Metallocompounds as anticancer agents against osteosarcoma

Metallocompounds are a class of anticancer compounds largely used in the treatment of several types of solid tumors, including bone cancer. Osteosarcoma (OS) is a primary malignant bone tumor that frequently affects children, adolescents and young adults. It is a very invasive type of tumor, so ∼40% of patients develop distant metastases, showing elevated mortality rates. In this review, we present an outline of the chemistry and antitumor properties of metal-based compounds in preclinical (in vitro and in vivo) and clinical OS models, focusing on the relationship between structure-activity, molecular targets and the study of the mechanism of action involved in metallocompound anticancer activity.

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.

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.

An Overview of Vanadium and Cell Signaling in Potential Cancer Treatments

Vanadium is an ultratrace element present in higher plants, animals, algae, and bacteria. In recent years, vanadium complexes have been studied to be considered as a representative of a new class of nonplatinum metal anticancer drugs. Nevertheless, the study of cell signaling pathways related to vanadium compounds has scarcely been reported on and reviewed thus far; this information is highly critical for identifying novel targets that play a key role in the anticancer activity of these compounds. Here, we perform a review of the activity of vanadium compounds over cell signaling pathways on cancer cells and of the underlying mechanisms, thereby providing insight into the role of these proteins as potential new molecular targets of vanadium complexes.

Antiproliferative activity of two copper (II) complexes on colorectal cancer cell models: Impact on ROS production, apoptosis induction and NF-κB inhibition

The main goal of this work was to screen the antiproliferative activity and mechanism of actions of two copper complexes: [Cu(dmp)₂(CH₃CN)]²⁺ (1) and [Cu(phen)₂(CH₃CN)]²⁺ (2) on 2D and 3D colorectal cancer cells models. Cell viability studies on three colorectal cancer cell lines (HT-29, LS174T, Caco-2) displayed that 1 showed more robust antiproliferative activity than 2 and cisplatin. Intracellular copper content (63.24% and 48.06% for 1 and 2, respectively) can explain the differences in the cytotoxicity assay. ROS production is the primary mechanism of action involved in the antiproliferative activity of 1 showing 4-, 70- and 2.5- fold increased values of ROS level for HT-29, LS174T, Caco-2 cancer cell lines, respectively. This effect takes place along with the depolarization of the mitochondrial membrane at 2 µM. Besides, both complexes increased apoptosis on three cancer cell lines at low micromolar concentrations (0.5-2.5 μM). Moreover, 1 and 2 inhibited NF-κB pathway both in HT-29-NF-kB-hrGFP monolayer (0.5 to 1 μM) and spheroids HT-29 GFP (5 to 10 μM). This inhibitory effect leads to an inactivation of the MMP-9 expression on HT-29 cell line. Altogether, these results showed that 1 exhibits antiproliferative activity on human colorectal cancer cells in the monolayer and the 3D model.

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.

Exploring the Potential of Metallodrugs as Chemotherapeutics for Triple Negative Breast Cancer

This review focuses on studies of coordination and organometallic compounds as potential chemotherapeutics against triple negative breast cancer (TNBC) which has one of the poorest prognoses and worst survival rates from all breast cancer types. At present, chemotherapy is still the standard of care for TNBC since only one type of targeted therapy has been recently developed. References for metal-based compounds studied in TNBC cell lines will be listed, and those of metal-specific reviews, but a detailed overview will also be provided on compounds studied in vivo (mostly in mice models) and those compounds for which some preliminary mechanistic data was obtained (in TNBC cell lines and tumors) and/or for which bioactive ligands have been used. The main goal of this review is to highlight the most promising metal-based compounds with potential as chemotherapeutic agents in TNBC.

DNA cleavage mechanism by metal complexes of Cu(II), Zn(II) and VO(IV) with a schiff-base ligand

Metal ions and metal complexes are important components of nucleic acid biochemistry, participating both in regulation of gene expression and as therapeutic agents. Three new transition metal complexes of copper(II), zinc(II) and oxidovanadium(IV) with a ligand derived from o-vanillin and thiophene were previously synthesized and their antitumor properties were studied in our laboratory. To elucidate some molecular mechanisms tending to explain the cytotoxic effects observed over tumor cells, we investigated the interaction of these complexes with DNA by gel electrophoresis, UV-Vis spectroscopy, docking studies and molecular dynamics simulations. Our spectroscopy and computational results have shown that all of them were able to bind to DNA, Cu(II) complex is located in the minor groove while Zn(II) and oxidovanadium(IV) complexes act as major groove binding molecules. Interestingly, only the Cu(II) complex caused double-strand DNA nicks, consistent with its higher cytotoxic activities previously observed in tumor cell lines. We propose that the DNA-complex interaction destabilize the molecule either disrupting the phosphodiester bonds or impairing DNA replication, giving those complexes strong antitumor potential.

Synthesis, Crystal Structure, Spectroscopic Characterization, DFT Calculations and Cytotoxicity Assays of a New Cu(II) Complex with an Acylhydrazone Ligand Derived from Thiophene

A new Cu(II) complex is synthetized by the reaction of copper nitrate and a N-acylhydrazone ligand obtained from the condensation of o-vanillin and 2-thiophecarbohydrazide (H2L). The solid-state structure of [Cu(HL)(H2O)](NO3)·H2O, or CuHL for simplicity, was determined by X-ray diffraction. In the cationic complex, the copper center is in a nearly squared planar environment with the nitrate interacting as a counterion. CuHL was characterized by spectroscopic techniques, including solid-state FTIR, Raman, electron paramagnetic resonance (EPR) and diffuse reflectance and solution UV-Vis electronic spectroscopy. Calculations based on the density functional theory (DFT) assisted the interpretation and assignment of the spectroscopic data. The complex does not show relevant antioxidant activity evaluated by the radical cation of 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) method, being even less active than the free ligand as a radical quencher. Cytotoxicity assays of CuHL against three human tumor cell lines, namely MG-63, A549 and HT-29, revealed an important enhancement of the effectiveness as compared with both the ligand and the free metal ion. Moreover, its cytotoxic effect was remarkably stronger than that of the reference metallodrug cisplatin in all cancer cell lines tested, a promissory result in the search for new metallodrugs of essential transition metals.

Anticancer activity of a new copper(II) complex with a hydrazone ligand. Structural and spectroscopic characterization, computational simulations and cell mechanistic studies on 2D and 3D breast cancer cell models

We report here the synthesis, crystal structure, characterization and anticancer activity of a copper(ii)-hydrazone complex, [Cu(MeBHoVa)(H2O)2](NO3) (for short, CuHL), against human breast cancer cells on monolayer (2D) and spheroids/mammospheres (3D). The solid-state molecular structure of the complex has been determined by X-ray diffraction methods. The conformational space was searched and geometries were optimized both in the gas phase and including solvent effects by computational methods based on DFT. The compound has been characterized in the solid state and in solution by spectroscopic (FTIR, Raman, UV-vis) methods. The results were compared with those obtained for the hydrazone ligand and complemented with DFT calculations. Cell viability assays on MCF7 (IC50(CuHL) = 1.7 ± 0.1 μM, IC50(CDDP) = 42.0 ± 3.2 μM) and MDA-MB-231 (IC50(CuHL) = 1.6 ± 0.1 μM, IC50(CDDP) = 131.0 ± 18 μM) demonstrated that the complex displays higher antitumor activity than cisplatin (CDDP) on 2D and 3D human breast cancer cell models. Molecular docking and molecular dynamics simulations showed that CuHL could interacts with DNA, inducing a significant genotoxic effect on both breast cancer cells from 0.5 to 1 μM. On the other hand, CuHL increases the ROS production and induces cell programmed death on breast cancer cells at very low micromolar concentrations (0.5-1.0 μM). Moreover, the compound decreased the amount of breast CSCs on MCF7 and MDA-MB-231 cells reducing the percentage of CD44+/CD24-/low cells from 0.5 to 1.5 μM. In addition, CuHL overcame CDDP with an IC50 value 65-fold lower against breast multicellular spheroids ((IC50(CuHL) = 2.2 ± 0.3 μM, IC50(CDDP) = 125 ± 4.5 μM)). Finally, CuHL reduced mammosphere formation capacity, hence affecting the size and number of mammospheres and showing that the complex exhibits antitumor properties on monolayer (2D) and spheroids (3D) derived from human breast cancer cells.