Therapeutic potential of a pyridoxal-based vanadium(IV) complex showing selective cytotoxicity for cancer versus healthy cells

Medicinal applications of vanadium complexes with Schiff bases

Many transition metal complexes have been explored for their therapeutic properties after the discovery of cisplatin. Schiff bases have an efficient complexation tendency with the transition metals and several medicinal properties have been reported. However, fewer studies have reported the medicinal utility of vanadium and its Schiff base complexes. This paper provides a comprehensive overview of vanadium complexes with Schiff bases along with their mechanistic insight. Vanadium complexes in + 4 and + 5 oxidation states have exhibited well-defined geometry and found to be thermodynamically stable. The studies have reported the G0/G1 phase cell cycle arrest and decreased delta psi m, inducing mitochondrial membrane depolarization in cancer cell lines along with the alterations in the metabolism of the cancer cells upon dosing with the vanadium complexes. Cancer cell invasion and growth are also found to be markedly reduced by peroxo complexes of vanadium. The studies included in the review paper have been taken from leading indexing databases and focus was laid on recent reports in literature. The biological potential of vanadium complexes of Schiff bases opens new horizons for future interdisciplinary studies and investigation focussed on understanding the biochemistry of these complexes, along with designing new complexes which have better bioavailability, solubility and low or non-toxicity.

Interaction with bioligands and in vitro cytotoxicity of a new dinuclear dioxido vanadium(V) complex

One centrosymmetric bis(μ-oxido)-bridged vanadium(V) dimer with molecular formula [(V^VO₂)₂(pedf)₂] (1) has been synthesized from the reaction of VOSO₄·5H₂O with a Schiff base ligand (abbreviated with pedf^-) obtained from 2-acetylpyridine and 2-furoic hydrazide in methanol. Complex 1 was characterized by elemental analysis, UV-visible (UV-Vis), Fourier-transform infrared spectra (FT-IR), cyclic voltammetry (CV), electron paramagnetic resonance spectroscopy (EPR) and electrospray ionization-mass spectrometry (ESI-MS) techniques along with single crystal X-ray diffraction (SCXRD). The FT-IR spectral data of 1 indicated the involvement of oxygen and azomethine nitrogen in coordination to the central metal ion. The crystallographic studies revealed a dinuclear oxovanadium(V) complex with the Schiff base coordinated via the ONN donor set with formation of two five-membered chelate rings resulting in a distorted octahedral geometry. The interaction of 1 with calf thymus DNA (CT-DNA) was investigated by spectroscopic measurements and results suggested that the complex binds to CT-DNA via moderate intercalative mode with a binding constant (K_b) around 10³ M^-1. In addition, the in vitro protein binding behavior was studied by fluorescence spectrophotometric method using both bovine serum albumin (BSA) and human serum albumin (HSA) and a static quenching mechanism was observed for the interaction of the complex with both albumins that occurs with a K_b in the range (5-6) × 10³ M^-1. In vitro cytotoxicity of complex 1 on lung cancer cells (A549) and human skin carcinoma cell line (A431) demonstrated that the complex had a broad-spectrum of anti-proliferative activity with IC₅₀ value of 64.2 μM and 56.2 μM.

Relationship between structure and cytotoxicity of vanadium and molybdenum complexes with pyridoxal derived ligands

In this work four vanadium complexes (compounds 1, 2, 3 and 4) and one molybdenum complex (compound 5) with hydrazone ligands derived from pyridoxal were synthesized and characterized. All compounds are mononuclear species, two of them (compounds 3 and 5) are dioxide complexes and the other three (compounds 1, 2 and 4) monoxide complexes. The vanadium atom of the compound 3 is five-coordinated and all the other compounds have a six coordinated environment polyhedron. The poses for the potential intercalation of the compounds 2 and 3 with DNA were obtained by using AutoDock software. Optimizations were also performed at PM6-D3H4 semi-empirical level whereas the study of the nature of the interaction was carried out by means of the Energy Decomposition Analysis and the Non-Covalent Interaction index by using in both cases Density Functional Theory computations. The cytotoxicity in lung cancer cells (A549 cell line) of all the compounds was also evaluated. After 24 h of treatment, vanadium complexes showed high values of IC₅₀, between 419.93 ± 22.58 and 685.88 ± 46.55 μM. After 48 h, the results showed that the compound 3 had the lowest IC₅₀ value, 65.32 ± 9.95 μM, and the compound 2 the highest value, 375.28 ± 32.09 μM. The molybdenum complex showed the lowest IC₅₀ value at 48 h (11.22 ± 1.34 μM). The toxicity of the compounds 3, 4 and 5 was tested in vivo, using zebrafish model, and the molybdenum complex showed higher toxic effects than the studied vanadium complexes.

Decavanadate and metformin-decavanadate effects in human melanoma cells

Decavanadate is a polyoxometalate (POMs) that has shown extensive biological activities, including antidiabetic and anticancer activity. Importantly, vanadium-based compounds as well as antidiabetic biguanide drugs, such as metformin, have shown to exert therapeutic effects in melanoma. A combination of these agents, the metformin-decavanadate complex, was also recognized for its antidiabetic effects and recently described as a better treatment than the monotherapy with metformin enabling lower dosage in rodent models of diabetes. Herein, we compare the effects of decavanadate and metformin-decavanadate on Ca²⁺-ATPase activity in sarcoplasmic reticulum vesicles from rabbit skeletal muscles and on cell signaling events and viability in human melanoma cells. We show that unlike the decavanadate-mediated non-competitive mechanism, metformin-decavanadate inhibits Ca²⁺-ATPase by a mixed-type competitive-non-competitive inhibition with an IC₅₀ value about 6 times higher (87 μM) than the previously described for decavanadate (15 μM). We also found that both decavanadate and metformin-decavanadate exert antiproliferative effects on melanoma cells at 10 times lower concentrations than monomeric vanadate. Western blot analysis revealed that both, decavanadate and metformin-decavanadate increased phosphorylation of extracellular signal-regulated kinase (ERK) and serine/threonine protein kinase AKT signaling proteins upon 24 h drug exposure, suggesting that the anti-proliferative activities of these compounds act independent of growth-factor signaling pathways.

Glassy-like Metal Oxide Particles Embedded on Micrometer Thicker Alginate Films as Promising Wound Healing Nanomaterials

Micrometer-thicker, biologically responsive nanocomposite films were prepared starting from alginate-metal alkoxide colloidal solution followed by sol-gel chemistry and solvent removal through evaporation-induced assembly. The disclosed approach is straightforward and highly versatile, allowing the entrapment and growth of a set of glassy-like metal oxide within the network of alginate and their shaping as crake-free transparent and flexible films. Immersing these films in aqueous medium triggers alginate solubilization, and affords water-soluble metal oxides wrapped in a biocompatible carbohydrate framework. Biological activity of the nano-composites films was also studied including their hemolytic activity, methemoglobin, prothrombin, and thrombine time. The effect of the films on fibroblasts and keratinocytes of human skin was also investigated with a special emphasis on the role played by the incorporated metal oxide. This comparative study sheds light on the crucial biological response of the ceramic phase embedded inside of the films, with titanium dioxide being the most promising for wound healing purposes.

Copper(II) and oxidovanadium(IV) complexes of chromone Schiff bases as potential anticancer agents

We report the synthesis, characterization and biological screening of new chromone Schiff bases derived from the condensation of three 6-substituted-3-formyl-chromones with pyridoxal (HL^1-3) and its Cu(II) complexes [Cu(L^1-3)Cl], 1-3. For the 6-methyl derivative, HL², the V^IVO-complex [VO(L²)Cl] (5), as well as ternary Cu and V^IVO complexes with 1,10-phenanthroline (phen), [Cu(L²)(phen)Cl] (4) and [VO(L²)(phen)Cl] (6), were also prepared and evaluated. Their stability in aqueous medium and radical scavenging activity toward DPPH are screened, with [Cu(L²)(phen)Cl] (4) showing hydrolytic stability and [VO(L²)(phen)Cl] (6) high radical scavenging activity. Spectroscopic studies establish bovine serum albumin (BSA), a model for HSA, as a potential reversible carrier of [Cu(L²)(phen)Cl] in blood with K_BC ≈ 10⁵ M^-1. The cytotoxic activity of a group of compounds is evaluated against a panel of human cancer cell lines of different origin (ovary, cervix, brain and breast) and compared to normal cells. Our results indicate that Cu complexes are more cytotoxic than the ligands but not selective towards cancer cells. The most potent complexes (4 and 6) are further evaluated for their apoptotic potential, induction of reactive oxygen species (ROS) and genotoxicity. Both complexes efficiently triggered cell death through apoptosis as evaluated by DNA morphology and TUNEL assay, increased ROS formation as determined by DCFDA (2',7'-dichlorodihydrofluorescein diacetate) analysis, and induced genotoxic damage as visualized via COMET assay in all cancer cells under study. Therefore, 4 and 6 may be potential precursor anticancer molecules, yet they need to be targeted toward cancer cells.

Recent reports on Pyridoxal derived Schiff base complexes

Pyridoxal and Pyridoxal 5-phosphate are two among the six aqua soluble vitamers of vitamin B6. They can form Schiff bases readily due to the presence of aldehyde group. Schiff bases can offer diverse coordination possibilities for many transition metals as has been found in a large volume of research till now. The coordination complexes thus formed gives insight into the active core structure and enzymatic activities of vit B6 containing enzymes. Apart from that, these complexes have been found useful as catalysts for synthesis of fine chemicals, as sensors and for their diverse biological activities.

A Dual Role of Vanadium in Environmental Systems-Beneficial and Detrimental Effects on Terrestrial Plants and Humans

The importance of vanadium (V) in the functioning of land systems is extremely diverse, as this element may exert both positive and harmful effects on terrestrial organisms. It recently become considered an element of beneficial character with a range of applications for human welfare. The health-ameliorative properties of this transition element depend on its degree of oxidation and on optimal concentration in the target cells. It was found that a similar relationship applies to vascular plants. However, excessive amounts of vanadium in the environment contaminate the soil and negatively affect the majority of living organisms. A significantly elevated level of V results in the destabilization of plant physiological balance, slowing down the growth of biomass which significantly reduces yield. In turn, low doses of the appropriate vanadium ions can stimulate plant growth and development, exert cytoprotective effects, and effectively enhance the synthesis of some biologically active compounds. We present the scientific achievements of research teams dealing with such topics. The issues discussed concern the role of vanadium in the environment, particular organisms, and highlight its dualistic influence on plants. Achievements in the field of V bioremediation, with the use of appropriately selected microorganisms and plant species, are emphasized.

Vanadium and Melanoma: A Systematic Review

The application of metals in biological systems has been a rapidly growing branch of science. Vanadium has been investigated and reported as an anticancer agent. Melanoma is the most aggressive type of skin cancer, the incidence of which has been increasing annually worldwide. It is of paramount importance to identify novel pharmacological agents for melanoma treatment. Herein, a systematic review of publications including “Melanoma and Vanadium” was performed. Nine vanadium articles in several melanoma cells lines such as human A375, human CN-mel and murine B16F10, as well as in vivo studies, are described. Vanadium-based compounds with anticancer activity against melanoma include: (1) oxidovanadium(IV); (2) XMenes; (3) vanadium pentoxide, (4) oxidovanadium(IV) pyridinonate compounds; (5) vanadate; (6) polysaccharides vanadium(IV/V) complexes; (7) mixed-metal binuclear ruthenium(II)–vanadium(IV) complexes; (8) pyridoxal-based oxidovanadium(IV) complexes and (9) functionalized nanoparticles of yttrium vanadate doped with europium. Vanadium compounds and/or vanadium materials show potential anticancer activities that may be used as a useful approach to treat melanoma.

Misinterpretations in Evaluating Interactions of Vanadium Complexes with Proteins and Other Biological Targets

In aqueous media, VIV- and VV-ions and compounds undergo chemical changes such as hydrolysis, ligand exchange and redox reactions that depend on pH and concentration of the vanadium species, and on the nature of the several components present. In particular, the behaviour of vanadium compounds in biological fluids depends on their environment and on concentration of the many potential ligands present. However, when reporting the biological action of a particular complex, often the possibility of chemical changes occurring has been neglected, and the modifications of the complex added are not taken into account. In this work, we highlight that as soon as most vanadium(IV) and vanadium(V) compounds are dissolved in a biological media, they undergo several types of chemical transformations, and these changes are particularly extensive at the low concentrations normally used in biological experiments. We also emphasize that in case of a biochemical interaction or effect, to determine binding constants or the active species and/or propose mechanisms of action, it is essential to evaluate its speciation in the media where it is acting. This is because the vanadium complex no longer exists in its initial form.

Biological activity of bis(pyrazolylpyridine) and terpiridine Os(ii) complexes in the presence of biocompatible ionic liquids

New bis(pyrazolylpyridine) Os(ii) complexes showing possible biological activity with diverse modes of action in the presence of biocompatible ionic liquids as non-toxic cosolvents for sparingly soluble complexes.

Antiproliferative activity of vanadium compounds: effects on the major malignant melanoma molecular pathways

Malignant melanoma (MM) is the most fatal skin cancer, whose incidence has critically increased in the last decades. Recent molecular therapies are giving excellent results in the remission of melanoma but often they induce drug resistance in patients limiting their therapeutic efficacy. The search for new compounds able to overcome drug resistance is therefore essential. Vanadium has recently been cited for its anticancer properties against several tumors, but only a few data regard its effect against MM. In a previous work we demonstrated the anticancer activity of four different vanadium species towards MM cell lines. The inorganic anion vanadate(v) (VN) and the oxidovanadium(iv) complex [VO(dhp)2] (VS2), where dhp is 1,2-dimethyl-3-hydroxy-4(1H)-pyridinonate, showed IC50 values of 4.7 and 2.6 μM, respectively, against the A375 MM cell line, causing apoptosis and cell cycle arrest. Here we demonstrate the involvement of Reactive Oxygen Species (ROS) production in the pro-apoptotic effect of these two V species and evaluate the activation of different cell cycle regulators, to investigate the molecular mechanisms involved in their antitumor activity. We establish that VN and VS2 treatments reduce the phosphorylation of extracellular-signal regulated kinase (ERK) by about 80%, causing the deactivation of the mitogen activated protein kinase (MAPK) pathway in A375 cells. VN and VS2 also induce dephosphorylation of the retinoblastoma protein (Rb) (VN 100% and VS2 90%), together with a pronounced increase of cyclin-dependent kinase inhibitor 1 p21 (p21Cip1) protein expression up to 1800%. Taken together, our results confirm the antitumor properties of vanadium against melanoma cells, highlighting its ability to induce apoptosis through generation of ROS and cell cycle arrest by counteracting MAPK pathway activation and strongly inducing p21Cip1 expression and Rb hypo-phosphorylation.

Fast, Facile and Solvent-Free Dry-Melt Synthesis of Oxovanadium(IV) Complexes: Simple Design with High Potency towards Cancerous Cells

A range of oxobis(phenyl-1,3-butanedione) vanadium(IV) complexes have been successfully synthesized from cheap starting materials and a simple and solvent-free one-pot dry-melt reaction. This direct, straightforward, fast and alternative approach to inorganic synthesis has the potential for a wide range of applications. Analytical studies confirm their successful synthesis, purity and solid-state coordination, and we report the use of such complexes as potential drug candidates for the treatment of cancer. After a 24 hour incubation of A549 lung carcinoma cells with the compounds, they reveal cytotoxicity values elevenfold greater than cisplatin and remain non-toxic towards normal cell types. Additionally, the complexes are stable over a range of physiological pH values and show the potential for interactions with bovine serum albumin.

Vanadium Compounds as Enzyme Inhibitors with a Focus on Anticancer Effects

Vanadium salts and coordination compounds have desirable cellular anticancer effects, and although they have been investigated in detail as a potential treatment for diabetes, less attention has been given to the anticancer effects. The inhibition of some signal transduction enzymes is known, and studies of the metabolism and activation pathways both in vitro and in vivo are important for future investigations and development of vanadium's role as a new potential drug. In addition, a new approach has demonstrated that the enhancement of oncolytic viruses using vanadium salts and coordination complexes for immunotherapy is very promising. Some differences exist between this approach and current antidiabetic and anticancer studies because vanadium(iv) complexes have been found to be most potent in the latter approach, but the few compounds investigated with oncolytic viruses show that vanadium(v) systems are more effective. We conclude that recent studies demonstrate effects on signal transduction enzymes and anticancer pathways, thus suggesting potential applications of vanadium as anticancer agents in the future both as standalone treatments as well as combination therapies.

New Oxidovanadium(IV) Coordination Complex Containing 2-Methylnitrilotriacetate Ligands Induces Cell Cycle Arrest and Autophagy in Human Pancreatic Ductal Adenocarcinoma Cell Lines

Pancreatic cancer is characterized by one of the lowest five-year survival rates. In search for new treatments, some studies explored several metal complexes as potential anticancer drugs. Therefore, we investigated three newly synthesized oxidovanadium(IV) complexes with 2-methylnitrilotriacetate (bcma3-), N-(2-carbamoylethyl)iminodiacetate (ceida3-) and N-(phosphonomethyl)-iminodiacetate (pmida4-) ligands as potential anticancer compounds using pancreatic cancer cell lines. We measured: Cytotoxicity using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), neutral red (NR) and lactate dehydrogenase (LDH) assay; antiproliferative activity by bromodeoxyuridine BrdU assay; reactive oxygen species (ROS) generation and cell cycle analysis by flow cytometry; protein level by Western blot and cellular morphology by confocal laser scanning microscopy. The results showed that these oxidovanadium(IV) complexes were cytotoxic on pancreatic cancer cells (PANC-1 and MIA PaCa2), but not on non-tumor human immortalized pancreas duct epithelial cells (hTERT-HPNE) over the concentration range of 10⁻25 μM, following 48 h incubation. Furthermore, molecular mechanisms of cytotoxicity of [4-NH₂-2-Me(Q)H][VO(bcma)(H₂O)]2H₂O (T1) were dependent on antiproliterative activity, increased ROS generation, cell cycle arrest in G2/M phase with simultaneous triggering of the p53/p21 pathway, binucleation, and induction of autophagy. Our study indicates that oxidovanadium(IV) coordination complexes containing 2-methylnitrilotriacetate ligand are good candidates for preclinical development of novel anticancer drugs targeting pancreatic cancer.

Synthesis, in vitro cytotoxicity, and structure-activity relationships (SAR) of multidentate oxidovanadium(iv) complexes as anticancer agents

Multidentate oxidovanadium(iv) complexes with different geometric configurations [VO(ox)(bpy)(H2O)] 1, [VO(ox)(phen)(H2O)] 2, [VO(ida)(bpy)]·2H2O 3, (phen)[VO(ida)(phen)]·4H2O 4, and (Hphen)[VO(H2O)(nta)]·2H2O 5 [ox = oxalic acid, bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline, ida = iminodiacetic acid, nta = nitrilotriacetic acid] have been obtained from the reactions of oxidovanadium sulfate or vanadium pentoxide with oxalates, amino-polycarboxylates and N-heterocyclic ligands in neutral solution by the hydrothermal method, and have been fully characterized by elemental, thermogravimetric analyses and single crystal X-ray diffraction, as well as a wide range of spectroscopic techniques such as FT-IR, UV/Vis, NMR, ESI-MS. The anti-tumor properties of oxidovanadium compounds 1-5 were further evaluated in human HepG2 and SMMC-7721 hepatocellular carcinoma cell lines in vitro. The profiles of cytotoxicity, cell cycle distribution, as well as cell apoptosis upon test compound exposure, were determined by MTT and flow cytometry assays. Compound 2 exhibited a much higher anti-tumor activity than others. The IC50 values of 2 were 5.34 ± 0.034 μM and 29.07 ± 0.017 μM in SMMC-7721 and HepG2 cells after 48 h treatment, respectively. Furthermore, compound 2 could significantly arrest the cell cycle in the S and G2/M phases and further induce cell apoptosis in a dose-dependent manner. The structure-activity relationship (SAR) studies revealed that structural elements, for example, metal components, variations of coordination mode, labile water molecules, chelated ligands etc., probably exert an essential cooperative effect on the antitumor activity. In short, these findings not only provide an accessible model system to exploit V-based complexes as potential simple, safe and effective multifunctional antitumor agents, but also open up a rational approach to shed new light on the selection and optimization of ideal drug candidates.

Vanadium Compounds as PTP Inhibitors

Phosphotyrosine signaling is regulated by the opposing actions of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). Here we discuss the potential of vanadium derivatives as PTP enzyme inhibitors and metallotherapeutics. We describe how vanadate in the V oxidized state is thought to inhibit PTPs, thus acting as a pan-inhibitor of this enzyme superfamily. We discuss recent developments in the biological and biochemical actions of more complex vanadium derivatives, including decavanadate and in particular the growing number of oxidovanadium compounds with organic ligands. Pre-clinical studies involving these compounds are discussed in the anti-diabetic and anti-cancer contexts. Although in many cases PTP inhibition has been implicated, it is also clear that many such compounds have further biochemical effects in cells. There also remain concerns surrounding off-target toxicities and long-term use of vanadium compounds in vivo in humans, hindering their progress through clinical trials. Despite these current misgivings, interest in these chemicals continues and many believe they could still have therapeutic potential. If so, we argue that this field would benefit from greater focus on improving the delivery and tissue targeting of vanadium compounds in order to minimize off-target toxicities. This may then harness their full therapeutic potential.

Syntheses, crystal structures, DFT calculations, protein interaction and anticancer activities of water soluble dipicolinic acid-imidazole based oxidovanadium(iv) complexes

Three novel water soluble neutral mononuclear oxidovanadium(iv) complexes 1-3, [VOLB₂] (where H₂L = dipicolinic acid (DPA) and B = imidazole (1)/1-methylimidazole (2)/1-allylimidazole (3)), were synthesized by the reaction of [VOL(H₂O)₂] with imidazole/1-methylimidazole/1-allylimidazole in ethanol. The complexes were thoroughly characterized by elemental analysis, IR, UV-Vis and EPR spectroscopy, magnetic susceptibility, cyclic voltammetry and single crystal X-ray diffraction techniques. In all the complexes the vanadium(iv) centre assumes a distorted octahedral environment. All the three complexes have similar structures and contain a range of intramolecular interactions such as hydrogen bonding, C-Hπ, and ππ stacking dominating their supramolecular architectures. A thermal study of the complexes was carried out to analyze their stability. The energy of non-covalent interactions and frontier orbitals for the complexes were also calculated by DFT. In order to investigate the binding interactions and conformational changes of the secondary structure of bovine serum albumin (BSA) with the complexes, absorption, fluorimetric titration and circular dichroism measurements in aqueous medium were carried out. Molecular docking studies have also been carried out to understand the binding modes and interaction patterns of the oxidovanadium(iv) complexes with BSA. The anticancer activities of the ligand and complexes 1-3 were tested against the human hepatic carcinoma cell line Hep3B. The complexes showed prominent cytotoxicity towards cancer cells.

Selective cytotoxicity of vanadium complexes on human pancreatic ductal adenocarcinoma cell line by inducing necroptosis, apoptosis and mitotic catastrophe process

The pancreatic cancer is the fourth leading cause of cancer-related death and characterized by one of the lowest five-year survival rate. The current therapeutic options are demonstrating minimal effectiveness, therefore studies on new potential anticancer compounds, with non-significant side effects are highly desirable. Recently, it was demonstrated that vanadium compounds, in particular organic derivatives, exhibit anticancer properties against different type of tumor as well as favorable biodistribution from a pancreatic cancer treatment perspective. In this research, we showed selective cytotoxic effect of vanadium complexes, containing phenanthroline and quinoline as an organic ligands, against human pancreatic ductal adenocarcinoma cell line (PANC-1), compared to non-tumor human immortalized pancreas duct epithelial cells (hTERT-HPNE). Results exhibited that vanadium complexes inhibited autophagy process in selective cytotoxic concentration as well as caused the cell cycle arrest in G2/M phase associated with mitotic catastrophe and increased level of reactive oxygen species (ROS). Moreover, in higher concentration, vanadium derivatives induced a mix type of cell death in PANC-1 cells, including apoptotic and necroptotic process. Our investigation emphasizes the anticancer potential of vanadium complexes by indicating their selective cytotoxic activity, through different process posed by alternative type of cell deaths to apoptosis-resistant cancer cells. Further studies supporting the therapeutic potential of vanadium in pancreatic cancer treatment is highly recommended.

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.

Antitumoral effect of vanadium compounds in malignant melanoma cell lines

In this study we evaluated the anticancer activity against malignant melanoma (MM) of four different vanadium species: the inorganic anion vanadate(V) (indicated with VN), and three oxidovanadium(IV) complexes, [V^IVO(dhp)₂] where dhp^- is the anion 1,2-dimethyl-3-hydroxy-4(1H)-pyridinonate (indicated with VS2), [V^IVO(mpp)₂] where mpp^- is 1-methyl-3-hydroxy-4(1H)-pyridinonate (indicated with VS3), and [V^IVO(ppp)₂] where ppp^- is 1-phenyl-2-methyl-3-hydroxy-4(1H)-pyridinonate (indicated with VS4). The antitumor effects of these compounds were studied against two different MM cell lines (A375 and CN-mel) and a fibroblast cell line (BJ) as normal control. All tested V compounds exert antiproliferative activity on MM cells in a dose dependent manner (IC₅₀ ranges from 2.4μM up to 14μM) being A375 the most sensitive cell line. VN and VS2 were the two most active compounds against A375 (IC₅₀ of 4.7 and 2.6μM, respectively), causing apoptosis and cell cycle block. The experimental data indicate that the cell cycle arrest occurs at different phases for the two V species analyzed (G2 checkpoint for VN and G0/G1 for VS2), showing the importance of the chemical form in determining their mechanism of action. These results add more insights into the landscape of vanadium versatility in biological systems and into its role as a potential cancer therapeutic agent.

Binding of an organo-osmium(II) anticancer complex to guanine and cytosine on DNA revealed by electron-based dissociations in high resolution Top-Down FT-ICR mass spectrometry

The Os(II) arene anticancer complex [(η(6)-bip)Os(en)Cl](+) (Os1-Cl; where bip = biphenyl, and en = ethylenediamine) binds strongly to DNA. Here we investigate reactions between Os1-Cl and the self-complementary 12-mer oligonucleotide 5'-TAGTAATTACTA-3' (DNA12) using ultra high resolution Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS). Identification of the specific sites of DNA osmiation with {(η(6)-bip)Os(en)}(2+) was made possible by the use of Electron Detachment Dissociation (EDD) which produced a wide range of assignable osmiated MS/MS fragments. In contrast, the more commonly used CAD and IRMPD techniques produced fragments which lose the bound osmium. These studies reveal that not only is guanine G3 a strong binding site for {(η(6)-bip)Os(en)}(2+) but, unexpectedly, so too is cytosine C10. Interestingly, the G3/C10 di-osmiated adduct of DNA12 also formed readily but did not undergo such facile fragmentation by EDD, perhaps due to folding induced by van der Waal's interactions of the bound osmium arene species. These new insights into osmium arene DNA adducts should prove valuable for the design of new organometallic drugs and contribute to understanding the lack of cross resistance of this organometallic anticancer complex with cisplatin.

Antiproliferative and apoptosis-inducing activity of an oxidovanadium(IV) complex with the flavonoid silibinin against osteosarcoma cells

Flavonoids are a large family of polyphenolic compounds synthesized by plants. They display interesting biological effects mainly related to their antioxidant properties. On the other hand, vanadium compounds also exhibit different biological and pharmacological effects in cell culture and in animal models. Since coordination of ligands to metals can improve or change the pharmacological properties, we report herein, for the first time, a detailed study of the mechanisms of action of an oxidovanadium(IV) complex with the flavonoid silibinin, Na2[VO(silibinin)2]·6H2O (VOsil), in a model of the human osteosarcoma derived cell line MG-63. The complex inhibited the viability of osteosarcoma cells in a dose-dependent manner with a greater potency than that of silibinin and oxidovanadium(IV) (p < 0.01), demonstrating the benefit of complexation. Cytotoxicity and genotoxicity studies also showed a concentration effect for VOsil. The increase in the levels of reactive oxygen species and the decrease of the ratio of the amount of reduced glutathione to the amount of oxidized glutathione were involved in the deleterious effects of the complex. Besides, the complex caused cell cycle arrest and activated caspase 3, triggering apoptosis as determined by flow cytometry. As a whole, these results show the main mechanisms of the deleterious effects of VOsil in the osteosarcoma cell line, demonstrating that this complex is a promising compound for cancer treatments.

Laser-induced drug release for local tumor control--a proof of concept

BACKGROUND

The systemic palliative chemotherapy of locally extended gastrointestinal and hepatobiliary tumors is associated with a considerable burden for the patient. The aim of this project was to develop a new drug release system to improve the local stent therapy in these patients as a proof of concept study. For this purpose, polymer filaments were modified with drug-loaded polymer microgels that allow selective release of the active substance by photochemical triggering using laser radiation. Integrated into a stent system, the better local tumor control could thus contribute to a significant increase in the quality of life of patients.

METHODS

A standard mammalian cell line and two carcinoma cell lines were established. By Fluorescence activated cell sorting (FACS), the cytotoxicity of the different materials was determined in vitro before and after drug loading with the chemotherapeutic agent 5-Fluorouracil (5-FU). For this purpose, the locally applied 5-FU concentration was previously determined by Bromdesoxyuridin assay. 5-FU dimer was synthesized by photo-induced dimerization of 5-FU in the presence of benzophenone in methanol. The chemical structure of 5-FU dimer was confirmed with Hydrogen-1 nuclear magnetic resonance and Fluorine-19 nuclear magnetic resonance. 5-FU dimer is nonsoluble in water and can be easily incorporated in polymer microgels modified with hydrophobic binding domains (cyclodextrin). After laser irradiation, 5-FU dimer decomposes and 5-FU can be released from microgels. Finally, the measurements were repeated after this laser-induced drug release.

RESULTS

In FACS analysis, neither the microgels nor the microgel cumarin complexes showed a significant difference in comparison with the negative control with H2O and therefore no toxic effect on the cell lines. After loading with the 5-FU dimer, there was no significant cell death (contrary to the pure 5-FU monomer, which dose had been previously tested as highly toxic). After laser-induced dissociation back to monomer and the associated drug release, FACS analysis showed cytotoxicity.

CONCLUSIONS

It was possible to develop 5-FU dimerloaded microgels, which show no cytotoxic effect on cell lines before laser irradiation. After dissociation back to 5-FU monomer by selective photochemical triggering using laser irradiation, the active substance was released. Thus, a new drug release system has been created and tested in vitro. For further development, integration into a stent system and for in vivo follow-up evaluation more studies need to be conducted.