Gold (I) N-heterocyclic carbene complex inhibits mouse melanoma growth by p53 upregulation

A New Class of Gold(I) NHC Complexes with Proapoptotic and Resensitizing Properties towards Multidrug Resistant Leukemia Cells Overexpressing BCL-2

From previous studies, it is evident that metal-organic gold(I) complexes have antiproliferative activities. The aim of this study is not only to find new anticancer agents but also to overcome existing cytostatic resistance in cancer cells. The synthesis and medicinal evaluation of two cationic 1,3-disubstituted gold(I) bis-tetrazolylidene complexes 1 and 2 are reported. To determine apoptosis-inducing properties of the complexes, DNA fragmentation was measured using propidium iodide staining followed by flow cytometry. Gold(I) complex 1 targets explicitly malignant cells, effectively inhibiting their growth and selectively inducing apoptosis without signs of necrosis. Even in cells resistant to common treatments such as doxorubicin, it overcomes multidrug resistance and sensitizes existing drug-resistant cells to common cytostatic drugs. It is assumed that gold(I) complex 1 involves the mitochondrial pathway in apoptosis and targets members of the BCL-2 family, enhancing its potential as a therapeutic agent in cancer treatment.

Metal-Based Anticancer Complexes and p53: How Much Do We Know?

P53 plays a key role in protecting the human genome from DNA-related mutations; however, it is one of the most frequently mutated genes in cancer. The P53 family members p63 and p73 were also shown to play important roles in cancer development and progression. Currently, there are various organic molecules from different structural classes of compounds that could reactivate the function of wild-type p53, degrade or inhibit mutant p53, etc. It was shown that: (1) the function of the wild-type p53 protein was dependent on the presence of Zn atoms, and (2) Zn supplementation restored the altered conformation of the mutant p53 protein. This prompted us to question whether the dependence of p53 on Zn and other metals might be used as a cancer vulnerability. This review article focuses on the role of different metals in the structure and function of p53, as well as discusses the effects of metal complexes based on Zn, Cu, Fe, Ru, Au, Ag, Pd, Pt, Ir, V, Mo, Bi and Sn on the p53 protein and p53-associated signaling.

The effects of two gold-N-heterocyclic carbene (NHC) complexes in ovarian cancer cells: a redox proteomic study

PURPOSE

Ovarian cancer is the fifth leading cause of cancer-related deaths in women. Standard treatment consists of tumor debulking surgery followed by platinum and paclitaxel chemotherapy; yet, despite the initial response, about 70-75% of patients develop resistance to chemotherapy. Gold compounds represent a family of very promising anticancer drugs. Among them, we previously investigated the cytotoxic and pro-apoptotic properties of Au(NHC) and Au(NHC)2PF6, i.e., a monocarbene gold(I) complex and the corresponding bis(carbene) complex. Gold compounds are known to alter the redox state of cells interacting with free cysteine and selenocysteine residues of several proteins. Herein, a redox proteomic study has been carried out to elucidate the mechanisms of cytotoxicity in A2780 human ovarian cancer cells.

METHODS

A biotinylated iodoacetamide labeling method coupled with mass spectrometry was used to identify oxidation-sensitive protein cysteines.

RESULTS

Gold carbene complexes cause extensive oxidation of several cellular proteins; many affected proteins belong to two major functional classes: carbohydrate metabolism, and cytoskeleton organization/cell adhesion. Among the affected proteins, Glyceraldehyde-3-phosphate dehydrogenase inhibition was proved by enzymatic assays and by ESI-MS studies. We also found that Au(NHC)2PF6 inhibits mitochondrial respiration impairing complex I function. Concerning the oxidized cytoskeletal proteins, gold binding to the free cysteines of actin was demonstrated by ESI-MS analysis. Notably, both gold compounds affected cell migration and invasion.

CONCLUSIONS

In this study, we deepened the mode of action of Au(NHC) and Au(NHC)2PF6, identifying common cellular targets but confirming their different influence on the mitochondrial function.

Detailed structural and spectroscopic elucidation of ferrocenium coupled N-heterocyclic carbene gold(I) complexes

Unambiguous assignment of redox sites on ferrocene coupled N-heterocyclic carbene gold(I) complexes [(Fc-NHC)2Au(I)]+ is critical to gain a greater mechanistic understanding of their activity in a cellular environment. Such information can be garnered with isolation and detailed characterization of the oxidized version of [(Fc-NHC)2Au(I)]+. Herein we disclose a study that unambiguously illustrates redox events pertaining to [(Fc-NHC)2Au(I)]+ that stem exclusively from ferrocene sites. This work also describes novel synthetic methodologies for isolating ferrocenium coupled N-heterocyclic carbene gold(I) complexes.

A comparative assessment of in vitro cytotoxic activity and phytochemical profiling of Andrographis nallamalayana J.L.Ellis and Andrographis paniculata (Burm. f.) Nees using UPLC-QTOF-MS/MS approach

Andrographis paniculata (Burm. f.) Nees and Andrographis nallamalayana J.L.Ellis have traditionally been used to treat various ailments such as mouth ulcers, intermittent fever, inflammation, snake bite. This study compares the comparative in vitro cytotoxic activity, and phytochemical profiling of methanol extract of A. nallamalayana (ANM) and A. paniculata (APM). UPLC-ESI-QTOF-MS/MS analysis has been performed. The cytotoxic activity of crude methanol extracts were evaluated against three different cancer cell lines (HCT 116, HepG2, and A549 cell line). Both plants' extract exhibited significant cytotoxic activity against tested cell lines in a dose-dependent manner. IC50 of ANM and APM in HCT 116 cell was 11.71 ± 2.48 μg ml-1 and 45.32 ± 0.86 μg ml-1 and in HepG2 cell line was 15.65 ± 2.25 μg ml-1 and 60.32 ± 1.05 μg ml-1 respectively. Cytotoxicity of these two extracts was comparatively similar in A549 cells. ANM induced cytotoxicity involved programmed cell death, externalisation of phosphatidylserine, ROS generation, up-regulation and down-regulation of major apoptotic markers. HRMS analysis of ANM and APM resulted in the identification of 59 and 42 compounds, respectively. Further, using the MS/MS fragmentation approach, 20 compounds, of which 18 compounds were identified for the first time from ANM, which belongs to phenolic acids, flavonoids, and their glycosides. Three known compounds, echioidinin, skullcapflavone I and 5,2',6'-trihydroxy-7-methoxyflavone 2'-O-β-d-glucopyranoside, were isolated from A. nallamalayana and their crystal structures were reported for the first time. Subsequently, seven major compounds were identified in A. nallamalayana by direct comparison (retention time and UV-spectra) with authentic commercial standards and isolated compounds using HPLC-UV analysis. The cytotoxicity of phytochemicals from both the plants using in silico tools also justify their in vitro cytotoxic activity. It is the first report on the comparative characterisation of phytochemicals present in the methanolic extract of both the species of Andrographis, along with the cytotoxic activity of A. nallamalayana.

α-MSH-PE38KDEL Kills Melanoma Cells via Modulating Erk1/2/MITF/TYR Signaling in an MC1R-Dependent Manner

Background/Objective

The immunotoxin α-MSH-PE38KDEL consisting of α-MSH and PE38KDEL showed high cytotoxicity on MSH receptor-positive melanoma cells, suggesting that α-MSH-PE38KDEL might be a potent drug for the treatment of melanoma. Herein, we explored whether the Erk1/2/MITF/TYR signaling, a verified target of α-MSH/MC1R, was involved in α-MSH-PE38KDEL-mediated cytotoxicity.

Methods

Human melanoma cell line A375, mouse melanoma cell line B16-F10, human breast cancer cell line MDA-MB-231 and human primary epidermal melanocytes (HEMa) with different expression levels of MC1R were used in this study. Cell apoptosis and viability were determined by using flow cytometry and MTT assays. Protein expressions were tested by Western blotting.

Results

The expression levels of MC1R in A375 and B16-F10 cells were significantly higher than that of MDA-MB-231 and HEMa. α-MSH-PE38KDEL treatment induced a significant inhibition in cell viability in A375 and B16-F10 cells, while showed no obvious influence in the viability of MDA-MB-231 and HEMa cells. However, knockdown of MC1R abolished α-MSH-PE38KDEL role in promoting cell apoptosis in A375 and B16-F10 cells, and upregulation of MC1R endowed α-MSH-PE38KDEL function to promote cell apoptosis in MDA-MB-231 and HEMa cells. Additionally, α-MSH-PE38KDEL treatment increased the phosphorylation levels of Erk1/2 and MITF (S73), and decreased MITF and TYR expressions in an MC1R-dependent manner. All of the treatments, including inhibition of Erk1/2 with PD98059, MC1R downregulation and MITF overexpression weakened the anti-tumor role of α-MSH-PE38KDEL in melanoma.

Conclusion

Collectively, this study indicates that α-MSH-PE38KDEL promotes melanoma cell apoptosis via modulating Erk1/2/MITF/TYR signaling in an MC1R-dependent manner.

124 I Radiolabeling of a AuIII -NHC Complex for In Vivo Biodistribution Studies

AuIII complexes with N-heterocyclic carbene (NHC) ligands have shown remarkable potential as anticancer agents, yet their fate in vivo has not been thoroughly examined and understood. Reported herein is the synthesis of new AuIII -NHC complexes by direct oxidation with radioactive [124 I]I2 as a valuable strategy to monitor the in vivo biodistribution of this class of compounds using positron emission tomography (PET). While in vitro analyses provide direct evidence for the importance of AuIII -to-AuI reduction to achieve full anticancer activity, in vivo studies reveal that a fraction of the AuIII -NHC prodrug is not immediately reduced after administration but able to reach the major organs before metabolic activation.

Is the Way to Fight Cancer Paved with Gold? Metal-Based Carbene Complexes with Multiple and Fascinating Biological Features

Herein, we report the synthesis and the multiple anti-tumor properties of new gold and silver carbene complexes. The chemical modifications, grounded on our previous studies, led us to identify a good lead complex, gold-based, whose biological features are very exciting and promising in the anti-cancer research and could be further developed. Indeed, the bis-[4,5-dichloro-(N-methyl-N’(2-hydroxy-2-phenyl)ethyl-imidazole-2-ylidene)gold(I)]⁺[dichloro-gold]⁻ (AuL7) complex possesses the ability to interfere with at least three important and different intracellular targets, namely the human topoisomerases I and II and tubulin, which are able to modulate metabolic processes not directly correlated each other. We proved that the modifications of the ligands structure in AuL7, with respect to another already published complex, i.e., bis-[4,5-dichloro-(N-methyl-N’(cyclopentane-2ol)-imidazole-2-ylidine)gold(I)]⁺[dichloro-gold]⁻ (AuL4), produce a different behavior toward tubulin-polymerization process, since AuL7 is a tubulin-polymerization inhibitor and AuL4 a stabilizer, with the final same result of hampering the tumor growth. Taken together, our outcomes designate AuL7 as a promising compound for the development of multi-targeted anti-cancer therapies.

Synthesis, characterization and anticancer activity in vitro evaluation of novel dicyanoaurate (I)-based complexes

Molecular structures containing gold, such as auranofin, have been extensively studied in the diagnosis and treatment of many diseases, including cancer treatment. The pharmacological properties of the newly synthesized unique gold-ligand structures have been reported for different cancer cell lines. However, findings on bishydeten-metal salt complexes with gold are rare. In this work, the synthesis of five novel cyanide-bridged coordination compounds having the closed formulae [Ni(bishydeten)][Au(CN)₂]₂ (1), [Cu(bishydeten)][Au(CN)₂]₂ (2), [Zn(bishydeten)₂Au₃(CN)₄][Au₂(CN)₃] (3), [Cd(bishydeten)_0,5]₂[Au(CN)₂]₄.2H₂O (4), and [Cd(bishydeten)₂][Au(CN)₂]₂ (5) (where bisyhdeten = N,N-bis(2-hydroxyethyl)ethylene diamine), and their characterization by elemental, infrared, ESI-MS, X-ray (for 2) and thermic measurement methods were performed. Complexes 1 and 3 are thermally more stable than the other three complexes. For these, pharmacological adequacies were also tested. The nucleic acid and protein binding affinities of the Au (I) compounds were also estimated by spectroscopic and electrophoretic techniques. Au (I) complexes were identified as strong chemotherapeutic with mild cytotoxicity, and they demonstrated a dose-dependent inhibition on the growth of cancer cells with IC50 at 0.11 to 0.47 μM. Investigation of mechanisms of action on cells revealed that Au (I) compounds managed to inhibit cell migration and led to a decrease in cytoskeletal proteins such as CK7 and CK20. However, Au (I) compounds failed to inhibit DNA topoisomerase I. Overall, and we suggest that potent antiproliferative activity, mild cytotoxicity, good solubility, and micromolar dosage of Au (I) compounds containing bisyhdeten-metal derivatives render them the potential focus of further studies as chemotherapeutic agents.

p53-Dependent Anti-Proliferative and Pro-Apoptotic Effects of a Gold(I) N-Heterocyclic Carbene (NHC) Complex in Colorectal Cancer Cells

The tumor suppressor p53 has a diverse mutational profile in human malignancies, which is known to influence the potency of various chemotherapeutics, such as platins and anti-metabolites. However, the impact of the mutations in the TP53 gene (coding for p53) on the anti-cancer efficacy of gold complexes remains incompletely understood. We therefore investigated the anti-tumor properties of a gold(I) N-heterocyclic carbene (NHC) complex-termed MC3-in human colorectal cancer (CRC) cell lines encompassing three different p53 variations: HCT116 wild-type (WT), HCT116 p53^-/-, and HT-29 (mutant; R273H). MC3 treatment induced intracellular reactive oxygen species (ROS) levels, and p21 expression, leading to cell cycle arrest in all cell lines, regardless of their p53 status. The pro-apoptotic response, however, was found to occur in a p53-dependent manner, with WT p53 harboring cells showing the highest responsiveness. Additionally, p73, which was speculated to substitute p53 in p53-deficient cells, was found to be markedly reduced with MC3 treatment in all the cell lines and knocking down its levels did not impact MC3's anti-tumor effects in HCT116 p53^-/- cells. Collectively, our results suggest that this small molecule has anti-cancer properties in the context of deficient or mutant p53 and may therefore have chemotherapeutic potential for clinical application.

Mitochondria-Targeting Anticancer Metal Complexes

Background:

Since the serendipitous discovery of the antitumor activity of cisplatin there has been a continuous surge in studies aimed at the development of new cytotoxic metal complexes. While the majority of these complexes have been designed to interact with nuclear DNA, other targets for anticancer metallodrugs attract increasing interest. In cancer cells the mitochondrial metabolism is deregulated. Impaired apoptosis, insensitivity to antigrowth signals and unlimited proliferation have been linked to mitochondrial dysfunction. It is therefore not surprising that mitochondria have emerged as a major target for cancer therapy. Mitochondria-targeting agents are able to bypass resistance mechanisms and to (re-) activate cell-death programs.

Methods:

Web-based literature searching tools such as SciFinder were used to search for reports on cytotoxic metal complexes that are taken up by the mitochondria and interact with mitochondrial DNA or mitochondrial proteins, disrupt the mitochondrial membrane potential, facilitate mitochondrial membrane permeabilization or activate mitochondria-dependent celldeath signaling by unbalancing the cellular redox state. Included in the search were publications investigating strategies to selectively accumulate metallodrugs in the mitochondria.

Results:

This review includes 241 references on antimitochondrial metal complexes, the use of mitochondria-targeting carrier ligands and the formation of lipophilic cationic complexes.

Conclusion:

Recent developments in the design, cytotoxic potency, and mechanistic understanding of antimitochondrial metal complexes, in particular of cyclometalated Au, Ru, Ir and Pt complexes, Ru polypyridine complexes and Au-N-heterocyclic carbene and phosphine complexes are summarized and discussed.

Cytotoxic effects of gold(i) complexes against colon, cervical and osteo carcinoma cell lines: a mechanistic approach

Water-soluble gold(i) complexes, [Au(Ipr)(L)]PF₆where L = thiourea (Tu)1andN,N′-dimethylthiourea (Me₂Tu)2, were synthesized from the parent 1,3-bis(2,6-di-isopropylphenyl)imidazol-2-ylidenechloridogold(i) [(Ipr)AuCl] (0).

A Ruthenium(II) N-Heterocyclic Carbene (NHC) Complex with Naphthalimide Ligand Triggers Apoptosis in Colorectal Cancer Cells via Activating the ROS-p38 MAPK Pathway

The p38 MAPK pathway is known to influence the anti-tumor effects of several chemotherapeutics, including that of organometallic drugs. Previous studies have demonstrated the important role of p38 both as a regulator and a sensor of cellular reactive oxygen species (ROS) levels. Investigating the anti-cancer properties of novel 1,8-naphthalimide derivatives containing Rh(I) and Ru(II) N-heterocyclic carbene (NHC) ligands, we observed a profound induction of ROS by the complexes, which is most likely generated from mitochondria (mtROS). Further analyses revealed a rapid and consistent activation of p38 signaling by the naphthalimide-NHC conjugates, with the Ru(II) analogue—termed MC6—showing the strongest effect. In view of this, genetic as well as pharmacological inhibition of p38α, attenuated the anti-proliferative and pro-apoptotic effects of MC6 in HCT116 colon cancer cells, highlighting the involvement of this signaling molecule in the compound’s toxicity. Furthermore, the influence of MC6 on p38 signaling appeared to be dependent on ROS levels as treatment with general- and mitochondria-targeted anti-oxidants abrogated p38 activation in response to MC6 as well as the molecule’s cytotoxic- and apoptogenic response in HCT116 cells. Altogether, our results provide new insight into the molecular mechanisms of naphthalimide-metal NHC analogues via the ROS-induced activation of p38 MAPK, which may have therapeutic interest for the treatment of various cancer types.

Synthesis of Triazole-Substituted Quinazoline Hybrids for Anticancer Activity and a Lead Compound as the EGFR Blocker and ROS Inducer Agent

A series of triazole-substituted quinazoline hybrid compounds were designed and synthesized for anticancer activity targeting epidermal growth factor receptor (EGFR) tyrosine kinase. Most of the compounds showed moderate to good antiproliferative activity against four cancer cell lines (HepG2, HCT116, MCF-7, and PC-3). Compound 5b showed good antiproliferative activity (IC₅₀ = 20.71 μM) against MCF-7 cell lines. Molecular docking results showed that compound 5b formed hydrogen bond with Met 769 and Lys 721 and π-sulfur interaction with Met 742 of EGFR tyrosine kinase (PDB ID: 1M17). Compound 5b decreases the expression of EGFR and p-EGFR. It also induces apoptosis through reactive oxygen species generation, followed by the change in mitochondrial membrane potential.

Cationic and Neutral N-Heterocyclic Carbene Gold(I) Complexes: Cytotoxicity, NCI-60 Screening, Cellular Uptake, Inhibition of Mammalian Thioredoxin Reductase, and Reactive Oxygen Species Formation

A structurally diverse library of 14 gold(I) cationic bis(NHC) and neutral mono(NHC) complexes (NHC: N-heterocyclic carbene) was synthesized and characterized in this work. Four of them were new cationic gold(I) complexes containing functionalized NHCs, and their X-ray crystal structures are presented herein. All of the complexes were investigated for their anticancer activities in four cancer cell lines, including a cisplatin-resistant variant, and a noncancerous cell line. Seven of the cationic gold(I) complexes were found to display high and specific cytotoxic activities toward cancer cells. Two of them were even able to overcome cisplatin resistance. Two highly potent cationic complexes (11 and 15) were also submitted to the NCI-60 cancer panel for further cytotoxicity evaluation. Complex 15 showed a surprisingly high potency toward leukemia among the nine examined cancer subtypes, particularly toward the CCRF-CEM leukemia cell line with a concentration for 50 % inhibition of growth down to 79.4 nm. In addition, cationic complex 13, which demonstrated a remarkable cytotoxicity against hepatocellular carcinoma, was selected to obtain insight into the mechanistic aspects in HepG2 cells. Cellular uptake measurements were indicative of good bioavailability. By various biochemical assays, this complex was found to effectively inhibit thioredoxin reductase and its cytotoxicity toward HepG2 cells was found to be reactive oxygen species dependent.

New insights in Au-NHCs complexes as anticancer agents

Within the research field of antitumor metal-based agents alternative to platinum drugs, gold(I/III) coordination complexes have always been in the forefront due mainly to the familiarity of medicinal chemists with gold compounds, whose application in medicine goes back in the ancient times, and to the rich chemistry shown by this metal. In the last decade, N-heterocyclic carbene ligands (NHC), a class of ligands that largely resembles the chemical properties of phosphines, became of interest for gold(I) medicinal applications, and since then, the research on NHC-gold(I/III) coordination complexes as potential antiproliferative agents boosted dramatically. Different classes of gold(I/III)-NHC complexes often showed an outstanding in vitro antiproliferative activity, however up to now very few in vivo data have been reported to corroborate the in vitro results. This review summarizes all achievements in the field of gold (I/III) complexes comprising NHC ligands proposed as potential antiproliferative agents in the period 2004-2016, and critically analyses biological data (mainly IC₅₀ values) in relation to the chemical structures of Au compounds. The state of art of the in vivo studies so far described is also reported.

Isoelectronic Pt(ii)– and Au(iii)–N-heterocyclic carbene complexes: a structural and biological comparison

To differentiate the intrinsic biological activities displayed by Pt vs. Au reagents, a series of square planar carbene complexes were compared.

Synthesis and cytotoxic characteristics displayed by a series of Ag(i)-, Au(i)- and Au(iii)-complexes supported by a common N-heterocyclic carbene

The design, synthesis and anticancer properties of a series of Ag(i), Au(i) and Au(iii)–NHC complexes supported by pyridyl[1,2-a]{2-acetylylphenylimidazol}-3-ylidene are described.

Covalent Organic Framework Material Bearing Phloroglucinol Building Units as a Potent Anticancer Agent

Covalent organic frameworks (COFs) having periodicity in pores of nanoscale dimensions can be suitably designed for the organic building units bearing reactive functional groups at their surfaces. Thus, they are an attractive option as an anticancer agent to overcome the limitations of chemotherapy. Herein, we first report a new porous biodegradable nitrogen containing COF material, EDTFP-1 (ethylenedianiline-triformyl phloroglucinol), synthesized using 4,4'-ethylenedianiline and 2,4,6-triformylphloroglucinol via Schiff base condensation reaction. EDTFP-1 exhibited 3D-hexagonal porous structure with average pores of ca. 1.5 nm dimension. Here, we have explored the anticancer potentiality of EDTFP-1. Result demonstrated an enhanced cytotoxicity was observed against four cancer cells HCT 116, HepG2, A549, and MIA-Paca2 with significant lower IC₅₀ on HCT116 cells. Additionally, EDTFP-1-induced cell death was associated with the characteristic apoptotic changes like cell membrane blebbing, nuclear DNA fragmentation, externalization of phosphatidylserine from the cell membrane followed by a loss of mitochondrial membrane potential as well as modulation of pro and antiapoptotic proteins. Further, the result depicted a direct correlation between the generations of ROS with mitochondrial-dependent apoptosis through the involvement of p53 phosphorylation upon EDTFP-1 induction, suggesting this COF material is a novel chemotherapeutic agent for cancer treatment.

A novel nanohybrid for cancer theranostics: folate sensitized Fe2O3 nanoparticles for colorectal cancer diagnosis and photodynamic therapy

Organic-inorganic nanohybrids are becoming popular for their potential biological applications, including diagnosis and treatment of cancerous cells. The motive of this study is to synthesise a nanohybrid for the diagnosis and therapy of colorectal cancer. Here we have developed a facile and cost-effective synthesis of folic acid (FA) templated Fe₂O₃ nanoparticles with excellent colloidal stability in water using a hydrothermal method for the theranostics applications. The attachment of FA to Fe₂O₃ was confirmed using various spectroscopic techniques including FTIR and picosecond resolved fluorescence studies. The nanohybrid (FA-Fe₂O₃) is a combination of two nontoxic ingredients FA and Fe₂O₃, showing remarkable photodynamic therapeutic (PDT) activity in human colorectal carcinoma cell lines (HCT 116) via generation of intracellular ROS. The light induced enhanced ROS activity of the nanohybrid causes significant nuclear DNA damage, as confirmed from the comet assay. Assessment of p53, Bax, Bcl2, cytochrome c (cyt c) protein expression and caspase 9/3 activity provides vivid evidence for cell death via an apoptotic pathway. In vitro magnetic resonance imaging (MRI) experiments in folate receptor (FR) overexpressed cancer cells (HCT 116) and FR deficient human embryonic kidney cells (HEK 293) reveal the target specificity of the nanohybrid towards cancer cells, and are thus pronounced MRI contrasting agents for the diagnosis of colorectal cancer.

A Schiff base platform: structures, sensing of Zn(ii) and PPi in aqueous medium and anticancer activity

A Schiff base platform was explored to present structural aspects of its Zn(ii) and Cd(ii) coordination compounds, sensing behavior towards Zn(ii) and PPi in aqueous medium and anticancer activity.

N-heterocyclic carbene complexes of silver and gold as novel tools against breast cancer progression

AIM

Metal carbenic complexes have received considerable attention in both the catalysis and biological fields for their potential applications in cancer and antimicrobial therapies.

RESULTS

A small series of new silver and gold N-heterocyclic carbene complexes has been designed and synthesized. Among the tested complexes, one compound was particularly active in inhibiting anchorage-dependent and -independent breast cancer proliferation, and inducing cell apoptosis via a mitochondria-related process. The antitumor activity was associated to the transcriptional activation of the tumor suppressor gene p53 in an Sp1-dependent manner, as evidenced by biological and docking studies.

CONCLUSION

Our results highlight the importance and the versatility of N-heterocyclic carbene complexes of gold and silver as useful tools against breast cancer progression.

Climacostol reduces tumour progression in a mouse model of melanoma via the p53-dependent intrinsic apoptotic programme

Climacostol, a compound produced by the ciliated protozoan Climacostomum virens, displayed cytotoxic properties in vitro. This study demonstrates that it has anti-tumour potential. Climacostol caused a reduction of viability/proliferation of B16-F10 mouse melanoma cells, a rapidly occurring DNA damage, and induced the intrinsic apoptotic pathway characterised by the dissipation of the mitochondrial membrane potential, the translocation of Bax to the mitochondria, the release of Cytochrome c from the mitochondria, and the activation of Caspase 9-dependent cleavage of Caspase 3. The apoptotic mechanism of climacostol was found to rely on the up-regulation of p53 and its targets Noxa and Puma. In vivo analysis of B16-F10 allografts revealed a persistent inhibition of tumour growth rate when melanomas were treated with intra-tumoural injections of climacostol. In addition, it significantly improved the survival of transplanted mice, decreased tumour weight, induced a remarkable reduction of viable cells inside the tumour, activated apoptosis and up-regulated the p53 signalling network. Importantly, climacostol toxicity was more selective against tumour than non-tumour cells. The anti-tumour properties of climacostol and the molecular events associated with its action indicate that it is a powerful agent that may be considered for the design of pro-apoptotic drugs for melanoma therapy.

Titanocene-Gold Complexes Containing N-Heterocyclic Carbene Ligands Inhibit Growth of Prostate, Renal, and Colon Cancers in Vitro

We report on the synthesis, characterization, and stability studies of new titanocene complexes containing a methyl group and a carboxylate ligand (mba = −OC(O)-p-C₆H₄-S−) bound to gold(I)–N-heterocyclic carbene fragments through the thiolate group: [(η⁵-C₅H₅)₂TiMe(μ-mba)Au(NHC)]. The cytotoxicities of the heterometallic compounds along with those of novel monometallic gold–N-heterocyclic carbene precursors [(NHC)Au(mbaH)] have been evaluated against renal, prostate, colon, and breast cancer cell lines. The highest activity and selectivity and a synergistic effect of the resulting heterometallic species was found for the prostate and colon cancer cell lines. The colocalization of both titanium and gold metals (1:1 ratio) in PC3 prostate cancer cells was demonstrated for the selected compound 5a, indicating the robustness of the heterometallic compound in vitro. We describe here preliminary mechanistic data involving studies on the interaction of selected mono- and bimetallic compounds with plasmid (pBR322) used as a model nucleic acid and the inhibition of thioredoxin reductase in PC3 prostate cancer cells. The heterometallic compounds, which are highly apoptotic, exhibit strong antimigratory effects on the prostate cancer cell line PC3.

Synthesis of gold(iii) ← gold(i)–NHC through disproportionation: the role of gold(i)–NHC in the induction of apoptosis in HepG2 cells

The anticancer activities of novel Au(i) and Au(iii)–NHC complexes based on 2-[(6-methylpyridin-2-yl)]imidazo[1,5-a]pyridin-4-ylium hexafluorophosphate have been investigated.

Biological Screening of Newly Synthesized BIAN N-Heterocyclic Gold Carbene Complexes in Zebrafish Embryos

N-Heterocyclic carbene (NHC) metal complexes possess diverse biological activities but have yet to be extensively explored as potential chemotherapeutic agents. We have previously reported the synthesis of a new class of NHC metal complexes N-heterocyclic with acetate [IPr(BIAN)AuOAc] and chloride [IPr(BIAN)AuCl] ligands. In the experiments reported herein, the zebrafish embryos were exposed to serial dilutions of each of these complexes for 10-12 h. One hundred percent mortality was observed at concentrations≥50 µM. At sub-lethal concentrations (10-30 µM), both compounds influenced zebrafish embryonic development. However, quite diverse categories of abnormalities were found in exposed embryos with each compound. Severe brain deformation and notochord degeneration were evident in the case of [IPr(BIAN)AuOAc]. The zebrafish embryos treated with [IPr(BIAN)AuCl] exhibited stunted growth and consequently had smaller body sizes. A depletion of 30%-40% glutathione was detected in the treated embryos, which could account for one of the possible mechanism of neurotoxicity. The fact that these compounds are capable of both affecting the growth and also compromising antioxidant systems by elevating intracellular ROS production implies that they could play an important role as a new breed of therapeutic molecules.

Investigating the role of Pluronic-g-Cationic polyelectrolyte as functional stabilizer for nanocrystals: Impact on Paclitaxel oral bioavailability and tumor growth

Paclitaxel (PTX) is a potent anticancer drug which suffers limitations of extremely low oral bioavailability due to low solubility, rapid metabolism and efflux by P-gp transporters. The main objective of this study was to overcome the limitation of PTX by designing delivery systems that can enhance the absorption using multiple pathways. A novel Pluronic-grafted chitosan (Pl-g-CH) copolymer was developed and employed as a functional stabilizer for nanocrystals (NCs) and hypothesized that it would improve PTX absorption by several mechanisms and pathways. Pl-g-CH was synthesized and characterized using (1)H NMR and then used as a stabilizer during nanocrystal development. To establish our proof of concept the optimized formulation having a particle size 192.7 ± 9.2 nm and zeta potential (+) 38.8 ± 3.12 mV was studied extensively on in vitro Caco-2 model. It was observed that nanocrystals rendered higher PTX accumulation inside the cell than Taxol™. P-gp inhibitory potential of Pl-g-CH was proved by flow cytometry and fluorescence microscopy where the much enhanced fluorescence intensity of Rhodamine 123 (Rho-123, P-gp substrate) was observed in the presence of Pl-g-CH. In addition, a significant decrease in Trans Epithelial Electrical Resistance (TEER) of Caco-2 cell monolayers was observed with nanocrystals as well as with Taxol™ (in the presence of free Pl-g-CH compared to only Taxol™). This supports the role of the stabilizer in reversible opening of tight junctions between cells which can allow paracellular transport of drug. The in vivo results were in complete corroboration with in vitro results. Nanocrystals resulted in much enhanced absorption with 12.6-fold improvement in relative bioavailability to that of Taxol™. Concomitantly efficacy data in B16 F10 murine melanoma model also showed a significant reduction in tumor growth with nanocrystals compared to Taxol™ and control. Based on the results it can be suggested that nanocrystals with functional stabilizers can be a promising approach for the oral delivery of anticancer drugs which are P-gp substrates

STATEMENT OF SIGNIFICANCE

Nanocrystals are currently one of the most explored novel drug delivery systems especially for oral delivery of drugs because of ease in synthesis and high drug loading. But their use is still limited for oral delivery of anticancer drugs which are P-gp substrates. This particular study aims at widening the scope of nanocrystals by using a functional stabilizer which participates in enhancing the oral absorption of anticancer drugs and controlling the tumor growth.

New 13-pyridinealkyl berberine analogues intercalate to DNA and induce apoptosis in HepG2 and MCF-7 cells through ROS mediated p53 dependent pathway: biophysical, biochemical and molecular modeling studies

A new series of 13-pyridinealkyl berberine analogues was synthesized and their DNA binding efficacy studied by employing spectroscopic, calorimetric and molecular modeling techniques.

A novel aminotriazole-based NHC complex for the design of gold(i) anti-cancer agents: synthesis and biological evaluation

A novel gold(i) complex based on an aminotriazole N-heterocylic carbene ligand represents a promising scaffold for the design of anticancer bioorganometallics.

Apoptotic effects of dipyrido [3,2-a:2',3'-c] phenazine (dppz) Au(III) complex against diethylnitrosamine/phenobarbital induced experimental hepatocarcinogenesis in rats

We evaluated the effects of dipyrido [3,2-a:2',3'-c] phenazine (dppz) Au(III) complex ([Au(dppz)Cl2]Cl) on apoptosis during chemically induced hepatocellular carcinoma. 48 male Spraque-Dawley rats were divided into six groups; group I (control), group II [Dimethyl sulfoxide (DMSO)], group III ([Au(dppz)Cl2]Cl), group IV [diethylnitrosamine + Phenobabital (DEN + PB)], group V (DEN + PB + [Au(dppz)Cl2]Cl (2nd week)), and group VI (DEN + PB + [Au(dppz)Cl2]Cl (7th week). The rats in groups IV through VI were administrated with DEN in a single dose of intraperitoneal 175 mg/kg. After 2 weeks of DEN administration, these groups of rats were given daily PB in a dose of 500 ppm. In group V, after two weeks of DEN administration, [Au(dppz)Cl2]Cl complex (2 mg/kg) was given once a week by intraperitoneal injection. In the group VI, the rats were given a dose of 2 mg/kg [Au(dppz)Cl2]Cl complex once a week, 7 weeks after DEN administration. At the end of the study, blood and tissue samples were collected from the rats to determine levels of serum AST, ALT, and LDH, and caspase 3, p53, Bax, Bcl-2 and DNA fragmentation in liver. AST, ALT, LDH, and Bcl-2 levels were higher in group IV, compared to group I, but caspase 3 and p53 levels were lower. In group V, caspase 3, p53, Bax, and DNA fragmentation levels were higher than those of group IV. Caspase 3 and p53 levels increased in group VI compared with group IV. In conclusion, [Au(dppz)Cl2]Cl complex induced apoptosis by elevating levels of caspase 3, p53, Bax, and DNA fragmentation.

Cytotoxicity of silver(i), gold(i) and gold(iii) complexes of a pyridine wingtip substituted annelated N-heterocyclic carbene

Cl–Ag(i)–NHC, Cl–Au(i)–NHC, and Cl₃–Au(i)–NHC complexes based on the 1-methyl-2-pyridin-2-yl-2H-imidazo[1,5-a]pyridin-4-ylium chloride, were tested for their cytotoxicity towards different cancer cell lines.