A Non-Conventional Platinum Drug against a Non-Small Cell Lung Cancer Line

A dinuclear Pt(II) complex with putrescine as bridging polyamine ligand ([Pt₂Put₂(NH₃)₄]Cl₄) was synthesized and assessed as to its potential anticancer activity against a human non-small cell lung cancer line (A549), as well as towards non-cancer cells (BEAS-2B). This effect was evaluated through in vitro cytotoxicity assays (MTT and SRB) coupled to microFTIR and microRaman spectroscopies, the former delivering information on growth-inhibiting and cytotoxic abilities while the latter provided very specific information on the metabolic impact of the metal agent (at the sub-cellular level). Regarding cancer cells, a major impact of [Pt₂Put₂(NH₃)₄]Cl₄ was evidenced on cellular proteins and lipids, as compared to DNA, particularly via the Amide I and Amide II signals. The effect of the chelate on non-malignant cells was lower than on malignant ones, evidencing a promising low toxicity towards healthy cells.

In vitro and In vivo Studies of Potential Anticancer Agents of Platinum(II) Complexes of Dicyclopentadiene and Dithiocarbamates

Three platinum(II) complexes of dicyclopentadiene (DCP) and dithiocarbamates (DTC), namely, [Pt(η4-DCP)(Me2DTC)]PF6 (1), [Pt(η4-DCP)(Et2DTC)]PF6 (2) and [Pt(η4-DCP)(Bz2DTC)]PF6 (3) [Me2DTC = dimethyldithiocarbamate, Et2DTC = diethyldithiocarbamate, and Bz2DTC = dibenzyldithiocarbamate] were prepared and characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy. The spectroscopic data indicated the coordination of both DCP and dithiocarbamate ligands to platinum(II). The solution chemisty of complex 1 revealed that the complexes are stable in both DMSO and 1:1 mixture of DMSO: H2O. In vitro cytotoxicity of the complexes relative to cisplatin was tested using MTT assay, against CHL-1 (human melanoma cancer cells), MDA-MB-231 (breast cancer cells), A549 (lung cancer cells), and B16 (murine melanoma cancer cells). The antiproliferative effect of all three prepared complexes was found to be significantly higher than cisplatin. Furthermore, flow cytometric analysis of complex 1 showed that the complex induced apoptosis, oxidative stress, mitochondrial potential depolarization and cell cycle arrest in a concentration-dependent pattern in the CHL-1 cells. Confirmation of apoptosis via gene expression analysis demonstrated down-regulation of anti-apoptotic genes and up-regulation of pro-apoptotic genes in the CHL-1 cells. Wound healing assays also lent support to the strong cytotoxicity of the complexes. In vivo studies showed a significant reduction of tumor volume at the end of the experiment. In addition, the drug did not change the weight of the mice. In conclusion, complex 1 inhibited cell proliferation in vitro and reduced tumor growth in vivo.

Data on synthesis and structure-activity relationships of tetrazolato-bridged dinuclear platinum(II) complexes

In this data file, the synthetic procedures for the preparation of a series of anticancer tetrazolato-bridged dinuclear platinum(II) complexes ([{cis-Pt(NH₃)₂}₂(μ-OH)(μ-5-R-tetrazolato-N2,N3)]ⁿ⁺ (n = 1 or 2, tetrazolato-bridged complexes)) and of the bridging ligands of 5-substituted 1H-tetrazoles (5-R-1H-tetrazoles) are described. These compounds were characterized by ¹H-, ¹³C-, ¹⁹F- and ¹⁹⁵Pt-NMR spectroscopy and mass spectrometry.

Palladium(ii) and platinum(ii) complexes with ONN donor pincer ligand: synthesis, characterization and in vitro cytotoxicity study

New Pd(ii) and Pt(ii) complexes with ONN donor pincer ligand are synthesized. Antiproliferative activity of the complexes is explored towards HCT116, HepG2, MCF-7 and A549 cell lines.

Cytotoxic oxidovanadium(IV) complexes of tridentate halogen-substituted Schiff bases: First dinuclear V(IV) complexes with O → VIV = O → VIV = O core

The reaction of potentially N,N,O-tridentate Schiff base ligands, Cl-LH, Br-LH, BrCl-LH and H-LH, with [V^IVO(acac)₂] in 2:1 ratio in methanol gave the corresponding mononuclear and dinuclear oxidovanadium(IV) complexes, VO(Cl-L)₂ (1), VO(Br-L)₂ (2), [(BrCl-L)₂(H₂O)V(μ-O)VO(BrCl-L)₂] (3) and [(H-L)₂(H₂O)V(μ -O)VO(H-L)₂] (4), in good yields. The ligands and complexes were fully characterized by elemental analysis and FT-IR spectroscopy. The ligands were also characterized by ¹H NMR spectroscopy. The oxidation state of V(IV)O with d¹ configuration in all synthesized complexes was confirmed by EPR. Moreover, the structures of 2 and 3 were determined by X-ray diffraction (XRD) analysis which revealed them as mono- and dinuclear vanadium(IV) complexes, respectively, with the ligands coordinated as bidentate chelates. The structure of 3 represents the first example of dinuclear V(IV) complex with O → V^IV = O → V^IV = O core (Cambridge Structural Database (CSD)​, version 5.42, update of May 2021). The cytotoxicity of ligands and complexes was evaluated towards ovarian (A2780), breast (MCF7) and prostate (PC3) cancer cells at 48 h. While ligands showed modest IC₅₀ values (>42 μM), all complexes turned out to be effective in the range 3.9-17.2 μM. In particular, A2780 and MCF7 cell lines were the most sensitive to the newly synthesized V(IV)O complexes.

Homo- and hetero-dinuclear Pt(II)/Pd(II) complexes: studies of hydrolysis, nucleophilic substitution reactions, DNA/BSA interactions, DFT calculations, molecular docking and cytotoxic activity

Three dinuclear complexes [Pd2(tpbd)Cl2]Cl2 (PP1), [Pt2(tpbd)Cl2]Cl2 (PP2) and [PdPt(tpbd)Cl2]Cl2 (PP3) (tpbd = N,N,N',N'-tetrakis(2-pyridylmethyl)benzene-1,4-diamine) have been synthesized and characterized and the protonation constants of their corresponding diaqua analogues have been determined. Also, in water solution, the aqua analogues of these complexes exist as mono-hydroxo, di-hydroxo and dimer μ-hydroxo complexes in the pH between 3.0 and 11.0. Substitution reactions with sulfur- and nitrogen-donor nucleophiles, such as thiourea (Tu), l-methionine (l-Met), glutathione (GSH) and guanosine-5'-monophosphate (5'-GMP), were studied at pH 7.2 by conventional and stopped-flow UV-Vis spectrophotometry and the observed reactivity follows the order: Tu > l-Met > GSH > 5'-GMP. Also, the interactions with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) were investigated. Competitive studies with DNA were performed in the presence of ethidium bromide and Hoechst dye 33258 as well. The complexes possess the strong ability to react with CT-DNA exhibiting intercalation and more preferable minor groove binding. Nevertheless, all complexes showed a good binding affinity toward BSA with relatively high binding constants. The nature of the binding forces between complexes and biomolecules has been identified as hydrophobic. Experimental results were compared with the molecular docking results, while the relative stability and thermodynamic properties of dinuclear complexes were compared with their mononuclear units by DFT calculations. Among three tested complexes, PP2 showed the most powerful cytotoxic effect on HTB140 and H460 cancer cell lines after 48 h of treatment and exerted a strong long-term influence on the proliferation potential of both tested cell lines. PP2 induced the inhibition of autophagy, G2/M cell cycle arrest and mitotic catastrophe.

Water soluble palladium(ii) and platinum(ii) acyclic diaminocarbene complexes: solution behavior, DNA binding, and antiproliferative activity

Water soluble Pd(ii) and Pt(ii)–ADC species synthesized via the metal-mediated coupling of isocyanides and 1,2-diaminobenzene have demonstrated antitumor potential.

Anticancer activity of palladium-based complexes against triple-negative breast cancer

Treatment of triple-negative breast carcinoma (TNBC) remains an unmet medical need with no targeted therapy available to date. Accounting for 10-30% of all human breast cancer tumors, this mammary carcinoma subtype has a particularly poor prognosis owing to its high metastatic potential, aggressive biology and limited pharmacological treatment options. Platinum chemotherapeutics are the mainstay therapy in patients with TNBC but their clinical use is limited by severe toxicity and acquired resistance. Palladium-based complexes are appealing alternative metal-based drugs because of significant similarities regarding structure and coordination chemistry with the platinum agents. This review summarizes the knowledge gathered so far on 121 Pd(II) complexes, emphasizing their anticancer activity and putative pharmacological targets toward TNBC.

Synthesis and structure-activity relationships of tetrazolato-bridged dinuclear platinum(II) complexes: A small modification at tetrazole C5 markedly influences the in vivo antitumor efficacy

We synthesized and characterized 15 new derivatives of the highly anticancer-active platinum(II) complex [{cis-Pt(NH₃)₂}₂(μ-OH)(μ-tetrazolato-N2,N3)]²⁺ (5-H-Y) by making substitutions at tetrazole C5. We then evaluated the comprehensive structure-cytotoxicity relationships of a total of 23 derivatives in two murine lymphocytic leukaemia cell lines, sensitive and resistant to cisplatin. We also report the in vivo antitumor efficacy of three ester derivatives, two of which exhibited much higher efficacy than oxaliplatin against mouse homografted Colon-26 colorectal tumor.

Water soluble, optically active monofunctional Pd(ii) and Pt(ii) compounds: promising adhesive and antimigratory effects on human prostate PC-3 cancer cells

Water soluble, enantiomerically pure “rule breakers” Pd(ii) and Pt(ii) compounds with promising anticancer potential are reported.

The Application of ATR-FTIR Spectroscopy and the Reversible DNA Conformation as a Sensor to Test the Effectiveness of Platinum(II) Anticancer Drugs

Platinum(II) complexes have been found to be effective against cancer cells. Cisplatin curbs cell replication by interacting with the deoxyribonucleic acid (DNA), reducing cell proliferation and eventually leading to cell death. In order to investigate the ability of platinum complexes to affect cancer cells, two examples from the class of polyfluorophenylorganoamidoplatinum(II) complexes were synthesised and tested on isolated DNA. The two compounds trans-[N,N′-bis(2,3,5,6-tetrafluorophenyl)ethane-1,2-diaminato(1-)](2,3,4,5,6-pentafluorobenzoato)(pyridine)platinum(II) (PFB) and trans-[N,N′-bis(2,3,5,6-tetrafluorophenyl)ethane-1,2-diaminato(1-)](2,4,6-trimethylbenzoato)(pyridine)platinum(II) (TMB) were compared with cisplatin through their reaction with DNA. Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy was applied to analyse the interaction of the Pt^(II) complexes with DNA in the hydrated, dehydrated and rehydrated states. These were compared with control DNA in acetone/water (PFB, TMB) and isotonic saline (cisplatin) under the same conditions. Principle Component Analysis (PCA) was applied to compare the ATR-FTIR spectra of the untreated control DNA with spectra of PFB and TMB treated DNA samples. Disruptions in the conformation of DNA treated with the Pt^(II) complexes upon rehydration were mainly observed by monitoring the position of the IR-band around 1711 cm⁻¹ assigned to the DNA base-stacking vibration. Furthermore, other intensity changes in the phosphodiester bands of DNA at ~1234 cm⁻¹ and 1225 cm⁻¹ and shifts in the dianionic phosphodiester vibration at 966 cm⁻¹ were observed. The isolated double stranded DNA (dsDNA) or single stranded DNA (ssDNA) showed different structural changes when incubated with the studied compounds. PCA confirmed PFB had the most dramatic effect by denaturing both dsDNA and ssDNA. Both compounds, along with cisplatin, induced changes in DNA bands at 1711, 1088, 1051 and 966 cm⁻¹ indicative of DNA conformation changes. The ability to monitor conformational change with infrared spectroscopy paves the way for a sensor to screen for new anticancer therapeutic agents.

Novel platinum-based anticancer drug: a complete vibrational study

The introduction of cisplatin to oncology, in the 1970s, marked the onset of the search for novel and improved metal-based anticancer drugs. Polynuclear PtII and PdII complexes with linear alkylamines as bridging ligands are a class of potential antineoplastic agents that have shown promising cytotoxicity against low-prognosis human cancers, such as metastatic breast adenocarcinoma and osteosarcoma. The present study reports an analysis of [μ-N,N′-bis(3-aminopropyl)butane-1,4-diamine-κ4 N,N′:N′′,N′′′]bis[dichloridoplatinum(II)], [Pt2Cl4(C10H26N4)], denoted Pt2Spm (Spm is spermine), by vibrational spectroscopy coupled to theoretical calculations. Within the latter, the Density Functional Theory (DFT – mPW1PW/6-31G*) and Effective Core Potential (ECP – LANL2DZ) approaches were used, in order to ensure the most accurate representation of the molecule and achieve a maximum agreement with the experimental data. The solid-state geometry of Pt2Spm corresponds to Ci symmetry, displaying 132 vibrational modes. A complete assignment of the experimental vibrational profile of the system was attained through the combined application of complementary Raman, FT–IR and Inelastic Neutron Scattering (INS) techniques. INS allowed an unequivocal identification of the CH2 and NH2 rocking modes, not clearly detected by the optical techniques, while Raman measurements led to a clear discrimination of the Pt—N stretching frequencies from the two distinct Pt—N moieties within the chelate. The metal-to-metal distances calculated for the molecule under study were found to allow the establishment of effective inter- and intrastrand crosslinks with DNA. These results will hopefully help to clarify the mode of action of the compound, at the molecular level, contributing to the development of improved cisplatin-like chemotherapeutic drugs having a higher efficacy and specificity coupled to lower acquired resistance and deleterious side effects.

Chemotherapeutic response to cisplatin-like drugs in human breast cancer cells probed by vibrational microspectroscopy

Studies of drug-cell interactions in cancer model systems are essential in the preclinical stage of rational drug design, which relies on a thorough understanding of the mechanisms underlying cytotoxic activity and biological effects, at a molecular level. This study aimed at applying complementary vibrational spectroscopy methods to evaluate the cellular impact of two Pt(ii) and Pd(ii) dinuclear chelates with spermine (Pt2Spm and Pd2Spm), using cisplatin (cis-Pt(NH3)2Cl2) as a reference compound. Their effects on cellular metabolism were monitored in a human triple-negative metastatic breast cancer cell line (MDA-MB-231) by Raman and synchrotron-radiation infrared microspectroscopies, for different drug concentrations (2-8 μM) at 48 h exposure. Multivariate data analysis was applied (unsupervised PCA), unveiling drug- and concentration-dependent effects: apart from discrimination between control and drug-treated cells, a clear separation was obtained for the different agents studied - mononuclear vs. polynuclear, and Pt(ii) vs. Pd(ii). Spectral biomarkers of drug action were identified, as well as the cellular response to the chemotherapeutic insult. The main effect of the tested compounds was found to be on DNA, lipids and proteins, the Pd(ii) agent having a more significant impact on proteins while its Pt(ii) homologue affected the cellular lipid content at lower concentrations, which suggests the occurrence of distinct and unconventional pathways of cytotoxicity for these dinuclear polyamine complexes. Raman and FTIR microspectroscopies were confirmed as powerful non-invasive techniques to obtain unique spectral signatures of the biochemical impact and physiological reaction of cells to anticancer agents.

Linker design for the modular assembly of multifunctional and targeted platinum(ii)-containing anticancer agents

A versatile and efficient modular synthetic platform was developed for assembling multifunctional conjugates and targeted forms of platinum-(benz)acridines, a class of highly cytotoxic DNA-targeted hybrid agents. The synthetic strategy involved amide coupling between succinyl ester-modified platinum compounds (P1, P2) and a set of 11 biologically relevant primary and secondary amines (N1-N11). To demonstrate the feasibility and versatility of the approach, a structurally and functionally diverse range of amines was introduced. These include biologically active molecules, such as rucaparib (a PARP inhibitor), E/Z-endoxifen (an estrogen receptor antagonist), and a quinazoline-based tyrosine kinase inhibitor. Micro-scale reactions in Eppendorf tubes or on 96-well plates were used to screen for optimal coupling conditions in DMF solution with carbodiimide-, uronium-, and phosphonium-based compounds, as well as other common coupling reagents. Reactions with the phosphonium-based coupling reagent PyBOP produced the highest yields and gave the cleanest conversions. Furthermore, it was demonstrated that the chemistry can also be performed in aqueous media and is amenable to parallel synthesis based on multiple consecutive reactions in DMF in a "one-tube" format. In-line LC-MS was used to assess the stability of the conjugates in physiologically relevant buffers. Hydrolysis of the conjugates occurs at the ester moiety and is facilitated by the aquated metal moiety under low-chloride ion conditions. The rate of ester cleavage greatly depends on the nature of the amine component. Potential applications of the linker technology are discussed.

The effect of alkyl chain tethers on the kinetics and mechanistic behaviour of bifunctional dinuclear platinum(ii) complexes bearing N,N′-dipyridylamine ligands

This study reports on non-classical dinuclear platinum(ii) complexes, with the ability to bind to DNA strands in a different manner from cisplatin and its analogues. This is an effort to design dinuclear Pt(ii) complexes that target DNA and are bifunctional.

Kinetic analysis of and platinum(II) migration in the reactions of tetrazolato-bridged dinuclear platinum(II) complexes with nucleotides

The series of tetrazolato-bridged complexes with the formula [{cis‑Pt(NH₃)₂}₂(μ-OH)(μ-5-H-tetrazolato-N1,N2)]²⁺ (5-H-X) or [{cis‑Pt(NH₃)₂}₂(μ-OH)(μ-5-R-tetrazolato-N2,N3)]ⁿ⁺ (R=H (5-H-Y), CH₃ (1), CH₂COOCH₂CH₃ (2), CH₂COO^- (3), n=2 (5-H-Y, 1, 2) or 1 (3)) are promising candidate complexes for formulation as next-generation platinum-based anticancer drugs that form multimodal bindings with DNA molecules. These multimodal bindings involve both non-covalent and covalent interactions, the latter of which are acknowledged to be essential for platinum-based drugs to exert their anticancer activity. In the present study, the tetrazolato-bridged complexes reacted with two molar equivalents of guanosine-5'-monophosphate (GMP) to yield the 1:2 reaction products [{cis‑Pt(NH₃)₂(GMP-N7)}₂(μ-5-R-tetrazolato-N1,N3)]^{2- or 1-}. This reaction was accompanied by an intramolecular Pt(II) migration that contributed to the formation of diverse DNA crosslinking, such as interhelical crosslinks. The second-order reaction rate constants for the reactions performed in phosphate-buffered D₂O solution showed that the reactivity of the complexes decreased in the order 5-H-X≳5-H-Y>2≳1>3 and that reactivity was correlated with the cytotoxicity of the complexes. A similar result was obtained for the reaction of the complexes with calf thymus DNA in which the formation of covalent DNA adducts was quantified by means of inductively coupled plasma mass spectrometry. These results suggest that overall charge affects the kinetics of the reactions of platinum complexes with GMP and calf thymus DNA. Thus, the positive charge of the complexes affects not only the non-covalent but also the covalent interactions between the complexes and nucleotides and DNA, which are negatively charged molecules.

Impact of the Pd2Spermine Chelate on Osteosarcoma Metabolism: An NMR Metabolomics Study

A metabolomics study of Pd₂Spermine(Spm) on osteosarcoma MG-63 and osteoblastic HOb cells is presented to assess the impact of the potential palladium drug on cell metabolism compared with cisplatin (cDDP). Despite its higher cytotoxicity, Pd₂Spm induced lower (and reversible) metabolic impact on MG-63 cells and the absence of apoptosis; conversely, it induced significant deviations in osteoblastic amino acid metabolism. However, when in combination with doxorubicin and methotrexate, Pd₂Spm induced strong metabolic deviations on lipids, choline compounds, amino acids, nucleotides, and compounds related to antioxidative mechanisms (e.g., glutathione, inositol, hypoxanthine), similarly to the cDDP cocktail. Synergetic effects included triggering of lipid biosynthesis by Pd₂Spm in the presence of doxorubicin (and reinforced by methotrexate) and changes in the glycosylation substrate uridine diphosphate acetylgalactosamine and methionine and serine metabolisms. This work provides promising results related to the impact of Pd₂Spm on osteosarcoma cellular metabolism, particularly in drug combination protocols. Lipid metabolism, glycosylation, and amino acid metabolisms emerge as relevant features for targeted studies to further understand a potential anticancer mechanism of combined Pd₂Spm.

Specific Conformational Change in Giant DNA Caused by Anticancer Tetrazolato-Bridged Dinuclear Platinum(II) Complexes: Middle-Length Alkyl Substituents Exhibit Minimum Effect

Derivatives of the highly antitumor-active compound [{cis-Pt(NH₃)₂}₂(μ-OH)(μ-tetrazolato-N2,N3)]²⁺ (5-H-Y), which is a tetrazolato-bridged dinuclear platinum(II) complex, were prepared by substituting a linear alkyl chain moiety at C5 of the tetrazolate ring. The general formula for the derivatives is [{cis-Pt(NH₃)₂}₂(μ-OH)(μ-5-R-tetrazolato-N2,N3)]²⁺, where R is (CH₂)_nCH₃ and n = 0 to 8 (complexes 1-9). The cytotoxicity of complexes 1-4 in NCI-H460 human non-small-cell lung cancer cells decreased with increasing alkyl chain length, and those of complexes 5-9 increased with increasing alkyl chain length. That is, the in vitro cytotoxicity of complexes 1-9 was found to have a U-shaped association with alkyl chain length. This U-shaped association is attributable to the degree of intracellular accumulation. Although circular dichroism spectroscopic measurement indicated that complexes 1-9 induced comparable conformational changes in the secondary structure of DNA, the tetrazolato-bridged complexes induced different degrees of DNA compaction as revealed by a single DNA measurement with fluorescence microsopy, which also had a U-shaped association with alkyl chain length that matched the association observed for cytotoxicity. Complexes 7-9, which had alkyl chains long enough to confer surfactant-like properties to the complex, induced DNA compaction 20 or 1000 times more efficiently than 5-H-Y or spermidine. A single DNA measurement with transmission electron microscopy revealed that complex 8 formed large spherical self-assembled structures that induced DNA compaction with extremely high efficiency. This result suggests that these structures may play a role in the DNA compaction that was induced by the complexes with the longer alkyl chains. The derivatization with a linear alkyl chain produced a series of complexes with unique cellular accumulation and DNA conformational change profiles and a potentially useful means of developing next-generation platinum-based anticancer drugs. In addition, the markedly high ability of these complexes to induce DNA compaction and their high intracellular accumulation emphasized the difference in mechanism of action from platinum-based anticancer drugs.

Intracellular water – an overlooked drug target? Cisplatin impact in cancer cells probed by neutrons

Intracellular water as a secondary pharmacological target?

Synthesis, reactivity and characterization of Pt(ii) complexes with N,N′ chelating ligands; structure and dimethylsulfoxide reactivity relationship

Chelated N-heterocycles can be replaced from the coordination sphere of square planar Pt(ii) complexes by DMSO.

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

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

Chromatin folding and DNA replication inhibition mediated by a highly antitumor-active tetrazolato-bridged dinuclear platinum(II) complex

Chromatin DNA must be read out for various cellular functions, and copied for the next cell division. These processes are targets of many anticancer agents. Platinum-based drugs, such as cisplatin, have been used extensively in cancer chemotherapy. The drug–DNA interaction causes DNA crosslinks and subsequent cytotoxicity. Recently, it was reported that an azolato-bridged dinuclear platinum(II) complex, 5-H-Y, exhibits a different anticancer spectrum from cisplatin. Here, using an interdisciplinary approach, we reveal that the cytotoxic mechanism of 5-H-Y is distinct from that of cisplatin. 5-H-Y inhibits DNA replication and also RNA transcription, arresting cells in the S/G2 phase, and are effective against cisplatin-resistant cancer cells. Moreover, it causes much less DNA crosslinking than cisplatin, and induces chromatin folding. 5-H-Y will expand the clinical applications for the treatment of chemotherapy-insensitive cancers.

Synthesis and analysis of the anticancer activity of platinum(ii) complexes incorporating dipyridoquinoxaline variants

Platinum complexes incorporating variants of dpq were synthesised. Their DNA affinity and cytotoxicity were compared to complexes containing phen variants, revealing unexpected trends in biological activity.

Platinum and Palladium Polyamine Complexes as Anticancer Agents: The Structural Factor

Since the introduction of cisplatin to oncology in 1978, Pt(II) and Pd(II) compounds have been intensively studied with a view to develop the improved anticancer agents. Polynuclear polyamine complexes, in particular, have attracted special attention, since they were found to yield DNA adducts not available to conventional drugs (through long-distance intra- and interstrand cross-links) and to often circumvent acquired cisplatin resistance. Moreover, the cytotoxic potency of these polyamine-bridged chelates is strictly regulated by their structural characteristics, which renders this series of compounds worth investigating and their synthesis being carefully tailored in order to develop third-generation drugs coupling an increased spectrum of activity to a lower toxicity. The present paper addresses the latest developments in the design of novel antitumor agents based on platinum and palladium, particularly polynuclear chelates with variable length aliphatic polyamines as bridging ligands, highlighting the close relationship between their structural preferences and cytotoxic ability. In particular, studies by vibrational spectroscopy techniques are emphasised, allowing to elucidate the structure-activity relationships (SARs) ruling anticancer activity.

Using a build-and-click approach for producing structural and functional diversity in DNA-targeted hybrid anticancer agents

An efficient screening method was developed for functionalized DNA-targeted platinum-containing hybrid anticancer agents based on metal-mediated amine-to-nitrile addition, a form of "click" chemistry. The goal of the study was to generate platinum-acridine agents for their use as cytotoxic "warheads" in targeted and multifunctional therapies. This was achieved by introducing hydroxyl, carboxylic acid, and azide functionalities in the acridine linker moiety and by varying the nonleaving groups attached to platinum. The assay, which was based on microscale reactions between 6 platinum-nitrile complexes and 10 acridine derivatives, yielded a small library of 60 platinum-acridines. Reactions were monitored, and product mixtures were quantitatively analyzed by automated in-line high-performance liquid chromatography-electrospray mass spectrometry (LC-ESMS) analysis and subjected to cell viability screening using a nonradioactive cell proliferation assay. The new prescreening methodology proves to be a powerful tool for establishing structure-activity relationships and for identifying target compounds.

Synthesis and biological studies of pyrazolyl-diamine Pt(II) complexes containing polyaromatic DNA-binding groups

New [PtCl(pz*NN)](n+) complexes anchored by pyrazolyl-diamine (pz*NN) ligands incorporating anthracenyl or acridine orange DNA-binding groups have been synthesized so as to obtain compounds that would display synergistic effects between platination and intercalation of DNA. Study of their interaction with supercoiled DNA indicated that the anthracenyl-containing complex L(2) Pt displays a covalent type of binding, whereas the acridine orange counterpart L(3) Pt shows a combination of intercalative and covalent binding modes with a strong contribution from the former. L(2) Pt showed a very strong cytotoxic effect on ovarian carcinoma cell lines A2780 and A2780cisR, which are, respectively, sensitive to and resistant to cisplatin. In these cell lines, L(2) Pt is nine to 27 times more cytotoxic than cisplatin. In the sensitive cell line, L(3) Pt showed a cytotoxic activity similar to that of cisplatin, but like L(2) Pt was able significantly to overcome cisplatin cross-resistance. Cell-uptake studies showed that L(2) Pt accumulates preferentially in the cytoplasm, whereas L(3) Pt reaches the cell nucleus more easily, as clearly visualized by time-lapse confocal imaging of live A2870 cells. Altogether, these findings seem to indicate that interaction with biological targets other than DNA might be involved in the mechanism of action of L(2) Pt because this compound, despite having a weaker ability to target the cell nucleus than L(3) Pt, as well as an inferior DNA affinity, is nevertheless more cytotoxic. Furthermore, ultrastructural studies of A2870 cells exposed to L(2) Pt and L(3) Pt revealed that these complexes induce different alterations in cell morphology, thus indicating the involvement of different modes of action in cell death.

Synthesis, aqueous reactivity, and biological evaluation of carboxylic acid ester-functionalized platinum-acridine hybrid anticancer agents

The synthesis of platinum-acridine hybrid agents containing carboxylic acid ester groups is described. The most active derivatives and the unmodified parent compounds showed up to 6-fold higher activity in ovarian cancer (OVCAR-3) and breast cancer (MCF-7, MDA-MB-231) cell lines than cisplatin. Inhibition of cell proliferation at nanomolar concentrations was observed in pancreatic (PANC-1) and nonsmall cell lung cancer cells (NSCLC, NCI-H460) of 80- and 150-fold, respectively. Introduction of the ester groups did not affect the cytotoxic properties of the hybrids, which form the same monofunctional-intercalative DNA adducts as the parent compounds, as demonstrated in a plasmid unwinding assay. In-line high-performance liquid chromatography and electrospray mass spectrometry (LC-ESMS) shows that the ester moieties undergo platinum-mediated hydrolysis in a chloride concentration-dependent manner to form carboxylate chelates. Potential applications of the chloride-sensitive ester hydrolysis as a self-immolative release mechanism for tumor-selective delivery of platinum-acridines are discussed.

Analysis of the DNA damage produced by a platinum-acridine antitumor agent and its effects in NCI-H460 lung cancer cells

High-performance liquid chromatography in conjunction with electrospray mass spectrometry (LC-ESMS) was used to structurally characterize the adducts formed by the platinum-acridine agent [PtCl(en)(N-(2-(acridin-9-ylamino)ethyl)-N-methylpropionimidamide)](NO(3))(2) (compound 1) in cell-free DNA. Compound 1 forms monofunctional adducts exclusively with guanine, based on the fragments identified in enzymatic digests (dG*, dGMP*, dApG*, and dTpG*, where the asterisk denotes bound drug). The time course of accumulation and DNA adduct formation of compound 1 and the clinical drug cisplatin in NCI-H460 lung cancer cells at physiologically relevant drug concentrations (0.1 μM) was studied by inductively-coupled plasma mass spectrometry (ICP-MS). Compound 1 accumulates rapidly in cells and reaches intracellular levels of up to 60-fold higher than those determined for cisplatin. The hybrid agent shows unusually high DNA binding levels: while cisplatin adducts form at a maximum frequency of 5 adducts per 10(6) nucleotides, compound 1 produces 25 adducts per 10(6) nucleotides after only 3 h of continuous incubation with the lung cancer cells. The high overall levels of compound 1 in the cells and in cellular DNA over the entire 12-h treatment period translate into a rapid decrease in cell viability. Possible implications of these findings for the mechanism of action of compound 1 and the agent's potential to overcome tumor resistance to cisplatin are discussed.

[Drug discovery research in in-vivo antitumor-active azolato-bridged dinuclear Pt(II) complexes]

Cis-diamminedichloridoplatinum(II) (cisplatin), which was first introduced as a clinical anticancer agent in the 1970s, is still among the most-utilized agents in current cancer chemotherapy. The discovery of cisplatin antitumor activity has catalyzed drug discovery research on antitumor platinum coordination compounds with improved efficacy. Some of new compounds show fewer side effects or expanded clinical applications. Apart from some clinical inconveniences, such as side effects, the high therapeutic efficacy of platinum-based agents implies that further modifications may lead to more effective anticancer platinum drugs which are effective against cancers that are typically resistant to chemotherapy, such as pancreatic cancer, and platinum-refractory cancer. Most of the cisplatin analogs cause cross-resistance to cisplatin, probably because of the similar biological consequences. It is suggested that platinum complexes which interact with DNA; the most probable target molecule, through a mechanism different from that of cisplatin can provide unique anticancer spectra required for next-generation anticancer drugs. Therefore, we synthesized a series of azolato-bridged dinuclear Pt(II) complexes with a general formula, [{cis-Pt(NH(3))(2)}(2)(µ-OH)(µ-azolato)](2+), which can form 1,2-intrastrand crosslinks with a minimal DNA distortion, whereas clinical platinum-based drugs provide 1,2-intrastrand crosslink with severe DNA distortion. Indeed, they exhibit much higher in vitro cytotoxicity than cisplatin, and we have recently found one of the dinuclear Pt(II) complexes exhibits markedly high in vivo antitumor efficacy against pancreatic cancer. Here, I update our drug-discovery research on the series of azolato-bridged dinuclear Pt(II) complexes that may be more effective and safer than current anticancer chemotherapeutic agents.

Pt(II) Complexes with Linear Diamines—Part I: Vibrational Study of Pt-Diaminopropane

A conformational analysis of the Pt(dap)Cl2complex (-diaminopropane) was performed by vibrational spectroscopy (FTIR, Raman, and INS), coupled to quantum mechanical methods within the density functional theory (DFT) and effective core potential (ECP) approaches. A complete spectral assignment of the system was achieved, due to the combined use of all available vibrational spectroscopic techniques. A good agreement was found between experimental and theoretical results, as well as with reported data for analogous complexes (e.g., cisplatin).