DNA interstrand cross-linking efficiency and cytotoxic activity of novel cadmium(II)-thiocarbodiazone complexes

Antitumor effects of cadmium against diethylnitrosamine-induced liver tumors in mice

Cadmium (Cd) has been reported to exhibit antitumor effects against chemically induced liver tumors. However, the antitumor effects of Cd are not completely understood. Metallotherapy, the use of a toxic metal to attack liver tumors, could be a viable strategy. In the present study, 8-week old, male, C57BL/6 mice were administered injections of diethylnitrosamine (DEN) (90 mg/kg, and then 50 mg/kg 2 weeks later), followed by liver tumor promotion with carbon tetrachloride. Cadmium chloride was administered in the drinking water (1000 ppm) from 21–40 weeks after DEN initiation. Body weights were recorded and liver tumor formation was monitored via ultrasound. At the end of experiments, livers were removed, weighed, and the tumor incidence, tumor numbers and tumor size scores were recorded. Liver histology and metallothionein (MT) immunostaining were performed. After DEN injection, animal body weight decreased, and then slowly recovered with time. Cd treatment did not affect animal body weight gain. Ultrasound analysis detected liver tumors 35 weeks after DEN injection, and the mice were necropsied at 40 weeks. Liver/body weight ratios increased in the DEN and DEN + Cd groups. Cd treatment decreased the tumor incidence (71 vs. 17%), tumor numbers (15 vs. 2) and tumor scores (22 vs. 3) when compared with the DEN only group. Histopathology showed hepatocyte degeneration in all groups, and immunohistochemistry showed MT-deficiency in the liver tumors, while MT staining was intensified in the surrounding tissues. Reverse transcription-quantitative PCR showed increases in α-fetoprotein level in DEN-treated livers, and increases in MT-2 and tumor necrosis factor α (TNFα) levels in Cd-treated livers. Thus, it was concluded that Cd is effective in the suppression of DEN-induced liver tumors, and that the mechanisms may be related to MT-deficiency in tumors and the induction of TNFα to kill tumor cells.

In vitro nephrotoxicity and anticancer potency of newly synthesized cadmium complexes

Complexes based on heavy metals have great potential for the treatment of a wide variety of cancers but their use is often limited due to toxic side effects. Here we describe the synthesis of two new cadmium complexes using N(4)-phenyl-2-formylpyridine thiosemicarbazone (L1) and 5-aminotetrazole (L2) as organic ligands and the evaluation of their anti-cancer and nephrotoxic potential in vitro. The complexes were characterized by Single-crystal X-ray data diffraction, 1HNMR, FT-IR, LC/MS spectrometry and CHN elemental analysis. Next, cytotoxicity of these cadmium complexes was evaluated in several cancer cell lines, including MCF-7 (breast), Caco-2 (colorectal) and cisplatin-resistant A549 (lung) cancer cell lines, as well as in conditionally-immortalized renal proximal tubule epithelial cell lines for evaluating nephrotoxicity compared to cisplatin. We found that both compounds were toxic to the cancer cell lines in a cell-cycle dependent manner and induced caspase-mediated apoptosis and caspase-independent cell death. Nephrotoxicity of these compounds was compared to cisplatin, a known nephrotoxic drug, in vitro. Our results demonstrate that compound {2}, but not compound {1}, exerts increased cytotoxicity in MCF-7 and A549 cell lines, combined with reduced nephrotoxic potential compared to cisplatin. Together these data make compound {2} a likely candidate for further development in cancer treatment.

Effect of Manganese Chloride and of Cotreatment with Cadmium Chloride on the In Vitro Proliferative, Motile and Invasive Behavior of MDA-MB231 Breast Cancer Cells

We examined the dose⁻response effect of MnCl₂ on the proliferative behavior of triple-negative breast cancer MDA-M231 cells vs. immortalized HB2 cells from breast epithelium taken as nontumoral counterparts. We also tested the effect of MnCl₂ on tumor cell invasiveness in vitro by evaluating the relative invasion indexes through Boyden chamber assays. Moreover, we checked whether cotreatment with both MnCl₂ and CdCl₂ could modify the observed biological response by MDA-MB231 cells. Our results show a promotional impact of MnCl₂ on cell proliferation, with 5 µM concentration inducing the more pronounced increase after 96-h exposure, which is not shared by HB2 cells. Exposure to 5 µM MnCl₂ induced also an elevation of the relative invasion index of cancer cells. The Mn-mediated stimulatory effects were counteracted by cotreatment with CdCl₂. These data support the concept that human exposure to high environmental concentrations of Mn may increase the risk of carcinogenesis and metastasis by prompting the expansion and dissemination of triple-negative breast cancer cells. On the other hand, the Mn-counteracting anticancer property of Cd looks promising and deserves a more detailed characterization of the involved intracellular targets aimed to the molecular modeling of specific antineoplastic agents against malignant breast cancer spreading.

A novel binuclear hydrazone-based Cd(II) complex is a strong pro-apoptotic inducer with significant activity against 2D and 3D pancreatic cancer stem cells

A novel binuclear Cd complex (1) with hydrazone-based ligand was prepared and characterized by spectroscopy and single crystal X-ray diffraction techniques. Complex 1 reveals a strong pro-apoptotic activity in both human, mammary adenocarcinoma cells (MCF-7) and pancreatic AsPC-1 cancer stem cells (CSCs). While apoptosis undergoes mostly caspase-independent, 1 stimulates the activation of intrinsic pathway with noteworthy down regulation of caspase-8 activity in respect to non-treated controls. Distribution of cells over mitotic division indicates that 1 caused DNA damage in both cell lines, which is confirmed in DNA interaction studies. Compared to 1, cisplatin (CDDP) does not achieve cell death in 2D cultured AsPC-1 cells, while induces different pattern of cell cycle changes and caspase activation in 2D cultured MCF-7 cells, implying that these two compounds do not share similar mechanism of action. Additionally, 1 acts as a powerful inducer of mitochondrial superoxide production with dissipated trans-membrane potential in the majority of the treated cells already after 6 h of incubation. On 3D tumors, 1 displays a superior activity against CSC model, and at 100 μM induces disintegration of spheroids within 2 days of incubation. Fluorescence spectroscopy, along with molecular docking show that compound 1 binds to the minor groove of DNA. Compound 1 binds to the human serum albumin (HSA) showing that the HSA can effectively transport and store 1 in the human body. Thus, our current study strongly supports further investigations on antitumor activity of 1 as a drug candidate for the treatment of highly resistant pancreatic cancer.

Quinoline based mono- and bis-(thio)carbohydrazones: synthesis, anticancer activity in 2D and 3D cancer and cancer stem cell models

Study of antitumor activity of mono- and bis-quinoline based (thio)carbohydrazones on THP-1 and AsPC-1 cancer stem cells, revealed that thiocarbohydrazones had superior pro-apoptotic activity than carbohydrazones with multi-target profile activities.

Iron(iii) and nickel(ii) complexes as potential anticancer agents: synthesis, physicochemical and structural properties, cytotoxic activity and DNA interactions

The iron complex 3 was cytotoxic at low concentrations in K562 cells and could damage the DNA, specifically the adenine base.

Synthesis, characterization and anti-proliferative activity of Cd(II) complexes with NNN type pyrazole-based ligand and pseudohalide ligands as coligand

Cd(II) complexes of tridentate nitrogen donor ligand, 2,6-bis(3,4,5-trimethylpyrazolyl)pyridine (btmpp), Cd(btmpp)X2 (X:Cl, ONO or N(CN)2) have been synthesized and characterized by elemental and spectral (FT-IR, (1)H NMR, (13)C NMR, UV-Vis) analyses, differential thermal analysis and single crystal X-ray diffraction studies. The molecular structure of reported complex 1, revealed distorted square-pyramidal geometry around Cadmium. Complexes 1-3 and corresponding ligand were tested for cytotoxic activity against the human carcinoma cell lines HEP3B (hepatocellular carcinoma), PC3 (prostate adenocarcinoma), MCF7 (breast adenocarcinoma) and Saos2 (osteosarcoma). The results show that, complexes are more cytotoxic than the free ligand and complex 2 is the most cytotoxic complex for PC3.

Palladium(II) and platinum(II) bis(thiosemicarbazone) complexes of the 2,6-diacetylpyridine series with high cytotoxic activity in cisplatin resistant A2780cisR tumor cells and reduced toxicity

Preparation and characterization of four novel 2,6-diacetylpyridine bis((4)N-tolylthiosemicarbazonato) palladium(II) and platinum(II) complexes, [PdL(1-2)] and [PtL(1-2)], are described. All compounds have been characterized by elemental analysis and by IR and NMR spectroscopy, and the crystal and molecular structures of complexes [PdL(2)] and [PtL(2)] have been determined by a single crystal X-ray diffraction. The ligands act as dianionic tetradentate donors coordinating to the metal center in a square planar geometry through the Npyridinic atom and the Niminic and the S atoms from one thiosemicarbazone arm, the fourth coordination position is occupied by the Nhydrazinic of the other arm. The new compounds synthesized have been evaluated for antiproliferative activity in vitro against NCI-H460, HepG2, MCF-7, A2780 and A2780cisR human cancer cell lines. The cytotoxicity data suggest that [PdL(1)], [PdL(2)] and [PtL(2)] may be endowed with important antitumor properties since they are capable of not only circumventing cisplatin resistance in A2780cisR cells but also exhibiting high antiproliferative activity in breast cancer MCF-7 cells. Subsequent toxicity study, in LLC-PK1 cells, has also been carried out and shows that none of these compounds are in vitro toxic in the tested concentration range.

Novel bis(thiosemicarbazones) of the 3,5-diacetyl-1,2,4-triazol series and their platinum(II) complexes: chemistry, antiproliferative activity and preliminary nephrotoxicity studies

The preparation and characterization of three novel (4)N-monosubstituted bis(thiosemicarbazone) ligands of 3,5-diacetyl-1,2,4-triazol series and their dinuclear platinum complexes are described. The crystal and molecular structure of the [Pt(μ-H(3)L(3))](2) complex derived of 3,5-diacetyl-1,2,4-triazol bis((4)N-p-tolylthiosemicarbazone), H(5)L(3), has been resolved by single crystal X-ray diffraction. The ligands coordinate, in an asymmetric dideprotonate form, to the platinum ions in a tridentate fashion (NNS) and S-bridging bonding modes. Thus the molecular units of the platinum complexes are stacked as dimers. The new compounds synthesized have been evaluated for antiproliferative activity in vitro against NCI-H460, A2780 and A2780cisR human cancer cell lines. The cytotoxicity data suggest that these compounds may be endowed with important antitumour properties since are capable of not only circumventing cisplatin resistance in A2780cisR cells but also exhibit high antiproliferative activity in human non-small cell lung cancer NCI-H460 cells. The interactions of these compounds with calf thymus DNA was investigated by UV-vis absorption and a nephrotoxic study, in LLC-PK1 cells, has also been carried out.

Apoptosis induction and DNA interstrand cross-link formation by cytotoxic trans-[PtCl2(NH(CH3)2)(NHCH(CH3)2) : cross-linking between d(G) and complementary d(C) within oligonucleotide duplexes

We have investigated the cytotoxic activity, the induction of apoptosis, and the interstrand cross-linking efficiency in the A2780cisR ovarian tumor cell line, after replacement of the two NH3 nonleaving groups in trans-[PtCl2(NH3)2] (trans-DDP) by dimethylamine and isopropylamine. The data show that trans-[PtCl2(NH(CH)2)(NHCH(CH3)2)] is able to circumvent resistance to cis-[PtCl2(NH3)2] (cis-DDP, cisplatin) in A2780cisR cells. In fact, trans-[PtCl2(NH(CH3)2)(NHCH(CH3)2)] shows a cytotoxic potency higher than that of cis-DDP and trans-DDP, with the mean IC50 values being 11, 58, and 300 microM, respectively. In addition, at equitoxic doses (concentrations of the platinum drugs equal to their IC50 values) and after 24 hours of drug treatment, the level of induction of apoptosis by trans-[PtCl2(NH(CH3)2)(NHCH(CH3)2)] is twice that produced by cis-DDP. Under the same experimental conditions, trans-DDP does not induce significant levels of apoptosis in A2780cisR cells. After 24 hours of incubation of A2780cisR cells at concentrations equal to the IC0o value of the platinum drugs, the level of DNA interstrand cross-links (ICLs) induced by trans-[PtCI2(NH(CH)2)(NHCH(CH3)] is two and three times higher, respectively, than those induced by cis-DDP and trans-DDP. We also found that trans-[PtCl2(NH(CH3)2)(NHCH(CH3)2)] formed DNA ICLs between guanine and complementary cytosine. We propose that, in A2780cisR cells, the induction of apoptosis by trans-[PtCl2(NH(CH3)2)(NHCH(CH3)2)] is related to its greater ability (relative to cis-DDP and trans-DDP) to form DNA ICLs.

Palladium and platinum 3,5-diacetyl-1,2,4-triazol bis(thiosemicarbazones): Chemistry, cytotoxic activity and structure–activity relationships

The preparation of platinum(II) complexes derived from 3,5-diacetyl-1,2,4-triazol bis(4-phenylthiosemicarbazone) (H(5)L(1)), 3,5-diacetyl-1,2,4-triazol bis(thiosemicarbazone) (H(7)L(2)), 3,5-diacetyl-1,2,4-triazol bis(4-methylthiosemicarbazone) (H(5)L(3)) and 3,5-diacetyl-1,2,4-triazol bis(4-ethylthiosemicarbazone) (H(5)L(3)) is described. The new complexes [Pt(mu-H(3)L(1))](2), [Pt(mu-H(5)L(2))](2), [Pt(mu-H(3)L(3))](2) and [Pt(mu-H(3)L(4))](2) have been characterized by elemental analyses, fast atom bombardment mass spectrometry (FAB(+)) and spectroscopic studies. The crystal and molecular structure of compounds [Pt(mu-H(3)L(1))](2), parent ligand H(5)L(1) and [Pt(mu-H(3)L(3))](2) have been determined by single crystal X-ray diffraction. The ligands coordinate, in a dideprotonate form to the platinum ions in a new tridentate fashion (NNS) and S-brigding bonding modes. Thus the molecular units of the platinum complexes are stacked as dimers. The testing of the cytotoxic activity of the synthesized compounds together with their palladium analogues against human A2780 and A2780cisR epithelial ovarian carcinoma cells lines suggests that the compounds may be endowed with important antitumor properties since they show IC(50) values in a micromolar range similar to those of cisplatin. The structure and antitumor activity relationships of platinum and palladium complexes are also discussed.

Synthesis, crystal structures and cytotoxicities of some transition metal complexes with N-[2-{(pyridin-2-ylmethylidene)amino}ethyl]acetamide

The synthesis and spectroscopic (IR, (1)H and (13)C NMR) characterization of new complexes of Pt(II), Pd(II), Cu(II), and Hg(II) with the Schiff base ligand MeCONHCH(2)CH(2)N=CHPy (L) (Py=pyridine) are reported, together with studies on the cytotoxicities of these complexes, L and [ReBr(CO)(3)(L)] against human leukemia (MOLT-4), breast cancer (MCF-7) and Chang Liver (non-cancerous) cells. The crystal structures of [Pt(L)Cl(2)] (2), [Cu(L)Cl(2)] (4) and [Hg(L)Cl(2)](2) (5) are also reported. Of the complexes studied, [Cu(L)Cl(2)] (4) was identified as the most cytotoxic active derivative against cells of neoplastic origin (MOLT-4, and MCF-7), while having low toxicity on cells of benign origin (Chang Liver).

Synthesis, characterisation and cytotoxic properties of the N1,N4-diarylidene-S-methyl-thiosemicarbazone chelates with Fe(III) and Ni(II)

Reactions of 2-hydroxy-3-methoxy, 2-hydroxy-4-methoxy-benzaldehyde with 3- and 4-methoxy-substituted salicylaldehyde S-methyl-thiosemicarbazones in the presence of FeCl(3) and NiCl(2) resulted in the corresponding methoxy-substituted N(1),N(4)-diarylidene-S-methyl-thiosemicarbazone chelates. Characterisation of the compounds in the [Fe(L)Cl] and [Ni(L)] general formula was accomplished by means of elemental analysis, conductivity and magnetic measurements, (1)H NMR, UV-vis, IR and mass spectroscopy. Cytotoxicity and proliferation experiments using K562 chronic myeloid leukemia cell line and ECV 304 human endothelial cell line imply that the iron(III) chelates may have anti-leukemic effects with 3.5 microg/dl LD(50) dose.

Synthesis, structure and biological activity of a new and efficient Cd(II)–uracil derivative complex system for cleavage of DNA

The new complex formed by Cd(II) and the 1:2 Schiff-base-type ligand 2,6-bis[1-(4-amino-1,2,3,6-tetrahydro-1,3-dimethyl-2,6-dioxopyrimidin-5-yl)imino]ethylpyridine (DAPDAAU) has been chemically and structurally characterized by X-ray diffraction: the ion Cd(II) is surrounded by six nitrogen atoms from two DAPDAAU ligands which coordinates each one in a tridentate fashion through the pyridine ring (N1) and both azomethine nitrogen atoms (N5). The interaction of the Cd(II) complex (compound I) with calf-thymus DNA as observed by circular dichroism spectroscopy suggests the initial unwinding of the DNA double helix strongly depends on increasing incubation times and metal-to-nucleic acid molar ratios. Electrophoretic experiments indicate that the cadmium complex induces cleavage of the plasmid pBR322 DNA to give ulterior nicking and shortening of this molecule, as a result of the complex binding to DNA, resulting in the conclusion that compound I behaves as a chemical nuclease. Cytotoxic activity of the Cd(II) complex against selected different human cancer cell lines is specific and increases with increasing concentration of the metal compound; this fact indicates the potential antitumor character of the complex. When the culture medium is supplemented with compound I, a remarkable inhibition of the growing cell is observed, important cell degeneration appears before 48 h and abundant precipitates are formed that correspond to cell residues and denatured proteins.

Structural models for the interaction of Cd(II) with DNA: trans-[Cd(9-RGH-N7)2(H2O)4]2+

Reactions of Cd(NO(3))(2) with the model nucleobases 9-alkylguanine in water at neutral pH, give the compounds trans-[Cd(9-RGH-N7)(2)(H(2)O)(4)](NO(3))(2)(R=Me, Et), with the 9-alkylguanine ligands bound to the metal cation at the N(7) position. The X-ray structures of both compounds are reported. The six-coordinate Cd(II) complexes consist of a highly regular octahedral geometry in which the two 9-alkylguanine ligands are in a trans position to each other and approximately collinear with the metal cation. In addition, the networks of both compounds show interesting features. Thus, intramolecular H-bonds between O(6) and a coordinated water molecule are present, and self-association of guanines via H-bonding of N(3)-H...N(2) take place, leading to a 1D supramolecular polymeric ribbon. Density functional theory calculations have been applied to both compounds in order to study the stability of N(7) metalated guanine-guanine associations by comparing experimental and theoretical results. The potential relevance with regard to possible Cd(II)-DNA cross-links is briefly discussed.

Toxic effects of bis(thiosemicarbazone) compounds and its palladium(II) complexes on herpes simplex virus growth

Here, we present data on the activity of benzyl bis(thiosemicarbazone); 3,5-diacyl-1,2,4-triazole bis(4-methylthiosemicarbazone) and their Pd(II) complexes against the replication of wild type and of acyclovir (ACV)-resistant, herpes simplex virus type 1 (HSV 1) and type 2 (HSV 2) strains. The data were compared to those under the action of acyclovir. The testing of cytotoxic activity suggests that these compounds may be endowed with important antiviral properties. It is interesting to note that the Pd(II)-benzyl bis(thiosemicarbazone) complex, 2, exhibits a significant activity against acyclovir-resistant viruses R-100 (HSV 1) and PU (HSV 2) with an in vitro selectivity index (SI) of 8.0 vs. 0.01 for acyclovir. This complex also negatively influenced the expression of key structural HSV 1 proteins (VP23, gH and gG/gD), thus suppressing simultaneously virus entry, transactivation of virus genome, capsid assembly, and cell-to-cell spread of infectious HSV progeny.

Preparation and characterization of platinum(II) and (IV) complexes of 1,3-diaminepropane and 1,4-diaminebutane: circumvention of cisplatin resistance and DNA interstrand cross-link formation in CH1cisR ovarian tumor cells

The reaction of Pt(dimethyl sulfoxide)(2)CBDCA (CBDCA = 1,1-cyclobutanedicarboxylate) with 1,4-diaminebutane and 1,3-diaminepropane ligands yields, under certain conditions, new [Pt(diamine)(2)]CBDCA complexes (1a,b), where the CBDCA ligand has been removed from the coordination sphere of the platinum atom by the diamine ligand, instead of forming the expected [Pt(diamine)CBDCA] complexes (1'a,b). The structure of complexes 1a and 1'b was solved by X-ray diffraction. Complex 1a crystallizes in the orthorhombic system, in the noncentrosymmetric C222 space group, with unit cell parameters: a = 20.053(2) A; b = 8.655(2) A, c = 5.711(3) A; V = 991.2(6) A(3); delta (calcd) = 1.627 mg/m(3); and R = 0.050. The Pt atom displays an unexpected distorted tetrahedral coordination with a N-Pt-N inner bond angle equal to 81(2) degrees for N atoms of the same 1,3-propanediamine ligand and a N-Pt-N bond angle for different ligands equal to 135.4(9) degrees. Complex 1'b crystallizes in the monoclinic system, in the centrosymmetric P2(1)/c space group, with unit cell parameters: a = 6.007(2) A; b = 15.336(4) A, c = 13.232(5) A; beta = 101.90(3) degrees; V = 1192.8(7) A(3); delta (calcd) = 2.369 mg/m(3); and R = 0.067. Cytotoxicity data show that of all the synthesized compounds, only complexes 1'a and 1'b exhibit remarkable cytotoxic properties. Thus, in contrast with carboplatin (cis-diammine-1,1-cyclobutane dicarboxilatoplatinum(II)), compounds 1'a and 1'b, which also contain the CBDCA ligand, are able to circumvent cisplatin (cis-diamminedichloroplatinum(II)) resistance in several tumor cells. Moreover, after 24 h of incubation of CH1cisR ovarian tumor cells with 10 microM of compounds 1'a and 1'b, the level of DNA interstrand cross-links (ICLs) induced by compounds 1'a and 1'b is 3.3 and 3.8 times higher, respectively, than that of carboplatin and 3.5 and 4.0 times higher, respectively, than that of cisplatin. Interestingly, under the same conditions, the intracellular accumulation of compounds 1'a and 1'b is similar to that of carboplatin and cisplatin. However, the extent of binding to DNA of compounds 1'a and 1'b is similar to that of cisplatin but slightly higher than that of carboplatin. We propose that circumvention of cisplatin resistance in CH1cisR cells by compounds 1'a and 1'b might be related to its higher ability to form DNA ICLs relative to carboplatin and cisplatin.