Bioinorganic chemistry of vanadocene dichloride

Cyclopentadienyl Molybdenum(II) Compounds Bearing Ether and Thioether Functions in the Side Chain: Synthesis, Characterization, and Cytotoxic/Cytostatic Studies

A series of molybdenum(II) compounds [(η5 -Cp')Mo(CO)2 (L2 )][BF4 ] (Cp'=C5 H4 (CH2 )2 SPh, C9 H6 (CH2 )2 OMe, L2= N,N-chelating ligand) have been synthesized and characterized by spectroscopic and analytical methods including X-ray crystallography. The in vitro assay on human leukemia cells MOLT-4 has shown that the substitution in the π-ligand in combination with suitable N,N-chelating ligand can lead to species with cytotoxicity considerably higher than reported to cisplatin. Unusually high activity was observed for compounds bearing phenanthroline ligands [{η5 -C9 H6 (CH2 )2 OMe}Mo(CO)2 (3,4,7,8-Me4 phen)][BF4 ] (IC50 =0.7±0.3 μM) and [{η5 -C9 H6 (CH2 )2 OMe}Mo(CO)2 (4,7-Ph2 phen)][BF4 ] (IC50 values 0.8±0.4 μM).

In Vitro and In Vivo Biological Activities of Dipicolinate Oxovanadium(IV) Complexes

The work is focused on anticancer properties of dipicolinate (dipic)-based vanadium(IV) complexes [VO(dipic)(N^∩N)] bearing different diimines (2-(1H-imidazol-2-yl)pyridine, 2-(2-pyridyl)benzimidazole, 1,10-phenanthroline-5,6-dione, 1,10-phenanthroline, and 2,2'-bipyridine), as well as differently 4,7-substituted 1,10-phenanthrolines. The antiproliferative effect of V(IV) systems was analyzed in different tumors (A2780, HCT116, and HCT116-DoxR) and normal (primary human dermal fibroblasts) cell lines, revealing a high cytotoxic effect of [VO(dipic)(N^∩N)] with 4,7-dimethoxy-phen (5), 4,7-diphenyl-phen (6), and 1,10-phenanthroline (8) against HCT116-DoxR cells. The cytotoxicity differences between these complexes can be correlated with their different internalization by HCT116-DoxR cells. Worthy of note, these three complexes were found to (i) induce cell death through apoptosis and autophagy pathways, namely, through ROS production; (ii) not to be cytostatic; (iii) to interact with the BSA protein; (iv) do not promote tumor cell migration or a pro-angiogenic capability; (v) show a slight in vivo anti-angiogenic capability, and (vi) do not show in vivo toxicity in a chicken embryo.

Therapeutic potential of vanadium complexes with 1,10-phenanthroline ligands, quo vadis? Fate of complexes in cell media and cancer cells

V^IVO-complexes formulated as [V^IVO(OSO₃)(phen)₂] (1) (phen = 1,10-phenanthroline), [V^IVO(OSO₃)(Me₂phen)₂] (2) (Me₂phen = 4,7-dimethyl-1,10-phenanthroline) and [V^IVO(OSO₃)(amphen)₂] (3) (amphen = 5-amino-1,10-phenanthroline) were prepared and stability in cell incubation media evaluated. Their cytotoxicity was determined against the A2780 (ovarian), MCF7 (breast) and PC3 (prostate) human cancer cells at different incubation times. While at 3 and 24 h the cytotoxicity differs for complexes and corresponding free ligands, at 72 h incubation all compounds are equally active presenting low IC₅₀ values. Upon incubation of A2780 cells with 1-3, cellular distribution of vanadium in cytosol, membranes, nucleus and cytoskeleton, indicate that the uptake of V is low, particularly for 1, and that the uptake pattern depends on the ligand. Nuclear microscopic techniques are used for imaging and elemental quantification in whole PC3 cells incubated with 1. Once complexes are added to cell culture media, they decompose, and with time most V^IV oxidizes to V^V-species. Modeling of speciation when [V^IVO(OSO₃)(phen)₂] (1) is added to cell media is presented. At lower concentrations of 1, V^IVO- and phen-containing species are mainly bound to bovine serum albumin, while at higher concentrations [V^IVO(phen)_n]²⁺-complexes become relevant, being predicted that the species taken up and mechanisms of action operating depend on the total concentration of complex. This study emphasizes that for these V^IVO-systems, and probably for many others involving oxidovanadium or other labile metal complexes, it is not possible to identify active species or propose mechanisms of cytotoxic action without evaluating speciation occurring in cell media.

Heterobimetallic platinum(ii) complexes with increased cytotoxicity against ovarian cancer cell lines

Two series of heterobimetallic compounds were prepared from the starting complex [cis-L2PtCl2] containing an aminophosphine ligand (L = 2,6-iPr2-C6H3-NHPPh2).

Vanadocene complexes bearing N,N'-chelating ligands: Synthesis, structures and in vitro cytotoxic studies on the A549 lung adenocarcinoma cell line

Ten new vanadocene complexes bearing N,N'-chelating ligands were prepared, characterized, and their cytotoxicity toward a panel of cancer cells was measured. Structures of four vanadocene compounds were determined by single crystal X-ray diffraction analysis. Complexes containing 1,2-bis(phenylimino)acenaphthene (bian) and 1,2-bis(4-methoxyphenylimino)acenaphthene (4-MeO-bian) exhibit higher cytotoxicity than those with dipyrido[3,2-a:2',3'-c]phenazine (dppz) and (E)-N-((pyridin-2-yl)methylene)benzenamine (pyma). In light of the finding, cytotoxic mechanisms of two highly effective complexes [(η⁵-C₅H₄Me)₂V(bian)][OTf]₂ (3b) and [(η⁵-C₅H₄Me)₂V(4-MeO-bian)][OTf]₂ (4b) against human A549 lung adenocarcinoma cells were investigated by following membrane leakage of intracellular lactate dehydrogenase, Trypan Blue staining and activation of tumor protein p53 (p53). Evaluated complexes have a potent dose-dependent antiproliferative activity, causing cell cycle redistribution by the increased accumulation of cells in the G2 and S phase. In accord with the observed cell cycle deceleration, cyclin-dependent kinase inhibitor-interacting protein 1 (p21^WAF1/Cip1), extracellular signal-regulated kinases 1 and 2 (ERK1/2), Checkpoint kinase 1 (Chk1), Checkpoint kinase 2 (Chk2) and their phosphorylated forms Chk1 at serine 345 and Chk2 at threonine 68 increased. In the cells exposed to complexes, dose- and time-dependent apoptotic process is initiated by the activation of the initiator caspase 8, followed by activation of effector caspase 3/7 and phosphatidylserine externalization. Moreover, because of treatment, A549 cells activate prosurvival mitogen-activated protein kinases (MAPK) signaling and up-regulate antiapoptotic protein B-cell lymphoma (Bcl-2), thereby promoting evasion of cell death. Both complexes exhibited considerably higher cytotoxic effect than the reference anticancer drug cis-platin and the cytotoxicity was more pronounced at higher treatment time.

Vanadium: History, chemistry, interactions with α-amino acids and potential therapeutic applications

In the last 30 years, since the discovery that vanadium is a cofactor found in certain enzymes of tunicates and possibly in mammals, different vanadium-based drugs have been developed targeting to treat different pathologies. So far, the in vitro studies of the insulin mimetic, antitumor and antiparasitic activity of certain compounds of vanadium have resulted in a great boom of its inorganic and bioinorganic chemistry. Chemical speciation studies of vanadium with amino acids under controlled conditions or, even in blood plasma, are essential for the understanding of the biotransformation of e.g. vanadium antidiabetic complexes at the physiological level, providing clues of their mechanism of action. The present article carries out a bibliographical research emphaticizing the chemical speciation of the vanadium with different amino acids and reviewing also some other important aspects such as its chemistry and therapeutical applications of several vanadium complexes.

Vanadocene dichloride inhibits cell proliferation by targeting Aurora B

Vanadocene dichloride induces chromosome misalignment by inhibiting Aurora B activity.

Interaction of [VIV O(acac)2 ] with Human Serum Transferrin and Albumin

[VO(acac)₂ ] is a remarkable vanadium compound and has potential as a therapeutic drug. It is important to clarify how it is transported in blood, but the reports addressing its binding to serum proteins have been contradictory. We use several spectroscopic and mass spectrometric techniques (ESI and MALDI-TOF), small-angle X-ray scattering and size exclusion chromatography (SEC) to characterize solutions containing [VO(acac)₂ ] and either human serum apotransferrin (apoHTF) or albumin (HSA). DFT and modeling protein calculations are carried out to disclose the type of binding to apoHTF. The measured circular dichroism spectra, SEC and MALDI-TOF data clearly prove that at least two VO-acac moieties may bind to apoHTF, most probably forming [V^IV O(acac)(apoHTF)] complexes with residues of the HTF binding sites. No indication of binding of [VO(acac)₂ ] to HSA is obtained. We conclude that V^IV O-acac species may be transported in blood by transferrin. At very low complex concentrations speciation calculations suggest that [(VO)(apoHTF)] species form.

Stabilities and Biological Activities of Vanadium Drugs: What is the Nature of the Active Species?

Diverse biological activities of vanadium(V) drugs mainly arise from their abilities to inhibit phosphatase enzymes and to alter cell signaling. Initial interest focused on anti-diabetic activities but has shifted to anti-cancer and anti-parasitic drugs. V-based anti-diabetics are pro-drugs that release active components (e.g., H₂ VO₄^- ) in biological media. By contrast, V anti-cancer drugs are generally assumed to enter cells intact; however, speciation studies indicate that nearly all drugs are likely to react in cell culture media during in vitro assays and the same would apply in vivo. The biological activities are due to V^V and/or V^IV reaction products with cell culture media, or the release of ligands (e.g., aromatic diimines, 8-hydroxyquinolines or thiosemicarbazones) that bind to essential metal ions in the media. Careful consideration of the stability and speciation of V complexes in cell culture media and in biological fluids is essential to design targeted V-based anti-cancer therapies.