Oxaliplatin(IV) Prodrugs Functionalized with Gemcitabine and Capecitabine Induce Blockage of Colorectal Cancer Cell Growth-An Investigation of the Activation Mechanism and Their Nanoformulation

The use of platinum-based anticancer drugs, such as cisplatin, oxaliplatin, and carboplatin, is a common frontline option in cancer management, but they have debilitating side effects and can lead to drug resistance. Combination therapy with other chemotherapeutic agents, such as capecitabine and gemcitabine, has been explored. One approach to overcome these limitations is the modification of traditional Pt(II) drugs to obtain new molecules with an improved pharmacological profile, such as Pt(IV) prodrugs. The design, synthesis, and characterization of two novel Pt(IV) prodrugs based on oxaliplatin bearing the anticancer drugs gemcitabine or capecitabine in the axial positions have been reported. These complexes were able to dissociate into their constituents to promote cell death and induce apoptosis and cell cycle blockade in a representative colorectal cancer cell model. Specifically, the complex bearing gemcitabine resulted in being the most active on the HCT116 colorectal cancer cell line with an IC50 value of 0.49 ± 0.04. A pilot study on the encapsulation of these complexes in biocompatible PLGA-PEG nanoparticles is also included to confirm the retention of the pharmacological properties and cellular drug uptake, opening up to the possible delivery of the studied complexes through their nanoformulation.

Cytotoxic auranofin analogues bearing phosphine, arsine and stibine ligands: A study on the possible role of the ligand on the biological activity

Three gold(I) linear compounds, sharing the general formula [AuI(LPh3)], have been synthesized and characterized. The nature of the ligand has been modified by moving down among some of the elements of group 15, i.e. phosphorus, arsenic and antimony. The structures of derived compounds have been solved through XRD and the reactivity behaviour towards selected biomolecules has been investigated through a multi-technique approach involving NMR, high-resolution mass spectrometry and IR. Moreover, the biological activity of the investigated compounds has been comparatively analyzed through classical methodologies and the disclosed differences are discussed in detail.

Target-Based Anticancer Indole Derivatives for the Development of Anti-Glioblastoma Agents

Glioblastoma (GBM) is the most aggressive and frequent primary brain tumor, with a poor prognosis and the highest mortality rate. Currently, GBM therapy consists of surgical resection of the tumor, radiotherapy, and adjuvant chemotherapy with temozolomide. Consistently, there are poor treatment options and only modest anticancer efficacy is achieved; therefore, there is still a need for the development of new effective therapies for GBM. Indole is considered one of the most privileged scaffolds in heterocyclic chemistry, so it may serve as an effective probe for the development of new drug candidates against challenging diseases, including GBM. This review analyzes the therapeutic benefit and clinical development of novel indole-based derivatives investigated as promising anti-GBM agents. The existing indole-based compounds which are in the pre-clinical and clinical stages of development against GBM are reported, with particular reference to the most recent advances between 2013 and 2022. The main mechanisms of action underlying their anti-GBM efficacy, such as protein kinase, tubulin and p53 pathway inhibition, are also discussed. The final goal is to pave the way for medicinal chemists in the future design and development of novel effective indole-based anti-GBM agents.

Chemical Modification of Auranofin Yields a New Family of Anticancer Drug Candidates: The Gold(I) Phosphite Analogues

A panel of four novel gold(I) complexes, inspired by the clinically established gold drug auranofin (1-Thio-β-D-glucopyranosatotriethylphosphine gold-2,3,4,6-tetraacetate), was prepared and characterized. All these compounds feature the replacement of the triethylphosphine ligand of the parent compound auranofin with a trimethylphosphite ligand. The linear coordination around the gold(I) center is completed by Cl^-, Br^-, I^- or by the thioglucose tetraacetate ligand (SAtg). The in-solution behavior of these gold compounds as well as their interactions with some representative model proteins were comparatively analyzed through ³¹PNMR and ESI-MS measurements. Notably, all panel compounds turned out to be stable in aqueous media, but significant differences with respect to auranofin were disclosed in their interactions with a few leading proteins. In addition, the cytotoxic effects produced by the panel compounds toward A2780, A2780R and SKOV-3 ovarian cancer cells were quantitated and found to be in the low micromolar range, since the IC₅₀ of all compounds was found to be between 1 μM and 10 μM. Notably, these novel gold complexes showed large and similar inhibition capabilities towards the key enzyme thioredoxin reductase, again comparable to those of auranofin. The implications of these results for the discovery of new and effective gold-based anticancer agents are discussed.

A New Manganese Superoxide Dismutase Mimetic Improves Oxaliplatin-Induced Neuropathy and Global Tolerance in Mice

Reactive oxygen species (ROS) are produced by every aerobic cell during mitochondrial oxidative metabolism as well as in cellular response to xenobiotics, cytokines, and bacterial invasion. Superoxide Dismutases (SOD) are antioxidant proteins that convert superoxide anions (O2•−) to hydrogen peroxide (H2O2) and dioxygen. Using the differential in the level of oxidative stress between normal and cancer cells, SOD mimetics can show an antitumoral effect and prevent oxaliplatin-induced peripheral neuropathy. New Pt(IV) conjugate prodrugs (OxPt-x-Mn1C1A (x = 1, 1-OH, 2)), combining oxaliplatin and a Mn SOD mimic (MnSODm Mn1C1A) with a covalent link, were designed. Their stability in buffer and in the presence of sodium ascorbate was studied. In vitro, their antitumoral activity was assessed by the viability and ROS production of tumor cell lines (CT16, HCT 116, KC) and fibroblasts (primary culture and NIH 3T3). In vivo, a murine model of colorectal cancer was created with subcutaneous injection of CT26 cells in Balb/c mice. Tumor size and volume were measured weekly in four groups: vehicle, oxaliplatin, and oxaliplatin associated with MnSODm Mn1C1A and the bis-conjugate OxPt-2-Mn1C1A. Oxaliplatin-induced peripheral neuropathy (OIPN) was assessed using a Von Frey test reflecting chronic hypoalgesia. Tolerance to treatment was assessed with a clinical score including four items: weight loss, weariness, alopecia, and diarrhea. In vitro, Mn1C1A associated with oxaliplatin and Pt(IV) conjugates treatment induced significantly higher production of H2O2 in all cell lines and showed a significant improvement of the antitumoral efficacy compared to oxaliplatin alone. In vivo, the association of Mn1C1A to oxaliplatin did not decrease its antitumoral activity, while OxPt-2-Mn1C1A had lower antitumoral activity than oxaliplatin alone. Mn1C1A associated with oxaliplatin significantly decreased OIPN and also improved global clinical tolerance of oxaliplatin. A neuroprotective effect was observed, associated with a significantly improved tolerance to oxaliplatin without impairing its antitumoral activity.

Novel Au Carbene Complexes as Promising Multi-Target Agents in Breast Cancer Treatment

Over the past decade, metal complexes based on N-heterocyclic carbenes (NHCs) have attracted great attention due to their wide and exciting applications in material sciences and medicinal chemistry. In particular, the gold-based complexes are the focus of research efforts for the development of new anticancer compounds. Literature data and recent results, obtained by our research group, reported the design, the synthesis and the good anticancer activity of some silver and gold complexes with NHC ligands. In particular, some of these complexes were active towards some breast cancer cell lines. Considering this evidence, here we report some new Au-NHC complexes prepared in order to improve solubility and biological activity. Among them, the compounds 1 and 6 showed an interesting anticancer activity towards the breast cancer MDA-MB-231 and MCF-7 cell lines, respectively. In addition, in vitro and in silico studies demonstrated that they were able to inhibit the activity of the human topoisomerases I and II and the actin polymerization reaction. Moreover, a downregulation of vimentin expression and a reduced translocation of NF-kB into the nucleus was observed. The interference with these vital cell structures induced breast cancer cells’ death by triggering the extrinsic apoptotic pathway.

Auranofin and its analogs as prospective agents for the treatment of colorectal cancer

Today colorectal cancer (CRC) is one of the leading causes of cancer death worldwide. This disease is poorly chemo-sensitive toward the existing medical treatments so that new and more effective therapeutic agents are urgently needed and intensely sought. Platinum drugs, oxaliplatin in particular, were reported to produce some significant benefit in CRC treatment, triggering the general interest of medicinal chemists and oncologists for metal-based compounds as candidate anti-CRC drugs. Within this frame, gold compounds and, specifically, the established antiarthritic drug auranofin with its analogs, form a novel group of promising anticancer agents. Owing to its innovative mechanism of action and its favorable pharmacological profile, auranofin together with its derivatives are proposed here as novel experimental agents for CRC treatment, capable of overcoming resistance to platinum drugs. Some encouraging results in this direction have already been obtained. A few recent studies demonstrate that the action of auranofin may be further potentiated through the preparation of suitable pharmaceutical formulations capable of protecting the gold pharmacophore from unselective reactivity or through the design of highly synergic drug combinations. The perspectives of the research in this field are outlined.

Iodide Analogs of Arsenoplatins-Potential Drug Candidates for Triple Negative Breast Cancers

Patients with triple negative breast cancers (TNBCs)—highly aggressive tumors that do not express estrogen, progesterone, and human epidermal growth factor 2 receptors—have limited treatment options. Fewer than 30% of women with metastatic TNBC survive five years after their diagnosis, with a mortality rate within three months after a recurrence of 75%. Although TNBCs show a higher response to platinum therapy compared to other breast cancers, drug resistance remains a major obstacle; thus, platinum drugs with novel mechanisms are urgently needed. Arsenoplatins (APs) represent a novel class of anticancer agents designed to contain the pharmacophores of the two FDA approved drugs cisplatin and arsenic trioxide (As₂O₃) as one molecular entity. Here, we present the syntheses, crystal structures, DFT calculations, and antiproliferative activity of iodide analogs of AP-1 and AP-2, i.e., AP-5 and AP-4, respectively. Antiproliferative studies in TNBC cell lines reveal that all AP family members are more potent than cisplatin and As₂O₃ alone. DFT calculations demonstrate there is a low energy barrier for hydrolysis of the platinum-halide bonds in arsenoplatins, possibly contributing to their higher cytotoxicities compared to cisplatin.

Intracellular delivery of oxaliplatin conjugate via cell penetrating peptide for the treatment of colorectal carcinoma in vitro and in vivo

Pt-based drugs are one of the main active agents in colorectal cancer treatment. However, drug resistance and dose-dependent side effects are the main barriers that restrict their clinical applications. As an alternative approach to these issues, we designed and synthesized a cell penetrating peptide (CPP) octaarginine-oxaliplatin conjugate that quickly and successfully delivered oxaliplatin into colon cancer cells. The CPP octaarginine is a well-studied cationic peptide that can play a role as a drug delivery vector. In this work, an octaarginine CPP (RRRRRRRR) was conjugated with oxaliplatin via a specific heterobifunctional linker. The in vitro studies showed the conjugate had affinity toward mitochondria inside cells and the MTT assay confirmed that conjugate is active in low micromolar range against colon cancer cells, requiring much lower concentrations than the oxaliplatin alone to reach IC₅₀. More importantly, in the in vivo mouse study, the conjugate effectively inhibited tumor growth and showed considerably high antitumor activity, demonstrating the conjugate can perform well in vivo. This strategy may offer a new approach for designing oxaliplatin derivatives or prodrugs with remarkable therapeutic capabilities.

Two mixed valence diruthenium(II,III) isomeric complexes show different anticancer properties

In this paper it is demonstrated that the nature of the ligands of two Ru2(ii,iii) paddlewheel complexes dramatically affects the overall anticancer properties in cells. Herein, the complex [Ru2(EB776)4Cl] was found to be more active against a glioblastoma model with respect to its isomer [Ru2(EB106)4Cl]. These different effects depend on the steric hindrance, on the allowed conformations of the complexes and on the presence of hydrophilic regions in [Ru2(EB776)4Cl], which overall lead to a lower "steric protection".

Strike a Balance: Between Metals and Non-Metals, Metalloids as a Source of Anti-Infective Agents

Most of the commercially available anti-infective agents are organic molecules. In fact, though, during the pioneering times of modern medicine, at the beginning of the 20th century, several inorganic compounds of transition metals were used for medicinal application, to date, only a small number of inorganic drugs are used in clinical practice. Beyond the transition metals, metalloids—or semimetals—offer a rich chemistry in between that of metallic and non-metallic elements, and accordingly, peculiar features for their exploitation in medicinal chemistry. A few important examples of metalloid-based drugs currently used for the treatment of various diseases do exist. However, the use of this group of elements could be further expanded on the basis of their current applications and the clinical trials they entered. Considering that metalloids offer the opportunity to expand the “chemical-space” for developing novel anti-infective drugs and protocols, in this paper, we briefly recapitulate and discuss the current applications of B-, Si-, As-, Sb- and Te-based anti-infective drugs.

Strategies for the Improvement of Metal-Based Chemotherapeutic Treatments

This article provides an overview of the various research approaches we have explored in recent years to improve metal-based agents for cancer or infection treatments. Although cisplatin, carboplatin, and oxaliplatin remain the cornerstones in tumor chemotherapy, the discovery and approval of novel inorganic anticancer drugs is a very slow process. Analogously, although a few promising inorganic drugs have found clinical application against parasitic or bacterial infections, their use remains relatively limited. Moreover, the discovery process is often affected by small therapeutic enhancements that are not attractive for the pharmaceutical industry. However, the availability of increasing mechanistic information for the modes of action of established inorganic drugs is fueling the exploration of various approaches for developing effective inorganic chemotherapy agents. Through a series of examples, some from our own research experience, we focus our attention on a number of promising strategies, including (1) drug repurposing, (2) the simple modification of the chemical structures of approved metal-based drugs, (3) testing novel drug combinations, and (4) newly synthesized complexes coupling different anticancer drugs. Accordingly, we aim to suggest and summarize a series of reliable approaches that are exploitable for the development of improved and innovative treatments.

Anticancer effects against colorectal cancer models of chloro(triethylphosphine)gold(I) encapsulated in PLGA-PEG nanoparticles

Chloro(triethylphosphine)gold(I), (Et₃PAuCl hereafter), is an Auranofin (AF)-related compound showing very similar biological and pharmacological properties. Like AF, Et₃PAuCl exhibits potent antiproliferative properties in vitro toward a variety of cancer cell lines and is a promising anticancer drug candidate. We wondered whether Et₃PAuCl encapsulation might lead to an improved pharmacological profile also considering the likely reduction of unwanted side-reactions that are responsible for adverse effects and for drug inactivation. Et₃PAuCl was encapsulated in biocompatible PLGA–PEG nanoparticles (NPs) and the new formulation evaluated in colorectal HCT-116 cancer cells in comparison to the free gold complex. Notably, encapsulated Et₃PAuCl (nano-Et₃PAuCl hereafter) mostly retains the cellular properties of the free gold complex and elicits even greater cytotoxic effects in colorectal cancer (CRC) cells, mediated by apoptosis and autophagy. Moreover, a remarkable inhibition of two crucial signaling pathways, i.e. ERK and AKT, by nano-Et₃PAuCl, was clearly documented. The implications of these findings are discussed.

Iodido equatorial ligands influence on the mechanism of action of Pt(IV) and Pt(II) anti-cancer complexes: A DFT computational study

A detailed computational exploration of the most relevant steps of iodido Pt(IV) complexes reduction and Pt(II) drugs mechanism of action and eventual deactivation is presented here inspired by the recent findings on iodido Pt(II) complexes and surprising re-evaluation of their cytotoxic activity. Pt(II) and Pt(IV) model systems are investigated and compared with cisplatin and its Pt(IV) derivative. Both monodeprotonated ascorbic acid and l-cysteine are used as reducing agents in the inner-sphere reduction mechanism of Pt(IV) complexes. Aquation mechanism of iodido Pt(II) complexes, interaction with guanine and sulfur containing compounds and reaction with the model protein hen egg white lysozyme are explored, due to a detected different behavior with respect to classical platinum drugs. The outcomes of such exploration allow to shed light on the role that the increased soft character together with bridging and leaving abilities of iodide over chloride could play in determining the cytotoxic profile of iodido Pt drugs.

Coinage Metal N-Heterocyclic Carbene Complexes: Recent Synthetic Strategies and Medicinal Applications

New weapons are constantly needed in the fight against cancer. The discovery of cisplatin as an anticancer drug prompted the search for new metal complexes. The successful history of cisplatin motivated chemists to develop a plethora of metal-based molecules. Among them, metal-N-heterocyclic carbene (NHC) complexes have gained significant attention because of their suitable qualities for efficient drug design. The enhanced applications of coinage metal-NHC complexes have encouraged a gradually increasing number of studies in the fields of medicinal chemistry that benefit from the fascinating chemical properties of these complexes. This review aims to present recent developments in synthetic strategies and medicinal applications of copper, silver and gold complexes supported by NHC ligands.

Ruthenium(II) 1,4,7-trithiacyclononane complexes of curcumin and bisdemethoxycurcumin: Synthesis, characterization, and biological activity

Two cationic ruthenium(II) 1,4,7-trithiacyclononane ([9]aneS₃) complexes of curcumin (curcH) and bisdemethoxycurcumin (bdcurcH), namely [Ru(curc)(dmso-S)([9]aneS₃)]Cl (1) and [Ru(bdcurc)(dmso-S)([9]aneS₃)]Cl (2) were prepared from the [RuCl₂(dmso-S)([9]-aneS₃)] precursor and structurally characterized, both in solution and in the solid state by X-ray crystallography. The corresponding PTA complexes [Ru(curc)(PTA)([9]aneS₃)]Cl (3) and [Ru(bdcurc)(PTA)([9]aneS₃)]Cl (4) have been also synthesized and characterized (PTA = 1,3,5-triaza-7-phosphaadamantane). Bioinorganic studies relying on mass spectrometry were performed on complexes 1-4 to assess their interactions with the model protein lysozyme. Overall, a rather limited reactivity with lysozyme was highlighted accompanied by a modest cytotoxic potency against three representative cancer cell lines. The moderate pharmacological activity is likely connected to the relatively high stability of these complexes.

An unexpected in-solution instability of diiodido analogue of picoplatin complicates its biological characterization

Complex cis-[PtI2(NH3)(pic)] (1; pic = 2-methylpyridine), a diiodido analogue of clinically studied picoplatin (2), is unstable in solution, which is intriguingly connected with the release of its pic ligand. This observation complicates the biological testing of e.g. cytotoxicity in human cancer cells for 1.

A mixed-valence diruthenium(II,III) complex endowed with high stability: from experimental evidence to theoretical interpretation

We herein report the synthesis and multi-technique characterization of [Ru2Cl((2-phenylindol-3-yl)glyoxyl-l-leucine-l-phenylalanine)4], a novel diruthenium(ii,iii) complex obtained by reacting [Ru2(μ-O2CCH3)4Cl] with a dual indolylglyoxylyl dipeptide anticancer agent. We soon realised that the compound is very stable under several different conditions including aqueous buffers or organic solvents. It is also completely unreactive toward proteins. The high stability is also suggested by cellular experiments in a glioblastoma cell line. Indeed, while the parent ligand exerts high cytotoxic effects in the low μM range, the complex is completely non-cytotoxic against the same line, most probably because of the lack of ligand release. To investigate the reasons for such high stability, we carried out DFT calculations that are fully consistent with the experimental findings. The results highlight that the stability of [Ru2Cl((2-phenylindol-3-yl)glyoxyl-l-leucine-l-phenylalanine)4] relies on the nature of the ligand, including its steric hindrance that prevents the reaction of any nucleophilic group with the Ru2 core. Ligand displacement is the key step to allow reactivity with the biological targets of metal-based prodrugs. Accordingly, we discuss the implications of some important aspects that should be considered when active molecules are chosen as ligands for the synthesis of paddle-wheel-like complexes with medicinal applications.

Mechanistic Insights Into the Anticancer Properties of the Auranofin Analog Au(PEt3)I: A Theoretical and Experimental Study

Au(PEt₃)I (AF-I hereafter), the iodide analog of the FDA-approved drug auranofin (AF hereafter), is a promising anticancer agent that produces its pharmacological effects through interaction with non-genomic targets such as the thioredoxin reductase system. AF-I is endowed with a very favorable biochemical profile showing potent in vitro cytotoxic activity against several cancer types including ovarian and colorectal cancer. Remarkably, in a recent publication, some of us reported that AF-I induces an almost complete and rapid remission in an orthotopic in vivo mouse model of ovarian cancer. The cytotoxic potency does not bring about highly severe side effects, making AF-I very well-tolerated even for higher doses, even more so than the pharmacologically active ones. All these promising features led us to expand our studies on the mechanistic aspects underlying the antitumor activity of AF-I. We report here on an integrated experimental and theoretical study on the reactivity of AF-I, in comparison with auranofin, toward relevant aminoacidic residues or their molecular models. Results point out that the replacement of the thiosugar moiety with iodide significantly affects the overall reactivity toward the amino acid residues histidine, cysteine, methionine, and selenocysteine. Altogether, the obtained results contribute to shed light into the enhanced antitumoral activity of AF-I compared with AF.

Reactions of cisplatin and cis-[PtI2(NH3)2] with molecular models of relevant protein sidechains: A comparative analysis

Quite surprisingly, cisplatin and cis-[PtI₂(NH₃)₂] were found to manifest significant differences in their reactions with the model protein lysozyme. We decided to explore whether these differences recur when reacting these two Pt compounds with other proteins. Notably, ESI-MS measurements carried out on cytochrome c nicely confirmed the reaction pattern observed for lysozyme. This prompted us to exploit a computational DFT approach to disclose the molecular basis of such behavior. We analyzed comparatively the reactions of cis-[PtCl₂(NH₃)₂] and cis-[PtI₂(NH₃)₂] with appropriate molecular models (Ls) of the sidechains of relevant aminoacids. We found that when Pt(II) complexes are reacted with sulfur ligands both quickly lose their halide ligands and then the resulting cis-[Pt(L)₂(NH₃)₂] species loses ammonia upon reaction with a ligand excess. In the case of imidazole, again cis-[PtCl₂(NH₃)₂] and cis-[PtI₂(NH₃)₂] quickly lose their halide ligands but the resulting cis-[Pt(L)₂(NH₃)₂] species does not lose ammonia by reaction with excess imidazole. These results imply that the two platinum complexes manifest a significantly different behavior in their reaction with representative small molecules in agreement with what observed in the case of model proteins. It follows that the protein itself must play a crucial role in triggering the peculiar reactivity of cis-[PtI₂(NH₃)₂] and in governing the nature of the formed protein adducts. The probable reasons for the observed behavior are critically commented and discussed.

Hexaiododiplatinate(ii) as a useful supramolecular synthon for halogen bond involving crystal engineering

By performing combined XRD and theoretical studies, we established the modes of R^EWGI⋯I–Pt XBs with [Pt₂(μ-I)₂I₄]²⁻acting as an XB acceptor.

A minimal structural variation can overcome tumour resistance of oxaliplatin: the case of 4,5-dehydrogenation of the cyclohexane ring

A new family of anticancer compounds has been derived from oxaliplatin by inserting a double-bond between carbons 4 and 5 of the 1,2-diaminocyclohexane ring. Testing against a panel of human tumour cell lines including cervical (A431), ovarian (2008), and colon carcinomas (HCT-15 and LoVo), and two oxaliplatin-resistant clones (LoVo OXP and LoVo MDR) has shown that the new compounds have, in general, equal if not better cytotoxic activity and are able to overcome the oxaliplatin-resistance. Moreover, the oxalato derivative induced lipid droplets increase in LoVo OXP cells thus suggesting the involvement of metabolism stress in its mechanism of action.

A new family of anticancer compounds has been derived from oxaliplatin by inserting a double-bond between carbons 4 and 5 of the 1,2-diaminocyclohexane ring.

New platinum(II) and palladium(II) complexes with substituted terpyridine ligands: synthesis and characterization, cytotoxicity and reactivity towards biomolecules

A series of palladium(II) (1-3) and platinum(II) chloride complexes (4 and 5) with 2,2':6',2″-terpyridine (terpy) derivatives substituted at the 4' position, was synthesized and fully characterized. Single crystal X-ray diffraction analysis of complexes 2, 3 and 5 showed tridentate coordination of the 4'-substituted terpyridine (terpy) ligands to the metal center. Moreover, in vitro cytotoxic activity of these complexes toward a panel of human cancer cell lines (lung cancer A549, colorectal cancer HCT116, ovarian cancer IGROV-1) and toward normal cell line HDF (dermal fibroblast) was determined by Trypan Blue exclusion assay. Overall, the tested compounds manifested a relevant cytotoxicity for the selected cancer cell lines with complex 4 also showing a modest cytotoxicity on the normal cell lines. To better understand the mode of action of these metal complexes, their reactivity with three model proteins, i.e. hen egg white lysozyme (HEWL), cytochrome c (cyt c) and ribonuclease A (RNase A) were comparatively investigated through ESI-MS analysis. The results highlighted a different behavior between the two series of complexes being platinum compounds more reactive toward RNase and cyt c than palladium compounds. Based on the obtained results, it is proposed that in presence of RNase A and cyt c, the platinum complexes undergo activation through release of labile ligands followed by binding to the protein. In contrast, palladium complexes revealed a far lower reactivity implying the likely occurrence of a different mechanism of action.

Synthesis, characterization and biological activity of new cyclometallated platinum(iv) iodido complexes

The synthesis of six novel cyclometallated platinum(iv) iodido complexes is accomplished by intermolecular oxidative addition of methyl iodide (compounds 2a-2c) or iodine (compounds 3a-3c) upon cyclometallated platinum(ii) compounds [PtX{(CH₃)₂N(CH₂)₃NCH(4-ClC₆H₃)}] (1a-1c: X = Cl, CH₃ or I). The X-ray molecular structures of platinum(ii) compound 1c and platinum(iv) compounds 3b and 3a' (an isomer of 3a) are reported. The cytotoxic activity against a panel of human adenocarcinoma cell lines (A-549 lung, MDA-MB-231 and MCF-7 breast, and HCT-116 colon), DNA interaction, topoisomerase I, IIα, and cathepsin B inhibition, and cell cycle arrest, apoptosis and ROS generation of the investigated complexes are presented. Remarkable antiproliferative activity was observed for most of the synthesized cycloplatinated compounds (series 1-3) in all the selected carcinoma cell lines. The best inhibition was provided for the octahedral platinum(iv) compounds 2a-2c exhibiting a methyl and an iodido axial ligand. Preliminary biological results point to a different mechanism of action for the investigated compounds. Cyclometallated platinum(ii) compounds 1a-1c modify the DNA migration as cisplatin. In contrast, cyclometallated platinum(iv) compounds 2a-2c and 3a-3c did not modify the DNA tertiary structure neither in the absence nor in the presence of ascorbic acid, which made them incapable of reducing platinum(iv) compounds 2b and 2c in a buffered aqueous medium (pH 7.40) according to ¹H NMR experiments. Remarkable topoisomerase IIα inhibitory activity is reported for platinum(iv) complexes 2b and 3a and in addition, for the last one, a moderate cathepsin B inhibition is reported. Cell cycle arrest (decrease in G0/G1 and G2 phases and arrest in the S phase), induction of apoptosis and ROS generation are related to the antiproliferative activity of some representative octahedral cyclometallated platinum(iv) compounds (2b and 2c).

Antiproliferative effects of two gold(I)-N-heterocyclic carbene complexes in A2780 human ovarian cancer cells: a comparative proteomic study

Au(NHC) and Au(NHC)₂, i.e. a monocarbene gold(I) complex and the corresponding bis(carbene) complex, are two structurally related compounds, endowed with cytotoxic properties against several cancer cell lines. Herein, we explore the molecular and cellular mechanisms at the basis of their cytotoxicity in A2780 human ovarian cancer cells. Through a comparative proteomic analysis, we demonstrated that the number of modulated proteins is far larger in Au(NHC)₂-treated than in Au(NHC)-treated A2780 cells. Both gold compounds mainly affected proteins belonging to the following functional classes: protein synthesis, metabolism, cytoskeleton and stress response and chaperones. Particularly, Au(NHC)₂ gave rise to an evident upregulation of several glycolytic enzymes. Moreover, only Au(NHC)₂ triggered a net impairment of respiration and a metabolic shift towards glycolysis, suggesting that mitochondria are relevant cellular targets. We also found that both carbenes, similarly to the gold(I) compound auranofin, caused a strong inhibition of the seleno-enzyme thioredoxin reductase (TrxR). In conclusion, we highlighted that coordination of two carbene ligands to the same gold(I) center greatly enhances the antiproliferative effects of the resulting compound in comparison to the monocarbene derivative. Moreover, TrxR inhibition and metabolic impairment seem to play a major role in the Au(NHC)₂ cytotoxicity. Overall, these antiproliferative effects were also confirmed on other two human ovarian cancer cell lines (i.e. SKOV3 and IGROV1).

Facile synthesis of highly biocompatible folic acid-functionalised SiO2nanoparticles encapsulating rare-earth metal complexes, and their application in targeted drug delivery

Herein, we report the facile synthesis of highly biocompatible folic acid-functionalized SiO₂nanoparticles encapsulating rare-earth metal complexes, and their application in targeted metal complex delivery.