ru per mg protein). Complex 1 localized evenly in HeLa cells whereas 2, was mainly visualized in the cell membrane by confocal microscopy. In the dark, complex 1 (IC₅₀ =36.5 μm) was found to be more toxic than complex 2 (IC₅₀ >100 μm) on a HeLa cells monolayer. Importantly, in view of PDT applications, both complexes were found to be non-toxic in the dark towards multicellular HeLa spheroids (IC₅₀ >100 μm). Upon one-photon irradiation (420 nm, 9.27 J cm^-2 ), 1 exhibited higher phototoxicity (IC₅₀ =3.1 μm) than 2 (IC₅₀ =16.7 μm) on HeLa cell monolayers. When two-photon irradiation (800 nm, 9.90 J cm^-2 ) was applied, only 1 (IC₅₀ =9.5 μm) was found to be active toward HeLa spheroids. This study demonstrates that the functional group on the intercalative ligand has a strong influence on the cellular localization and anticancer activity of Ru^II polypyridyl complexes. Show less

CHS-828 (N-(6-(4-chlorophenoxy)hexyl)-N'-cyano-N″-4-pyridyl guanidine) is an anticancer agent with low bioavailability and high systemic toxicity. Here we present an approach to improve the therapeutic profile of the drug using photolabile ruthenium complexes to generate light-activated prodrugs of CHS-828. Both prodrug complexes are stable in the dark but release CHS-828 when irradiated with visible light. The complexes are water-soluble and accumulate in tumour cells in very high concentrations, predominantly in the mitochondria. Both prodrug complexes are significantly less cyototoxic than free CHS-828 in the dark but their toxicity increases up to 10-fold in combination with visible light. The cellular responses to light treatment are consistent with release of the cytotoxic CHS-828 ligand. Show less

Four mononuclear [(L-L)₂ Ru(tatpp)]²⁺ and two dinuclear [(L-L)₂ Ru(tatpp)Ru(L-L)₂ ]⁴⁺ ruthenium(II) polypyridyl complexes (RPCs) containing the 9,11,20,22-tetraazatetrapyrido[3,2-a:2',3'-c:3'',2''-l:2''',3'''-n]pentacene (tatpp) ligand were synthesized, in which L-L is a chelating diamine ligand such as 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), 3,4,7,8-tetramethyl-1,10-phenanthroline (Me₄ phen) or 4,7-diphenyl-1,10-phenanthroline (Ph₂ phen). These Ru-tatpp analogues all undergo reduction reactions with modest reducing agents, such as glutathione (GSH), at pH 7. These, plus several structurally related but non-redox-active RPCs, were screened for DNA cleavage activity, cytotoxicity, acetylcholinesterase (AChE) inhibition, and acute mouse toxicity, and their activities were examined with respect to redox activity and lipophilicity. All of the redox-active RPCs show single-strand DNA cleavage in the presence of GSH, whereas none of the non-redox-active RPCs do. Low-micromolar cytotoxicity (IC₅₀ ) against malignant H358, CCL228, and MCF7 cultured cell lines was mainly restricted to the redox-active RPCs; however, they were substantially less toxic toward nonmalignant MCF10 cells. The IC₅₀ values for AChE inhibition in cell-free assays and the acute toxicity of RPCs in mice revealed that whereas most RPCs show potent inhibitory action against AChE (IC₅₀ values <15 μm), Ru-tatpp complexes as a class are surprisingly well tolerated in animals relative to other RPCs. Show less

Two coumarin based Ru^II-polyimine complexes (Ru-1 and Ru-2) showing intense absorption of visible light and long-lived triplet excited states (~12-15μs) were used for study of the interaction with DNA. The binding of the complexes with CT-DNA were studied by UV-vis, fluorescence and time-resolved nanosecond transient absorption (ns-TA) spectroscopy. The results suggesting that the complexes interact with CT-DNA by intercalation mode of binding, showing the binding constants (K_b) 6.47×10⁴ for Ru-1 and 5.94×10⁴ M^-1 for Ru-2, in contrast no such results were found for Ru-0. The nanosecond transient absorption spectra of these systems in the presence of CT-DNA showing a clear perturbation in the bleaching region was observed compare to buffer alone. Visible light photoirradiation DNA cleavage was investigated for these complexes by treating with the supercoiled pUC19 DNA and irradiated at 450nm. The reactive species produced upon irradiation of current agents is singlet oxygen (¹O₂), which results in the generation of other reactive oxygen species (ROS). The complexes shown efficient cleavage activity, converted complete supercoiled DNA to nicked circular at as low as 20μM concentration in 30min of light irradiation time. Significant amount of linear form was generated by Ru-1 at the same conditions. Even though Ru-0 has significant ¹O₂ quantum yield but shown lower cleavage activity compared to other two analogs is due the miserable interaction (binding) with DNA. The cytotoxicity in vitro of the complexes toward HeLa, BEL-7402 and MG-63 cells was assessed by MTT assay. The cellular uptake was observed on BEL-7402 cells under fluorescence microscope. The complexes shown appreciable cytotoxicity towards the cancer cell lines. Show less

In this paper a novel ligand debip (2-(4-N,N-diethylbenzenamine)1H-imidazo[4,5-f] [1, 10]phenanthroline) and its Ru(II) polypyridyl complexes [Ru(L)₂(debip)]²⁺, (L = phen (1), bpy (2) and dmb (3)) have been synthesized and characterized by spectroscopic techniques. The DNA binding studies for all these complexes were examined by absorption, emission, quenching studies, viscosity measurements and cyclic voltammetry. The light switching properties of complexes 1-3 have been evaluated. Molecular docking, Density Functional Theory (DFT) and time dependent DFT calculations were performed. The Ru(II) complexes exhibited efficient photocleavage activity against pBR322 DNA upon irradiation and exhibited good antimicrobial activity. Also investigated 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay, lactate dehydrogenase (LDH) release assay and reactive oxygen species (ROS) against selected cancer cell lines (HeLa, PC3, Lancap, MCF-7 and MD-MBA 231). Show less

Chemotherapy is limited by its poor selectivity towards cancer cells over normal cells. Herein, we designed half-sandwich ruthenium imino-pyridyl complexes [(η⁶-bz)Ru(N^N)Cl]PF₆ to achieve selective cytotoxicity to cancer cells. This kind of ruthenium complex has unique characteristics and is worthy of further exploration in the design of new anticancer drugs. Show less