Fenamates: Forgotten treasure for cancer treatment and prevention: Mechanisms of action, structural modification, and bright future

Fenamates as classical nonsteroidal anti-inflammatory agents are widely used for relieving pain. Preclinical studies and epidemiological data highlight their chemo-preventive and chemotherapeutic potential for cancer. However, comprehensive reviews of fenamates in cancer are limited. To accelerate the repurposing of fenamates, this review summarizes the results of fenamates alone or in combination with existing chemotherapeutic agents. This paper also explores targets of fenamates in cancer therapy, including COX, AKR family, AR, gap junction, FTO, TEAD, DHODH, TAS2R14, ion channels, and DNA. Besides, this paper discusses other mechanisms, such as regulating Wnt/β-catenin, TGF-β, p38 MAPK, and NF-κB pathway, and the regulation of the expressions of Sp, EGR-1, NAG-1, ATF-3, ErbB2, AR, as well as the modulation of the tumor immune microenvironment. Furthermore, this paper outlined the structural modifications of fenamates, highlighting their potential as promising leads for anticancer drugs.

Gold(I) Complexes Based on Nonsteroidal Anti-Inflammatory Derivatives as Multi-Target Drugs against Colon Cancer

Targeting inflammation and the molecules involved in the inflammatory process could be an effective cancer prevention and therapy strategy. Therefore, the use of anti-inflammatory strategies, such as NSAIDs and metal-based drugs, has become a promising approach for preventing and treating cancer by targeting multiple pathways involved in tumor progression. The present work describes new phosphane gold(I) complexes derived from nonsteroidal anti-inflammatory drugs as multitarget drugs against colon cancer. The antiproliferative effect of the most active complexes, [Au(L3)(JohnPhos)] (3b), [Au(L4)(CyJohnPhos)] (4a) and [Au(L4)(JohnPhos)] (4b) against colon cancer cells (Caco2-/TC7) seems to be mediated by the inhibition of the enzyme cyclooxygenase-1/2, modulation of reactive oxygen species levels by targeting thioredoxin reductase (TrxR) activity, and induction of apoptosis in cancer cells. Additionally, the three complexes exhibit high selectivity index values toward noncancerous cells. The research highlights the importance of maintaining cellular redox balance and the role of TrxR in cancer cell survival.

Silver(I) Complexes with Mefenamic Acid and Nitrogen Heterocyclic Ligands: Synthesis, Characterization, and Biological Evaluation

Four Ag(I) complexes with mefenamato and nitrogen heterocyclic ligands, [Ag(2-apy)(mef)]2 (1), [Ag(3-apy)(mef)] (2), [Ag2(tmpyz)(mef)2] (3), and {[Ag(4,4'-bipy)(mef)]2(CH3CN)1.5(H2O)2}n (4), (mef = mefenamato, 2-apy = 2-aminopyridine, 3-apy = 3-aminopyridine, tmpyz = 2,3,5,6-tetramethylpyrazine, 4,4'-bipy = 4,4'-bipyridine), were synthesized and characterized. The interactions of these complexes with BSA were investigated by fluorescence spectroscopy, which indicated that these complexes quench the fluorescence of BSA by a static mechanism. The fluorescence data also indicated that the complexes showed good affinity for BSA, and one binding site on BSA was suitable for the complexes. The in vitro cytotoxicity of the four complexes against human cancer cell lines (MCF-7, HepG-2, A549, and MDA-MB-468) and one normal cell line (HTR-8) was evaluated by the MTT assay. Complex 1 displayed high cytotoxic activity against A549 cells. Further studies revealed that complex 1 could enhance the intracellular levels of ROS (reactive oxygen species) in A549 cells, cause cell cycle arrest in the G0/G1 phase, and induce apoptosis in A549 cells in a dose-dependent manner.

Multiple drug-delivery strategies to enhance the pharmacological and toxicological properties of Mefenamic acid

OBJECTIVE

To improve the biological and toxicological properties of Mefenamic acid (MA), the galactosylated prodrug of MA named MefeGAL was included in polymeric solid dispersions (PSs) composed of poly(glycerol adipate) (PGA) and Pluronic® F68 (MefeGAL-PS). MefeGAL-PS was compared with polymeric solid formulations of MA (MA-PS) or a mixture of equal ratio of MefeGAL/MA (Mix-PS).

METHODS

The in vitro and in vivo pharmacological and toxicological profiles of PSs have been investigated. In detail, we evaluated the anti-inflammatory (carrageenan-induced paw edema test), analgesic (acetic acid-induced writhing test) and ulcerogenic activity in mice after oral treatment. Additionally, the antiproliferative activity of PSs was assessed on in vitro models of colorectal and non-small cell lung cancer.

RESULTS

When the PSs were resuspended in water, MefeGAL's, MA's and their mixture's apparent solubilities improved due to the interaction with the polymeric formulation. By comparing the in-vivo biological performance of MefeGAL-PS with that of MA, MefeGAL and MA-PS, it was seen that MefeGAL-PS exhibited the same sustained and delayed analgesic and anti-inflammatory profile as MefeGAL but did not cause gastrointestinal irritation. The pharmacological effect of Mix-PS was present from the first hours after administration, lasting about 44 hours with only slight gastric mucosa irritation. In-vitro evaluation indicated that Mix-PS had statistically significant higher cytotoxicity than MA-PS and MefeGAL-PS.

CONCLUSIONS

These preliminary data are promising evidence that the galactosylated prodrug approach in tandem with a polymer-drug solid dispersion formulation strategy could represent a new drug delivery route to improve the solubility and biological activity of NSAIDs.

Photocytotoxic kinetically stable ruthenium(II)-N,N-donor polypyridyl complexes of oxalate with anticancer activity against HepG2 liver cancer cells

Liver cancer is one of the leading causes of death that motivating scientists worldwide to synthesize novel chemotherapeutics. Ru(II)-polypyridyl complexes are extensively studied for possible therapeutic and cellular applications due to their tunable coordination chemistry, structural diversity, ligand-exchange kinetics, accessible redox states, and rich photophysical or photochemical properties. Herein, we have synthesized a series of Ru(II) polypyridyl complexes [RuII(N^N)2(ox)] (1-3), where ox is oxalate (C2O42-) and N^N is 1,10-phenanthroline (phen) (1), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq) (2), and dipyrido[3,2,-a:2',3'-c]phenazine (dppz) (3). Oxalate (ox2-) was opted as a bioactive dioxo ligand to prevent facile hydrolysis in aqueous media, thereby increasing the stability of the Ru(II)-polypyridyl complexes in physiological media. We thoroughly characterized all the complexes using ESI-MS, FT-IR, UV-vis, and 1H NMR spectroscopy and other physicochemical methods. The complexes were stable under physiological conditions and under low-energy green LED light (λirr = 530 nm). However, the photoirradiation of complexes resulted in the efficient generation of singlet oxygen (1O2) as a major reactive oxygen species (ROS). The role of the extended aromatic conjugation of the N^N-donor ligands in the complexes was demonstrated by their binding propensities with CT-DNA and bovine serum albumin (BSA). Both DNA intercalation and groove binding were evidenced, while tryptophan (Trp) and tyrosine (Tyr) binding site preferences were revealed from the synchronous fluorescence spectra (SFS) of BSA. The cytotoxic profiling of the complexes performed on hepatocellular carcinoma cells (HepG2) in the dark and in the presence of green light indicated their dose-dependent cytotoxicity. The [RuII(N^N)2(ox)] complexes exhibited enhanced photocytotoxicity mediated by efficient generation of cytotoxic 1O2 and effective interaction with DNA. All the complexes were internalized by the HepG2 liver cancer cells efficiently and localized to the cytoplasm and nucleus. The complexes exhibited potent anti-proliferative, anti-clonogenic, and anti-migratory effects on the cancer cells, suggesting their potential for therapeutic applications.

Tumor selective Ru(III) Schiff bases complexes with strong in vitro activity toward cisplatin-resistant MDA-MB-231 breast cancer cells

Novel ruthenium(III) complexes of general formula Na[RuCl2(L1-3-N,O)2] where L(1-3) denote deprotonated Schiff bases (HL1-HL3) derived from 5-substituted salicyladehyde and alkylamine (propyl- or butylamine) were prepared and characterized based on elemental analysis, mass spectra, infrared, electron spin/paramagnetic resonance (ESR/EPR) spectroscopy, and cyclovoltammetric study. Optimization of five isomers of complex C1 was done by DFT calculation. The interaction of C1-C3 complexes with DNA (Deoxyribonucleic acid) and BSA (Bovine serum albumin) was investigated by electron spectroscopy and fluorescence quenching. The cytotoxic activity of C1-C3 was investigated in a panel of four human cancer cell lines (K562, A549, EA.hy926, MDA-MB-231) and one human non-tumor cell line (MRC-5). Complexes displayed an apparent cytoselective profile, with IC50 values in the low micromolar range from 1.6 ± 0.3 to 23.0 ± 0.1 µM. Cisplatin-resistant triple-negative breast cancer cells MDA-MB-231 displayed the highest sensitivity to complexes, with Ru(III) compound containing two chlorides and two deprotonated N-propyl-5-chloro-salicylidenimine (hereinafter C1) as the most potent (IC50 = 1.6 µM), and approximately ten times more active than cisplatin (IC50 = 21.9 µM). MDA-MB-231 cells treated for 24 h with C1 presented with apoptotic morphology, as seen by acridine orange/ethidium bromide staining, while 48 h of treatment induced DNA fragmentation, and necrotic changes in cells, as seen by flow cytometry analysis. Drug-accumulation study by inductively coupled plasma mass spectrometry (ICP-MS) demonstrated markedly higher intracellular accumulation of C1 compared with cisplatin.

Half-Sandwich Ruthenium Arene Complexes Bearing Clinically Approved Drugs as Ligands: The Importance of Metal-Drug Synergism in Metallodrug Design

A novel strategy in metallodrug discovery today is incorporating clinically approved drugs into metal complexes as coordinating ligands. Using this strategy, various drugs have been repurposed to prepare organometallic complexes to overcome the resistance of drugs and to design promising alternatives to currently available metal-based drugs. Notably, the combination of organoruthenium moiety and clinical drug in a single molecule has been shown, in some instances, to enhance pharmacological activity and reduce toxicity in comparison to the parent drug. Thus, for the past two decades, there has been increasing interest in exploiting metal-drug synergism to develop multifunctional organoruthenium drug candidates. Herein, we summarized the recent reports of rationally designed half-sandwich Ru(arene) complexes containing different FDA-approved drugs. This review also focuses on the mode of coordination of drugs, ligand-exchange kinetics, mechanism of action, and structure-activity relationship of organoruthenated complexes containing drugs. We hope this discussion may serve to shed light on future developments in ruthenium-based metallopharmaceuticals.

Recognition and mechanistic investigation of anion sensing by ruthenium(II) arene complexes and bio-imaging application

In this work, four new ruthenium complexes [Ru(η⁶-p-cymene)(L1)Cl] 1, [Ru(η⁶-p-cymene)(L2)Cl] 2, [Ru(η⁶-p-cymene)(L3)Cl] 3 and [Ru(η⁶-p-cymene)(L4)Cl] 4 [HL1 = (2-cyanophenyl)glycine; HL2 = (5-chloro-2-cyanophenyl)glycine; HL3 = (2-cyano-3-fluorophenyl)glycine; HL4 = (4-cyanophenyl)glycine] were synthesized and well characterized by several spectroscopic and analytical techniques. Complexes 1 and 3 were found to be fluorescent in most of the solvents; however, 2 and 4 were found to be fluorescent mostly in EtOAc, DMF and ethanol. Amongst these four complexes, 3 has shown selective sensing against CO₃^2- and SO₄^2- anions by quenching of fluorescence. The LOD values are found to be in the sub-micromolar range. Investigations of the sensing mechanism performed by computation and NMR studies indicate a possible adduct formation between the NH group of the ligand and the anion(s) through hydrogen bond formation, which ultimately might lead to proton transfer to the bi-negative anion. The quantum yield of the complex 3 was found to decrease on addition of CO₃^2- and SO₄^2- anions from 0.46 to 0.13 and 0.12, respectively. The Job's plot indicates the binding between the probe and anion in a 1 : 1 ratio for both CO₃^2- and SO₄^2- anions. Along with that, all the complexes were found to be biocompatible when tested against several cell lines showing very high IC₅₀ values. It can also be observed that 1 is capable of penetrating within the cells and can act as a cell imaging agent showing fluorescence, and thus can be used for bio-imaging purposes.

Stability of a half-sandwich Os(II) complex with indomethacin-functionalized ligand in the presence of carboxypeptidase A

In the presence of carboxypeptidase, the hydrolytically stable complex [Os(η⁶-pcym)(L2)Cl]PF₆ (2) partially released the bioactive substituent indomethacin, bound through the amide bond to the chelating 2-(1,3,4-thiadiazol-2-yl)pyridine-based moiety of L2. Stability in the presence of other relevant biomolecules (GSH, NADH, GMP) and cancer cell viability were also studied.

Anti-melanoma effect of ruthenium(II)-diphosphine complexes containing naphthoquinone ligand

The use of natural products as potential ligands has been explored as a strategy in the development of metal-based chemotherapy. Since ruthenium complexes are promising alternatives to traditional antitumor agents, this study evaluated the anti-melanoma potential of two ruthenium(II) complexes containing the naphthoquinone ligands lapachol (lap), [Ru(lap)(dppm)2]PF6, and lawsone (law), [Ru(law)(dppm)2]PF6, in addition to the bis(diphenylphosphino)methane (dppm) ligand, referred to as complexes (1) and (2), respectively, using a syngeneic murine melanoma model. Activation of the apoptotic pathway by the treatments was assessed by immunohistochemistry in tumor tissue. Additionally, toxicity of the treatments was evaluated by variation in body and organ weight, quantification of biochemical indicators of renal damage, and genotoxicity in bone marrow and hepatocytes. First, the antiproliferative activity of (1) and (2) was observed in B16F10 cells, with IC50 values of 2.78 and 1.68 μM, respectively. The results obtained in mice showed that, unlike complex (1), (2) possesses significant anti-melanoma activity demonstrated by a reduction in tumor volume and mass (88.42%), as well as in mitosis frequency (83.86%). Additionally, complex (2) increased the levels of cleaved caspase-3, inducing tumor cell apoptosis. When compared to the metallodrug cisplatin, complex (2) exhibited similar anti-melanoma activity and lower toxicity considering all parameters evaluated. In silico studies demonstrated no difference in the binding energy of the naphthoquinone complex between complexes (1) and (2). However, the complex containing the lawsone ligand has a lower molar volume, which may be important for interactions with minor DNA grooves. The present results demonstrate the antitumor efficiency of complex (2) and a significantly lower systemic toxicity compared to cisplatin.

Ru(II)/diclofenac-based complexes: DNA, BSA interaction and their anticancer evaluation against lung and breast tumor cells

Ruthenium(ii) diclofenac-based complexes of the general formula [Ru(dicl)(P-P)(bpy)]PF6 [dicl = diclofenac, bpy = 2,2'-bipyridine, and P-P = 1,4'-bis(diphenylphosphino)butane (dppb) (1), 1,2'-bis(diphenylphosphino)ethane (dppe) (2), 1,3'-bis(diphenylphosphino)propane (dppp) (3) and 1,1'-bis(diphenylphosphino)ferrocene (dppf) (4)] are synthesized. The complexes (1-4) are characterized by elemental analyses, infrared, NMR, and UV-vis spectroscopy and (3) and (4) are characterized by single crystal X-ray diffraction. The DNA binding of complexes (1-4), studied by circular dichroism (CD) and Hoechst 33 258 staining assay, indicates their binding with the minor grooves. The complexes interact with BSA with binding constants (Kb) in the range of 2.5 × 103-5.5 × 104 M-1. The complexes exhibit high cytotoxicity against the tumor cell lines A549, MDA-MB-231, and MCF-7 with IC50 values ranging from 0.56 to 15.28 μM. The complexes are more selective for the hormone-dependent MCF-7 breast tumor cell line and complex (1) is the most potent one. The study demonstrates the anticancer activity of ruthenium(ii)/diclofenac-based complexes.

Two isostructural Co(II) flufenamato and niflumato complexes with bathocuproine: Analogues with a different cytotoxic activity

Two novel Co(II) fenamato complexes containing bathocuproine (bcp), namely [Co(bcp)(flu)₂] (1) and [Co(bcp)(nif)₂] (2) (flu = flufenamato, nif = niflumato) were synthesized and characterized by elemental analysis, single-crystal X-ray structure analysis as well as absorption and fluorescence spectroscopy. Investigation of their molecular structure revealed that both complexes are isostructural and form analogous complex molecules, with a Co(II) atom hexacoordinated by two nitrogen atoms of bcp and four oxygen atoms of two chelate bonded flu (1) and nif (2) ligands in a distorted octahedral arrangement. Surprisingly, the results of cytotoxicity experiments on four cancer cell lines (HeLa, HT-29, PC-3 and MCF-7) have revealed that despite similar structure of the complexes, the nif complex exhibits significantly higher activity, being the most effective against the PC-3 cell line (IC₅₀ (MTT) = 6.11 ± 1.95 μM). Further studies performed on PC-3 cell line have shown that the mechanism of the cytotoxic action of nif complex (2) might involve activation of autophagic processes and apoptosis, while for its flu analogue (1) apoptosis was detected.

Synthesis, chemical characterization, PARP inhibition, DNA binding and cellular uptake of novel ruthenium(II)-arene complexes bearing benzamide derivatives in human breast cancer cells

Inhibitors of poly(ADP-ribose) polymerase-1 (PARP-1) showed remarkable clinical efficacy in BRCA-mutated tumors. Based on the rational drug design, derivatives of PARP inhibitor 3-aminobenzamide (3-AB), 2-amino-4-methylbenzamide (L1) and 3-amino-N-methylbenzamide (L2), were coordinated to the ruthenium(II) ion, to form potential drugs affecting DNA and inhibiting PARP enzyme. The four conjugated complexes of formula: C1 [(ƞ⁶-toluene)Ru(L1)Cl]PF₆, C2 [(ƞ⁶-p-cymene)Ru(L1)Cl]PF₆, C3 [(ƞ⁶-toluene)Ru(L2)Cl₂] and C4 [(ƞ⁶-p-cymene)Ru(L2)Cl₂], have been synthesized and characterized. Colorimetric 3-(4.5-dimethylthiazol-2-yl)-2.5-diphenyltetrazolium bromide (MTT) assay showed the highest antiproliferative activity of C1 in HCC1937, MDA-MB-231, and MCF-7 breast cancer cells. Efficiency of inhibition of PARP-1 enzymatic activity in vitro decreased in order: C2 > C4 > 3-AB>C1 > C3. ICP-MS study of intracellular accumulation and distribution in BRCA1-mutated HCC1937 revealed that C1-C4 entered cells within 24 h. The complex C1 showed the highest intracellular accumulation, nuclear-targeting properties, and exhibited the highest DNA binding (39.2 ± 0.6 pg of Ru per μg of DNA) that resulted in the cell cycle arrest in the S phase.

Ruthenium(II)-Arene Thiocarboxylates: Identification of a Stable Dimer Selectively Cytotoxic to Invasive Breast Cancer Cells

Ru^II -arene complexes provide a versatile scaffold for novel anticancer drugs. Seven new Ru^II -arene-thiocarboxylato dimers were synthesized and characterized. Three of the complexes (2 a, b and 5) showed promising antiproliferative activities in MDA-MB-231 (human invasive breast cancer) cells, and were further tested in a panel of fifteen cancerous and noncancerous cell lines. Complex 5 showed moderate but remarkably selective activity in MDA-MB-231 cells (IC₅₀ =39±4 μm Ru). Real-time proliferation studies showed that 5 induced apoptosis in MDA-MB-231 cells but had no effect in A549 (human lung cancer, epithelial) cells. By contrast, 2 a and b showed moderate antiproliferative activity, but no apoptosis, in either cell line. Selective cytotoxicity of 5 in aggressive, mesenchymal-like MDA-MB-231 cells over many common epithelial cancer cell lines (including noninvasive breast cancer MCF-7) makes it an attractive lead compound for the development of specifically antimetastatic Ru complexes with low systemic toxicity.

Dual-Action Ru(II) Complexes with Bulky π-Expansive Ligands: Phototoxicity without DNA Intercalation

We report the synthesis and photochemical and biological characterization of Ru(II) complexes containing π-expansive ligands derived from dimethylbenzo[i]dipyrido[3,2-a:2',3'-c]phenazine (Me₂dppn) adorned with flanking aryl substituents. Late-stage Suzuki couplings produced Me₂dppn ligands substituted at the 10 and 15 positions with phenyl (5), 2,4-dimethylphenyl (6), and 2,4-dimethoxyphenyl (7) groups. Complexes of the general formula [Ru(tpy)(L)(py)](PF₆)₂ (8-10), where L = 4-7, were characterized and shown to have dual photochemotherapeutic (PCT) and photodynamic therapy (PDT) behavior. Quantum yields for photodissociation of monodentate pyridines from 8-10 were about 3 times higher than that of parent complex [Ru(tpy)(Me₂dppn)(py)](PF₆)₂ (1), whereas quantum yields for singlet oxygen (¹O₂) production were ∼10% lower than that of 1. Transient absorption spectroscopy indicates that 8-10 possess long excited state lifetimes (τ = 46-50 μs), consistent with efficient ¹O₂ production through population and subsequent decay of ligand-centered ³ππ* excited states. Complexes 8-10 displayed greater lipophilicity relative to 1 and association to DNA but do not intercalate between the duplex base pairs. Complexes 1 and 8-10 showed photoactivated toxicity in breast and prostate cancer cell lines with phototherapeutic indexes, PIs, as high as >56, where the majority of cell death was achieved 4 h after treatment with Ru(II) complexes and light. Flow cytometric data and rescue experiments were consistent with necrotic cell death mediated by the production of reactive oxygen species, especially ¹O₂. Collectively, this study confirms that DNA intercalation by Ru(II) complexes with π-expansive ligands is not required to achieve photoactivated cell death.

Unprecedented inhibition of P-gp activity by a novel ruthenium-cyclopentadienyl compound bearing a bipyridine-biotin ligand

Two new ruthenium complexes, [Ru(η⁵-Cp)(PPh₃)(2,2'-bipy-4,4'-R)]⁺ with R = -CH₂OH (Ru1) or dibiotin ester (Ru2) were synthesized and fully characterized. Both compounds were tested against two types of breast cancer cells (MCF7 and MDA-MB-231), showing better cytotoxicity than cisplatin in the same experimental conditions. Since multidrug resistance (MDR) is one of the main problems in cancer chemotherapy, we have assessed the potential of these compounds to overcome resistance to treatments. Ru2 showed exceptional selectivity as P-gp inhibitor, while Ru1 is possibly a substrate. In vivo studies in zebrafish showed that Ru2 is well tolerated up to 1.17 mg/L, presenting a LC₅₀ of 5.73 mg/L at 5 days post fertilization.