Inhibition of adhesion, migration and of α5β1 integrin in the HCT-116 colorectal cancer cells treated with the ruthenium drug NAMI-A

Metal Coordination and Biological Screening of a Schiff Base Derived from 8-Hydroxyquinoline and Benzothiazole

Designing new metallodrugs for anticancer therapy is a driving force in the scientific community. Aiming to contribute to this field, we hereby report the development of a Schiff base (H2L) derived from the condensation of 2-carbaldehyde-8-hydroxyquinoline with 2-hydrazinobenzothiazole and its complexation with transition metal ions. All compounds were characterised by analytical and spectroscopic techniques, which disclosed their structure: [Cu(HL)Cl], [Cu(HL)2], [Ni(HL)(acetate)], [Ni(HL)2], [Ru(HL)Cl(DMSO)], [VO(HL)2] and [Fe(HL)2Cl(H2O)]. Different binding modes were proposed, showing the ligand’s coordination versatility. The ligand proton dissociation constants were determined, and the tested compounds showed high lipophilicity and light sensitivity. The stability of all complexes in aqueous media and their ability to bind to albumin were screened. Based on an antiproliferative in vitro screening, [Ni(HL)(acetate)] and [Ru(HL)Cl(DMSO)] were selected for further studies aiming to investigate their mechanisms of action and therapeutic potential towards colon cancer. The complexes displayed IC50 < 21 μM towards murine (CT-26) and human (HCT-116) colon cancer cell lines. Importantly, both complexes exhibited superior antiproliferative properties compared to the clinically approved 5-fluorouracil. [Ni(HL)(acetate)] induced cell cycle arrest in S phase in CT-26 cells. For [Ru(HL)Cl(DMSO)] this effect was observed in both colon cancer cell lines. Additionally, both compounds significantly inhibited cell migration particularly in the human colon cancer cell line, HCT-116. Overall, the therapeutic potential of both metal complexes was demonstrated.

Ruthenium-based antitumor drugs and delivery systems from monotherapy to combination therapy

Ruthenium complex is an important compound group for antitumor drug research and development. NAMI-A, KP1019, TLD1433 and other ruthenium complexes have entered clinical research. In recent years, the research on ruthenium antitumor drugs has not been limited to single chemotherapy drugs; other applications of ruthenium complexes have emerged such as in combination therapy. During the development of ruthenium complexes, drug delivery forms of ruthenium antitumor drugs have also evolved from single-molecule drugs to nanodrug delivery systems. The review summarizes the following aspects: (1) ruthenium complexes from monotherapy to combination therapy, including the development of single-molecule compounds, carrier nanomedicine, and self-assembly of carrier-free nanomedicine; (2) ruthenium complexes in the process of ADME in terms of absorption, distribution, metabolism and excretion; (3) the applications of ruthenium complexes in combination therapy, including photodynamic therapy (PDT), photothermal therapy (PTT), photoactivated chemotherapy (PACT), immunotherapy, and their combined application; (4) the future prospects of ruthenium-based antitumor drugs.

A Dual-Pronged Approach: A Ruthenium(III) Complex That Modulates Amyloid-β Aggregation and Disrupts Its Formed Aggregates

Alzheimer's disease (AD) is a devastating neurological disorder for which soluble oligomers of the peptide amyloid-β (Aβ) are now recognized as the neurotoxic species. Metal-based therapeutics are uniquely suited to target Aβ, with ruthenium-based (Ru) complexes emerging as propitious candidates. Recently, azole-based Ru(III) complexes were observed to modulate the aggregation of Aβ in solution, where the inclusion of a primary amine proximal to the ligand coordination site improved the activity of the complexes. To advance these structure-activity relationships, a series of oxazole-based Ru complexes were prepared and evaluated for their ability to modulate Aβ aggregation. From these studies, a lead candidate, Oc, emerged that had superior activity relative to its azole predecessors in modulating the aggregation of soluble Aβ and diminishing its cytotoxicity. Further evaluation of Oc demonstrated its ability to disrupt formed Aβ aggregates, resulting in smaller amorphous species. Because altering both sides of the aggregation equilibrium for Aβ has not been previously suggested for metal-based complexes for AD, this work represents an exciting new avenue for improved therapeutic success.

Ruthenium(ii)-arene complexes as anti-metastatic agents, and related techniques

With the discovery of cisplatin, a vast area of applications of metallodrugs in cancer treatment was opened but due to the side effects caused by the cisplatin complexes, researchers began to look for alternatives with similar anticancer properties but fewer side effects. Ruthenium was found to be a promising candidate, considering its significant anticancer properties and low side effects. Several ruthenium complexes, viz. NAMI-A, KP1019, KP1339, and TLD1433, have entered clinical trials. Some other arene ruthenium complexes such as RM175 and RAPTA-C have also entered clinical trials but very few of them have shown anti-metastatic properties. Herein, we provide information and probable mechanistic pathways for ruthenium(ii)-arene complexes that have been studied, so far, for their anti-metastatic activities. Also, we discuss the techniques and their significance for determining the anti-metastatic effects of the complexes.

Ruthenium Complexes: An Alternative to Platinum Drugs in Colorectal Cancer Treatment

Colorectal cancer (CRC) is one of the intimidating causes of death around the world. CRC originated from mutations of tumor suppressor genes, proto-oncogenes and DNA repair genes. Though platinum (Pt)-based anticancer drugs have been widely used in the treatment of cancer, their toxicity and CRC cells' resistance to Pt drugs has piqued interest in the search for alternative metal-based drugs. Ruthenium (Ru)-based compounds displayed promising anticancer activity due to their unique chemical properties. Ru-complexes are reported to exert their anticancer activities in CRC cells by regulating different cell signaling pathways that are either directly or indirectly associated with cell growth, division, proliferation, and migration. Additionally, some Ru-based drug candidates showed higher potency compared to commercially available Pt-based anticancer drugs in CRC cell line models. Meanwhile Ru nanoparticles coupled with photosensitizers or anticancer agents have also shown theranostic potential towards CRC. Ru-nanoformulations improve drug efficacy, targeted drug delivery, immune activation, and biocompatibility, and therefore may be capable of overcoming some of the existing chemotherapeutic limitations. Among the potential Ru-based compounds, only Ru (III)-based drug NKP-1339 has undergone phase-Ib clinical trials in CRC treatment.

Insights into the Protein Ruthenation Mechanism by Antimetastatic Metallodrugs: High-Resolution X-ray Structures of the Adduct Formed between Hen Egg-White Lysozyme and at Various Time Points

The pharmacological profile of medicinally relevant Ru(III) coordination compounds has been ascribed to their interactions with proteins, as several studies have provided evidence that DNA is not the primary target. In this regard, numerous spectroscopic and crystallographic studies have indicated that the Ru(III) ligands play an important role in determining the metal binding site, acting as the recognition element in the early stages of the protein-complex formation. Herein, we present a series of near-atomic-resolution X-ray crystal structures of the adducts formed between the antimetastatic metallodrug imidazolium trans-[tetrachlorido(S-dimethyl sufoxide)(1H-imidazole)ruthenate(III)] (NAMI-A) and hen egg-white lysozyme (HEWL). These structures elucidate a series of binding events starting from the noncovalent interaction of intact NAMI-A ions with HEWL (1.5 h), followed by the stepwise exchange of all Ru ligands except for 1H-imidazole (26 h) to the final "ruthenated" protein comprising one aquated Ru ion coordinated to histidine-15 of HEWL (98 h). Our structural data clearly support a two-step mechanism of protein ruthenation, illustrating the ligand-mediated recognition step of the process.

A dual-targeting ruthenium nanodrug that inhibits primary tumor growth and lung metastasis via the PARP/ATM pathway

Background

Many studies have found that ruthenium complexes possess unique biochemical characteristics and inhibit tumor growth or metastasis.

Results

Here, we report the novel dual-targeting ruthenium candidate 2b, which has both antitumor and antimetastatic properties and targets tumor sites through the enhanced permeability and retention (EPR) effect and transferrin/transferrin receptor (TF/TFR) interaction. The candidate 2b is composed of ruthenium-complexed carboline acid and four chloride ions. In vitro, 2b triggered DNA cleavage and thus blocked cell cycle progression and induced apoptosis via the PARP/ATM pathway. In vivo,2b inhibited not only Lewis lung cancer (LLC) tumor growth but also lung metastasis. We detected apoptosis and decreased CD31 expression in tumor tissues, and ruthenium accumulated in the primary tumor tissue of C57BL/6 mice implanted with LLC cells.

Conclusions

Thus, we conclude that 2b targets tumors, inhibits tumor growth and prevents lung metastasis.

Anti-adhesive action of novel ruthenium(II) chlorophenyl terpyridine complexes with a high affinity for double-stranded DNA: in vitro and in silico

Interactions of three Ru(II) chlorophenyl terpyridine complexes: [Ru(Cl-Ph-tpy)(en)Cl]Cl (1), [Ru(Cl-Ph-tpy)(dach)Cl]Cl (2) and [Ru(Cl-Ph-tpy)(bpy)Cl]Cl (3) (Cl-Ph-tpy = 4'-(4-chlorophenyl)-2,2':6',2''-terpyridine, en = 1,2-diaminoethane, dach = 1,2-diaminocyclohexane, bpy = 2,2'-bipyridine) with human serum albumin (HSA), calf thymus DNA and a double-helical oligonucleotide d(CGCGAATTCGCG)₂ (1BNA) were examined. Fluorescence emission studies were used to assess the interactions of complexes with HSA, which were of moderate strength for 1 and 2. Molecular docking allowed us to predict mostly π-π stacking and van der Waals interactions between the complexes and the protein. We suggest that the complexes bind to a novel site on HSA, which is different from its druggable sites I, II or III. We suggest a partial intercalation of complexes through the minor groove as a possible mode of interaction with double-helical DNA. Finally, when applied to normal extravillous cell line HTR8/SVneo and JAr choriocarcinoma cell line, complexes 1 and 2 exerted anti-adhesive properties at very low doses, whereas complex 3 had a negligible effect. The obtained results are completion of our studies of Ru(II) terpyridyl complexes that carry N-N ancillary ligands. We suggest a new research direction towards studying the cellular effects of Ru(II) polypyridyl compounds.

Synthesis, X-ray structure, physicochemical properties and anticancer activity of mer and fac Ru(iii) triphenylphosphine complexes with a benzothiazole derivative as a co-ligand

Two mononuclear ruthenium(iii) mer- and fac-isomers of the formula [RuCl3(PPh3)(dmpbt)] (where PPh3 = triphenylphosphine, dmpbt = 2-(3,5-dimethylpyrazoll-yl)benzothiazole) have been synthesised from the reaction of [RuCl3(PPh3)3] with a bidentate ligand - dmpbt. Appropriate reaction conditions allowed obtaining the two isomers separately without separation techniques. X-ray crystallography has determined the crystal and molecular structures of the new complexes. mer-Ru(iii) (1) crystallised in the monoclinic P2(1)/n group, and fac-Ru(iii) (2, 2') in the triclinic P1[combining macron] space group. The composition of the ruthenium coordination sphere was confirmed and characterised using spectroscopic techniques (FT-IR, UV-vis and EPR), elemental analysis and mass spectrometry (MS-FAB). The structures of the complexes obtained were analysed using X-ray and other spectroscopic methods (IR and UV-vis). The electrochemical properties of the ligand and the complex compound were identified using cyclic voltammetry, determining the potential and charge of faradaic processes. Both isomers are redox active and display quasi-reversible metal centered redox processes for the Ru(iii)/Ru(ii) pair. Moreover, preliminary tests of their biological activity were performed. The cytotoxicity of these compounds has been tested for human lung carcinoma (A549), chronic myelogenous leukemia (K562), human cervix carcinoma (HeLa) cells, acute lymphoblastic leukemia (MOLT-4), human breast adenocarcinoma cell line (MCF-7) and normal human umbilical vein endothelial cells (HUVEC). The ability to induce apoptosis has been demonstrated in caspase 3/7 activity assay. In addition, the lipophilicity of both isomers was described by a partition coefficient, log P, values of which were estimated by the shake-flask method. The interesting and promising preliminary results of the biological and chemical activities of the new octahedral mer/fac Ru(iii) complexes motivate further in vitro and in vivo studies.

NAMI-A preferentially reacts with the Sp1 protein: understanding the anti-metastasis effect of the drug

The anti-metastasis drug NAMI-A selectively reacts with Sp1, a protein associated with cancer metastasis.

GLI1 activation by non-classical pathway integrin αvβ3/ERK1/2 maintains stem cell-like phenotype of multicellular aggregates in gastric cancer peritoneal metastasis

Peritoneal metastasis is one of the most important causes of postoperative death in patients with gastric cancer, and the exact mechanism remains unclear. The proliferation of multicellular aggregates of exfoliated malignant gastric cells in the abdominal cavity is the focus of current research. However, the mechanism how gastric cancer multicellular aggregates survive remains unclear. In this study, we demonstrated that multicellular aggregates of exfoliated gastric cancer cells in the abdominal cavity expressed a stem cell-Like phenotype. We found that Integrin α_vβ₃ not only mediated adhesion of gastric cancer multicellular aggregates to form independent functional units, but also maintained their stem cell-like phenotype by the non-classical pathway Integrin α_vβ₃/ERK1/2/GLI1. In addition, ERK1/2 directly regulates the transcriptional activity of GLI1. GLI1 is a key effector of the Integrin α_vβ₃ pathway in regulating stem cell-like phenotype in multicellular aggregates. Our data indicates that although there is a crosstalk between the non-classical Integrin α_vβ₃ pathway and the classical Hedgehog pathway, the activation of GLI1 is almost independent of the Hedgehog pathway in multicellular aggregates of gastric cancer cells. Our study provides a basis for blocking GLI1 activity in the prevention and treatment of peritoneal metastases of gastric cancer.

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

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

Designing Ruthenium Anticancer Drugs: What Have We Learnt from the Key Drug Candidates?

After nearly 20 years of research on the use of ruthenium in the fight against cancer, only two Ru(III) coordination complexes have advanced to clinical trials. During this time, the field has produced excellent candidate drugs with outstanding in vivo and in vitro activity; however, we have yet to find a ruthenium complex that would be a viable alternative to platinum drugs currently used in the clinic. We aimed to explore what we have learned from the most prominent complexes in the area, and to challenge new concepts in chemical design. Particularly relevant are studies involving NKP1339, NAMI-A, RM175, and RAPTA-C, which have paved the way for current research. We explored the development of the ruthenium anticancer field considering that the mechanism of action of complexes no longer focuses solely on DNA interactions, but explores a diverse range of cellular targets involving multiple chemical strategies.

Directly observing alterations of morphology and mechanical properties of living cancer cells with atomic force microscopy

Epithelial-mesenchymal transition (EMT) is a biological process during which cells lose their characteristic structure and biochemical properties then adopt typical features of a mesenchymal phenotype. Alterations in the morphology, structure, and mechanical properties of cells during EMT are associated with a series of pathological processes. In this work, atomic force microscopy (AFM) is used for investigating effects of TGF-β1 on morphology and mechanical properties of living bladder cancer cells (T24) during EMT for the first time. High-resolution topography and Young's modulus images of T24 living cell are obtained simultaneously. The results show that TGF-β1 is able to induce EMT, leading to the increased F-actin stress fibers and much higher Young's modulus values of T24 living cells. It reveals that the cytoskeletal-associated cell architecture is closely related to the mechanical dynamics of T24 cells during EMT. This work provides new insights into the changes of cell morphology and mechanical properties during EMT. It enables us to gain a deeper understanding of the growth, development and metastasis of the bladder cancer cell therefore it is of great significance for studying the pathological mechanism of cells at single-cell level.

Reduced-gliotoxin induces ROS-mediated anoikis in human colorectal cancer cells

Reduced-gliotoxin is a small molecule derived from the secondary metabolites of marine fungi; compared to other gliotoxin analogues, it exhibits potent anticancer effects. However, the molecular basis of the death of colorectal cancer (CRC) cells induced by reduced-gliotoxin is unclear. Thus, the aim of this study was to investigate the potency of reduced-gliotoxin against CRC cells and to elucidate the underlying mechanisms. Cell morphology, flow cytometric analysis and western bolt analysis were performed to examine the functions and mechanisms of cell death induced by reduced-gliotoxin. Our findings demonstrated that reduced-gliotoxin triggered rapid cell detachment and induced anoikis in CRC cells. Mechanistically, our data indicated that the anoikis induced by reduced-gliotoxin was associated with the disruption of integrin-associated cell detachment and multiple signaling pathways. Furthermore, reduced-gliotoxin induced the excessive production of reactive oxygen species (ROS) and the disruption of mitochondrial membrane potential (MMP), resulting in the activation of both endogenous and exogenous apoptotic pathways and eventually, in the apoptosis of CRC cells. The blockage of ROS generation with N-acetylcysteine (NAC) attenuated the anoikis induced by reduced-gliotoxin. Taken together, these results suggest that reduced-gliotoxin may prove to be a potential candidate in the treatment of CRC.

Study of morphological and mechanical features of multinuclear and mononuclear SW480 cells by atomic force microscopy

This article studies the morphological and mechanical features of multinuclear and mononuclear SW480 colon cancer cells by atomic force microscopy to understand their drug-resistance. The SW480 cells were incubated with the fullerenol concentrations of 1 mg/ml and 2 mg/ml. Morphological and mechanical features including the height, length, width, roughness, adhesion force and Young's modulus of three multinuclear cell groups and three mononuclear cell groups were imaged and analyzed. It was observed that the features of multinuclear cancer cells and mononuclear cancer cells were significantly different after the treatment with fullerenol. The experiment results indicated that the mononuclear SW480 cells were more sensitive to fullerenol than the multinuclear SW480 cells, and the multinuclear SW480 cells exhibited a stronger drug-resistance than the mononuclear SW480 cells. This work provides a guideline for the treatments of multinuclear and mononuclear cancer cells with drugs.

The Differential Distribution of RAPTA-T in Non-Invasive and Invasive Breast Cancer Cells Correlates with Its Anti-Invasive and Anti-Metastatic Effects

Nanoscale secondary ion mass spectrometry (NanoSIMS) combined with transmission electron microscopy (TEM) can be a powerful approach to visualize the exact distribution of drugs at the sub-cellular level. In this work, we exploit this approach to identify the distribution and localisation of the organometallic ruthenium(II)-arene drug Ru(η⁶-C₆H₅Me)(pta)Cl₂, termed RAPTA-T, in MDA-MB-231 and MCF-7 human breast cancer cells. These cell lines have been chosen because the former cell lines are highly invasive and resistant to most chemotherapeutic agents and the latter ones are very sensitive to hormonal-based therapies. In the MDA-MB-231 cells, RAPTA-T was found to predominantly localise on the cell membrane and to a lesser extent in the nucleolus. These findings are consistent with the previously reported anti-metastatic properties of RAPTA-T and the observation that once internalized RAPTA-T is associated with chromatin. RAPTA-T shows a lack of membrane accumulation on the non-invasive MCF-7 cells, which correlates well with its selective anti-metastatic properties on invasive cell lines.

Sensitivity towards the GRP78 inhibitor KP1339/IT-139 is characterized by apoptosis induction via caspase 8 upon disruption of ER homeostasis

The ruthenium drug and GRP78 inhibitor KP1339/IT-139 has already demonstrated promising anticancer activity in a phase I clinical trial. This study aimed to identify mechanisms underlying increased sensitivity to KP1339 treatment. Based on a screen utilizing 23 cell lines, a small panel was selected to compare KP1339-sensitive and low-responsive models. KP1339 sensitivity was neither based on differences in ruthenium accumulation, nor sensitivity to oxidative stress or constituents of KP1339 (ruthenium chloride and indazole). Subsequently, the biochemical response to KP1339 was analyzed using whole genome expression arrays indicating that, while sensitive cell lines were characterized by "response to chemical stimuli" and "regulation of cell death", low-responsive cells preferentially activated pathways controlling cell cycle, DNA repair, and metabolism. Cell culture experiments confirmed that, while low-responsive cells executed cell cycle arrest in G2 phase, pronounced apoptosis induction via activation of caspase 8 was found in sensitive cells. Cell death induction is based on a unique disruption of the ER homeostasis by depletion of key cellular chaperones including GRP78 in combination with enhanced KP1339-mediated protein damage.

Combination of ruthenium(II)-arene complex [Ru(η6-p-cymene)Cl2(pta)] (RAPTA-C) and the epidermal growth factor receptor inhibitor erlotinib results in efficient angiostatic and antitumor activity

Ruthenium-based compounds show strong potential as anti-cancer drugs and are being investigated as alternatives to other well-established metal-based chemotherapeutics. The organometallic compound [Ru(η6-p-cymene)Cl2(pta)], where pta = 1,3,5-triaza-7-phosphaadamantane (RAPTA-C) exhibits broad acting anti-tumor efficacy with intrinsic angiostatic activity. In the search for an optimal anti-angiogenesis drug combination, we identified synergistic potential between RAPTA-C and the epidermal growth factor receptor (EGFR) inhibitor, erlotinib. This drug combination results in strong synergistic inhibition of cell viability in human endothelial (ECRF24 and HUVEC) and human ovarian carcinoma (A2780 and A2780cisR) cells. Additionally, erlotinib significantly enhances the cellular uptake of RAPTA-C relative to treatment with RAPTA-C alone in human ovarian carcinoma cells, but not endothelial cells. Drug combinations induce the formation of chromosome bridges that persist after mitotic exit and delay abscission in A2780 and A2780cisR, therefore suggesting initiation of cellular senescence. The therapeutic potential of these compounds and their combination is further validated in vivo on A2780 tumors grown on the chicken chorioallantoic membrane (CAM) model, and in a preclinical model in nude mice. Immunohistochemical analysis confirms effective anti-angiogenic and anti-proliferative activity in vivo, based on a significant reduction of microvascular density and a decrease in proliferating cells.