Synthesis, Characterization, and Comparative in Vitro Cytotoxicity Studies of Platinum(II), Palladium(II), and Gold(III) Methylsarcosinedithiocarbamate Complexes

This work reports on the synthesis, characterization, and in vitro cytotoxic activity of some new platinum(II), palladium(II), and gold(III) derivatives of methylsarcosinedithiocarbamate and its S-methyl ester, to study their behavior as potential antitumor agents. The biological activity of these compounds, as determined by growth inhibition and apoptosis induction, has been investigated in both human leukemic promyelocites HL60 and human squamous cervical adenocarcinoma HeLa cell lines, and their activity has been compared to the well-known platinum-based anticancer agent cisplatin. On the basis of these experimental results, [Pd(MSDT)X]n (MSDT = methylsarcosinedithiocarbamate; X = Cl, Br) complexes show a strong dose-dependent growth inhibition of both HL60 and HeLa cells, with IC50 values slightly higher than those recorded for cisplatin; moreover, [Au(MSDT)X2] activity appears significantly higher or, at least, comparable to that of the reference drug. Exposure of both cell lines to [Pd(MSDT)X]n and [Au(MSDT)X2] complexes induces apoptosis, as determined by an Apo2.7 assay

Chemical structures of investigated gold(III)-based compounds AuD6 (A) and AuD8 (B).

<p>Chemical structures of investigated gold(III)-based compounds AuD6 (A) and AuD8 (B).</p

Western blot <i>in vivo</i> analysis.

<p>Female nude mice bearing MDA-MB-231 tumors were treated with either vehicle (control) or the compounds AuD6 and AuD8 at 1 mg kg⁻¹ d⁻¹. Tumors were collected and the corresponding tissues prepared for Western blot analysis after either 13-day treatment (<b>A</b>) or 27-day treatment (<b>B</b>) [I and II denote distinct experiments]. Tissues were also prepared for the assays of caspase-3 activity (<b>C</b>) and of proteasomal CT-like activity (<b>D</b>) after 27 days of treatment.</p

Annexin–V FITC/PI assay.

<p>MDA-MB-231 cells were treated with the complexes AuD6 and AuD8 (20 µM) for 16 and 24 h. Then, cells were labeled with Annexin–V FITC and PI and analyzed by flow cytometry in order to evaluate the percentage of apoptotic cells. Apoptotic cells at early stage occur in the lower right quadrant while apoptotic cells at late stage set in the up-right part. The percentage in the lower left quadrant is due to viable cells whereas the upper left part to non-apoptotic cell death.</p

Structural Characterization of a Gold/Serum Albumin Complex

The medicinal gold­(III) dithiocarbamato complex AuL12 forms a stable adduct with bovine serum albumin. The crystal structure reveals that a single gold­(I) center is bound to Cys34, with the dithiocarbamato ligand being released. To the best of our knowledge, this is the first structure for a gold adduct of serum albumin

Gold Dithiocarbamate Derivatives as Potential Antineoplastic Agents: Design, Spectroscopic Properties, and in Vitro Antitumor Activity

At present, cisplatin (cis-diamminodichloroplatinum(II)) is one of the most largely employed anticancer drugs as it is effective in the treatment of 70−90% of testicular and, in combination with other drugs, of ovarian, small cell lung, bladder, brain, and breast tumors. Anyway, despite its high effectiveness, it exhibits some clinical problems related to its use in the curative therapy, such as a severe normal tissue toxicity (in particular, nephrotoxicity) and the frequent occurrence of initial and acquired resistance to the treatment. To obtain compounds with superior chemotherapeutic index in terms of increased bioavailability, higher cytotoxicity, and lower side effects than cisplatin, we report here on some gold(I) and gold(III) complexes with dithiocarbamate ligands (DMDT = N,N-dimethyldithiocarbamate; DMDTM = S-methyl-N,N-dimethyldithiocarbamate; ESDT = ethylsarcosinedithiocarbamate), which have been synthesized, purified, and characterized by means of elemental analyses, conductivity measurements, mono- and bidimensional NMR, FT-IR, and UV−vis spectroscopy, and thermal analyses. Moreover, the electrochemical properties of the designed compounds have been studied through cyclic voltammetry. All the synthesized gold complexes have been tested for their in vitro cytotoxic activity. Remarkably, most of them, in particular gold(III) derivatives of N,N-dimethyldithiocarbamate and ethylsarcosinedithiocarbamate, have been proved to be much more cytotoxic in vitro than cisplatin, with IC50 values about 1- to 4-fold lower than that of the reference drug, even toward human tumor cell lines intrinsically resistant to cisplatin itself. Moreover, they appeared to be much more cytotoxic also on the cisplatin-resistant cell lines, with activity levels comparable to those on the corresponding cisplatin-sensitive cell lines, ruling out the occurrence of cross-resistance phenomena and supporting the hypothesis of a different antitumor activity mechanism of action

Western blot and morphological analysis (concentration-dependent study).

<p><b>A</b>, Western blot analysis of breast cancer MDA-MB-231 cell extracts. Cells were treated with the complexes AuD6 and AuD8 at the indicated concentrations for 24 h. <b>B</b>, Western blot analysis of the p27 protein amount in MDA-MB-231 cell extract after treatment with the compound AuD8 at the indicated concentrations for 24 h. The solvent DMSO was used as a control while GAPDH as a loading control. <b>C</b>, Apoptotic morphological changes of MDA-MB-231 cells after treatment with AuD6 and AuD8 at the indicated concentrations for 24 h (phase contrast imaging, 100× magnification).</p

<i>In vitro</i> inhibition of proteasome.

<p>IC₅₀ values (µM±SD) obtained for the three proteasomal activities on the purified 20S proteasome and on MDA-MB-231 cell extract after 2 h incubation.</p

Antitumor activity <i>in vivo</i> on MDA-MB-231 xenografts.

<p>Female nude mice bearing MDA-MB-231 tumors were treated with either vehicle (control) or the compounds AuD6 and AuD8 at 1 mg kg⁻¹ d⁻¹. <b>A,</b> Inhibition of xenograft growth by both complexes. Tumor volumes were measured every other day using a caliper. Points represent the mean ± SD (bars) of seven mice per group. The insert depicts representative tumors from each treatment group; * = p<0.05. <b>B</b>, If only the most responsive mice are considered, the xenograft growth inhibition is greater. The insert shows average weights of mice over time; ** = p<0.01. <b>C</b>, Immunohistochemical p27 and TUNEL staining of tumor samples indicates proteasome inhibition and apoptosis as a result of both compounds. Stronger p27 staining is observed following AuD8 treatment, and more TUNEL positive cells are observed following AuD6 treatment. Brown colored cells are considered positive.</p

Gold(III) Dithiocarbamate Derivatives for the Treatment of Cancer: Solution Chemistry, DNA Binding, and Hemolytic Properties

Gold(III) compounds are emerging as a new class of metal complexes with outstanding cytotoxic properties and are presently being evaluated as potential antitumor agents. We report here on the solution and electrochemical properties, and the biological behavior of some gold(III) dithiocarbamate derivatives which have been recently proved to be one to 4 orders of magnitude more cytotoxic in vitro than the reference drug (cisplatin) and to be able to overcome to a large extent both intrinsic and acquired resistance to cisplatin itself. Their solution properties have been monitored in order to study their stability under physiological conditions; remarkably, they have shown to undergo complete hydrolysis within 1 h, the metal center remaining in the +3 oxidation state. Their DNA binding properties and ability in hemolyzing red blood cells have been also evaluated. These gold(III) complexes show high reactivity toward some biologically important isolated macromolecules, resulting in a dramatic inhibition of both DNA and RNA synthesis and inducing DNA lesions with a faster kinetics than cisplatin. Nevertheless, they also induce a strong and fast hemolytic effect (compared to cisplatin), suggesting that intracellular DNA might not represent their primary or exclusive biological target