Gold(III) to Ruthenium(III) Metal Exchange in Dithiocarbamato Complexes Tunes Their Biological Mode of Action for Cytotoxicity in Cancer Cells.

Malignant tumors have affected the human being since the pharaoh period, but in the last century the incidence of this disease has increased due to a large number of risk factors, including deleterious lifestyle habits (i.e., smoking) and the higher longevity. Many efforts have been spent in the last decades on achieving an early stage diagnosis of cancer, and more effective cures, leading to a decline in age-standardized cancer mortality rates. In the last years, our research groups have developed new metal-based complexes, with the aim to obtain a better selectivity for cancer cells and less side effects than the clinically established reference drug cisplatin. This work is focused on four novel Au(III) and Ru(III) complexes that share the piperidine dithiocarbamato (pipe-DTC) as the ligand, in a different molar ratio. The compounds [AuCl2(pipeDTC)], [Au(pipeDTC)2]Cl, [Ru(pipeDTC)3] and ß-[Ru2(pipeDTC)5] have been synthesized and fully characterized by several chemical analyses. We have then investigated their biological properties in two different cell lines, namely, AGS (gastric adenocarcinoma) and HCT116 (colon carcinomas), showing significant differences among the four compounds. First, the two gold-based compounds and ß-[Ru2(pipeDTC)5] display IC50 in the µM range, significantly lower than cisplatin. Second, we showed that [AuCl2(pipeDTC)] and ß-[Ru2(pipeDTC)5]Cl drive different molecular mechanisms. The first was able to induce the protein level of the DNA damage response factor p53 and the autophagy protein p62, in contrast to the second that induced the ATF4 protein level, but repressed p62 expression. This study highlights that the biological activity of different complexes bringing the same organic ligand depends on the electronic and structural properties of the metal, which are able to fine tune the biological properties, giving us precious information that can help to design more selective anticancer drugs.

Labelled micelles for the delivery of cytotoxic Cu(II) and Ru(III) compounds in the treatment of aggressive orphan cancers: Design and biological in vitro data.

A recent study on our metal-dithiocarbamato complexes pointed out the antiproliferative properties and the druglikeness of some new patented derivatives. In this work, the best compounds have been encapsulated in micellar nanocarriers, being also carbohydrate-functionalized on their hydrophilic surface to investigate the possibility of a cancer-selective delivery. In particular, the nonionic block copolymer Pluronic® F127 (PF127) has been chemically modified with sugars and the derivatives characterized by means of NMR spectroscopy and FT-IR spectrophotometry. Then, the two selected complexes (ß-[Ru2(PipeDTC)5]Cl (PipeDTC = piperidine dithiocarbamate) and [Cu(ProOMeDTC)2] (ProOMeDTC = L-proline methyl ester dithiocarbamate)), have been loaded into the hydrophobic core of PF127 micelles and cancer-targeting counterparts. These nanoformulations have been studied for their dimensions (DLS, TEM) and stability, and tested for their cytotoxicity against aggressive human cancer cell lines. The in vitro results were paralleled with mechanistic studies through Confocal Laser Scanning Microscopy and xCELLigence analysis.

CuII and AuIII Complexes with Glycoconjugated Dithiocarbamato Ligands for Potential Applications in Targeted Chemotherapy.

This work is focused on the synthesis, characterization, and preliminary biological evaluation of bio-conjugated AuIII and CuII complexes with the aim of overcoming the well-known side effects of chemotherapy by improving the selective accumulation of an anticancer metal payload in malignant cells. For this purpose, carbohydrates were chosen as targeting agents, exploiting the Warburg effect that accounts for the overexpression of glucose-transporter proteins (in particular GLUTs) in the phospholipid bilayer of most neoplastic cells. We linked the dithiocarbamato moiety to the C1 position of three different monosaccharides: d-glucose, d-galactose, and d-mannose. Altogether, six complexes with a 1:2 metal-to-ligand stoichiometry were synthesized and in vitro tested as anticancer agents. One of them showed high cytotoxic activity toward the HCT116 colorectal human carcinoma cell line, paving the way to future in vivo studies aimed at evaluating the role of carbohydrates in the selective delivery of whole molecules into cancerous cells.

New comprehensive studies of a gold(III) Dithiocarbamate complex with proven anticancer properties: Aqueous dissolution with cyclodextrins, pharmacokinetics and upstream inhibition of the ubiquitin-proteasome pathway.

The gold(III)-dithiocarbamate complex AuL12 (dibromo [ethyl-N-(dithiocarboxy-kS,kS')-N-methylglycinate] gold(III)), is endowed with promising in vitro/in vivo antitumor activity and toxicological profile. Here, we report our recent strategies to improve its water solubility and stability under physiological conditions along with our efforts for unravelling its tangled mechanism of action. We used three types of α-cyclodextrins (CDs), namely ß-CD, Me-ß-CD and HP-ß-CD to prepare aqueous solutions of AuL12. The ability of these natural oligosaccharide carriers to enhance water solubility of hydrophobic compounds, allowed drug stability of AuL12 to be investigated. Moreover, pharmacokinetic experiments were first carried out for a gold(III) coordination compound, after i.v. injection of the nanoformulation AuL12/HP-ß-CD to female mice. The gold content in the blood samples was detected at scheduled times by AAS (atomic absorption spectrometry) analysis, highlighting a fast biodistribution with a tß1/2 of few minutes and a slow escretion (tα1/2 of 14.3 h). The in vitro cytotoxic activity of AuL12 was compared with the AuL12/HP-ß-CD mixture against a panel of three human tumor cell lines (i.e., HeLa, KB and MCF7). Concerning the mechanism of action, we previously reported the proteasome-inhibitory activity of some our gold(III)-based compounds. In this work, we moved from the proteasome target to upstream of the important ubiquitin-proteasome pathway, testing the effects of AuL12 on the polyubiquitination reactions involving the Ub-activating (E1) and -conjugating (E2) enzymes.

Gold Complexes for Therapeutic Purposes: an Updated Patent Review (2010-2015).

Gold has always aroused great interest in the history of mankind. It has been used for thousands of years for jewelry, religious cult valuables, durable goods and in the art world. However, few know that such a precious and noble metal was exploited in the past by the ancients also for its therapeutic properties. More recently, in the twentieth century some complexes containing gold centers in the oxidation state +1 were studied for the treatment of the rheumatoid arthritis and the orally-administered drug Auranofin was approved by the FDA in 1985. From the chemical point of view, gold derivatives deserve special attention due to the unique position of this metal within the periodic table, which results in unconventional relativistic effects and, ultimately, in the highest electronegativity, electron affinity and redox potential among all metals. In this review, after an introduction concerning the use of gold complexes in medicine, we have examined all the patents internationally or nationally published in the years 2010-2015 (until December 31, 2015) and describing new inorganic compounds containing gold(I) and gold(III) with proved therapeutic properties. These patents were filed to mainly protect compounds with promising anticancer and anti-inflammatory activities (total 18 and 4, respectively). In particular, this work explores both coordination compounds containing ligands with various donor atoms (e.g., N-, O-, S- and -P) and organo-gold derivatives with at least one Au-C bond. The toxicological profile and the intracellular targets reported for some among the patented gold derivatives are discussed.