Cytotoxic gold compounds: synthesis, biological characterization and investigation of their inhibition properties of the zinc finger protein PARP-1

Anticancer Activity of Metallodrugs and Metallizing Host Defense Peptides-Current Developments in Structure-Activity Relationship

This article provides an overview of the development, structure and activity of various metal complexes with anti-cancer activity. Chemical researchers continue to work on the development and synthesis of new molecules that could act as anti-tumor drugs to achieve more favorable therapies. It is therefore important to have information about the various chemotherapeutic substances and their mode of action. This review focuses on metallodrugs that contain a metal as a key structural fragment, with cisplatin paving the way for their chemotherapeutic application. The text also looks at ruthenium complexes, including the therapeutic applications of phosphorescent ruthenium(II) complexes, emphasizing their dual role in therapy and diagnostics. In addition, the antitumor activities of titanium and gold derivatives, their side effects, and ongoing research to improve their efficacy and reduce adverse effects are discussed. Metallization of host defense peptides (HDPs) with various metal ions is also highlighted as a strategy that significantly enhances their anticancer activity by broadening their mechanisms of action.

Cu(I)-Catalyzed Click Chemistry in Glycoscience and Their Diverse Applications

Copper(I)-catalyzed 1,3-dipolar cycloaddition between organic azides and terminal alkynes, commonly known as CuAAC or click chemistry, has been identified as one of the most successful, versatile, reliable, and modular strategies for the rapid and regioselective construction of 1,4-disubstituted 1,2,3-triazoles as diversely functionalized molecules. Carbohydrates, an integral part of living cells, have several fascinating features, including their structural diversity, biocompatibility, bioavailability, hydrophilicity, and superior ADME properties with minimal toxicity, which support increased demand to explore them as versatile scaffolds for easy access to diverse glycohybrids and well-defined glycoconjugates for complete chemical, biochemical, and pharmacological investigations. This review highlights the successful development of CuAAC or click chemistry in emerging areas of glycoscience, including the synthesis of triazole appended carbohydrate-containing molecular architectures (mainly glycohybrids, glycoconjugates, glycopolymers, glycopeptides, glycoproteins, glycolipids, glycoclusters, and glycodendrimers through regioselective triazole forming modular and bio-orthogonal coupling protocols). It discusses the widespread applications of these glycoproducts as enzyme inhibitors in drug discovery and development, sensing, gelation, chelation, glycosylation, and catalysis. This review also covers the impact of click chemistry and provides future perspectives on its role in various emerging disciplines of science and technology.

Translational Theragnosis of Ovarian Cancer: where do we stand?

BACKGROUND

Ovarian cancer is the second most common gynecologic malignancy, accounting for approximately 220,000 deaths annually worldwide. Despite radical surgery and initial high response rates to platinum- and taxane-based chemotherapy, most patients experience a relapse, with a median progression-free survival of only 18 months. Overall survival is approximately 30% at 5 years from the diagnosis. In comparison, patients out from breast cancer are more than 80 % after ten years from the disease discovery. In spite of a large number of published fundamental and applied research, and clinical trials, novel therapies are urgently needed to improve outcomes of the ovarian cancer. The success of new drugs development in ovarian cancer will strongly depend on both fully genomic disease characterization and, then, availability of biomarkers able to identify women likely to benefit from a given new therapy.

METHODS

In this review, the focus is given to describe how complex is the diseases under the simple name of ovarian cancer, in terms of cell tumor types, histotypes, subtypes, and specific gene mutation or differently expressed in the tumor with respect the healthy ovary. The first- and second-line pharmacological treatment clinically used over the last fifty years are also described. Noteworthy achievements in vitro and in vivo tested new drugs are also summarized. Recent literature related to up to date ovarian cancer knowledge, its detection by biomarkers and chemotherapy was searched from several articles on Pubmed, Google Scholar, MEDLINE and various Governmental Agencies till April 2019.

RESULTS

The papers referenced by this review allow a deep analysis of status of the art in the classification of the several types of ovarian cancer, the present knowledge of diagnosis based on biomarkers and imaging techniques, and the therapies developed over the past five decades.

CONCLUSION

This review aims at stimulating more multi-disciplinary efforts to identify a panel of novel and more specific biomarkers to be used to screen patients for a very early diagnosis, to have prognosis and therapy efficacy indications. The desired final goal would be to have available tools allowing to reduce the recurrence rate, increase both the disease progression free interval and of course the overall survival at five years from the diagnosis that today is still very low.

Therapeutic potential of dithiocarbamate supported gold compounds

Chrysotherapy or aurotherapy, the use of gold as medicine, is two thousand years old. Hitherto, numerous diverse gold stabilizing ligands for instance vitamins, pyridine, phosphines, naphthylamine and xanthanes have been developed and their 'chelating effect' in addition to their anti-proliferative properties have been extensively studied. Recent advances in the field of bioinorganic chemistry have led to the design of biologically relevant metal complexes with appropriate fine-tuned ligands such as metallic conjugates of dithiocarbamates (DTCs). DTC compounds have been recognised to possess diverse applications and have demonstrated interesting biological properties. For instance, the chemoprotective and antitumour properties of gold metal ions and DTC compounds respectively, presents an innovative and effective approach to cancer management. This review presents therefore the therapeutic potential of DTC ligand systems as a support for gold compounds. The importance of dithiocarbamate supported gold compounds as potential therapeutic agents is highlighted with emphasis on the therapeutic potential of gold(iii) and gold(i) dithiocarbamate derivatives.

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

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

Dinuclear gold(i) complexes: from bonding to applications

The last two decades have seen a veritable explosion in the use of gold(i) complexes bearing N-heterocyclic carbene (NHC) and phosphine (PR₃) ligands.

Ex vivo toxicological evaluation of experimental anticancer gold(i) complexes with lansoprazole-type ligands

Gold-based compounds are of great interest in the field of medicinal chemistry as novel therapeutic (anticancer) agents due to their peculiar reactivity and mechanisms of action with respect to organic drugs. Despite their promising pharmacological properties, the possible toxic effects of gold compounds need to be carefully evaluated in order to optimize their design and applicability. This study reports on the potential toxicity of three experimental gold-based anticancer compounds featuring lansoprazole ligands (1-3) studied in an ex vivo model, using rat precision cut kidney and liver slices (PCKS and PCLS, respectively). The results showed a different toxicity profile for the tested compounds, with the neutral complex 2 being the least toxic, even less toxic than cisplatin, followed by the cationic complex 1. The dinuclear cationic gold complex 3 was the most toxic in both liver and kidney slices. This result correlated with the metal uptake of the different compounds assessed by ICP-MS, where complex 3 showed the highest accumulation of gold in liver and kidney slices. Interestingly compound 1 showed the highest selectivity towards cancer cells compared to the healthy tissues. Histomorphology evaluation showed a similar pattern for all three Au(i) complexes, where the distal tubular cells suffered the most extensive damage, in contrast to the damage in the proximal tubules induced by cisplatin. The binding of representative gold compounds with the model ubiquitin was also studied by ESI-MS, showing that after 24 h incubation only 'naked' Au ions were bound to the protein following ligands' loss. The mRNA expression of stress response genes appeared to be similar for both evaluated organs, suggesting oxidative stress as the possible mechanism of toxicity. The obtained results open new perspectives towards the design and testing of bifunctional gold complexes with chemotherapeutic applications.

Synthesis, characterization and biological activities of imidazo[1,2-a]pyridine based gold(III) metal complexes

Five imidazo [1,2-a]pyridine derivatives and their Au(III) complexes were synthesized. The compounds were characterized by ¹H-NMR, ¹³C-NMR, IR, mass, UV-visible, elemental analysis, conductivity and magnetic measurement studies. All the compounds were screened for diverse biological activities to check the effect of coordination of Au(III) with imidazo [1,2-a]pyridine heterocycles. The DNA interaction ability of compounds were studied as the change in absorption maxima and position of HS-DNA in presence of compounds and viscosity measurement due to change in DNA length under the influence of compounds. The computational insight of compound-DNA interaction was taken in docking study. All the results suggest intercalation mode of binding. The cellular level cytotoxic nature of compounds was evaluated using trypan blue dye staining of dead cell in cell viability assay. The smearing of DNA was observed, while DNA extracted from S. pombe cells in presence of complexes was subjected to gel electrophoresis, which shows their toxic effect on DNA. The complexes were evaluated for cytotoxicity on human A549 (Lung adenocarcinoma) cell line by MTT assay (IC₅₀ values). The in vitro cytotoxicity in terms of LC₅₀ value was checked on a simple zoological organism, brine shrimp.

Zeise's salt as powerful platinating agent for proteins investigated by top-down-mass spectrometry

Metallodrugs have become an integral part of modern medicinal chemistry with platinum drugs as anti-cancer agents being well-known examples. The historically interesting compound Zeise's salt, potassium trichlorido(ethene)platinate(II) has scarcely been investigated in this context yet. This study is geared towards shedding light on the biological reactivity of this platinum complex. Mass Spectrometry tools were used to obtain a deeper understanding of its interactions with biomolecules on the molecular level. Angiotensin I and Ubiquitin were chosen as model systems. Comparison to Cisplatin show that Zeise's salt is more reactive towards nucleophilic sites in proteins. Our data indicate that the ethylene ligand remains on the platinum when coordinated to a nitrogen donor in the biomolecule and therefore offers a linkage for the introduction of further functionality. When attached to sulfur donors in the biomolecule, platinum(II) provides a site for the formation of crosslinks and loops in the biomolecules by losing all four of its initial ligands.

New bipyridine gold(III) dithiocarbamate-containing complexes exerted a potent anticancer activity against cisplatin-resistant cancer cells independent of p53 status

We synthesized, characterized and tested in a panel of cancer cell lines, nine new bipyridine gold(III) dithiocarbamate-containing complexes. In vitro studies demonstrated that compounds 1, 2, 4, 5, 7 and 8 were the most cytotoxic in prostate, breast, ovarian cancer cell lines and in Hodgkin lymphoma cells with IC₅₀ values lower than the reference drug cisplatin. The most active compound 1 was more active than cisplatin in ovarian (A2780cis and 2780CP-16) and breast cancer cisplatin-resistant cells. Compound 1 determined an alteration of the cellular redox homeostasis leading to increased ROS levels, a decrease in the mitochondrial membrane potential, cytochrome-c release from the mitochondria and activation of caspases 9 and 3. The ROS scavenger NAC suppressed ROS generation and rescued cells from damage. Compound 1 resulted more active in tumor cells than in normal human Mesenchymal stromal cells. Gold compounds were active independent of p53 status: exerted cytotoxic effects on a panel of non-small cell lung cancer cell lines with different p53 status and in the ovarian A2780 model where the p53 was knocked out. In conclusion, these promising results strongly indicate the need for further preclinical evaluation to test the clinical potential of these new gold(III) complexes.

A Gold(III) Pincer Ligand Scaffold for the Synthesis of Binuclear and Bioconjugated Complexes: Synthesis and Anticancer Potential

Cyclometalated (C^N^C)Au^III complexes bearing functionalized N-heterocyclic carbene (NHC) ligands provide a high-yielding, modular route to bioconjugated and binuclear complexes. This methodology has been applied to the synthesis of bioconjugated complexes presenting biotin and 17α-ethynylestradiol vectors, as well as to the synthesis of bimetallic Au^III /Au^I complexes. The in vitro antiproliferative activities of these compounds against various cancer cells lines depend on the linker length, with the longer linker being the most potent. The estradiol conjugate AuC₆ Estra proved to be more toxic against the estrogen receptor positive (ER+) cancer cells than against the ER- cancer cells and non-cancer cells. The bimetallic complex AuC₆ Au was more selective for breast cancer cells with respect to a healthy cell standard than the monometallic complex AuNHC. The metal uptake study on cells expressing or not biotin and estrogen receptors revealed an improved and targeted delivery of gold for both the bioconjugated complexes AuC₆ Biot and AuC₆ Estra compared to the non-vectorised analogue AuNHC. The investigations of the interaction of the bioconjugates and bimetallic complexes with human telomeric G-quadruplex DNA using FRET-melting techniques revealed a reduced ability to stabilize this DNA structure with respect to the non-vectorised analogue AuNHC.

The effects of phosphanegold(I) thiolates on the biological properties of Acanthamoeba castellanii belonging to the T4 genotype

BACKGROUND

Gold compounds have shown promise in the treatment of non-communicable diseases such as rheumatoid arthritis and cancer, and are considered of value as anti-microbial agents against Gram-negative and Gram-positive bacteria, and have anti-parasitic properties against Schistosoma mansoni, Trypanosoma brucei, Plasmodium falciparum, Leishmania infantinum, Giardia lamblia, and Entamoeba histolytica. They are known to affect enzymatic activities that are required for the cellular respiration processes.

METHODS

Anti-amoebic effects of phosphanegold(I) thiolates were tested against clinical isolate of A. castellanii belonging to the T4 genotype by employing viability assays, growth inhibition assays, encystation assays, excystation assays, and zymographic assays.

RESULTS

The treatment of A. castellanii with the phosphanegold(I) thiolates tested (i) had no effect on the viability of A. castellanii as determined by Trypan blue exclusion test, (ii) did not affect amoebae growth using PYG growth medium, (iii) did not inhibit cellular differentiation, and (iv) had no effect on the extracellular proteolytic activities of A. castellanii.

CONCLUSION

Being free-living amoeba, A. castellanii is a versatile respirator and possesses respiratory mechanisms that adapt to various aerobic and anaerobic environments to avoid toxic threats and adverse conditions. For the first time, our findings showed that A. castellanii exhibits resistance to the toxic effects of gold compounds and could prove to be an attractive model to study mechanisms of metal resistance in eukaryotic cells.

Au(iii) compounds as HIV nucleocapsid protein (NCp7)-nucleic acid antagonists

The HIV nucleocapsid NCp7-SL2 RNA interaction is interrupted in the presence of a formally substitution-inert gold(dien)-nucleobase/N-heterocycle AuN4 compound where the N-heterocycle serves the dual purposes of a template for "non-covalent" molecular recognition of the essential tryptophan of the protein, mimicking the natural reaction and subsequent "fixation" by Au-Cys bond formation providing a chemotype for a new distinct class of nucleocapsid-nucleic acid antagonist.

Nanoformulations of a potent copper-based aquaporin inhibitor with cytotoxic effect against cancer cells

AIM

Development of liposomal formulations of Cuphen, a potent copper-based aquaporin inhibitor with therapeutic potential against melanoma and colon cancer.

MATERIALS & METHODS

Cuphen was incorporated into liposomes using the dehydration-rehydration method. The ability of Cuphen to induce cancer cell death was evaluated by MTS and ViaCount assays. In vivo toxicity studies were performed in BALB/c mice.

RESULTS

In vitro studies illustrated the antiproliferative effects of Cuphen in different cancer cell lines, in free form or after incorporation into liposomes. In vivo studies revealed no toxic effects after parenteral administration of Cuphen liposomes.

CONCLUSIONS

Cuphen liposomes are highly attractive to be further tested in murine models due to the possibility of stabilizing and specifically deliver this metallodrug to tumor sites.

Proteomic analysis of the cytotoxic effects induced by the organogold(III) complex Aubipyc in cisplatin-resistant A2780 ovarian cancer cells: further evidence for the glycolytic pathway implication

The cellular alterations produced in cisplatin-resistant A2780 ovarian cancer cells (A2780/R) upon treatment with the cytotoxic organogold(III) complex Aubipyc were investigated in depth through a classical proteomic approach. We observed that A2780/R cell exposure to a cytotoxic concentration of Aubipyc for 24 hours results in a conspicuous number of alterations at the protein level that were carefully examined. Notably, we observed that several affected proteins belong to the glucose metabolism system further supporting the idea that the cytotoxic effects of Aubipyc in A2780/R cells are mostly mediated by an impairment of glucose metabolism in excellent agreement with previous observations on the parent cisplatin-sensitive cell line.

Toward anticancer gold-based compounds targeting PARP-1: a new case study

A new gold(iii) complex bearing a 2-((2,2′-bipyridin)-5-yl)-1H-benzimidazol-4-carboxamide ligand has been synthesized and characterized for its biological properties in vitro.

Cytotoxicity and biodistribution studies of luminescent Au(i) and Ag(i) N-heterocyclic carbenes. Searching for new biological targets

Gold and silver NHC complexes have been developed as theranostic agents. The unexpected biodistribution opens the door to new biological targets for gold and silver complexes.

A study on the inhibition of dihydrofolate reductase (DHFR) from Escherichia coli by gold(i) phosphane compounds. X-ray crystal structures of (4,5-dichloro-1H-imidazolate-1-yl)-triphenylphosphane-gold(i) and (4,5-dicyano-1H-imidazolate-1-yl)-triphenylphosphane-gold(i)

An unprecedented study on the inhibitory activities of a class of phosphane gold(i) complexes on E. coli dihydrofolate reductase (DHFR) is reported. The gold(i) complexes considered in this work consist of azolate or chloride ligands and phosphane as co-ligands. The ligands have been functionalized with polar groups (-COOH, -COO(-), NO2, Cl, CN) to obtain better solubility in polar media. Neutral, anionic and cationic gold(i) complexes have been tested as DHFR inhibitors by means of a continuous direct spectrophotometric method. X-ray structural characterizations were performed on ((triphenylphosphine)-gold(i)-(4,5-dicyanoimidazolyl-1H-1yl) and on the analog (triphenylphosphine)-gold(i)-(4,5-dichloroimidazolyl-1H-1yl). The inhibition constants obtained from the enzyme tests range from 20 μM to 63 nM (auranofin) and are conducive to promoting these compounds as potential DHFR inhibitors.

Heterometallic titanium-gold complexes inhibit renal cancer cells in vitro and in vivo

Heterometallic compounds as anticancer agents demonstrating in vivo potential for the first time. Titanocene–gold derivatives: promising candidates for renal cancer.

Following recent work on heterometallic titanocene–gold complexes as potential chemotherapeutics for renal cancer, we report here on the synthesis, characterization and stability studies of new titanocene complexes containing a methyl group and a carboxylate ligand (mba = S–C₆H₄–COO^–) bound to gold(i)-phosphane fragments through a thiolate group [(η-C₅H₅)₂TiMe(μ-mba)Au(PR₃)]. The compounds are more stable in physiological media than those previously reported and are highly cytotoxic against human cancer renal cell lines. We describe here preliminary mechanistic data involving studies on the interaction of selected compounds with plasmid (pBR322) DNA used as a model nucleic acid, and with selected protein kinases from a panel of 35 protein kinases having oncological interest. Preliminary mechanistic studies in Caki-1 renal cells indicate that the cytotoxic and anti-migration effects of the most active compound 5 [(η-C₅H₅)₂TiMe(μ-mba)Au(PPh₃)] involve inhibition of thioredoxin reductase and loss of expression of protein kinases that drive cell migration (AKT, p90-RSK, and MAPKAPK3). The co-localization of both titanium and gold metals (1 : 1 ratio) in Caki-1 renal cells was demonstrated for 5 indicating the robustness of the heterometallic compound in vitro. Two compounds were selected for further in vivo studies on mice based on their selectivity in vitro against renal cancer cell lines when compared to non-tumorigenic human kidney cell lines (HEK-293T and RPTC) and the favourable preliminary toxicity profile in C57BL/6 mice. Evaluation of Caki-1 xenografts in NOD.CB17-Prkdc SCID/J mice showed an impressive tumor reduction (67%) after treatment for 28 days (3 mg per kg per every other day) with heterometallic compound 5 as compared with the previously described [(η-C₅H₅)₂Ti{OC(O)-4-C₆H₄-P(Ph₂)AuCl}₂] 3 which was non-inhibitory. These findings indicate that structural modifications on the ligand scaffold affect the in vivo efficacy of this class of compounds.

Exploring the potential of gold(III) cyclometallated compounds as cytotoxic agents: variations on the C^N theme

A series of novel (C^N) cyclometallated Au(III) complexes of general formula [Au(py(b)-H)L(1)L(2)](n+) (py(b)-H = C^N cyclometallated 2-benzylpyridine, L(1) and L(2) being chlorido, phosphane or glucosethiolato ligands, n = 0 or 1) have been synthesized and fully characterized using different techniques, including NMR, IR and far-IR, mass spectrometry, as well as elemental analysis. The crystal structure of one compound has been solved using X-ray diffraction methods. All compounds were tested in vitro in five human cancer cell lines including the lung, breast, colon and ovarian cancer cells. For comparison purposes, all compounds were also tested in a model of healthy human cells from the embryonic kidney. Notably, all new compounds were more toxic than their cyclometallated precursor bearing two chlorido ligands, and the derivative bearing one phosphane ligand presented the most promising toxicity profile in our in vitro screening, displaying a p53 dependent activity in colorectal cancer HCT116 cells. Finally, for the first time C^N cyclometallated gold(III) complexes were shown to be potent inhibitors of the zinc finger protein PARP-1, involved in the mechanism of cisplatin resistance.

Detailed analysis of pro-apoptotic signaling and metabolic adaptation triggered by a N-heterocyclic carbene-gold(I) complex

Due to their broad spectrum of biological activity and antiproliferative effect on different human cancer cell lines, gold compounds have been in the focus of drug research for many years. Gold(I)-N-heterocyclic carbene complexes are of particular interest, because of their stability, ease of derivatization and clear cytotoxicity in cancer cells. To obtain a more detailed view of the molecular mechanisms underlying their cellular activity, we used a novel gold(I)-N-heterocyclic carbene complex, [triphenylphosphane-(1,3-diethyl-5-methoxy-benzylimidazol-2-ylidene)]gold(I) iodide and investigated changes in cellular signaling pathways using quantitative signal transduction protein microarray analysis. We also analyzed changes in cell metabolism in a time-dependent manner by on-line metabolic measurements and used isolated mitochondria to elucidate the direct effects on this cell organelle. We found strong cytotoxic effects in cancer cells, accompanied by an immediate and irreversible loss of mitochondrial respiration as well as by a crucial imbalance of the intracellular redox state, resulting in apoptotic cell death. ELISA microarray analysis of signal transduction pathways revealed a time-dependent up-regulation of pro-apoptotic signaling proteins, e.g. p38 and JNK, whereas pro-survival signals that are directly linked to the thioredoxin system were down-regulated, which pinpoints to thioredoxin reductase as a central target of the compound. Further results suggest that DNA is an indirect target of the compound. Based on our findings, we outline a signaling model for the molecular mechanism underlying the antiproliferative activity of the gold(I)-N-heterocyclic carbene complex investigated, which provides a good general model for the known pattern of cell death induced by this class of substances.

Gold finger formation studied by high-resolution mass spectrometry and in silico methods

Combining high-resolution MS and QM/MM studies to investigate the reactivity of gold compounds with zinc finger domains at a molecular level.

Organometallic Titanocene-Gold Compounds as Potential Chemotherapeutics in Renal Cancer. Study of their Protein Kinase Inhibitory Properties

Early-late transition metal TiAu2 compounds [(η-C5H5)2Ti{OC(O)CH2PPh2AuCl}2] (3) and new [(η-C5H5)2Ti{OC(O)-4-C6H4PPh2AuCl}2] (5) were evaluated as potential anticancer agents in vitro against renal and prostate cancer cell lines. The compounds were significantly more effective than monometallic titanocene dichloride and gold(I) [{HOC(O)RPPh2}AuCl] (R = -CH2- 6, -4-C6H4- 7) derivatives in renal cancer cell lines, indicating a synergistic effect of the resulting heterometallic species. The activity on renal cancer cell lines (for 5 in the nanomolar range) was considerably higher than that of cisplatin and highly active titanocene Y. Initial mechanistic studies in Caki-1 cells in vitro coupled with studies of their inhibitory properties on a panel of 35 kinases of oncological interest indicate that these compounds inhibit protein kinases of the AKT and MAPKAPK families with a higher selectivity toward MAPKAPK3 (IC503 = 91 nM, IC505 = 117 nM). The selectivity of the compounds in vitro against renal cancer cell lines when compared to a nontumorigenic human embryonic kidney cell line (HEK-293T) and the favorable preliminary toxicity profile on C57black6 mice indicate that these compounds (especially 5) are excellent candidates for further development as potential renal cancer chemotherapeutics.

A monofunctional platinum(II)-based anticancer agent from a salicylanilide derivative: Synthesis, antiproliferative activity, and transcription inhibition

Cationic monofunctional platinum(II)-based anticancer agents with a general formula of cis-[Pt(NH3)2(N-donor)Cl](+) have recently drawn significant attention due to their unique mode of action, distinctive anticancer spectrum, and promising antitumor activity both in vitro and in vivo. Understanding the mechanism of action of novel monofunctional platinum compounds through rational drug design will aid in the further development of active agents. In this study, we synthesized and evaluated a monofunctional platinum-based anticancer agent SA-Pt containing a bulky salicylanilide moiety. The antiproliferative activity of SA-Pt was close to that of cisplatin. Mechanism studies revealed that SA-Pt entered HeLa cells more efficiently than cisplatin, blocked the cell cycle at the S-phase, and induced apoptosis. The compound bound to DNA as effectively as cisplatin, but did not block RNA polymerase II-mediated transcription as strongly as cisplatin, indicating that once the compound formed Pt-DNA lesions, the salicylanilide group was more easily recognized and removed. This study not only enriches the family of monofunctional platinum-based anticancer agents but also guides the design of more potent monofunctional platinum complexes.

Gold(III) complexes in medicinal chemistry

A number of gold(III) compounds has been designed with the objective of overcoming the disadvantages associated with the platinum-based drugs for cancer treatment. Compounds of a remarkable structural manifold show significant antiproliferative effects in vitro against a number of cancer cells, including cisplatin resistant ones. The target of most of them is, unlike that of cisplatin, not the DNA. Although the mechanisms of action displayed by the gold compounds in biological media are still under investigation, many studies show evidence that the cellular targets are mitochondria-based. Recent advances in gold(III) medicinal chemistry also recommend such compounds for other pharmacological applications such as the treatment of viral or parasitic diseases. The radioactive isotopes 198Au and 199Au present potential in radiotherapy.

Luminescent iminophosphorane gold, palladium and platinum complexes as potential anticancer agents

A series of coordination gold(III), palladium(II), and platinum(II) complexes with a luminescent iminophosphorane ligand derived from 8-aminoquinoline [Ph3P=N-C9H6N] (1), have been synthesized and structurally characterized. The coordination palladium(II) and platinum(II) compounds can evolve further, under appropriate conditions, to give stable cyclometalated endo species [M{κ3-C,N,N-C6H4(PPh2=N-8-C9H6N}Cl] (M = Pd, Pt) by C-H activation of the phenyl group of the PPh 3 fragment. Iminophosphorane 1 and the new metallic complexes are luminescent in DMSO or DMSO:H2O (1:1 mixture) solutions at RT. The compounds have been evaluated for their antiproliferative properties in a human ovarian cancer cell line (A2780S), in human lung cancer cells (A-549) and in a non-tumorigenic human embryonic kidney cell line (HEK-293T). Most compounds have been more toxic to the ovarian cancer cell line than to the non-tumorigenic cell line. The new complexes interact with human serum albumin (HSA) faster than cisplatin. Studies of the interactions of the compounds with DNA indicate that, in some cases, they exert anticancer effects in vitro based on different mechanisms of action with respect to cisplatin.

Metal-based anticancer chemotherapeutic agents

Since the discovery of the cisplatin antitumor activity, great efforts have focused on the rational design of metal-based anticancer agents that can be potentially used in cancer chemotherapy. Over the last four decades, a large number of metal complexes have been extensively investigated and evaluated in vitro and in vivo, and some of them were at different stages of clinical studies. Amongst these complexes, platinum (Pt(II) and Pt(IV)), ruthenium (Ru(II) and Ru(III)), gold (Au(I) and Au(III)) and titanium (Ti(IV)) complexes are the most studied metals. We describe here some most recent progresses on Pt(IV) prodrugs which can be activated once enter tumor cells, polynuclear Pt(II) complexes which have unique DNA binding ability and mode, anti-metastatic Ru(II)/Ru(III) complexes, and Au(I)/Au(III) and Ti(IV) antitumor active complexes. The key focuses of these studies lie in finding novel metal complexes which could potentially overcome the hurdles of current clinical drugs including toxicity, resistance and other pharmacological deficiencies.

Cascade sensing of gold and thiols with imidazole-bearing functional porphyrins

An imidazole-bearing zinc porphyrin (PZn) has been designed for the selective detection of Au³⁺, and the porphyrin and gold complex (PZn·Au³⁺) can additionally be used to identify gold-binding functional groups such as cysteine residues and other mercaptans.

Some new [(thione)2Au(diamine)]Cl3 complexes: synthesis, spectroscopic characterization, computational and in vitro cytotoxic studies

Recent advances in oncology are focused on developing new complexes of gold(III) with various ligands that show augmented anti-proliferative potential and reduced toxicity as compared to cis-platin. In this study, new Au(III) complexes of the type [(thione)2Au(diamine)]Cl3 are reported, where thione=1,3-imidazolidine-2-thione (Imt), 1,3-Diazinane-2-thione (Diaz) and diamine=1,2-diaminoethane (en), 1,3-diaminopropane (pn) or 1,4-diaminobutane (bn). The solid state IR as well as (13)C and (15)N NMR data indicate that Au(III) center is bonded via sulfur of thiocarbonyl SC site of the thiones and also chelated by the diamines from the trans side of coordinated thiones. Spectroscopic data are evaluated by comparisons with calculated data from the built and optimized structure by GAUSSIAN 09 at the RB3LYP level with LanL2DZ bases set. These new Au(III) complexes based on mixed thione and diamine ligands are very similar to the square planar structure of tetracoordinate [Au(en)2]Cl3complex. In this study, cytotoxicity data for these gold(III) complexes against C6 glioma cell lines are also reported, and the results indicate some complexes have cytotoxicity comparable to cis-platin.

Potential anticancer heterometallic Fe-Au and Fe-Pd agents: initial mechanistic insights

A series of gold(III) and palladium(II) heterometallic complexes with new iminophosphorane ligands derived from ferrocenylphosphanes [{Cp-P(Ph2)═N-Ph}2Fe] (1), [{Cp-P(Ph2)═N-CH2-2-NC5H4}2Fe] (2), and [{Cp-P(Ph2)═N-CH2-2-NC5H4}Fe(Cp)] (3) have been synthesized and structurally characterized. Ligands 2 and 3 afford stable coordination complexes [AuCl2(3)]ClO4, [{AuCl2}2(2)](ClO4)2, [PdCl2(3)], and [{PdCl2}2(2)]. The complexes have been evaluated for their antiproliferative properties in human ovarian cancer cells sensitive and resistant to cisplatin (A2780S/R), in human breast cancer cells (MCF7) and in a nontumorigenic human embryonic kidney cell line (HEK-293T). The highly cytotoxic trimetallic derivatives M2Fe (M = Au, Pd) are more cytotoxic to cancer cells than their corresponding monometallic fragments. Moreover, these complexes were significantly more cytotoxic than cisplatin in the resistant A2780R and the MCF7 cell lines. Studies of the interactions of the trimetallic compounds with DNA and the zinc-finger protein PARP-1 indicate that they exert anticancer effects in vitro based on different mechanisms of actions with respect to cisplatin.

The influence of R substituents in triphenylphosphinegold(I) carbonimidothioates, Ph3PAu[SC(OR)=NPh] (R=Me, Et and iPr), upon in vitro cytotoxicity against the HT-29 colon cancer cell line and upon apoptotic pathways

The Ph3PAu[SC(OR)=NPh], R=Me (1), Et (2) and iPr (3), compounds are significantly cytotoxic to the HT-29 cancer cell line with 1 being the most active. Based on human apoptosis PCR-array analysis, caspase activities, DNA fragmentation, cell apoptotic assays, intracellular reactive oxygen species (ROS) measurements and human topoisomerase I inhibition, induction of apoptosis is demonstrated and both the extrinsic and intrinsic pathways of apoptosis have been shown to occur. Compound 1 activates the p73 gene, whereas each of 2 and 3 activates the p53 gene. An additional apoptotic mechanism is exhibited by 2, that is, via the JNK/MAP pathway.

Aquaporin inhibition by gold(III) compounds: new insights

Aquaporins (AQPs) are membrane water/glycerol channels with essential roles in biological systems, as well as being promising targets for therapy and imaging. Using a stopped-flow method, a series of gold(III), platinum(II) and copper(II) complexes bearing nitrogen donor ligands, such as 1,10-phenatroline, 2,2'-bipyridine, 4,4'-dimethyl-2,2'-bipyridine, 4,4'-diamino-2,2'-bipyridine and 2,2';6',2"-terpyridine, were evaluated in human red blood cells expressing AQP1 and AQP3, responsible for water and glycerol movement, respectively. The results showed that the gold(III) complexes selectively modulate AQP3 over AQP1. Molecular modeling and density functional theory (DFT) calculations were subsequently performed to rationalize the observations and to investigate the possible molecular mechanism through which these gold compounds act on their putative target (AQP3). In the absence of any crystallographic data, a previously reported homology model was used for this purpose. Combined, the findings of this study show that potent and selective modulation of these solute channels is possible, however further investigation is required into the selectivity of this class of agents against all AQP isoforms and their potential therapeutic uses.