Towards a selective cytotoxic agent for prostate cancer: Interaction of zinc complexes of polyhydroxybenzaldehyde thiosemicarbazones with topoisomerase I

Identification of Promising Drug Candidates against Prostate Cancer through Computationally-Driven Drug Repurposing

Prostate cancer (PC) is one of the most common types of cancer in males. Although early stages of PC are generally associated with favorable outcomes, advanced phases of the disease present a significantly poorer prognosis. Moreover, currently available therapeutic options for the treatment of PC are still limited, being mainly focused on androgen deprivation therapies and being characterized by low efficacy in patients. As a consequence, there is a pressing need to identify alternative and more effective therapeutics. In this study, we performed large-scale 2D and 3D similarity analyses between compounds reported in the DrugBank database and ChEMBL molecules with reported anti-proliferative activity on various PC cell lines. The analyses included also the identification of biological targets of ligands with potent activity on PC cells, as well as investigations on the activity annotations and clinical data associated with the more relevant compounds emerging from the ligand-based similarity results. The results led to the prioritization of a set of drugs and/or clinically tested candidates potentially useful in drug repurposing against PC.

Natural Compounds as Therapeutic Agents: The Case of Human Topoisomerase IB

Natural products are widely used as source for drugs development. An interesting example is represented by natural drugs developed against human topoisomerase IB, a ubiquitous enzyme involved in many cellular processes where several topological problems occur due the formation of supercoiled DNA. Human topoisomerase IB, involved in the solution of such problems relaxing the DNA cleaving and religating a single DNA strand, represents an important target in anticancer therapy. Several natural compounds inhibiting or poisoning this enzyme are under investigation as possible new drugs. This review summarizes the natural products that target human topoisomerase IB that may be used as the lead compounds to develop new anticancer drugs. Moreover, the natural compounds and their derivatives that are in clinical trial are also commented on.

Structural investigation, DNA interactions and in vitro anticancer studies of transition metal complexes of 3-(2-(2, 4-dihydroxy benzylidene) hydrazinyl) quinoxalin-2(1H) -one

The Schiff base ligand, 3-(2-(2, 4-dihydroxybenzylidene) hydrazinyl) quinoxalin-2(1H)-one (RHQO) has been synthesized and characterized by spectral and single crystal X-ray analysis. The Mn(II), Ni(II) and Cu(II) complexes of RHQO have been synthesized and characterized by FT-IR, UV-VIS, mass, EPR spectra, CHN, thermo gravimetric analysis, magnetic susceptibility and conductivity measurements. The morphology of the ligand and complexes is studied by Scanning Electron Microscopy. The metal complexes formed were found to be polymeric in nature. The abilities of the ligand and its metal complexes to interact and bind with calf thymus DNA (CT-DNA) has been studied by electronic absorption spectroscopy and their quantitative binding strength was evaluated in terms of their intrinsic binding constant (K_b). The cleavage interaction of the ligand and its metal complexes with super coiled pBR 322 DNA has been investigated by agarose gel electrophoresis. Cytotoxicity of the Cu(II) and Ni(II) complexes was evaluated using various cancer cell lines, Human cervical cancer cell line (Hela), B16 melanoma F10(B16-F10), Human ovarian cancer cell (SKOV3) and Breast cancer cell line (MCF7) by MTT assay. The results indicated that the ligand and its metal complexes bind with CT-DNA by groove binding mode and cleaved the supercoiled pBR 322 DNA in to nicked form. The Ni(II) and Cu(II) complexes exhibited anticancer activity without affecting the normal CHO-K1 cell lines. Communicated by Vsevolod Makeev.

4-Fluorobenzaldehyde limonene-based thiosemicarbazone induces apoptosis in PC-3 human prostate cancer cells

AIMS

This study evaluated parameters of toxicity and antiproliferative effects of (+)-N(1)-4-fluorobenzaldehyde-N(4)-{1-methyl-1-[(1R)-4-methylcyclohexene-3-il]-ethyl}-thiossemicarbazone (4-FTSC) in PC-3 adenocarcinoma prostate cells.

MAIN METHODS

Cytotoxicity of 4-FTSC in PC-3 cells was evaluated using MTT assay. Morphology examination of PC-3 cells treated with 4-FTSC was also performed as well as the cell death mechanisms induced were investigated using flow cytometry. Parameters of toxicity of 4-FTSC was conducted by the investigation of its potential myelotoxicity and lymphotoxicity, hemolytic activity and acute oral toxicity profile.

KEY FINDINGS

4-FTSC showed promising cytotoxic effects against PC-3 cells (IC₅₀ = 18.46 μM). It also triggered apoptotic morphological changes, phosphatidylserine externalization and a significant increase of DNA fragmentation in PC-3 cells. Moreover, 4-FTSC did not show changes in the PC-3 cell cycle with levels of p21, p27, NFĸB and cyclin D1 similar to those found in both control and treated cells. 4-FTSC also promoted an increase of p53 levels associated with mitochondrial impairment through loss of ∆Ψm and ROS overproduction. 4-FTSC-induced cell death mechanism in PC-3 cells involved activation of caspase-3/-7 through apoptosis intrinsic pathway via caspase-9. Regarding toxicological profile, 4-FTSC showed in vitro lymphotoxicity, although with low cytotoxicity for bone marrow progenitors and no hemolytic potential. Moreover, it was classified as GHS category 5 (LD₅₀ > 2000-5000 mg/Kg), suggesting it has low acute oral systemic toxicity.

SIGNIFICANCE

4-FTSC seems to be a promising candidate to be used as a clinical tool in prostate cancer treatment. Further studies are required to better clarify its toxicopharmacological effects found in this compound.

Human topoisomerase IB is a target of a thiosemicarbazone copper(II) complex

The human topoisomerase IB inhibition and the antiproliferative activity of 3-(4-bromophenyl)-1-pyridin-2-ylprop-2-en-1-one thiosemicarbazone HPyCT4BrPh alone and its copper(II) complex [Cu(PyCT4BrPh)Cl] was investigated. [Cu(PyCT4BrPh)Cl] inhibits both the DNA cleavage and religation step of the enzyme, whilst the ligand alone does not display any effect. In addition we show that coordination to copper(II) improves the cytotoxicity of HPyCT4BrPh against THP-1 leukemia and MCF-7 breast cancer cells. The data indicate that the copper(II) thiosemicarbazone complex may hit human topoisomerase IB and that metal coordination can be useful to improve cytotoxicity of this versatile class of compounds.

Synthesis, spectroscopy, structures and antimicrobial activity of mixed-ligand zinc(ii) complexes of 5-nitro-salicylaldehyde thiosemicarbazones

Zinc(ii)-thiosemicarbazone complexes have high antimicrobial activity against MRSA,S. aureus,K. pneumoniae,Sh. flexneri,S. typhimuriumandC. albicans.

Synthesis of a DNA-targeting nickel (II) complex with testosterone thiosemicarbazone which exhibits selective cytotoxicity towards human prostate cancer cells (LNCaP)

Testosterone thiosemicarbazone, L and its nickel (II) complex 1 were synthesized and characterized by using FTIR, CHN, (1)H NMR, and X-ray crystallography. X-ray diffraction study confirmed the formation of L from condensation of testosterone and thiosemicarbazide. Mononuclear complex 1 is coordinated to two Schiff base ligands via two imine nitrogens and two tautomeric thiol sulfurs. The cytotoxicity of both compounds was investigated via MTT assay with cisplatin as positive reference standard. L is more potent towards androgen-dependent LNCaP (prostate) and HCT 116 (colon). On the other hand, complex 1, which is in a distorted square planar environment with L acting as a bidentate NS-donor ligand, is capable of inhibiting the growth of all the cancer cell lines tested, including PC-3 (prostate). It is noteworthy that both compounds are less toxic towards human colon cell CCD-18Co. The intrinsic DNA binding constant (Kb) of both compounds were evaluated via UV-Vis spectrophotometry. Both compounds showed Kb values which are comparable to the reported Kb value of typical classical intercalator such as ethidium bromide. The binding constant of the complex is almost double compared with ligand L. Both compounds were unable to inhibit the action topoisomerase I, which is the common target in cancer treatment (especially colon cancer). This suggest a topoisomerase I independent-cell death mechanism.

Synthesis, characterization, crystal structure and cytotoxic properties of thiosemicarbazide Ni(II) and Zn(II) complexes

Synthesis of new complexes of Ni(II) (1) and Zn(II) (2) with [1-(2-hydroxy-3,5-diiodobenzylidene)-4-phenylthiosemicarbazide] have been reported. The composition of these two complexes 1 and 2 is discussed on the basis of IR, (1)H NMR and UV spectral data along with their X-ray crystallographic data. The crystal structure of these two complexes has revealed that the free ligand (L) is deprotonated twice at the oxygen and sulfur atoms and they are coordinated with the complexes through phenoxide-O, azomethine-N and thiolate-S atoms. The single-crystal X-ray structures of complex (1) exhibits a square planar structure, while complex (2) reveals trigonal bipyramidal distorted square based pyramidal structure. Anticancer activity of ligand and the complexes 1-2 are evaluated in human adenocarcinoma (MCF-7) cells. The preliminary bioassay indicates that the free ligand and the complexes 1-2 exhibit inhibitory activity against the human adenocarcinoma cancer cell lines.

Crystal structure of a new monoclinic polymorph of 2,4-di-hydroxy-benzaldehyde 4-methyl-thio-semi-carbazone

A new monoclinic (P2₁/c) polymorph of the title compound has the same overall conformation as a previously reported (Cc) form with the exception of the conformation of the outer hy­droxy H atom. This difference results in very different crystal packing based on hydrogen bonding, i.e. supra­molecular tubes in the new form as opposed to a three-dimensional architecture in the Cc form.

The title compound, C₉H₁₁N₃O₂S, is a second monoclinic (P2₁/c) polymorph of the previously reported Cc form [Tan et al. (2008b ▸). Acta Cryst. E64, o2224]. The mol­ecule is non-planar, with the dihedral angle between the N₃CS residue (r.m.s. deviation = 0.0816 Å) and the benzene ring being 21.36 (4)°. The conformation about the C=N bond [1.292 (2) Å] is E, the two N-bound H atoms are anti, and the inner hy­droxy O-bound and outer amide N-bound H atoms form intra­molecular hydrogen bonds to the imine N atom. Crucially, the H atom of the outer hy­droxy group is approximately syn to the H atom of the benzene C atom connecting the two C atoms bearing the hy­droxy substituents. This arrangement enables the formation of supra­molecular tubes aligned along [010] and sustained by N—H⋯O, O—H⋯S and N—H⋯S hydrogen bonds; the tubes pack with no specific inter­actions between them. While the mol­ecular structure in the Cc form is comparable, the H atom of the outer hy­droxy group is approximately anti, rather than syn. This different orientation leads to the formation a three-dimensional architecture based on N—H⋯O and O—H⋯S hydrogen bonds.

Effects of terminal dimethylation and metal coordination of proline-2-formylpyridine thiosemicarbazone hybrids on lipophilicity, antiproliferative activity, and hR2 RNR inhibition

The nickel(II), copper(II), and zinc(II) complexes of the proline-thiosemicarbazone hybrids 3-methyl-(S)-pyrrolidine-2-carboxylate-2-formylpyridine thiosemicarbazone (L-Pro-FTSC or (S)-H2L(1)) and 3-methyl-(R)-pyrrolidine-2-carboxylate-2-formylpyridine thiosemicarbazone (D-Pro-FTSC or (R)-H2L(1)), as well as 3-methyl-(S)-pyrrolidine-2-carboxylate-2-formylpyridine 4,4-dimethyl-thiosemicarbazone (dm-L-Pro-FTSC or (S)-H2L(2)), namely, [Ni(L-Pro-FTSC-2H)]2 (1), [Ni(D-Pro-FTSC-2H)]2 (2), [Ni(dm-L-Pro-FTSC-2H)]2 (3), [Cu(dm-L-Pro-FTSC-2H)] (6), [Zn(L-Pro-FTSC-2H)] (7), and [Zn(D-Pro-FTSC-2H)] (8), in addition to two previously reported, [Cu(L-Pro-FTSC-2H)] (4), [Cu(D-Pro-FTSC-2H)] (5), were synthesized and characterized by elemental analysis, one- and two-dimensional (1)H and (13)C NMR spectroscopy, circular dichroism, UV-vis, and electrospray ionization mass spectrometry. Compounds 1-3, 6, and 7 were also studied by single-crystal X-ray diffraction. Magnetic properties and solid-state high-field electron paramagnetic resonance spectra of 2 over the range of 50-420 GHz were investigated. The complex formation processes of L-Pro-FTSC with nickel(II) and zinc(II) were studied in aqueous solution due to the excellent water solubility of the complexes via pH potentiometry, UV-vis, and (1)H NMR spectroscopy. The results of the antiproliferative activity in vitro showed that dimethylation improves the cytotoxicity and hR2 RNR inhibition. Therefore, introduction of more lipophilic groups into thiosemicarbazone-proline backbone becomes an option for the synthesis of more efficient cytotoxic agents of this family of compounds.

Effect of oxindolimine copper(II) and zinc(II) complexes on human topoisomerase I activity

The ability of oxindolimine copper(II) and zinc(II) complexes, known to have antitumor activity, to inhibit human topoisomerase IB has been tested through enzymatic kinetic assays and molecular docking simulations. These copper and zinc compounds are able to inhibit remarkably the cleavage reaction and only partially the religation step, the copper compound being more efficient than the zinc one. A complete inhibition activity of the cleavage is only obtained when the enzyme is pre-incubated with the compound, the inhibition being irreversible and reversible for the copper and zinc compounds, respectively. The relative stability of such complexes was estimated by competitive equilibria with human serum albumin (HSA), monitored by CD spectroscopy. The copper species shows a log KCuL = 17.2, while the analogous zinc complex exhibits a log KZnL = 7.2. Molecular docking simulation studies show that the almost square planar geometry of the copper compound allows a direct coordination of the metal with two amino acids (Glu492, Asp563) of the enzyme at variance of the zinc compound which has a more tetrahedral geometry. Altogether, the data indicate that the different coordination geometry achieved by the two transition metal ions has an important role in modulating their efficiency as topoisomerase I inhibitors.

Zinc, copper and nickel derivatives of 2-[2-bromoethyliminomethyl]phenol as topoisomerase inhibitors exhibiting anti-proliferative and anti-metastatic properties

Transition metal (Zn, Cu and Ni) derivatives of (2-[2-bromoethyliminomethyl]phenol), were found to inhibit topoisomerase I activity, induce DNA cleavage and bind to calf thymus DNA. The compounds are also cytotoxic and anti-invasive against PC3.

The synthesis, characterization, antimicrobial and antimutagenic activities of hydroxyphenylimino ligands and their metal complexes of usnic acid isolated from Usnea longissima

Novel Schiff base ligands of usnic acid isolated from Usnea longissima and their metal complexes were synthesized and characterized. Investigated their antimicrobial and antimutagenic activities.

Synthesis and characterization of some new Cu(II), Ni(II) and Zn(II) complexes with salicylidene thiosemicarbazones: antibacterial, antifungal and in vitro antileukemia activity

Thirty two new Cu(II), Ni(II) and Zn(II) complexes (1–32) with salicylidene thiosemicarbazones (H₂L¹–H₂L¹⁰) were synthesized. Salicylidene thiosemicarbazones, of general formula (X)N-NH-C(S)-NH(Y), were prepared through the condensation reaction of 2-hydroxybenzaldehyde and its derivatives (X) with thiosemicarbazide or 4-phenylthiosemicarbazide (Y = H, C₆H₅). The characterization of the new formed compounds was done by ¹H-NMR, ¹³C-NMR, IR spectroscopy, elemental analysis, magnetochemical, thermoanalytical and molar conductance measurements. In addition, the structure of the complex 5 has been determined by X-ray diffraction method. All ligands and metal complexes were tested as inhibitors of human leukemia (HL-60) cells growth and antibacterial and antifungal activities.