Insights into the strong in-vitro anticancer effects for bis(triphenylphosphane)iminium compounds having perchlorate, tetrafluoridoborate and bis(chlorido)argentate anions

Significance of the mitochondrial thioredoxin reductase in cancer cells: An update on role, targets and inhibitors

Thioredoxin reductase 2 (TrxR2) is a key component of the mitochondrial thioredoxin system able to transfer electrons to peroxiredoxin 3 (Prx3) in a reaction mediated by thioredoxin 2 (Trx2). In this way, both the level of hydrogen peroxide and thiol redox state are modulated. TrxR2 is often overexpressed in cancer cells conferring apoptosis resistance. Due to their exposed flexible arm containing selenocysteine, both cytosolic and mitochondrial TrxRs are inhibited by a large number of molecules. The various classes of inhibitors are listed and the molecules acting specifically on TrxR2 are extensively described. Particular emphasis is given to gold(I/III) complexes with phosphine, carbene or other ligands and to tamoxifen-like metallocifens. Also chemically unrelated organic molecules, including natural compounds and their derivatives, are taken into account. An important feature of many TrxR2 inhibitors is provided by their nature of delocalized lipophilic cations that allows their accumulation in mitochondria exploiting the organelle membrane potential. The consequences of TrxR2 inhibition are presented focusing especially on the impact on mitochondrial pathophysiology. Inhibition of TrxR2, by hindering the activity of Trx2 and Prx3, increases the mitochondrial concentration of reactive oxygen species and shifts the thiol redox state toward a more oxidized condition. This is reflected by alterations of specific targets involved in the release of pro-apoptotic factors such as cyclophilin D which acts as a regulator of the mitochondrial permeability transition pore. Therefore, the selective inhibition of TrxR2 could be utilized to induce cancer cell apoptosis.

Bis(triphenylphosphine)iminium tetrafluoroborate chloroform monosolvate

In the title compound, C36H30NP2 +·BF4 −·CHCl3 or [PPN]BF4·CHCl3, where [PPN] = [(Ph3P)2N]+, two triphenylphosphine units are attached to a central N atom. The P—N—P bond angle is 137.69 (11)°. The two P—N bonds are nearly equivalent, with lengths of 1.5834 (18) and 1.5798 (17) Å. Both the BF4 − anion and the chloroform solvent molecule are disordered over two positions, with occupancy ratios of 0.872 (3):0.128 (3) and 0.9628 (9):0.0372 (9), respectively. In the crystal, C—H...F and C—H...Cl hydrogen bonds link the [PPN]+ cations, the BF4 − anions, and the chloroform solvent molecules into an array which extends along the b-axis direction.

Dual targeting of the cancer antioxidant network with 1,4-naphthoquinone fused Gold(i) N-heterocyclic carbene complexes

To achieve a systems-based approach to targeting the antioxidant pathway, 1,4-naphthoquinone annulated N-heterocyclic carbene (NHC) [bis(1,3-dimesityl-4,5-naphthoquino-imidazol-2-ylidene)-gold(i)] [silver(i) dichloride] (1), [bis(1,3-dimesityl-4,5-naphthoquino-imidazol-2-ylidene)-gold(i)] chloride (2), and 1,3-dimesityl-4,5-naphthoquino-imidazol-2-ylidene)-gold(i) chloride (3)) were designed, synthesized, and tested for biological activity in a series of human cancer cell lines. The solution phase of complexes 1-3 were assigned using several spectroscopy techniques, including NMR spectroscopic analysis. Complexes 1 and 3 were further characterized by single crystal X-ray diffraction analysis. Electrochemical and spectroelectrochemical studies revealed that quinone reductions are reversible and that the electrochemically generated semiquinone and quinone dianions are stable under these conditions. Complex 1, containing two NHC-quinone moieties (to accentuate exogenous ROS via redox cycling) centered around a Au(i) center (to inactivate thioredoxin reductase (TrxR) irreversibly), was found to inhibit cancer cell proliferation to a much greater extent than the individual components (i.e., Au(i)-NHC alone or naphthoquinone alone). Treatment of A549 lung cancer cells with 1 produced a 27-fold increase in exogenous reactive oxygen species (ROS) which was found to localize to the mitochondria. The inhibition of TrxR, an essential mediator of ROS homeostasis, was achieved in the same cell line at low administrated concentrations of 1. TrxR inhibition by 1 was similar to that of auranofin, a gold(i) containing complex known to inhibit TrxR irreversibly. Complex 1 was found to induce cell death via an apoptotic mechanism as confirmed by annexin-V staining. Complex 1 was demonstrated to be efficacious in zebrafish bearing A549 xenografts. These results provide support for the suggestion that a dual targeting approach that involves reducing ROS tolerance while concurrently increasing ROS production can perturb antioxidant homeostasis, enhance cancer cell death in vitro, and reduce tumor burden in vivo, as inferred from preliminary zebra fish model studies.

Targeting the Thioredoxin System for Cancer Therapy

Thioredoxin (Trx) and thioredoxin reductase (TrxR) are essential components of the Trx system which plays pivotal roles in regulating multiple cellular redox signaling pathways. In recent years TrxR/Trx have been increasingly recognized as an important modulator of tumor development, and hence targeting TrxR/Trx is a promising strategy for cancer treatment. In this review we first discuss the structural details of TrxR, the functions of the Trx system, and the rational of targeting TrxR/Trx for cancer treatment. We also highlight small-molecule TrxR/Trx inhibitors that have potential anticancer activity and review their mechanisms of action. Finally, we examine the challenges of developing TrxR/Trx inhibitors as anticancer agents and perspectives for selectively targeting TrxR/Trx.

Heteroleptic Copper(I) Complexes of "Scorpionate" Bis-pyrazolyl Carboxylate Ligand with Auxiliary Phosphine as Potential Anticancer Agents: An Insight into Cytotoxic Mode

New copper(I) complexes [CuCl(PPh₃)(L)] (1: L = L_A = 4-carboxyphenyl)bis(3,5-dimethylpyrazolyl)methane; (2: L = L_B = 3-carboxyphenyl)bis(3,5-dimethylpyrazolyl)methane) were prepared and characterised by elemental analysis and various spectroscopic techniques such as FT-IR, NMR, UV–Vis, and ESI-MS. The molecular structures of complexes 1 and 2 were analyzed by theoretical B3LYP/DFT method. Furthermore, in vitro DNA binding studies were carried out to check the ability of complexes 1 and 2 to interact with native calf thymus DNA (CT-DNA) using absorption titration, fluorescence quenching and circular dichroism, which is indicative of more avid binding of the complex 1. Moreover, DNA mobility assay was also conducted to study the concentration-dependent cleavage pattern of pBR322 DNA by complex 1, and the role of ROS species to have a mechanistic insight on the cleavage pattern, which ascertained substantial roles by both hydrolytic and oxidative pathways. Additionally, we analyzed the potential of the interaction of complex 1 with DNA and enzyme (Topo I and II) with the aid of molecular modeling. Furthermore, cytotoxic activity of complex 1 was tested against HepG2 cancer cell lines. Thus, the potential of the complex 1 is promising though further in vivo investigations may be required before subjecting it to clinical trials.

Theoretical and Synthetic Study on the Existence, Structures, and Bonding of the Halide-Bridged [B2X7](-) (X = F, Cl, Br, I) Anions

While hydrogen bridging is very common in boron chemistry, halogen bridging is rather rare. The simplest halogen-bridged boron compounds are the [B2X7](-) anions (X = F, Cl, Br, I), of which only [B2F7](-) has been reported to exist experimentally. In this paper a detailed theoretical and synthetic study on the [B2X7](-) anions is presented. The structures of [B2X7](-) anions have been calculated at the MP2/def2-TZVPP level of theory, and their local minima have been shown to be of C2 symmetry in all cases. The bonding situation varies significantly between the different anions. While in [B2F7](-) the bonding is mainly governed by electrostatics, the charge is almost equally distributed over all atoms in [B2I7](-) and additional weak iodine···iodine interactions are observed. This was shown by an atoms in molecules (AIM) analysis. The thermodynamic stability of the [B2X7](-) anions was estimated in all phases (gas, solution, and solid state) based on quantum-chemical calculations and estimations of the lattice enthalpies using a volume-based approach. In the gas phase the formation of [B2X7](-) anions from [BX4](-) and BX3 is favored in accord with the high Lewis acidity of the BX3 molecules. In solution and in the solid state only [B2F7](-) is stable against dissociation. The other three anions are borderline cases, which might be detectable under favorable conditions. However, experimental attempts to identify [B2X7](-) (X = Cl, Br, I) anions in solution by (11)B NMR spectroscopy and to prepare stable [PNP][B2X7] salts failed.

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.