Antitumor Effect of Organometallic Half-Sandwich Ru(II)-Arene Complexes Bearing a Glutathione S-Transferase Inhibitor

Positively-charged, chalcone-hydroxypyrone hybrid ruthenium(II)-arene complexes functionalized with ethacrynic acid: Synthesis, characterizaion, and antitumor effect

A new family of ethacrynic acid-functionalized, chalcone-hydroxypyrone hybrid ruthenium(II)-arene complexes (4a-4e) have been designed, synthesis and fully characterized by 1H and 13C NMR, ESI-MS, elemental analysis, and melting point tests. The molecular structure of 3a, one of the precursor complexes, has been determined by single-crystal X-ray diffraction. The cytotoxicity of the obtained complexes toward human cancer cell lines such as HeLa, MGC803, A549, MDA-MB-231, and MCF-7 cells have been investigated by MTT assay. Whereas complexes 4d and 4e showed significantly higher cytotoxicity than cisplatin (the positive control group) and complexes 3a-3e. Moreover, complexes 4d and 4e exhibited a certain selectivity (selectivity index: 7.33 and 7.57) toward MCF-7 cells over MCF-10a normal cells. Glutathione S-transferases (GSTs) activity assay indicate that complexes 4d and 4e exhibited higher GST inhibitory activity than ethacrynic acid (EA, the best characterized GST inhibitor), consistent with their higher cytotoxicity. Further mechanistic studies showed that 4e-induced cell apoptosis may be aroused by the production of ROS, the loss of mitochondrial membrane potential and G2/M phase cell arrest in MCF-7 cells. In addition, the in vivo antitumor effect study on the xenograft mouse models of MCF-7 cells reveal that complex 4e significantly inhibited tumor growth with a higher inhibition efficiency of 68.80 %, in comparison with the groups treated with cisplatin (59.25 %). These results highlight the strong possibility to develop positively-charged, chalcone-hydroxypyrone hybrid ruthenium(II)-arene complexes funcionalized with GST inhibitor as promising anticancer agents.

Insights into the antineoplastic activity and mechanisms of action of coumarin-coordinated 8-hydroxyquinoline ruthenium(II/III) compounds

Ruthenium(II/III) coordination compounds have gained widespread attention as chemotherapy drugs, photosensitizers, and photodynamic therapy reagents. Herein, a family of 11 novel coumarin-coordinated 8-hydroxyquinoline ruthenium(II/III) compounds, i.e., [RuII2(μ2-Cl)2(QL1a)2(DMSO)4] (YNU-4a = Yulin Normal University-4a), [RuII2(μ2-Cl)2(QL1b)2(DMSO)4] (YNU-4b), [RuII2(μ2-Cl)2(QL1c)2(DMSO)4] (YNU-4c), [RuII2(μ2-Cl)2(QL1d)2(DMSO)4]⋅2CH3OH (YNU-4d), [RuII(QL1e)2(DMSO)2] (YNU-4e), [RuIII(QL1e)2(QL3a)] (YNU-4f), [RuIII(QL1e)2(QL3b)] (YNU-4g), [RuIII(QL1e)2(QL3c)] (YNU-4h), [RuIICl2(H-QL3a)2(DMSO)2] (YNU-4i), [RuIICl2(H-QL3b)2(DMSO)2] (YNU-4j), and [RuIICl2(H-QL3c)2(DMSO)2] (YNU-4k), featuring the coligands 5,7-diiodo-8-hydroxyquinoline (H-QL1a), 5,7-dichloro-8-quinolinol (H-QL1b), 5-chloro-7-iodo-8-hydroxyquinolin (H-QL1c), 5,7-dibromo-8-hydroxyquinoline (H-QL1d), and 5,7-dichloro-8-hydroxy-2-methylquinoline (H-QL1e) and the main ligands 6,7-dichloro-3-pyridin-2-yl-chromen-2-one (H-QL3a), 6-bromo-3-pyridin-2-yl-chromen-2-one (H-QL3b), and 6-chloro-3-pyridin-2-yl-chromen-2-one (H-QL3c), respectively. The structure of compounds YNU-4a-YNU-4k was fully confirmed by conducting various spectroscopic analyses. The anticancer activity of YNU-4a-YNU-4k was evaluated in cisplatin-resistant A549/DDP lung cancer cells (LC549) versus normal embryonic kidney (HEK293) cells. Notably, compound YNU-4f bearing QL1e and QL3a ligands showed a more pronounced antiproliferative effect against LC549 cells (IC50 = 1.75 ± 0.09 μM) with high intrinsic selectivity toward LC549 cancer cells than YNU-4a-YNU-4e, H-QL1a-H-QL1e, cisplatin (PDD), YNU-4g-YNU-4k, and H-QL3a-H-QL3c. Additionally, a colocalization assay analysis of YNU-4e and YNU-4f showed that these two ruthenium(II/III) compounds were subcellularly accumulated in the mitochondria and other regions of the cytoplasm, where they induce mitophagy, adenosine triphosphate (ATP) reduction, mitochondrial respiratory chain complex I/IV(RC1/RC4) inhibition, and mitochondrial dysfunction. Accordingly, compounds YNU-4a-YNU-4k can be regarded as mitophagy inductors for the eradication of cisplatin-resistant LC549 cancer cells.

Promoting the Anticancer Activity with Multidentate Furan-2-Carboxamide Functionalized Aroyl Thiourea Chelation in Binuclear Half-Sandwich Ruthenium(II) Complexes

A new set of binuclear arene ruthenium complexes [Ru2(p-cymene)2(k4-N2OS)(L1-L3)Cl2] (Ru2L1-Ru2L3) encompassing furan-2-carboxamide-based aroylthiourea derivatives (H2L1-H2L3) was synthesized and characterized by various spectral and analytical techniques. Single-crystal XRD analysis unveils the N^O and N^S mixed monobasic bidentate coordination of the ligands constructing N, S, Cl/N, O, and Cl legged piano stool octahedral geometry. DFT analysis demonstrates the predilection for the formation of stable arene ruthenium complexes. In vitro antiproliferative activity of the complexes was examined against human cervical (HeLa), breast (MCF-7), and lung (A549) cancerous and noncancerous monkey kidney epithelial (Vero) cells. All the complexes are more efficacious against HeLa and MCF-7 cells with low inhibitory doses (3.86-11.02 μM). Specifically, Ru2L3 incorporating p-cymene and -OCH3 fragments exhibits high lipophilicity, significant cytotoxicity against cancer cells, and lower toxicity on noncancerous cells. Staining analysis indicates the apoptosis-associated cell morphological changes expressively in MCF-7 cells. Mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) analyses reveal that Ru2L3 can raise ROS levels, reduce MMP, and trigger mitochondrial dysfunction-mediated apoptosis. The catalytic oxidation of glutathione (GSH) to its disulfide form (GSSG) by the complexes may simultaneously increase the ROS levels, alluding to their observed cytotoxicity and apoptosis induction. Flow cytometry determined the quantitative classification of late apoptosis and S-phase arrest in MCF-7 and HeLa cells. Western blotting analysis confirmed that the complexes promote apoptosis by upregulating Caspase-3 and Caspase-9 and downregulating BCL-2. Molecular docking studies unfolded the strong binding affinities of the complexes with VEGFR2, an angiogenic signaling receptor, and BCL2, Cyclin D1, and HER2 proteins typically overexpressed on tumor cells.

Exploring the cytotoxicity of dinuclear Ru(II) p-cymene complexes appended N,N'-bis(4-substituted benzoyl)hydrazines: insights into the mechanism of apoptotic cell death

Cancer is a perilous life-threatening disease, and attempts are constantly being made to create multinuclear transition metal complexes that could lead to the development of potential anticancer medications and administration procedures. Hence, this work aims to design, synthesize, characterize, and assess the anticancer efficacy of ruthenium p-cymene complexes incorporating N,N'-bis(4-substituted benzoyl)hydrazine ligands. The formation of the new complexes (Ru2H1-Ru2H3) has been thoroughly established by elemental analysis, and FT-IR, UV-vis, NMR, and HR-MS spectral techniques. The solid-state molecular structures of the complexes Ru2H1 and Ru2H3 have been determined using the SC-XRD study, which confirms the N, O, and Cl-legged piano stool pseudo-octahedral geometry of each ruthenium(II) ion. The stability of these complexes in the solution state and their lipophilicity profile have been determined. Furthermore, the title complexes were tested for their in vitro anticancer activity against cancerous H460 (lung cancer cells), SkBr3 (breast cancer cells), HepG2 (liver cancer cells), and HeLa (cervical cancer cells) along with non-cancerous (HEK-293) cells. The IC50 results revealed that complex Ru2H3 exhibits potent activity against the proliferation of all four cancer cells and outscored the effect of the standard metallodrug cisplatin. This may be attributed to the presence of a couple of lipophilic electron-donating methoxy groups in the ligand scaffold and also the ruthenium(II) p-cymene motifs. Advantageously, all the complexes (Ru2H1-Ru2H3) displayed cytotoxic specificity only towards cancerous cells by leaving the off-target non-cancerous cells undamaged. Acridine orange/ethidium bromide (AO/EB) staining, Hoechst 33342, mitochondrial membrane potential (MMP), and reactive oxygen species (ROS) staining assays were used to investigate the apoptotic pathway and ROS levels in mitochondria. The results of western blot analysis confirmed that the complexes triggered apoptosis through an intrinsic mitochondrial pathway by upregulating Bax and downregulating Bcl-2 proteins. Finally, the extent of apoptosis triggered by the complex Ru2H3 was quantified with the aid of flow cytometry using the Annexin V-FITC/propidium iodide (PI) double-staining technique.

Antitumor studies evaluation of triphenylphosphine ruthenium complexes with 5,7-dihalo-substituted-8-quinolinoline targeting mitophagy pathways

Both ruthenium-containing complexes and 8-quinolinoline compounds have emerged as a potential novel agent for malignant tumor therapy. Here, three triphenylphosphine ruthenium complexes, [Ru(ZW1)(PPh3)2Cl2] (PPh3 = triphenylphosphine) (RuZ1), [Ru(ZW2)(PPh3)2Cl2] (RuZ2) and [Ru(ZW2)2(PPh3)Cl2]·CH2Cl2 (RuZ3) bearing 5,7-dichloro-8-quinolinol (H-ZW1) and 5,7-dichloro-8-hydroxyquinaldine (H-ZW2), have been synthesized, characterized and tested for their anticancer potential. We showed that triphenylphosphine ruthenium complexes RuZ1-RuZ3 impaired the cell viability of ovarian adenocarcinoma cisplatin-resistant SK-OV-3/DDP (SKO3CR) and SK-OV-3 (SKO3) cancer cells with greater selectivity and specificity than cisplatin. In addition, RuZ1-RuZ3 show higher excellent cytotoxicity than cisplatin towards SKO3CR cells, with IC50 values of 9.66 ± 1.08, 4.05 ± 0.67 and 7.18 ± 0.40 μM, respectively, in which the SKO3CR cells was the most sensitive to RuZ1-RuZ3. Depending on the substituent type, the antiproliferative ability of RuZ1-RuZ3 followed the trend: -CH3 > -H. However, RuZ1-RuZ3 have no obvious toxicity to normal cell HL-7702. Besides, RuZ1 and RuZ2 could induce mitophagy related-apoptosis pathways through suppression of mitochondrial membrane potential (ΔΨm), accumulation of [Ca2+] and reactive oxygen species (ROS), and regulation of LC3 II/LC3 I, Beclin-1, P62, FUNDC1, PINK1, Parkin, cleaved-caspase-3, caspase-9 and cytochrome c signaling pathway, and hindering the preparation of mitochondrial respiration complexes I and IV and ATP levels. Mechanistic study revealed that RuZ1 and RuZ2 induce apoptosis in SKO3CR cells via mitophagy related-apoptosis pathways induction and energy (ATP) generation disturbance. Taken together, the studied triphenylphosphine ruthenium complexes RuZ1-RuZ3 are promising chemotherapeutic agents with high effectiveness and low toxicity.

Naphthalene Diimide-Functionalized Half-Sandwich Ru(II) Complexes as Mitochondria-Targeted Anticancer and Antimetastatic Agents

In this work, four naphthalene diimide (NDI)-functionalized half-sandwich Ru(II) complexes Ru1-Ru4 bearing the general formula [(η⁶-arene)Ru^II(N^N)Cl]PF₆, where arene = benzene (bn), p-cymene (p-cym), 1,3,5-trimethylbenzene (tmb), and hexamethylbenzene (hmb), have been synthesized and characterized. By introducing the NDI unit into the N,N-chelating ligand of these half-sandwich complexes, the poor luminescent half-sandwich complexes are endowed with excellent emission performance. Besides, modification on the arene ligand of arene-Ru(II) complexes can influence the electron density of the metal center, resulting in great changes in the kinetic properties, catalytic activities in the oxidative conversion of NADH to NAD⁺, and biological activities of these compounds. Particularly, Ru4 exhibits the highest reactivity and the strongest inhibitory activity against the growth of three tested cancer cell lines. Further study revealed that Ru4 can enter cells quickly in an energy-dependent manner and preferentially accumulate in the mitochondria of MDA-MB-231 cells, inducing cell apoptosis via reactive oxygen species overproduction and mitochondrial dysfunction. Significantly, Ru4 can effectively inhibit the cell migration and invasion. Overall, the complexation with NDI and modification on the arene ligand endowed the half-sandwich Ru(II) complexes with improved spectroscopic properties and anticancer activities, highlighting their potential applications for cancer treatment.

Synthesis, characterization and biological evaluation of two cyclometalated iridium(III) complexes containing a glutathione S-transferase inhibitor

The cyclometalated iridium(III) compounds have been intensively studied for health-related applications due to their outstanding luminescent properties and multiple anticancer modes of action. Herein, two iridium(III) compounds Ir-1 and Ir-3 containing glutathione S-transferase inhibitor (GSTi) were developed and studied together with two unfunctionalized compounds Ir-2 and Ir-4 as a comparison. Biological study indicated that GSTi-bearing complexes Ir-1 and Ir-3 exert a synergistic effect on the inhibition of cancer cells. The photophysical properties of Ir-1 ∼ Ir-4 were investigated by UV/vis absorption and fluorescence spectroscopy and rationalized with TD-DFT calculations. As expected, GSTi-bearing complexes Ir-1 and Ir-3 exhibited considerable cytotoxicity against both A549 and cisplatin-resistant A549/cis cancer cells, much higher than the unfunctionalized iridium compounds Ir-2 and Ir-4. Further study indicated that Ir-1 and Ir-3 mainly localize in the mitochondria of tumor cells, and exert their cytotoxicity via generating ROS and inhibiting GST activity. The flow cytometry investigations demonstrated that Ir-1 and Ir-3 can arrest the cell cycle in S phase and induce the cell death through apoptosis process. Overall, the complexation of GST inhibitors with cyclometalated iridium(III) agents provides an effective way for potentiating the cytotoxicity of iridium(III) anticancer agents and resensitizing the efficacy against cisplatin resistant cancer cells.

Bonding in Nitrile Photo-dissociating Ruthenium Drug Candidates --A Local Vibrational Mode Study

In this work, we investigated bonding features 15 ruthenium complexes of the type [Ru(tpy)(L)-(CH3CN)]n+, containing the tridentate tpy ligand (tpy = 2,2':6',2'--terpyridine) and various bidentate ancillary ligands, 12 compounds originally synthesized by Loftus et al. (J. Phys. Chem. C 123, 10291-10299 (2019)) complemented with three additional complexes. The main focus of our work was to relate these local features to the experimental data of Loftus et al. which assess the efficiency of nitrile release in an indirect way via observed quantum yields for ruthenium water association after nitrile release. As a tool to quantitatively assess Ru-NC and Ru-L bonding we utilized the local vibrational mode analysis complemented by the topological analysis of the electron density and the natural bond orbital analysis. Interestingly, the stronger Ru-NC bonds have the greater observed quantum yields, leading to the conclusion that the observed quantum yields are a result of a complex interplay of several processes excluding a direct relationship between QY and Ru-NC or Ru-L bond strengths. We identified the ST splitting as one of the key players and not the Ru-NC bond strength, as one may have thought. In summary, this work has presented a modern computational tool set for the investigation of bonding features applied to nitrile photo-dissociating ruthenium drug candidates forming a valuable basis for future design and fine tuning of nitrile releasing ruthenium compounds, as well as for the understanding of how local properties affect overall experimental outcomes.

Multifunctional platinum(IV) complex bearing HDAC inhibitor and biotin moiety exhibits prominent cytotoxicity and tumor-targeting ability

Despite the wide clinical use of platinum drugs in cancer treatment, their severe side effects and lack of tumor selectivity seriously limit their further clinical application. To address the limitations of the current platinum drugs, herein a multifunctional platinum(IV) compound 1 containing a histone deacetylase (HDAC) inhibitor (4-phenylbutyric acid, 4-PBA) and a tumor-targeting group (biotin) has been designed and prepared. An in vitro cytotoxicity study indicated that compound 1 exhibits comparable or superior cytotoxicity to cisplatin against the tested cancer cell lines, but greatly reduced toxicity in human normal liver LO2 cells, implying the potential tumor-targeting ability of compound 1. Molecular docking results indicate that compound 1 can effectively interact with a biotin-specific receptor (streptavidin) through its biotin moiety, enabling potential tumor-targeting capability. Further studies indicated that compound 1's cytotoxicity stems from inducing DNA damage via the mitochondrial apoptotic pathway and inhibiting HDACs. Consequently, this compound can not only take advantage of the tumor selectively of biotin to improve its tumor-targeting ability but also strengthen its anticancer activity via simultaneously targeting DNA and HDACs.

Ruthenium(ii) complex containing cinnamic acid derivative inhibits cell cycle progression at G0/G1 and induces apoptosis in melanoma cells

Melanoma is a highly aggressive skin cancer with a limited targeted therapy arsenal.