Cytotoxicity, DNA damage, and cell cycle perturbations induced by two representative gold(III) complexes in human leukemic cells with different cisplatin sensitivity

Conjugation of a gold(iii) complex with vitamin B1 and chlorambucil derivatives: anticancer evaluation and mechanistic insights

A gold(iii) complex containing vitamin B1 and chlorambucil derivatives was investigated for mechanistic insights in colon and breast cancer treatment.

Potent In Vitro and In Vivo Anticancer Activity of New Bipyridine and Bipyrimidine Gold (III) Dithiocarbamate Derivatives

We synthesized eight new bipyridine and bipyrimidine gold (III) dithiocarbamate-containing complexes (C1-C8) and tested them in a panel of human cancer cell lines. We used osteosarcoma (MG-63), lung (A549), prostate (PC3 and DU145), breast (MCF-7), ovarian (A2780 and A2780cis, cisplatin- and doxorubicin-resistant), and cervical (ME-180 and R-ME-180, cisplatin resistant) cancer cell lines. We found that C2, C3, C6, and C7 were more cytotoxic than cisplatin in all cell lines tested and overcame cisplatin and doxorubicin resistance in A2780cis and R-ME-180 cells. In the PC3 prostate cancer cell line, the gold (III) complex C6 ([Au₂(BPM)(DMDTC)₂]Cl₄) induced apoptosis and double-stranded DNA breaks, modified cell cycle phases, increased Reactive Oxigen Species (ROS) generation, and reduced thioredoxin reductase and proteasome activities. It inhibited PC3 cell migration and was more cytotoxic against PC3 cells than normal human adipose-derived stromal cells. In mice bearing PC3 tumor xenografts, C6 reduced tumor growth by more than 70% without causing weight loss. Altogether, our results demonstrate the anticancer activity of these new gold (III) complexes and support the potential of C6 as a new agent for prostate cancer treatment.

Development and characterization of an in vitro model of colorectal adenocarcinoma with MDR phenotype

The major cause of failure in cancer chemotherapy is the development of multidrug resistance (MDR), and the characterization of biological factors involved in this response to therapy is particularly needed. A doxorubicin-resistant HCT-8/R clone was selected from sensitive parental cells and characterized analyzing several parameters (cell cycle phase distribution, apoptotic activity, expression, distribution and functionality of the P-gp efflux pump, the response to other chemotherapy agents, its ultrastructural features, invasiveness, and transcriptomic profile). HCT-8/R cells showed a peculiar S phase distribution, characterized by a single pulse of proliferation, resistance to drug-mediated apoptosis, increased expression and functionality of P-gp and overexpression of stem cell markers (CD44 and aldehyde dehydrogenase 1A2). At the ultrastructural level, HCT-8/R presented a greater cell volume and several intracytoplasmic vesicles respect to HCT-8. Moreover, the resistant clone was characterized by cross resistance to other cytotoxic drugs and a greater capacity for migration and invasion, compared to parental cells. Our data reinforce the concept that the MDR phenotype in HCT-8/R cells is multifactorial and involves multiple mechanisms, representing an interesting tool to understand the biological basis of MDR and to test strategies that overcome resistance to chemotherapy.

Mass Spectrometry Uncovers Molecular Reactivities of Coordination and Organometallic Gold(III) Drug Candidates in Competitive Experiments That Correlate with Their Biological Effects

The reactivity of three cytotoxic organometallic gold(III) complexes with cyclometalated C,N,N and C,N ligands (either six- or five-membered metallacycles), as well as that of two representative gold(III) complexes with N-donor ligands, with biological nucleophiles has been studied by ESI-MS on ion trap and time-of-flight instruments. Specifically, the gold compounds were reacted with mixtures of nucleophiles containing l-histidine (imine), l-methionine (thioether), l-cysteine (thiol), l-glutamic acid (carboxylic acid), methylseleno-l-cysteine (selenoether), and in situ generated seleno-l-cysteine (selenol) to judge the preference of the gold compounds for binding to selenium-containing amino acid residues. Moreover, the gold compounds' reactivity was studied with proteins and nucleic acid building blocks. These experiments revealed profound differences between the coordination and organometallic families and even within the family of organometallics, which allowed insights to be gained into the compounds mechanisms of action. In particular, interactions with seleno-l-cysteine appear to reflect well the compounds' inhibition properties of the seleno-enzyme thioredoxin reductase and to a certain extent their antiproliferative effects in vitro. Therefore, mass spectrometry is successfully applied for linking the molecular reactivity and target preferences of metal-based drug candidates to their biological effects. Finally, this experimental setup is applicable to any other metallodrug that undergoes ligand substitution reactions and/or redox changes as part of its mechanism of action.

Gold finger formation studied by high-resolution mass spectrometry and in silico methods

Combining high-resolution MS and QM/MM studies to investigate the reactivity of gold compounds with zinc finger domains at a molecular level.

Synthesis, characterization and in vitro cytotoxicity of gold(iii) dialkyl/diaryldithiocarbamato complexes

A series of six dialkyl/diaryldithiocarbamato (dtc) gold(iii) complexes [Au(R₂dtc)₂]Cl (1,3, and5), and [Au(R₂dtc)Cl₂] (2,4, and6), (R = methyl, ethyl, and benzyl) was synthesised and evaluated for anticancer activity with promising results (EC₅₀≈ 9.5 μM).

In vitro anticancer activity of gold(III) complexes with some esters of (S,S)-ethylenediamine-N,N'-di-2-propanoic acid

Five novel gold(III) complexes of general formulas [AuCl2{(S,S)-R2eddip}]PF6, ((S,S)-eddip = (S,S)-ethylenediamine-N,N'-di-2-propanoate, R = n-Bu, n-Pe, i-Bu, i-Am, cPe; 1-5, respectively) were synthesized and characterized by UV/Vis, IR and NMR spectroscopy and mass spectrometry. DFT calculations indicated that (R,R)-N,N'-configuration diastereoisomers were the most stable for 1-5. 3 is stable in DMSO for at least 24 h, but immediate hydrolysis in PBS occurs. 3 is readily reduced with ascorbic acid and forms adducts with bovine serum albumin (BSA). In vitro anticancer activity of the gold(III) complexes against human cervix adenocarcinoma HeLa, human myelogenous leukemia K562, human melanoma Fem-x tumor cell lines, as well as against non-cancerous human embryonic lung fibroblast cell line MRC-5 was determined using MTT assay. Complex 4 showed highest activity and selectivity (IC50(Fem-x) = 1.3 ± 0.2; IC50(MRC-5)/IC50(Fem-x) = 72.5 ± 12.4), 4 times more active and 28 times more selective than cisplatin. Complexes induced apoptotic mode of death in a time-dependent manner in HeLa cells.

Nanoscale drug delivery platforms overcome platinum-based resistance in cancer cells due to abnormal membrane protein trafficking

The development of cellular resistance to platinum-based chemotherapies is often associated with reduced intracellular platinum concentrations. In some models, this reduction is due to abnormal membrane protein trafficking, resulting in reduced uptake by transporters at the cell surface. Given the central role of platinum drugs in the clinic, it is critical to overcome cisplatin resistance by bypassing the plasma membrane barrier to significantly increase the intracellular cisplatin concentration enough to inhibit the proliferation of cisplatin-resistant cells. Therefore, rational design of appropriate nanoscale drug delivery platforms (nDDPs) loaded with cisplatin or other platinum analogues as payloads is a possible strategy to solve this problem. This review will focus on the known mechanism of membrane trafficking in cisplatin-resistant cells and the development and employment of nDDPs to improve cell uptake of cisplatin.

Novel thiocyanato complexes with potent cytotoxic and antimicrobial properties

The aim of the present study was to assess the cytotoxic and antimicrobial properties of seven new thiocyanato complexes: Ni(C9H11N2O)(SCN), Cu(C9H11N2O)(SCN), Pd(C9H11N2O)(SCN), Pt(C9H11N2O) (SCN), K[Ti(C9H11N2O)(SCN)3], Au(C9H11N2O)(SCN), and K[V(O)(C9H11N2O)(SCN)] (T1-T7, respectively). All the complexes showed toxicity against brine shrimp nauplii (Artemia salina L.). The titanium-based complex, T5, exhibited potent toxicity, with a lethal concentration 50% (the concentration of test compound that kills 50% of A. salina) value of 1.59 μg mL−1. These new complexes also exhibited promising antibacterial and antifungal properties. A macrodilution technique was used to estimate the minimum inhibitory concentrations of the seven bioactive complexes. Minimum inhibitory concentrations were found to be 8–64 μg mL−1 against the tested bacterial species.

Gold(III) compounds as anticancer agents: relevance of gold-protein interactions for their mechanism of action

Gold(III) compounds constitute an emerging class of biologically active substances, of special interest as potential anticancer agents. During the past decade a number of structurally diverse gold(III) complexes were reported to be acceptably stable under physiological-like conditions and to manifest very promising cytotoxic effects against selected human tumour cell lines, making them good candidates as anti-tumour drugs. Some representative examples will be described in detail. There is considerable interest in understanding the precise biochemical mechanisms of these novel cytotoxic agents. Based on experimental evidence collected so far we hypothesize that these metallodrugs, at variance with classical platinum(II) drugs, produce in most cases their growth inhibition effects through a variety of "DNA-independent" mechanisms. Notably, strong inhibition of the selenoenzyme thioredoxin reductase and associated disregulation of mitochondrial functions were clearly documented in some selected cases, thus providing a solid biochemical basis for the pronounced proapoptotic effects. These observations led us to investigate in detail the reactions of gold(III) compounds with a few model proteins in order to gain molecular-level information on the possible interaction modes with possible protein targets. Valuable insight on the formation and the nature of gold-protein adducts was gained through ESI MS (electrospray ionization mass spectrometry) and spectrophotometric studies of appropriate model systems as it is exemplified here by the reactions of two representative gold(III) compounds with cytochrome c and ubiquitin. The mechanistic relevance of gold(III)-induced oxidative protein damage and of direct gold coordination to protein sidechains is specifically assessed. Perspectives for the future of this topics are briefly outlined.

Mitochondria are primary targets in apoptosis induced by the mixed phosphine gold species chlorotriphenylphosphine-1,3-bis(diphenylphosphino)propanegold(I) in melanoma cell lines

Based on previous evidence indicating a selective cytotoxic activity of the mixed phosphine gold complex chlorotriphenylphosphine-1,3-bis(diphenylphosphino)propanegold(I) for melanoma cells, we investigated the cellular bases of its antiproliferative effect in a panel of human melanoma cell lines (JR8, SK-Mel-5, Mel-501, 2/60, 2/21 and GRIG). The drug consistently induced a dose-dependent inhibition of cell growth, with IC50 values ranging from 0.8 to 2.3 microM and, when tested under the same experimental conditions, its cytotoxic activity was higher than (from 2- to 5-fold) or comparable to that of cisplatin as a function of cell lines. The ability of the gold complex to activate programmed cell death was assessed in JR8 and 2/60 cells, and a dose-dependent increase in cells with an apoptotic nuclear morphology was observed in both cell lines (up to 40 and 66% of the overall cell population, for JR8 and 2/60 cell lines, respectively). Such an apoptotic response was mediated by a dose-dependent loss of mitochondrial membrane potential, cytochrome c and Smac/DIABLO release from mitochondria into cytosol and enhanced caspase-9 and caspase-3 catalytic activity. A reduced or completely abrogated expression of the anti-apoptotic proteins c-IAP1, XIAP and survivin in drug-treated cells was also observed. Overall, results from the study indicate that chlorotriphenylphosphine-1,3-bis(diphenylphosphino)propanegold(I) markedly inhibits melanoma cell growth by inducing mitochondria-mediated apoptosis and suggest it as a good candidate for additional evaluation as an anticancer agent against melanoma.

Cellular pharmacological properties of gold(III) porphyrin 1a, a potential anticancer drug lead

The development of gold(III) complexes as potential anticancer drugs with higher cytotoxicity and fewer side effects than existing metal anticancer drugs has been actively pursued in recent years. In this study, we explored the cellular pharmacological properties of gold(III) porphyrin 1a, an anticancer drug lead we previously described. The cytotoxicity study of gold(III) porphyrin 1a by naphthol blue black (NBB) staining assay demonstrated that the higher cytotoxicity of gold(III) porphyrin 1a was not related to its photosensitizing activity. Serum dependent test revealed that serum proteins exhibited lesser effects on the activity of gold(III) porphyrin 1a. In addition, in vivo and in vitro binding assays showed that gold(III) porphyrin 1a acted on DNA noncovalently, which was differently from cisplatin. Flow cytometric study indicated that gold(III) porphyrin 1a inhibited cell growth partly through abrogating cell cycle at G(0)-G(1), and induced apoptosis in SUNE1 cells. The enhanced expression of p53, a cell cycle-controlling and apoptosis-related protein, further demonstrated that the cell cycle arrest and apoptosis induced by gold porphyrin 1a were p53 dependent. Our results highlighted the potential of gold(III) porphyrin 1a as an anticancer drug.

Cytotoxic activity of 3-nitropyrazolo[5,1-c][1,2,4]benzotriazine derivatives: a new series of anti-proliferative agents

We report the synthesis and biological evaluation of a new series of 3-nitropyrazolo[5,1-c][1,2,4]benzotriazine derivatives (compounds 1-4) bearing appropriate substitutions in positions 7 and/or 8. The objective of this investigation was to study the effects of these substitutions on the cytotoxic activity of four new compounds against established human cancer cell lines (i.e. HT29 and HCT-8, colon carcinoma, MCF7, breast carcinoma, and A549, lung carcinoma cells). The inhibitory effects of compounds 1-4 on cell growth were assessed by the sulforhodamine B assay. Also, the effects of these compounds on cell cycle distribution of human colon carcinoma cells (HCT-8) were analyzed by flow cytometry. 3-Nitropyrazolo[5,1-c][1,2,4]benzotriazine derivatives displayed IC(50) values in the micromolar range on the growth of the four cell lines tested. Cell cycle perturbations induced on HCT-8 cells by study compounds at the IC(50) values consisted prevalently of a slight accumulation of cells in G(0)/G(1) phase and a slight decrease in G(2)/M phase. However, compound 3 induced a marked accumulation of cells into S phase with concomitant decrease in G(0)/G(1) and G(2)/M phases. Cytotoxicity data, compared to those obtained with 3-cyano-8-chloropyrazolo[5,1-c][1,2,4]benzotriazine 5-oxide (compound 5, NSC 683334) and other compounds previously synthesized in our laboratory, demonstrated a similar or even improved cytotoxic potency. Cell cycle perturbations caused by these compounds support the hypothesis that they may act by a direct or an indirect inhibition of DNA synthesis.

Mechanisms of Cytotoxicity of Selected Organogold(III) Compounds

The effects of a few cytotoxic organogold(III) compounds on ovarian A2780 human cancer cells were investigated in comparison to cisplatin and oxaliplatin. The tested compounds produced significant antiproliferative effects and promoted apoptosis to a greater extent than platinum drugs while causing only modest cell cycle modifications. The mechanistic implications of these findings are discussed: mitochondrial pathways are proposed to be directly involved in the apoptotic process in relation to selective inhibition of thioredoxin reductase.

Copper transporters regulate the cellular pharmacology and sensitivity to Pt drugs

Recent studies have demonstrated that the major Cu influx transporter CTR1 regulates tumor cell uptake of cisplatin (DDP), carboplatin (CBDCA) and oxaliplatin (L-OHP), and that the two Cu efflux transporters ATP7A and ATP7B regulate the efflux of these drugs. Evidence for the concept that these platinum (Pt) drugs enter cells and are distributed to various subcellular compartments via transporters that have evolved to manage Cu homeostasis includes the demonstration of: (1) bidirectional cross-resistance between cells selected for resistance to either the Pt drugs or Cu; (2) parallel changes in the transport of Pt and Cu drugs in resistant cells; (3) altered cytotoxic sensitivity and Pt drug accumulation in cells transfected with Cu transporters; and (4) altered expression of Cu transporters in Pt drug-resistant tumors. Appreciation of the role of the Cu transporters in the development of resistance to DDP, CBDCA, and L-OHP offers novel insights into strategies for preventing or reversing resistance to this very important family of anticancer drugs.

Antitumor activity of the mixed phosphine gold species chlorotriphenylphosphine-1,3-bis(diphenylphosphino)propanegold(I)

The title compound has been designed for antitumor activity based on structural features of related known antitumor gold agents, that is, gold-monophosphine and gold-diphosphine derivatives. It is a gold complex that contains both types of phosphine ligands, thus suggesting a possible synergistic action. The results of a single crystal X-ray structure determination of this molecule show the metal surrounded by 3 P atoms and one Cl anion in a distorted tetrahedral arrangement. The chloro anion, however, is weakly bound to the metal and so the species shows ionic character. The P NMR study, performed in solution, confirms the structural features observed in the solid and, in addition, indicates partial formation of other known gold(I)-diphosphine antitumor agents. The ionic character and strong Au-P bonds of this novel gold(I) species are similar to those of the most active antitumor gold compounds so far studied. The former feature contributes to solubility in biological fluids, and the latter prevents fast biomolecular attack. In addition, the title compound is less lipophilic, a feature recently correlated to lower liver toxicity. The title compound shows in vitro antitumor activity in the two initial National Cancer Institute protocols against human tumors. In the first screening, a unique dose (0.10 mM) of the title compound reduced cell growth of MCF7 (breast cancer), NCI-H460 (lung cancer), and SF-268 (Central Nervous System cancer-CNS) to 5, 8, and 11%, respectively. In the second protocol a 60-cell line panel was analyzed with the title compound concentration in the 0.1 mM-0.01 microM range. The highest activity was for the breast tumor cell line MCF7 with a LC(50) less than 0.01 microM. LC(50) values in the micromolar range were obtained for 29 cell lines. With the exception of leukemia, these micromolar activities were observed in at least one cell line for each subgroup tumor (non small lung, colon, CNS, melanoma, renal, prostate, breast, and ovarian). The leukemia inactivity was unexpected, as all antitumor gold(I) phosphine compounds in the literature described thus far are active. Melanoma was the most sensitive subgroup screened (five out of seven cell lines).

In vitro and in vivo antitumor properties of tetrakis((trishydroxy- methyl)phosphine)gold(I) chloride

A novel hydrophilic gold compound, tetrakis((trishydroxymethyl)phosphine)gold(I) chloride 1, has been investigated for its antitumor properties. In vitro studies demonstrate that 1 is active against HCT-15, AGS, PC-3, and LNCaP tumor cells. Cell cycle analysis of the HCT-15 cells by flow cytometry revealed elongation of the G1 phase of the cell cycle leading to growth inhibition. Administration of 1 to Balb/C mice inoculated with syngenic meth/A cells demonstrated statistically significant dose-dependent survival time.

Gold(III) complexes with bipyridyl ligands: solution chemistry, cytotoxicity, and DNA binding properties

Gold(III) compounds generally exhibit significant cytotoxic effects on cancer cell lines and are of potential interest as antitumor drugs. We report here on the solution chemistry, the cytotoxicity, and the DNA binding properties of two new bipyridyl gold(III) compounds: [Au(bipy)(OH)(2)][PF(6)] (1) and the organometallic compound [Au(bipy(c)-H)(OH)][PF(6)] (2) (bipy(c) = 6-(1,1-dimethylbenzyl)-2,2'-bipyridine). Both compounds are sufficiently soluble, and stable for hours, within a physiological buffer at 37 degrees C; [Au(bipy)(OH)(2)][PF(6)], at variance with [Au(bipy(c)-H)(OH)][PF(6)], is quickly and quantitatively reduced by ascorbate. Both compounds showed relevant cytotoxic effects toward the A2780S, A2780R, and SKOV3 tumor cell lines; lower effects were detected on the CCRF-CEM/S and CCRF-CEM/R lines. In most cases the mechanisms of resistance to CDDP are only marginally effective against these gold(III) complexes. The interactions of [Au(bipy)(OH)(2)][PF(6)] and [Au(bipy(c)-H)(OH)][PF(6)] with calf thymus DNA were investigated in vitro by various techniques to establish whether DNA represents a primary target for these compounds. Addition of saturating amounts of DNA did not affect appreciably the visible spectra of these gold(III) complexes. Some slight modifications of the CD spectra of calf thymus DNA and of the DNA melting parameters were observed; in any case, ultrafiltration experiments showed that binding of these gold(III) complexes to DNA is weak and reversible. The mechanistic implications of these findings are discussed.