A ruthenium(II) complex inhibits tumor growth in vivo with fewer side-effects compared with cisplatin

Safety and Efficacy Evaluation In Vivo of a Cationic Nucleolipid Nanosystem for the Nanodelivery of a Ruthenium(III) Complex with Superior Anticancer Bioactivity

Simple Summary

The availability of selective, effective, and safe anticancer agents is a major challenge in the field of cancer research. As part of a multidisciplinary research project, in recent years our group has proposed an original class of nanomaterials for the delivery of new anticancer drugs based on ruthenium(III) complexes. In cellular models, these nanosystems have been shown to be effective in counteracting growth and proliferation of human breast cancer cells. Compared to conventional metallochemotherapeutics such as platinum-based agents whose clinical practice is associated with serious undesirable effects, ruthenium complexes share improved biochemical profiles making them more selective towards cancer cells and less cytotoxic to healthy cells. Their combination with biocompatible nanocarriers further enhances these promising features, as here showcased by our research carried out in an animal model which underscores the efficacy and safety in vivo of one of our most promising ruthenium-based nanosystems.

Abstract

Selectivity and efficacy towards target cancer cells, as well as biocompatibility, are current challenges of advanced chemotherapy powering the discovery of unconventional metal-based drugs and the search for novel therapeutic approaches. Among second-generation metal-based chemotherapeutics, ruthenium complexes have demonstrated promising anticancer activity coupled to minimal toxicity profiles and peculiar biochemical features. In this context, our research group has recently focused on a bioactive Ru(III) complex—named AziRu—incorporated into a suite of ad hoc designed nucleolipid nanosystems to ensure its chemical stability and delivery. Indeed, we proved that the structure and properties of decorated nucleolipids can have a major impact on the anticancer activity of the ruthenium core. Moving in this direction, here we describe a preclinical study performed by a mouse xenograft model of human breast cancer to establish safety and efficacy in vivo of a cationic Ru(III)-based nucleolipid formulation, named HoThyRu/DOTAP, endowed with superior antiproliferative activity. The results show a remarkable reduction in tumour with no evidence of animal suffering. Blood diagnostics, as well as biochemical analysis in both acute and chronic treated animal groups, demonstrate a good tolerability profile at the therapeutic regimen, with 100% of mice survival and no indication of toxicity. In addition, ruthenium plasma concentration analysis and tissue bioaccumulation were determined via appropriate sampling and ICP-MS analysis. Overall, this study supports both the efficacy of our Ru-containing nanosystem versus a human breast cancer model and its safety in vivo through well-tolerated animal biological responses, envisaging a possible forthcoming use in clinical trials.

Smart ion imprinted polymer for selective adsorption of Ru(Ⅲ) and simultaneously waste sample being transformed as a catalyst

In this work, a temperature-sensitive block polymer PDEA-b-P(DEA-co-AM) was synthesized and then introduced into the preparation of a smart Ru(Ⅲ) imprinted polymer (Ru-IIP) to selectively adsorption Ru(Ⅲ) first. Then the waste Ru-IIP was converted into a catalyst in-situ for recycle. The structure and morphology of the prepared polymer were characterized by Fourier transform infrared spectrometer, Scanning electron microscope, BET surface area and Thermogravimetric analysis. The adsorption properties of the synthesized smart material were investigated in terms of adsorption pH, adsorption kinetics and adsorption isotherm. Results documented that the optimal adsorption temperature and pH were 35 °C and 1.5 respectively, the maximum adsorption capacity was 0.153 mmol/g, and the adsorption processes of Ru-IIP were more suitable to be expressed by pseudo-first-order kinetic and Langmuir model. The selectivity studied in different binary mixed solutions showed that Ru-IIP has good selectivity, and reusability results showed that Ru-IIP still maintains a good adsorption effect after 8 cycles. In addition, the waste Ru-IIP, a Ru(Ⅲ) remained waste sample was employed as the catalyst for the synthesis of imines, and result showed the mass of adsorbent would reduce after the completion of catalysis, which could not only catalyze the reaction but also reduce pollution.

High anticancer activity and apoptosis- and autophagy-inducing properties of novel lanthanide(III) complexes bearing 8-hydroxyquinoline-N-oxide and 1,10-phenanthroline

In the quest for rare earth metal complexes with enhanced cancer chemotherapeutic properties, the discovery of seven lanthanide(iii) complexes bearing 8-hydroxyquinoline-N-oxide (NQ) and 1,10-phenanthroline (phen) ligands, i.e., [SmIII(NQ)(phen)(H2O)Cl2] (Ln1), [EuII(NQ)(phen)(H2O)Cl2] (Ln2), [GdIII(NQ)(phen)(H2O)Cl2] (Ln3), [DyIII(NQ)(phen)(H2O)Cl2] (Ln4), [HoIII(NQ)(phen)(H2O)Cl2] (Ln5), [ErIII(NQ)(phen)(H2O)Cl2] (Ln6), and [YbIII(NQ)(phen)(H2O)Cl2] (Ln7), as potential anticancer drugs is described. Complexes Ln1-Ln7 exhibit high antiproliferative activity against cisplatin-resistant A549/DDP cells (IC50 = 0.025-0.097 μM) and low toxicity to normal HL-7702 cells. Moreover, complex Ln1, and to a lesser extent Ln7, can upregulate the expression of LC3 and Beclin1 and downregulate p62 to induce apoptosis in cisplatin-resistant A549/DDP cell lines, which is related to the cell autophagy-inducing properties of Ln1 and Ln7. Furthermore, in vivo assays suggest that Ln1 significantly inhibits A549/DDP xenograft tumor growth (56.5%). These results indicate that lanthanide(iii) complex Ln1 is a promising candidate as an anticancer drug against cisplatin-resistant A549/DDP cells.

[Ru(phen)2podppz]2+ significantly inhibits glioblastoma growth in vitro and vivo with fewer side-effects than cisplatin

To overcome the acquired resistance and the significant side-effects of the reported drugs, four new ruthenium(ii) complexes with alkynyl (Ru1, Ru2, Ru3, Ru4) were designed and synthesized. Ru1, Ru2, Ru3 and Ru4 were characterized by ESI-MS, 1H NMR, 1H-1H COSY NMR and elemental analysis. Compared with Ru2, Ru3, Ru4 and cisplatin, the anti-tumor experiments in vitro and vivo confirmed that Ru1 could most effectively inhibit tumor growth. In the experiments of safety evaluation in vivo, Ru1 could avoid any detectable side-effects compared with cisplatin. DNA binding experiments and cell cycle experiments showed that Ru1 exhibited the strongest DNA binding ability and interfered with the cell cycle by inserting DNA to inhibit tumor growth. The study demonstrated that Ru1 had the potential to be an exciting new drug candidate for glioblastoma treatment.

Oxidative stress cytotoxicity induced by platinum-doped magnesia nanoparticles in cancer cells

The aim of this study was to prepare, characterize, and determine the in vitro anticancer effects of platinum-doped magnesia (Pt/MgO) nanoparticles. The chemical compositions, functional groups, and size of nanoparticles were determined using X-ray diffraction, Fourier transform infrared spectroscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, and scanning electron microscopy. Pt/MgO nanoparticles were cuboid and in the nanosize range of 30-50 nm. The cytotoxicity of Pt/MgO nanoparticles was determined via the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay on the human lung and colonic cancer cells (A549 and HT29 respectively) and normal human lung and colonic fibroblasts cells (MRC-5 and CCD-18Co repectively). The Pt/MgO nanoparticles were relatively innocuous to normal cells. Pt/MgO nanoparticles downregulated Bcl-2 and upregulated Bax and p53 tumor suppressor proteins in the cancer cells. Pt/MgO nanoparticles also induced production of reactive oxygen species, decreased cellular glutathione level, and increased lipid peroxidation. Thus, the anticancer effects of Pt/MgO nanoparticles were attributed to the induction of oxidative stress and apoptosis. The study showed the potential of Pt/MgO nanoparticles as an anti-cancer compound.

Mitochondria-localizing curcumin-cryptolepine Zn(II) complexes and their antitumor activity

Many metal complexes are potent candidates as mitochondrial-targeting agents. In this study, four novel Zn(II) complexes, [Zn(BPQA)Cl₂] (Zn1), [Zn(BPQA)(Curc)]Cl (Zn2), [Zn(PQA)Cl₂] (Zn3), and [Zn(PQA)(Curc)]Cl (Zn4), containing N,N-bis(pyridin-2-ylmethyl)benzofuro[3,2-b]quinolin-11-amine (BPQA), N-(pyridin-2-ylmethyl)benzofuro[3,2-b]quinolin-11-amine (PQA), and curcumin (H-Curc) were synthesized. An MTT assay showed that Zn1-Zn4 had strong anticancer activities against SK-OV-3/DDP and T-24 tumor cells with IC₅₀ values of 0.03-6.19 μM. Importantly, Zn1 and Zn2 displayed low toxicities against normal HL-7702 cells. Mechanism experiments demonstrated that probe Zn2 showed appreciable fluorescence in the red region of the spectrum, and substantial accumulation of Zn2 occurred in the mitochondria after treatment, indicating increases in Ca²⁺ and reactive oxygen species levels, loss of the mitochondrial membrane potential, and consequent induction of mitochondrial dysfunction at low concentrations. In addition, the probe Zn2 effectively (50.7%) inhibited the growth of T-24 bladder tumor cells in vivo. The probe Zn2 shows potential for use in cancer therapy while retaining the H-Curc as an imaging probe.

Molecular and Functional Analysis of Choline Transporters and Antitumor Effects of Choline Transporter-Like Protein 1 Inhibitors in Human Pancreatic Cancer Cells

Choline, an organic cation, is one of the biofactors that play an important role in the structure and the function of biological membranes, and it is essential for the synthesis of phospholipids. Choline positron emission tomography-computed tomography (PET/CT) provides useful information for the imaging diagnosis of cancers, and increased choline accumulation has been identified in a variety of tumors. However, the molecular mechanisms of choline uptake and choline transporters in pancreatic cancer have not been elucidated. Here, we examined molecular and functional analyses of choline transporters in human pancreatic-cancer cell line MIA PaCa-2 and the elucidation of the action mechanism behind the antitumor effect of novel choline-transporter-like protein 1 (CTL1) inhibitors, Amb4269951 and its derivative Amb4269675. CTL1 and CTL2 mRNAs were highly expressed in MIA PaCa-2 cells, and CTL1 and CTL2 proteins were localized in the plasma membrane and the intracellular compartments, respectively. Choline uptake was characterized by Na⁺-independence, a single-uptake mechanism, and inhibition by choline-uptake inhibitor HC-3, similar to the function of CTL1. These results suggest that the uptake of extracellular choline in MIA PaCa-2 cells is mediated by CTL1. Choline deficiency and HC-3 treatment inhibited cell viability and increased caspase 3/7 activity, suggesting that the inhibition of CTL1 function, which is responsible for choline transport, leads to apoptosis-induced cell death. Both Amb4269951 and Amb4269675 inhibited choline uptake and cell viability and increased caspase-3/7 activity. Ceramide, which is increased by inhibiting choline uptake, also inhibited cell survival and increased caspase-3/7 activity. Lastly, both Amb4269951 and Amb4269675 significantly inhibited tumor growth in a mouse-xenograft model without any adverse effects such as weight loss. CTL1 is a target molecule for the treatment of pancreatic cancer, and its inhibitors Amb4269951 and Amb4269675 are novel lead compounds.

Imaging and therapeutic applications of Zn(ii)-cryptolepine-curcumin molecular probes in cell apoptosis detection and photodynamic therapy

Novel red Zn(ii) complex-based fluorescent probes featuring cryptolepine-curcumin derivatives, namely, [Zn(BQ)Cl₂] (BQ-Zn) and [Zn(BQ)(Cur)]Cl (BQCur-Zn), were developed for the simple and fluorescent label-free detection of apoptosis, an important biological process. The probes could synergistically promote mitochondrion-mediated apoptosis and enhance tumor therapeutic effects in vitro and vivo.

New ruthenium polypyridyl complexes functionalized with fluorine atom or furan: Synthesis, DNA-binding, cytotoxicity and antitumor mechanism studies

Two novel ruthenium(II) polypyridyl complexes, namely, [Ru(dmp)₂(CAPIP)](ClO₄)₂ (Ru(II)-1) and [Ru(dmp)₂(CFPIP)](ClO₄)₂ (Ru(II)-2), which respectively contain (E)-2-(2-(furan-2-yl)vinyl)-1H-imidazo[4,5-f][1,10]phen-anthroline (CAPIP) and (E)-2-(4-fluorostyryl)-1H-imidazo[4,5-f][1,10]phenanthroline. (CFPIP), were first designed and characterized (dmp = 2,9-dimethyl-1,10-phenanthroline). DNA binding experiments indicated that Ru(II) complexes interact with CT DNA through intercalative mode. In addition, the complexes Ru(II)-1 and Ru(II)-2, showed remarkable cell cytotoxicity, giving the respective IC₅₀ values of 4.1 ± 1.4 μM and 6.1 ± 1.4 μM on the A549 cancer cells. These values indicated higher activity than CAPIP, CFPIP, cisplatin (8.2 ± 1.4 μM) and other corresponding Ru(II) polypyridyl complexes. Furthermore, the Ru(II) complexes could arrive the cytoplasm through the cell membrane and accumulate in the mitochondria. Significantly, complexes Ru(II)-1 and Ru(II)-2 induced A549 cells apoptosis was mediated by increase of ROS levels and dysfunction of mitochondria, and resulted in cell cycle arrest and increased anti-migration activity on A549 cells. Overall, these results indicated that complexes Ru(II)-1 and Ru(II)-2 could be suitable candidates for further investigation as a chemotherapeutic agent in the treatment of tumors.

Two telomerase-targeting Pt(ii) complexes of jatrorrhizine and berberine derivatives induce apoptosis in human bladder tumor cells

Two novel Pt(ii) complexes, [Pt(B-TFA)Cl]Cl (Pt1) and [Pt(J-TFA)Cl]Cl (Pt2) with jatrorrhizine and berberine derivatives (B-TFA and J-TFA) were first prepared as desirable luminescent agents for cellular applications and potent telomerase inhibitors, which can induce bladder T-24 tumor cell apoptosis by targeting telomerase, together with induction of mitochondrial dysfunction, telomere DNA damage and cell-cycle arrest. Importantly, T-24 tumor inhibition rate (TIR) was 50.4% for Pt2, which was higher than that of Pt1 (26.4%) and cisplatin (37.1%). Taken together, all the results indicated that jatrorrhizine and berberine derivatives Pt1 and Pt2 show low toxicity and could be novel Pt-based anti-cancer drug candidates.

Complexes of oxoplatin with rhein and ferulic acid ligands as platinum(iv) prodrugs with high anti-tumor activity

We herein designed two new Pt^IV prodrugs of oxoplatin (cis,cis,cis-[PtCl₂(NH₃)₂(OH)₂]), [Pt^IVCl₂(NH₃)₂(O₂C-FA)₂] (Pt-2) and [Pt^IVCl₂(NH₃)₂(O₂C-RH)₂] (Pt-3), by conjugating with ferulic acid (FA-COOH) and rhein (RH-COOH) which have well-known biological activities. Three other Pt(iv) complexes of [Pt^IVCl₂(NH₃)₂(O₂C-BA)₂] (Pt-1), [Pt^IVCl₂(NH₃)₂(O₂C-CA)₂] (Pt-4) and [Pt^IVCl₂(NH₃)₂(O₂C-TCA)₂] (Pt-5) (where BA-COOH = benzoic acid, CA-COOH = crotonic acid and TCA-COOH = trans-cinnamic acid) were also prepared for the comparative study. Like most Pt^IV prodrug complexes, the cytotoxicity of Pt-3 containing the biologically active rhein (RH-COOH) ligand against lung carcinoma (A549 and A549/DDP) cells was higher than those of Pt-1, Pt-2, Pt-4, cisplatin and Pt-5. Moreover, the cytotoxicity of Pt-3 in HL-7702 normal cells was lower than those of Pt^IV derivatives bearing BA-COOH, FA-COOH, TCA-COOH and CA-COOH ligands. The highly efficacious Pt-2 and Pt-3 were found to accumulate strongly in the A549/DDP cells, with the prodrug Pt-3 showing highest levels of penetration into the mitochondria. The prodrug Pt-3 effectively entered the A549/DDP cells and caused mitochondrial damage, significantly greater than Pt-2. In addition, the prodrug Pt-3 exhibited higher antitumor efficacy (inhibition rates (IR) = 67.45%) than Pt-2 (28.12%) and cisplatin (33.05%) in the A549/DDP xenograft mouse model. Thus, the prodrug Pt-3 containing the rhein (RH-COOH) ligand is a promising candidate drug targeting the mitochondria.

Eighteen 5,7-Dihalo-8-quinolinol and 2,2'-Bipyridine Co(II) Complexes as a New Class of Promising Anticancer Agents

Here we first report the design of a series of bis-chelate Co(II) 5,7-dihalo-8-quinolinol-phenanthroline derivative complexes, [Co(py)(QL1)₂] (Co1), [Co(py)(QL2)₂] (Co2), [Co(Phen)(QL1)₂] (Co3), [Co(Phen)(QL2)₂] (Co4), [Co(DPQ)(QL1)₂]·(CH₃OH)₄ (Co5), [Co(DPQ)(QL2)₂] (Co6), [Co(DPPZ)(QL1)₂]·CH₃OH (Co7), [Co(MDP)(QL1)₂]·3H₂O (Co8), [Co(ODP)(QL1)₂]·CH₃OH (Co9), [Co(PPT)(QL1)₂]·CH₃OH (Co10), [Co(ClPT)(QL1)₂] (Co11), [Co(dpy)(QL3)₂] (Co12), [Co(mpy)(QL1)₂] (Co13), [Co(Phen)(QL4)₂] (Co14), [Co(ODP)(QL4)₂] (Co15), [Co(mpy)(QL4)₂]I (Co16), [Co(ClPT)(QL4)₂] (Co17), and [Co(ClPT)(QL5)₂] (Co18), with 5,7-dihalo-8-quinolinol and 2,2′-bipyridine mixed ligands. The antitumor activity of Co1–Co18 has been evaluated against human HeLa (cervical) cancer cells in vitro (IC₅₀ values = 0.8 nM–11.88 μM), as well as in vivo against HeLa xenograft tumor growth (TIR = 43.7%, p < 0.05). Importantly, Co7 exhibited high safety in vivo and was more effective in inhibiting HeLa tumor xenograft growth (43.7%) than cisplatin (35.2%) under the same conditions (2.0 mg/kg). In contrast, the H-QL1 and DPPZ ligands greatly enhanced the activity and selectivity of Co7 in comparison to Co1–Co6, Co8–Co18, and previously reported cobalt(II) compounds. In addition, Co7 (0.8 nM) inhibited telomerase activity, caused G2/M phase arrest, and induced mitochondrial dysfunction at a concentration 5662.5 times lower than Co1 (4.53 μM) in related assays. Taken together, Co7 showed low toxicity, and the combination could be a novel Co(II) antitumor compound candidate.

Ruthenium(II) Complexes as Potential Apoptosis Inducers in Cancer Therapy

The compound cis-diamminedichloroplatinum(II) (cisplatin) is the most widely used anticancer drug, but due to its serious side effects (including gastrointestinal symptoms, renal tubular injury, neuromuscular complications, and ototoxicity), clinical applications of cisplatin are limited. Therefore, these limitations have provided an encouragement for further research into other transition metal complexes, with an aim to overcome the disadvantages related with cisplatin therapy. In the search for effective complexes that can be targeted against tumor cells, many research groups synthesized various ruthenium( II) complexes with different ligands. Also, newly synthesized ruthenium(II) complexes showed selective anticancer activity against different types of cancer cells. Activity of ruthenium(II) complexes in some cases was even higher than that of cisplatin against the same cells. Precise mechanism of action of ruthenium(II) complexes is not fully understood. The different examples mentioned in this review showed that ruthenium(II) complexes decreased viability of cancer cells by induction of apoptosis and/or by cell cycle arrest which implies their different mechanism of action against different types of cancer cells.

Discovery of high in vitro and in vivo antitumor activities of organometallic ruthenium(ii)–arene complexes with 5,7-dihalogenated-2-methyl-8-quinolinol

MClClQ-RuCl induced HeLa cell apoptosis was mediated by the inhibition of telomerase activity and dysfunction of mitochondria. Remarkably, MClClQ-RuCl obviously inhibited HeLa xenograft tumor growth in vivo.

In vitro and in vivo activity of novel platinum(ii) complexes with naphthalene imide derivatives inhibiting human non-small cell lung cancer cells

3 induced NCI-H460 cell apoptosis via inhibition of the telomerase and dysfunction of mitochondria. Remarkably, 3 obviously inhibited NCI-H460 xenograft tumor growth in vivo.

Complexes of lanthanides(iii) with mixed 2,2′-bipyridyl and 5,7-dibromo-8-quinolinoline chelating ligands as a new class of promising anti-cancer agents

MeOMBrQ-Ho induced HeLa cell apoptosis was mediated by inhibition of telomerase activity and dysfunction of mitochondria. Remarkably, MeOMBrQ-Ho obviously inhibited HeLa xenograft tumor growth in vivo.

Acute toxic effects of ruthenium (II)/amino acid/diphosphine complexes on Swiss mice and zebrafish embryos

Anticancer potential of ruthenium complexes has been widely investigated, but safety evaluation studies are still scarce. Despite of ruthenium-based anticancer agents are known to cause fewer side effects compared to other metal-based drugs, these compounds are not fully free of toxicity, causing mainly nephrotoxicity. Based on the promising results from antitumor activity of the complexes [Ru(L-Met)(bipy)(dppb)]PF₆ (RuMet) and [Ru(L-Trp)(bipy)(dppb)]PF₆ (RuTrp), for the first time we investigated the toxicity profile of these complexes in rodent and zebrafish models. The acute oral toxicity was evaluated in Swiss mice. The mutagenic and genotoxic potential was determined by a combination of Micronucleus (MN) and Comet assay protocols, after exposure of Swiss mice to RuMet and RuTrp in therapeutic doses. Zebrafish embryos were exposed to these complexes, and their development observed up to 96 h post-fertilization. RuMet and RuTrp complexes showed low acute oral toxicity. Recorded behavioral changes were not recorded, nor were macroscopic morphological changes or structural modifications in the liver and kidneys. These complexes did not cause genetic toxicity, presenting a lack of micronuclei formation and low DNA damage induction in the cells from Swiss mice. In contradiction, cisplatin treatment exhibited high mutagenicity and genotoxicity. RuMet and RuTrp showed low toxicity in the embryo development of zebrafish. The RuMet and RuTrp complexes demonstrated low toxicity in the two study models, an interesting property in preclinical studies for novel anticancer agents.

Possible Molecular Targets of Novel Ruthenium Complexes in Antiplatelet Therapy

In oncotherapy, ruthenium (Ru) complexes are reflected as potential alternatives for platinum compounds and have been proved as encouraging anticancer drugs with high efficacy and low side effects. Cardiovascular diseases (CVDs) are mutually considered as the number one killer globally, and thrombosis is liable for the majority of CVD-related deaths. Platelets, an anuclear and small circulating blood cell, play key roles in hemostasis by inhibiting unnecessary blood loss of vascular damage by making blood clot. Platelet activation also plays a role in cancer metastasis and progression. Nevertheless, abnormal activation of platelets results in thrombosis under pathological settings such as the rupture of atherosclerotic plaques. Thrombosis diminishes the blood supply to the heart and brain resulting in heart attacks and strokes, respectively. While currently used anti-platelet drugs such as aspirin and clopidogrel demonstrate efficacy in many patients, they exert undesirable side effects. Therefore, the development of effective therapeutic strategies for the prevention and treatment of thrombotic diseases is a demanding priority. Recently, precious metal drugs have conquered the subject of metal-based drugs, and several investigators have motivated their attention on the synthesis of various ruthenium (Ru) complexes due to their prospective therapeutic values. Similarly, our recent studies established that novel ruthenium-based compounds suppressed platelet aggregation via inhibiting several signaling cascades. Our study also described the structure antiplatelet-activity relationship (SAR) of three newly synthesized ruthenium-based compounds. This review summarizes the antiplatelet activity of newly synthesized ruthenium-based compounds with their potential molecular mechanisms.

The development of ruthenium(ii) polypyridyl complexes and conjugates for in vitro cellular and in vivo applications

Ruthenium(ii) [Ru(ii)] polypyridyl complexes have been the focus of intense investigations since work began exploring their supramolecular interactions with DNA. In recent years, there have been considerable efforts to translate this solution-based research into a biological environment with the intention of developing new classes of probes, luminescent imaging agents, therapeutics and theranostics. In only 10 years the field has expanded with diverse applications for these complexes as imaging agents and promising candidates for therapeutics. In light of these efforts this review exclusively focuses on the developments of these complexes in biological systems, both in cells and in vivo, and hopes to communicate to readers the diversity of applications within which these complexes have found use, as well as new insights gained along the way and challenges that researchers in this field still face.

Insufficient radiofrequency ablation promotes proliferation of residual hepatocellular carcinoma via autophagy

Radiofrequency ablation (RFA) is considered to be a potentially curative therapy for hepatocellular carcinoma (HCC). However, insufficient RFA (IRFA) can promote rapid progression of the residual tumor. The mechanisms underlying IRFA-induced tumor promotion remain poorly understood. In the present study, we have established a subcutaneous xenograft mouse model and monitored the location and extent of IRFA by dual monitoring with ultrasonography and a thermal imager. For the first time, we provide evidence of the activation of autophagic pathways in mice exposed to IRFA. We show that autophagy plays an important role in relapse and proliferation after IRFA and that hydroxychloroquine (HCQ) can suppress these effects. Our findings indicate that autophagy is involved in experimental IRFA and that inhibition of autophagy may be a novel approach in the treatment of local recurrences of HCC after IRFA in the clinic.

Synthesis and anticancer properties of ruthenium (II) complexes as potent apoptosis inducers through mitochondrial disruption

A new ligand MHPIP (MHPIP = 2-(1-methyl-1H-pyrazol-4-yl)-1H-imidazo[4,5-f][1,10]phenanthroline) and its three ruthenium (II) complexes [Ru(N-N)₂(MHPIP)](ClO₄)₂ (N-N = phen: 1,10-phenanthroline 1; dmp = 2,9-dimethyl-1,10-phenanthroline 2; ttbpy = 4,4'-ditertiarybutyl-2,2'-bipyridine 3) were synthesized and characterized. The cytotoxic activity in vitro was studied by MTT method. The complexes 1-3 show moderate cytotoxic effects on the cell growth in HepG2 cells with an IC₅₀ value of 25.5 ± 3.5, 35.6 ± 1.9 and 27.4 ± 2.3 μM, respectively. The apoptosis was investigated with AO/EB and Annex V/PI staining methods and comet assay. The reactive oxygen species, mitochondrial membrane potential were investigated under a fluorescent microscope. Autophagy assay shows that the complexes can cause autophagy and up-regulate the expression of Beclin-1 protein. Additionally, the complexes inhibit the cell growth in HepG2 cells at G0/G1 phase, and the complexes can regulate the expression of caspase 3 and Bcl-2 family proteins. The studies demonstrate that the complexes induce apoptosis in HepG2 cells through DNA damage and ROS-mediated mitochondrial dysfunction pathways.

A ruthenium polypyridyl intercalator stalls DNA replication forks, radiosensitizes human cancer cells and is enhanced by Chk1 inhibition

Ruthenium(II) polypyridyl complexes can intercalate DNA with high affinity and prevent cell proliferation; however, the direct impact of ruthenium-based intercalation on cellular DNA replication remains unknown. Here we show the multi-intercalator [Ru(dppz)2(PIP)](2+) (dppz = dipyridophenazine, PIP = 2-(phenyl)imidazo[4,5-f][1,10]phenanthroline) immediately stalls replication fork progression in HeLa human cervical cancer cells. In response to this replication blockade, the DNA damage response (DDR) cell signalling network is activated, with checkpoint kinase 1 (Chk1) activation indicating prolonged replication-associated DNA damage, and cell proliferation is inhibited by G1-S cell-cycle arrest. Co-incubation with a Chk1 inhibitor achieves synergistic apoptosis in cancer cells, with a significant increase in phospho(Ser139) histone H2AX (γ-H2AX) levels and foci indicating increased conversion of stalled replication forks to double-strand breaks (DSBs). Normal human epithelial cells remain unaffected by this concurrent treatment. Furthermore, pre-treatment of HeLa cells with [Ru(dppz)2(PIP)](2+) before external beam ionising radiation results in a supra-additive decrease in cell survival accompanied by increased γ-H2AX expression, indicating the compound functions as a radiosensitizer. Together, these results indicate ruthenium-based intercalation can block replication fork progression and demonstrate how these DNA-binding agents may be combined with DDR inhibitors or ionising radiation to achieve more efficient cancer cell killing.

Acute toxicity evaluation of a thiazolo arene ruthenium (II) complex in rats

Recently, a series of thiazolo arene ruthenium complexes were found to be highly cytotoxic in vitro, on both cisplatin-sensitive and cisplatin-resistant ovarian cancer cells. The most active compound of the series, [(η(6)-p-cymene)Ru(L)Cl]Cl (L = 1-(2-(2-(3-chlorobenzylidene)hydrazinyl)-4-methylthiazol-5-yl)ethanone), was selected for an in vivo study in order to assess its safety profile. The ruthenium complex was administered to female Crl:WI rats orally, by gastric intubation and intraperitoneal injection. The hematological parameters and the histopathological changes in liver, kidneys, spleen and brain were investigated after a 14-days treatment. The substance was very well tolerated orally, with a LD50 value of over 2000 mg/kg body weight. Symptoms were observed only in the first day after intraperitoneal administration of the highest dose, with a LD50 value between 300 and 2000 mg/kg bw. The hematological profile was not modified at any of the tested doses, after both oral and intraperitoneal acute administration. Structural modifications (moderate lymphocytolysis) were identified only in the spleen at the highest tested dose. In conclusion, the thiazolo arene ruthenium complex was very well tolerated orally and had a low acute toxicity after intraperitoneal administration in Crl:WI rats The results justify further investigation to determine the in vivo therapeutic potential of this promising ruthenium complex.