An oxygen-chelate complex, palladium bis-acetylacetonate, induces apoptosis in H460 cells via endoplasmic reticulum stress pathway rather than interacting with DNA

Palladium(ii), platinum(ii), and silver(i) complexes with 3-acetylcoumarin benzoylhydrazone Schiff base: Synthesis, characterization, biomolecular interactions, cytotoxic activity, and computational studies

New Pd(ii) (C1), Pt(ii) (C2), and Ag(i) (C3) complexes derived from 3-acetylcoumarin benzoylhydrazone (HL) Schiff base were synthesized and characterized by FTIR, 1H NMR, UV-visible spectroscopies along with elemental analysis (C, H, N), magnetic, molar conductivity measurements, and DFT calculations. The obtained results suggested that the ligand had different behaviors in the complexes: mono-negative tridentate (C1) and neutral tridentate (C2) as an ONO-donor and neutral bidentate (C3) as an ON-donor. Quantum chemistry calculations were performed to validate the stability of the suggested geometries and indicated that all the complexes possess tetra-coordinated metal ions. The binding affinity of all the compounds toward calf thymus (ctDNA), yeast (tRNA), and bovine serum albumin (BSA) was evaluated by absorption/emission spectral titration studies, which revealed the intercalative binding to ctDNA and tRNA and static binding upon complex formation with BSA. Molecular insights into the binding affinity of the characterized complexes were provided through conducting molecular docking analysis. Moreover, the cytotoxic activity (in vitro) of the compounds was screened against human cancerous cell lines and a non-cancerous lung fibroblast (WI38) one using cis-platin as a reference drug. The IC50 and selective index (SI) values indicated the higher cytotoxic activity of all the metal complexes compared to their parent ligand. Among all the compounds, the complex C2 showed the highest activity. These results confirmed the improvement of the anticancer activity of the ligand by incorporating the metal ions. In addition, flow cytometry results showed that complexes C1 and C2 induced cell cycle arrest at S and G1/S, respectively.

Metal-(Acyclic Diaminocarbene) Complexes Demonstrate Nanomolar Antiproliferative Activity against Triple-Negative Breast Cancer

Hydrolytically stable PdII and PtII complexes supported by acyclic diaminocarbene ligands represent a novel class of structural organometallic anticancer agents exhibiting nanomolar antiproliferative activity in a panel of cancer cell lines (IC50 0.07-0.81 μM) and up to 300-fold selectivity for cancer cells over normal primary fibroblasts. The lead drug candidate was 300 times more potent than cisplatin in vitro and showed higher efficacy in reducing the growth of aggressive MDA-MB-231 xenograft tumors in mice.

Novel Indole-Chalcone Derivative-Ligated Platinum(IV) Prodrugs Attenuate Cisplatin Resistance in Lung Cancer through ROS/ER Stress and Mitochondrial Dysfunction

Developing multifunctional platinum(IV) prodrugs via integrating bioactive pharmacophores into one entity is an attractive strategy to ameliorate the defects of platinum(II) drugs. Herein, a series of indole-chalcone derivative-ligated platinum(IV) complexes were synthesized and evaluated for their anticancer activities. Among them, optimal complex 17a exerted superior activity compared to that of cisplatin (CDDP) against the tested cells but showed lower cytotoxicity toward human normal lung cells. Detailed mechanisms demonstrated that 17a significantly enhanced intracellular accumulation, induced DNA damage, and inhibited migration in A549/CDDP cells. Furthermore, 17a efficiently disturbed the tubulin-microtubule system, initiated reactive oxygen species (ROS)-mediated endoplasmic reticulum stress, and activated a mitochondrion-dependent apoptosis signaling pathway. Besides, 17a was superior to free drugs or their combination in inhibiting cancer growth in A549/CDDP xenografts without inducing obvious side effects. The physical mixture of 16a and CDDP was almost identical to 17a but showed apparent systematic side effects. In summary, our studies may provide an efficient treatment regimen for CDDP resistance.

Highlights of New Strategies to Increase the Efficacy of Transition Metal Complexes for Cancer Treatments

Although important progress has been made, cancer still remains a complex disease to treat. Serious side effects, the insurgence of resistance and poor selectivity are some of the problems associated with the classical metal-based anti-cancer therapies currently in clinical use. New treatment approaches are still needed to increase cancer patient survival without cancer recurrence. Herein, we reviewed two promising-at least in our opinion-new strategies to increase the efficacy of transition metal-based complexes. First, we considered the possibility of assembling two biologically active fragments containing different metal centres into the same molecule, thus obtaining a heterobimetallic complex. A critical comparison with the monometallic counterparts was done. The reviewed literature has been divided into two groups: the case of platinum; the case of gold. Secondly, the conjugation of metal-based complexes to a targeting moiety was discussed. Particularly, we highlighted some interesting examples of compounds targeting cancer cell organelles according to a third-order targeting approach, and complexes targeting the whole cancer cell, according to a second-order targeting strategy.

Novel Nickel(II), Palladium(II), and Platinum(II) Complexes with O,S Bidendate Cinnamic Acid Ester Derivatives: An In Vitro Cytotoxic Comparison to Ruthenium(II) and Osmium(II) Analogues

(1) Background: Since the discovery of cisplatin’s cytotoxic properties, platinum(II) compounds have attracted much interest in the field of anticancer drug development. Over the last few years, classical structure−activity relationships (SAR) have been broken by some promising new compounds based on platinum or other metals. We focus on the synthesis and characterization of 17 different complexes with β-hydroxydithiocinnamic acid esters as O,S bidendate ligands for nickel(II), palladium(II), and platinum(II) complexes. (2) Methods: The bidendate compounds were synthesized and characterized using classical methods including NMR spectroscopy, MS spectrometry, elemental analysis, and X-ray crystallography, and their cytotoxic potential was assessed using in vitro cell culture assays. Data were compared with other recently reported platinum(II), ruthenium(II), and osmium(II) complexes based on the same main ligand system. (3) Results: SAR analyses regarding the metal ion (M), and the alkyl-chain position (P) and length (L), revealed the following order of the effect strength for in vitro activity: M > P > L. The highest activities have Pd complexes and ortho-substituted compounds. Specific palladium(II) complexes show lower IC50 values compared to cisplatin, are able to elude cisplatin resistance mechanisms, and show a higher cancer cell specificity. (4) Conclusion: A promising new palladium(II) candidate (Pd3) should be evaluated in further studies using in vivo model systems, and the identified SARs may help to target platinum-resistant tumors.

Structural, biological and computational study of oxamide derivative

A dicarboxylato-diamide-type compound 2,2'-[(1,2-dioxoethane-1,2- -diyl)diimino]dibenzoic acid (H4obbz) (1) was synthesized and characterized. The crystal structure of K2H2obbz?2H2O (2) was determined by X-ray diffracttion analysis. The cytotoxic activities of the compounds were tested against four different cancer cell lines MCF-7, A549, HT-29, HeLa and a human normal cell line MRC-5. The results indicate reasonable dose-dependent cytotoxicity of the ligands that show selectivity against the tested carcinoma and healthy cell lines. Flow cytometric analysis and fluorescence microscopy showed that the most active compound, H4obbz, induced apoptosis and G0/G1 cell cycle arrest, indicating blockage of DNA synthesis as a possible mechanism that triggers apoptosis. Docking and molecular dynamics simulations gave similar responses regarding interactions (binding) between their ligands and chaperon Grp78. The MMGBSA determined ?G binding energies were in the range from -104 to -140 kJ mol-1.

A novel palladium(II) antitumor agent: Synthesis, characterization, DFT perspective, CT-DNA and BSA interaction studies via in-vitro and in-silico approaches

Since numerous people annually pass away due to cancer, research in this field is essential. Thus a newly made and water like palladium(II) complex of formula [Pd(phen)(acac)]NO₃, where phen is 1,10-phenanthroline and acac is acetylacetonato ligand, has been synthesized by the reaction between [Pd(phen)(H₂O)₂](NO₃)₂ and sodium salt of acetylacetone in the molar ratio of 1:1. It has been structurally characterized via the methods such as conductivity measurement, elemental analysis and spectroscopic methods (FT-IR, UV-Vis and ¹H NMR). The geometry optimization of this complex at the DFT level of theory reveals that Pd(II) atom is situated in a square-planar geometry. The complex has been screened for its antitumor activity against K562 cancer cells which demonstrated efficacious activity. The interaction of above palladium(II) complex with CT-DNA as a target molecule for antitumor agents and BSA as a transport protein was studies by a variety of techniques. The results of UV-Vis absorption and fluorescence emission indicated that the Pd(II) complex interacts with EB + CT-DNA through hydrophobic and with BSA by hydrogen bonding and van der Waals forces at very low concentrations. In these processes, the fluorescence quenching mechanism of both the macromolecules seems to be the combined dynamic and static. The interaction was further supported for CT-DNA by carrying out the gel electrophoresis and viscosity measurement and for BSA by the circular dichroism and Förster resonance energy transfer experiments. Furthermore, results of partition coefficient determination showed that the [Pd(phen)(acac)]NO₃ complex is more lipophilic than that of cisplatin. Moreover, molecular docking simulation confirms the obtained results from experimental tests and reveals that the complex tends to be located at the intercalation site of DNA and Sudlow's site I of BSA.

Metabolic Aspects of Palladium(II) Potential Anti-Cancer Drugs

This mini-review reports on the existing knowledge of the metabolic effects of palladium [Pd(II)] complexes with potential anticancer activity, on cell lines and murine models. Most studies have addressed mononuclear Pd(II) complexes, although increasing interest has been noted in bidentate complexes, as polynuclear structures. In addition, the majority of records have reported in vitro studies on cancer cell lines, some including the impact on healthy cells, as potentially informative in relation to side effects. Generally, these studies address metabolic effects related to the mechanisms of induced cell death and antioxidant defense, often involving the measurement of gene and protein expression patterns, and evaluation of the levels of reactive oxygen species or specific metabolites, such as ATP and glutathione, in relation to mitochondrial respiration and antioxidant mechanisms. An important tendency is noted toward the use of more untargeted approaches, such as the use of omic sciences e.g., proteomics and metabolomics. In the discussion section of this mini-review, the developments carried out so far are summarized and suggestions of possible future developments are advanced, aiming at recognizing that metabolites and metabolic pathways make up an important part of cell response and adaptation to therapeutic agents, their further study potentially contributing valuably for a more complete understanding of processes such as biotoxicity or development of drug resistance.

Novel nickel(II), palladium(II), and platinum(II) complexes having a pyrrolyl-iminophosphine (PNN) pincer: Synthesis, crystal structures, and cytotoxic activity

A pyrrolyl-iminophosphine (PNNH) which would act as a potential terdentate ligand has been prepared by Schiff base reaction. Complexes [M(PNN)X] (M = Ni; X = Cl (1), Pd; X = Cl (2), Br (3), I (4), M = Pt; X = Cl (5)) were prepared. The title complexes were characterized by various spectroscopic (IR, ¹H, ¹³C, and ³¹P NMR) and elemental analyses. The molecular structures of 1, 2, and 5 have been established by single-crystal X-ray crystallography, demonstrating a distorted square planar geometry comprising two 5-membered metallacyclic rings. Complexes 1 and 2 were found to crystallize in the orthorhombic while complex 5 crystallizes in the monoclinic. Cytotoxicities of the complexes along with PNNH were evaluated against A549 (lung), SK-OV-3 (ovarian), SM-MEL-2 (skin), and HCT15 (colon) human cancer cell lines by sulforhodamine B assay. Notably, the palladium(II) complex (2) shows the highest activity. Apoptosis activity along with the caspase inhibitor Z-VAD (Z-Val-Ala-Asp-fluoromethyl ketone) assay of 2 and 5 against A549 and HCT15 cancer cell lines were investigated to learn a mechanistic pathway for the observed cytotoxicity, practically eliminating an apoptotic cell-death route. Complexes 2 and 5 were studied to DNA cleavage assay and molecular docking simulation. The DNA (pcDNA3.0) cleavage experiment evaluates complex 5 interacting with DNA, more effectively, in comparison to complex 2. Molecular docking simulation of 2 and 5 toward DNA and GRP78 (glucose-regulated protein 78) was performed to predict binding sites of ligand-receptors and a plausible mechanistic aspect of metallodrug-action.

Endoplasmic reticulum stress: an arising target for metal-based anticancer agents

Metal anticancer agents are rapidly emerging as selective, potent therapeutics that exhibit anticancer activity by inducing endoplasmic reticulum stress.

A trans-dichloridoplatinum(II) complex of a monodentate nitrogen mustard: Synthesis, stability and cytotoxicity studies

A trans-dichloridoplatinum(II) complex, trans-[Pt^IICl₂(L)(DMSO)] (1) of a monodentate nitrogen mustard, bis(2-chloroethyl)amine (L), was synthesized by the reaction of cis-[Pt^IICl₂(DMSO)₂] &L.HCl in presence of Et₃N. 1 was characterised by NMR, FT-IR and elemental analysis. L is unstable in aqueous solution while 1 displayed moderate stability. In aqueous buffer solution of pD 7.4, 1 starts to loose L slowly upon dissolution and even after 48 h there is still intact/aquated complex present in solution. 1 interacts with the model nucleobase 9-ethyl guanine. The ligand L was non-toxic against MCF-7, A549, HepG2 & MIA PaCa-2 up to 200 μM. In contrast, the Pt(II) complex 1 showed an excellent IC₅₀ (ca. 600 nM) against MIA PaCa-2 and also displayed good IC₅₀ value (3-7 μM) against the other cancer cell lines probed. The in vitro cytotoxicity of 1 is better than cisplatin against each of the treated cancer cell lines and it is not affected by hypoxia as per the in vitro studies. Complex 1 displays higher cellular accumulation than cisplatin and arrests the cell cycle in both S & G2/M phase inducing apoptotic cell death. The G2/M phase arrest is dominant at higher concentrations. The depolarisation of mitochondria by 1 combined with activation of caspase-7 indicates apoptotic cell death. Complex 1 induces low hemolysis of human blood signifying excellent blood compatibility.

A Rhenium Isonitrile Complex Induces Unfolded Protein Response-Mediated Apoptosis in Cancer Cells

Complexes of the element Re have recently been shown to possess promising anticancer activity through mechanisms of action that are distinct from the conventional metal-based drug cisplatin. In this study, we report our investigations on the anticancer activity of the complex [Re(CO)₃ (dmphen)(p-tol-ICN)]⁺ (TRIP) in which dmphen=2,9-dimethyl-1,10-phenanthroline and p-tol-ICN=para-tolyl isonitrile. TRIP was synthesized by literature methods and exhaustively characterized. This compound exhibited potent in vitro anticancer activity in a wide variety of cell lines. Flow cytometry and immunostaining experiments indicated that TRIP induces intrinsic apoptosis. Comprehensive biological mechanistic studies demonstrated that this compound triggers the accumulation of misfolded proteins, which causes endoplasmic reticulum (ER) stress, the unfolded protein response, and apoptotic cell death. Furthermore, TRIP induced hyperphosphorylation of eIF2α, translation inhibition, mitochondrial fission, and expression of proapoptotic ATF4 and CHOP. These results establish TRIP as a promising anticancer agent based on its potent cytotoxic activity and ability to induce ER stress.

A survey of the mechanisms of action of anticancer transition metal complexes

Metal complexes have been the subject of numerous investigations in oncology but, despite the plethora of newly synthesized compounds, their precise mechanisms of action remain generally unknown or, for the best, incompletely determined. The continuous development of efficient and sensitive techniques in analytical chemistry and molecular biology gives scientists new tools to gather information on how metal complexes can be effective toward cancer. This review focuses on recent findings about the anticancer mechanism of action of metal complexes and how the ligands can be used to tune their pharmacological and physicochemical properties.

Evodiamine induces G2/M arrest and apoptosis via mitochondrial and endoplasmic reticulum pathways in H446 and H1688 human small-cell lung cancer cells

The goal of this study was to evaluate the ability of EVO to decrease cell viability and promote cell cycle arrest and apoptosis in small cell lung cancer (SCLC) cells. Lung cancer has the highest incidence and mortality rates among all cancers. Chemotherapy is the primary treatment for SCLC; however, the drugs that are currently used for SCLC are less effective than those used for non-small cell lung cancer (NSCLC). Therefore, it is necessary to develop new drugs to treat SCLC. In this study, the effects of evodiamine (EVO) on cell growth, cell cycle arrest and apoptosis were investigated in the human SCLC cell lines NCI-H446 and NCI-H1688. The results represent the first report that EVO can significantly inhibit the viability of both H446 and H1688 cells in dose- and time-dependent manners. EVO induced cell cycle arrest at G2/M phase, induced apoptosis by up-regulating the expression of caspase-12 and cytochrome C protein, and induced the expression of Bax mRNA and by down-regulating of the expression of Bcl-2 mRNA in both H446 and H1688 cells. However, there was no effect on the protein expression of caspase-8. Taken together, the inhibitory effects of EVO on the growth of H446 and H1688 cells might be attributable to G2/M arrest and subsequent apoptosis, through mitochondria-dependent and endoplasmic reticulum stress-induced pathways (intrinsic caspase-dependent pathways) but not through the death receptor-induced pathway (extrinsic caspase-dependent pathway). Our findings suggest that EVO is a promising novel and potent antitumor drug candidate for SCLC. Furthermore, the cell cycle, the mitochondria and the ER stress pathways are rational targets for the future development of an EVO delivery system to treat SCLC.