Unique DNA Binding Mode of Antitumor Trinuclear Tridentate Platinum(II) Compound

Controlled polymerization of metal complex monomers - fabricating random copolymers comprising different metal species and nano-colloids

Acrylate monomers with metal complexes were designed to build polymer metal complexes. The ideal copolymerization of monomers with zinc and platinum was performed to obtain random copolymers with a feeding metal composition. The successful nano-colloid preparation from the polymers further highlighted the potential of the method for building multimetallic materials.

Luminescent terpyridine appended geminal bisazide and bistriazoles: multinuclear Pt(II) complexes and AIPE-based DNA detection with the naked eye

We report square planar Pt(ii) complexes as luminescent biosensors for DNA detection in solution. The sensing is attributed to the aggregation induced bright red photoluminescence (AIPE) of the complexes in the presence of DNA that can be seen with the naked eye using only a 360 nm light source. Terpyridine appended luminescent geminal bistriazoles (L1-L4, from geminal bisazide A through azide-alkyne 'click' cycloaddition) with versatile chelating sites were explored for metal coordination and reaction with Pt(dmso)2Cl2 yielding tetranuclear and dinuclear complexes of Pt(ii) with different N∩N ligand environments. Thermally stable gem-bisazide and bistriazoles are hardly reported in the literature and this is the first report of terpyridine appended geminal bisazide and bistriazoles.

New Platinum(II) agent induces bimodal death of apoptosis and autophagy against A549 cancer cell

Agents with multiple modes of tumor cell death can be effective chemotherapeutic drugs. One example of a bimodal chemotherapeutic approach is an agent that can induce both apoptosis and autophagic death. Thus far, no clinical anticancer drug has been shown to simultaneously induce both these pathways. Mono-functional platinum complexes are potent anticancer drug candidates which act through mechanisms distinct from cisplatin. Here, we describe the synthesis and characterize of two mono-functional platinum complexes containing 8-substituted quinoline derivatives as ligands. In comparison to cisplatin, n-Mon-Pt-1 exhibited a greater in vitro cytotoxicity, was more effective in resistant cells and elicited a better anticancer effect. Mechanistic experiments indicate that n-Mon-Pt-1 mainly accumulates in mitochondria, and stimulates significant TrxR inhibition, ROS release and an ER stress response, ultimately resulting in a simultaneous induction of apoptosis and autophagy. Importantly, compared to cisplatin, n-Mon-Pt-1 exhibits lower acute toxicity and better anticancer activity in a murine tumor model.

Linear Bidentate Ligands (L) with Two Terminal Pyridyl N-Donor Groups Forming Pt(II)LCl2 Complexes with Rare Eight-Membered Chelate Rings

NMR and X-ray diffraction studies were conducted on Pt(II)LCl₂ complexes prepared with the new N-donor ligands N(SO₂R)Me _ndpa (R = Me, Tol; n = 2, 4). These ligands differ from N(H)dpa (di-2-picolylamine) in having the central N within a tertiary sulfonamide group instead of a secondary amine group and having Me groups at the 6,6'-positions ( n = 2) or 3,3',5,5'-positions ( n = 4) of the pyridyl rings. The N(SO₂R)3,3',5,5'-Me₄dpa ligands are coordinated in a bidentate fashion in Pt( N(SO₂R)3,3',5,5'-Me₄dpa)Cl₂ complexes, forming a rare eight-membered chelate ring. The sulfonamide N atom did not bind to Pt(II), consistent with indications in the literature that tertiary sulfonamides are unlikely to anchor two meridionally coordinated five-membered chelate rings in solutions of coordinating solvents. The N(SO₂R)6,6'-Me₂dpa ligands coordinate in a monodentate fashion to form the binuclear complexes [ trans-Pt(DMSO)Cl₂]₂( N(SO₂R)6,6'-Me₂dpa). The monodentate instead of bidentate N(SO₂R)6,6'-Me₂dpa coordination is attributed to 6,6'-Me steric bulk. These binuclear complexes are indefinitely stable in DMF- d₇, but in DMSO- d₆ the N(SO₂R)6,6'-Me₂dpa ligands dissociate completely. In DMSO- d₆, the bidentate ligands in Pt( N(SO₂R)3,3',5,5'-Me₄dpa)Cl₂ complexes also dissociate, but incompletely; these complexes provide rare examples of association-dissociation equilibria of N,N bidentate ligands in Pt(II) chemistry. Like typical cis-PtLCl₂ complexes, the Pt( N(SO₂R)3,3',5,5'-Me₄dpa)Cl₂ complexes undergo monosolvolysis in DMSO- d₆ to form the [Pt( N(SO₂R)3,3',5,5'-Me₄dpa)(DMSO- d₆)Cl]⁺ cations. However, unlike typical cis-PtLCl₂ complexes, the Pt( N(SO₂R)3,3',5,5'-Me₄dpa)Cl₂ complexes surprisingly do not react readily with the excellent N-donor bioligand guanosine. A comparison of the structural features of over 50 known relevant Pt(II) complexes having smaller chelate rings with those of the very few relevant Pt(II) complexes having eight-membered chelate rings indicates that the pyridyl rings in Pt( N(SO₂R)3,3',5,5'-Me₄dpa)Cl₂ complexes are well positioned to form strong Pt-N bonds. Therefore, the dissociation of the bidentate ligand and the poor biomolecule reactivity of the Pt( N(SO₂R)3,3',5,5'-Me₄dpa)Cl₂ complexes arise from steric consequences imposed by the -CH₂-N(SO₂R)-CH₂- chain in the eight-membered chelate ring.

Mitochondria-targeted platinum(II) complexes induce apoptosis-dependent autophagic cell death mediated by ER-stress in A549 cancer cells

Agents with multiple modes of tumor cell death can be effective chemotherapeutic drugs. One example of a bimodal chemotherapeutic approach is an agent that can induce both apoptosis and autophagic death. Thus far, no clinical anticancer drug has been shown to simultaneously induce both these pathways. Mono-functional platinum complexes are potent anticancer drug candidates which act through mechanisms distinct from cisplatin. Here, we describe the synthesis and characterize of two mono-functional platinum complexes containing 8-substituted quinoline derivatives as ligands, [PtL₁Cl]Cl [L₁ = (Z)-1-(pyridin-2-yl)-N-(quinolin-8-ylmethylene) methanamine] (Mon-Pt-1) and [PtL₂Cl]Cl [L₂ = (Z)-2-(pyridin-2-yl)-N-(quinolin-8-ylmethylene) ethanamine] (Mon-Pt-2). In comparison to cisplatin, Mon-Pt-2 exhibited a greater in vitro cytotoxicity, was more effective in resistant cells and elicited a better anticancer effect. Mechanistic experiments indicate that Mon-Pt-2 mainly accumulates in mitochondria, and stimulates significant TrxR inhibition ROS release and an ER stress response, mediated by mitochondrial dysfunction, ultimately resulting in a simultaneous induction of apoptosis and autophagy. Importantly, compared to cisplatin, Mon-Pt-2 exhibits lower acute toxicity and better anticancer activity in a murine tumor model. To the best of our knowledge, Mon-Pt-2 is the first mono-functional platinum complex inducing pro-death autophagy and apoptosis of cancer cells.

Organometallic Gold(III) Complexes Similar to Tetrahydroisoquinoline Induce ER-Stress-Mediated Apoptosis and Pro-Death Autophagy in A549 Cancer Cells

Agents inducing both apoptosis and autophagic death can be effective chemotherapeutic drugs. In our present work, we synthesized two organometallic gold(III) complexes harboring C^N ligands that structurally resemble tetrahydroisoquinoline (THIQ): Cyc-Au-1 (AuL¹Cl₂, L¹ = 3,4-dimethoxyphenethylamine) and Cyc-Au-2 (AuL²Cl₂, L² = methylenedioxyphenethylamine). In screening their in vitro activity, we found both gold complexes exhibited lower toxicity, lower resistance factors, and better anticancer activity than those of cisplatin. The organometallic gold(III) complexes accumulate in mitochondria and induce elevated ROS and an ER stress response through mitochondrial dysfunction. These effects ultimately result in simultaneous apoptosis and autophagy. Importantly, compared to cisplatin, Cyc-Au-2 exhibits lower toxicity and better anticancer activity in a murine tumor model. To the best of our knowledge, Cyc-Au-2 is the first organometallic Au(III) compound that induces apoptosis and autophagic death. On the basis of our results, we believe Cyc-Au-2 to be a promising anticancer agent or lead compound for further anticancer drug development.

Cycloplatinated(ii) complexes bearing 1,1′-bis(diphenylphosphino)ferrocene ligand: biological evaluation and molecular docking studies

Cycloplatinated(ii) complexes containing dppf ligand were prepared. These complexes exhibited high cytotoxicity and apoptosis-inducing activities to human cancer cell lines.

Targeting human telomeric and c-myc G-quadruplexes with alkynylplatinum(II) terpyridine complexes under molecular crowding conditions

The interactions between alkynylplatinum(II) terpyridine complexes 1-3 and the G-quadruplex DNA, including c-myc and telomeric quadruplex DNA, are investigated both in dilute solution and under molecular crowding conditions. The UV-vis absorption spectroscopy, circular dichroism and molecular docking studies suggest that 1-3 associate with telomeric and c-myc G-quadruplexes via groove binding, and electrostatic interactions. Experimental studies indicate that under molecular crowding conditions (in the presence of 40wt% PEG 200), 1-2 show weak affinity for c-myc, while 3 still displays high affinity and selectivity for c-myc. On the other hand, 1-3 act as efficient and selective ligand for telomeric quadruplex DNA under molecular crowding conditions. The complex 3 exhibits excellent cytotoxicity against A549, K562 and SGC-7901, with IC₅₀ values that are 35.0-fold, 10.0-fold, and 12.1-fold lower than the values of cisplatin under the same conditions, respectively.

Effect of cobalt(II) chloride hexahydrate on some human cancer cell lines

The present study investigates the anti-proliferative and apoptosis inducing mechanism of CoCl2·6H2O in PC-3 cancer cell line. Preliminary, three different forms of cobalt i.e., cobaltous (CoCl2·6H2O), macro-Co(II,III) oxide and nano-Co(II,III) oxide were screened for antiproliferative activity in PC-3 cell line. The CoCl2·6H2O being the most effective antiproliferative agent, hence it was further tested against lung (A549), prostrate (PC-3) and brain (IMR-32) cell lines. Human embryonic kidney cell line (293T) was used as a normal cell line to compare the toxicity of CoCl2·6H2O. The CoCl2·6H2O induced morphological and anatomical changes in PC-3 cancer cell which were studied using light, confocal and scanning electron microscopy. The lactate dehydrogenase was estimated which showed mild necrotic mode of cell death. The Annexin/PI staining confirmed the apoptotic mode of cell death in PC-3 cells. Further, production of reaction of reactive oxygen species and changes in mitochondrial membrane potential was also assessed spectrofluorimetrically. The cell cycle arrest was also investigated using flow cytometery. Finally, the caspase activity was estimated in CoCl2·6H2O treated PC-3 cancer cell line. Interestingly, it was found that CoCl2·6H2O induces more cell death in cancerous cells as compared to normal non-cancerous cells. These findings presented CoCl2·6H2O as potential antiproliferative agent.

The induction of lysis in lysogenic strains of Escherichia coli by a new antitumor transplatin derivative and its DNA interactions

DNA is the cellular target for antitumor derivatives of transplatin including those containing small aliphatic amino ligands.

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.

Pt-based drugs: the spotlight will be on proteins

Platinum-complexes represent some of the most successful groups of clinically used anticancer drugs. Their mechanism of action relies on the formation of stable DNA adducts occurring at the nitrogen in position 7 of guanine (N7) and involving one or two spatially close residues. The formation of stable DNA adducts is recognized as a DNA damaging event and, ultimately, drives cells to death. Nevertheless, nucleobases are not the only reliable targets of these drugs and other biomolecules can be involved. Among them large interest has been devoted to proteins since they contain several potential reactive sites for platinum (His, Met, and Cys) and, in particular, because the reaction of the metal with sulfur containing groups is a kinetically favored process. As a result, the occurrence of protein adducts and DNA-protein cross-links must be further taken into account in order to fully define cisplatin mechanism of action. Herein, we will summarize the most recent experimental evidence collected so far on protein-cisplatin adduct formation to better dissect its correlation with the drug pharmacological profile. Indeed, in addition to modulation of drug bioavailability and toxicity, the potential role of proteins as reaction intermediates or reservoir systems in platinum drugs can be envisaged. Additionally, the effects of Pt-coordinating groups on the chemical reactivity of the metal complexes will be reviewed. From all these outcomes a general model for Pt-based drugs mechanism of action can be drawn which is more articulate than the one currently supported. It claims proteins as reactive intermediates for DNA platination and it defines them as relevant to fully describe the clinical potential of this class of anticancer drugs.

Synthesis, molecular structure, DNA interaction and antioxidant activity of novel naphthoxazole compound

A novel naphthoxazole compound 1 was synthesized and characterized. The crystal structure of the compound shows that N atom locates at β-position and oxygen atom at α-position in naphthalene cycle. The DNA binding was studied by absorption spectroscopy, viscosity and luminescence spectra. The DNA binding constant was determined to be 6.16×10(3). The stoichiometry of compound/DNA is 1:1. The pBR322 DNA cleavage induced by the compound was investigated. The antioxidant activity of the compound against hydroxyl radical was also explored.

Activation of trans geometry in bifunctional mononuclear platinum complexes by a non-bulky methylamine ligand

In order to shed light on the mechanism that underlies activity of bifunctional mononuclear Pt(II) analogs of transplatin we examined in the present work a DNA binding mode of the analog of transplatin, namely trans-[Pt(CH3NH2)2Cl2], in which NH3 groups were replaced only by a small, non-bulky methylamine ligand. This choice was made because we were interested to reveal the role of the bulkiness of the amines used to substitute NH3 in transplatin to produce antitumor-active Pt(II) drug. The results indicate that trans-[Pt(CH3NH2)2Cl2] forms a markedly higher amount of more distorting intrastrand cross-links than transplatin which forms in DNA preferentially less distorting and persisting monofunctional adducts. Also importantly, the accumulation of trans-[Pt(CH3NH2)2Cl2] in tumor cells was considerably greater than that of transplatin and cisplatin. In addition, the results of the present work demonstrate that the replacement of ammine groups by the non-bulky methylamine ligand in the molecule of ineffective transplatin results in a radical enhancement of its activity in tumor cell lines including cisplatin-resistant tumor cells. Thus, activation of the trans geometry in bifunctional mononuclear Pt(II) complexes can be also accomplished by replacement of ammine groups in transplatin by non-bulky methylamine ligands so that it is not limited only to the replacement by relatively bulky and stereochemically more demanding amino ligands.

Toxicity in tumor cells, DNA binding mode, and resistance to decomposition by sulfur nucleophiles of new dinuclear bifunctional trans-PtII complexes containing long alkane linkers

In an effort to design dinuclear PtII compounds that maintain the target (DNA) binding profile of the trans-oriented dinuclear bifunctional PtII complexes containing aliphatic linker chains but are less susceptible to metabolic decomposition, the new, long-chain dinuclear PtII complexes—[{trans-PtCl(dien)}2-μ-(CH2)n]2+ (n = 7,10,12, dien = diethylenetriamine)—were synthesized. The toxicity of these metallodrugs was examined in ovarian tumor cell lines. The results showed that the activity of these complexes increased with growing length of the linker; the activity of complex containing the longest linker (n = 12) was comparable with that of cis-diamminedichloridoplatinum(II) (cisplatin). This observation correlated with the results of DNA binding studies performed in cell-free media. The results of these studies demonstrated that the growing length of the aliphatic bridge promoted more distorting conformational alterations induced in DNA. Attention was also paid to the reactivity of {[Pt(dien)Cl]2-alkane} compounds with glutathione (GSH). The results of these experiments support the thesis that the dinuclear structure of {[Pt(dien)Cl]2-alkane} complexes remains stable in the presence of S-containing compounds without undergoing chemical degradation as previously observed for some di/trinuclear bifunctional PtII complexes. This enhanced stability represents a favorable property which may contribute to reduce side effects and increase therapeutic efficacy of the dinuclear {[Pt(dien)Cl]2-alkane} compounds.