Simultaneous observation of the metabolism of cisplatin and NAMI-A in human plasma in vitro by SEC-ICP-AES

Dual drug delivery system of RAPTA-C and paclitaxel based on fructose coated nanoparticles for metastatic cancer treatment

Ruthenium complexes have been widely studied as potential alternatives to platinum-type anticancer drugs due to their unique medical properties such as high selectivity, strong ability to inhibit solid tumour metastasis. However, non-specific biodistribution, and weak lethality of ruthenium to cancer cells limit its use in medical application. Drug delivery systems offer the ability to integrate multiple drugs in one system, which is particularly important to enhance the chemotherapeutic efficacy and to potentially achieve a synergistic effect of both drugs. Here, we report a dual drug nanocarrier that is based on a self-assembled biodegradable block copolymer, where the ruthenium complex (RAPTA-C) is chemically attached to the polymer chain, while another drug, paclitaxel (PTX), is entrapped in the core of the micelle. The dual drug delivery system was studied via in vitro tests using MDA-MB-231 breast cancer cells and it was observed that RAPTA-C in combination with PTX significantly enhanced anti-tumour and anti-metastasis activity.

Application of a Novel Metallomics Tool to Probe the Fate of Metal-Based Anticancer Drugs in Blood Plasma: Potential, Challenges and Prospects

Although metallodrugs are used to treat a variety of human disorders and exhibit a remarkable diversity of therapeutic properties, they constitute only a tiny minority of all medicinal drugs that are currently on the market. This undesirable situation must be partially attributed to our general lack of understanding the fate of metallodrugs in the extremely ligand-rich environment of the bloodstream. The challenge of gaining insight into these bioinorganic processes can be overcome by the application of 'metallomics tools', which involve the analysis of biological fluids (e.g., blood plasma) with a separation method in conjunction with multi-element specific detectors. To this end, we have developed a metallomics tool that is based on size-exclusion chromatography (SEC) hyphenated to an inductively coupled plasma atomic emission spectrometer (ICP-AES). After the successful application of SEC-ICPAES to analyze plasma for endogenous copper, iron and zinc-metalloproteins, it was subsequently applied to probe the metabolism of a variety of metal-based anticancer drugs in plasma. The versatility of this metallomics tool is exemplified by the fact that it has provided insight into the metabolism of individual Pt-based drugs, the modulation of the metabolism of cisplatin by sulfur-containing compounds, the metabolism of two metal-based drugs that contain different metals as well as a bimetallic anticancer drug, which contained two different metals. After adding pharmacologically relevant doses of metallodrugs to plasma, the temporal analysis of aliquots by SEC-ICP-AES allows to observe metal-protein adducts, metallodrug-derived degradation products and the parent metallodrug(s). This unique capability allows to obtain comprehensive insight into the fate of metal-based drugs in plasma and can be extended to in vivo studies. Thus, the application of this metallomics tool to probe the fate of novel metalcomplexes that exert the desired biological activity in plasma has the potential to advance more of these to animal/preclinical studies to fully explore the potential that metallodrugs inherently offer.

SEC hyphenated to a multielement-specific detector unravels the degradation pathway of a bimetallic anticancer complex in human plasma

The bimetallic metal complex Titanocref exhibits relevant anticancer activity, but it is unknown if it is stable to reach target tissues intact. To gain insight, a pharmacologically relevant dose was added to human blood plasma and the mixture was incubated at 37 °C. The obtained mixture was analyzed 5 and 60 min later by size-exclusion chromatography hyphenated to an inductively coupled plasma atomic emission spectrometer (SEC-ICP-AES). We simultaneously detected several titanium (Ti), gold (Au) and sulfur (S)-peaks, which corresponded to a Ti degradation product that eluted partially, and a Au degradation product that eluted entirely bound to plasma proteins (both time points). Although ~70% of the intact Titanocref was retained on the column after 60 min, our results allowed us to establish - for the first time - its likely degradation pathway in human plasma at near physiological conditions. These results suggest that ~70% of Titanocref remain in plasma after 60 min, which supports results from a recent in vivo study in which mice were treated with Titanocref and revealed Ti:Au molar ratios in tumors and organs close to 1:1. Thus, our stability studies suggest that the intact drug is able to reach target tissue. Overall, our results exemplify that SEC-ICP-AES enables the execution of intermediate in vitro studies with human plasma in the context of advancing bimetallic metal-based drugs to more costly clinical studies.

Combination of Ruthenium Complex and Doxorubicin Synergistically Inhibits Cancer Cell Growth by Down-Regulating PI3K/AKT Signaling Pathway

Combinational use of drugs has been a common strategy in cancer treatment because of synergistic advantages in reducing dose and toxicity, minimizing or delaying drug resistance. To improve the efficacy of chemotherapy, various potential combinations have been investigated. Ruthenium complex is considered a potential alternative of the platinum-based drugs due to its significant efficacy and safety. Previously, we reported that ruthenium(II) complex (Δ-Ru1) has great anticancer potential and minor toxicity toward normal tissues. However, the therapeutic efficacy and mechanism of action of ruthenium(II) complex combined with other anticancer drugs is still unknown. Here, we investigated the combinational effect of Δ-Ru1 and doxorubicin in different cancer cells. The data assessed by Chou-Talalay method showed significant synergism in MCF-7 cells. Furthermore, the results in antiproliferation efficacy indicated that the combination showed strong cytotoxicity and increasing apoptosis of MCF-7 cells in 2D and 3D multicellular tumor spheroids (MCTSs). Significant inhibition of MCF-7 cells accompanied with increased ROS generation was observed. Furthermore, the expression of PI3K/AKT was significantly down-regulated, while the expression of PTEN was strongly up-regulated in cells treated with combination of Δ-Ru1 and doxorubicin. The expression of NF-κB and XIAP decreased while the expression of P53 increased and associated with apoptosis. These findings suggest that the combination of ruthenium complex and doxorubicin has a significant synergistic effect by down-regulating the PI3K/AKT signaling pathway in MCF-7 cells. This study may trigger more research in ruthenium complex and combination therapy that will be able to provide opportunities for developing better therapeutics for cancer treatment.

Advanced LC-analysis of human plasma for metallodrug metabolites

Understanding the fate of metallodrugs in the bloodstream is critical to assess if the parent drug has a reasonable probability to reach the intended target tissue and to predict toxic side-effects. To gain insight into these processes, we have added pharmacologically relevant doses of metallodrugs to blood plasma and applied an LC-method to directly analyze the latter for metallodrug metabolites. Using human or rabbit plasma, this LC-method was employed to gain insight into the metabolism of clinically used as well as emerging anticancer metallodrugs and to unravel the mechanisms by which small molecular weight compounds that - when co-administered with a metallodrug - decrease the toxic side-effects of the metallodrug by modulating its metabolism. The results suggest that the developed LC-method is useful to probe the fate of biologically active novel metal-complexes in plasma to help select those which may be advanced to animal/clinical studies to ultimately develop safer metallodrugs.

Albumin binding and ligand-exchange processes of the Ru(III) anticancer agent NAMI-A and its bis-DMSO analogue determined by ENDOR spectroscopy

The ruthenium anticancer compound NAMI-A, imidazolium [trans-RuCl4(1H-imidazole)(DMSO-S)], is currently undergoing advanced clinical evaluation. As with other Ru(iii) chemotherapeutic candidates, interactions with human serum albumin (HSA) have been identified as a key component of the speciation of NAMI-A following intravenous administration. To characterize coordination to HSA, we have performed electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) spectroscopic analysis of deuterium-labelled isotopologues of both NAMI-A and its bis-DMSO analogue, [(DMSO)2H][trans-RuCl4(DMSO-S)2] (Ru-bis-DMSO). Samples were prepared using phosphate buffered saline, in the presence of HSA, and with the individual amino acids histidine, cysteine, and alanine. Analysis of (1)H ENDOR spectra shows characteristic hyperfine interactions from DMSO, water, and imidazole ligands. Furthermore, coordination of imidazole ligands was confirmed from diagnostic (14)N ENDOR signals. Combined with the EPR data from the complexes following incubation in the presence of histidine, the ENDOR data demonstrate that both complexes bind to HSA via histidine imidazoles. Furthermore, the protein-bound species are shown to have water ligands and, in the case of Ru-bis-DMSO, one species has a remaining coordinated DMSO.

Impact of low- and high-molecular-mass components of human serum on NAMI-A binding to transferrin

Imidazolium trans-tetrachloridodimethylsulfoxideimidazolruthenate(III), NAMI-A, a novel antimetastatic ruthenium complex was investigated towards affinity to transferrin (Tf), whether Tf–Ru adducts might be formed after its intravenous injection. Studies were focused on the holotransferrin due to its preferential binding to transferrin receptor. Here, we showed that holotransferrin is able to bind NAMI-A as readily as apotransferrin. The simulation of biological conditions of human serum performed by application of simplified serum models allowed to analyse ruthenium distribution between transferrin and albumin. The presence of physiological concentration of albumin (ca. 18-fold excess over Tf) resulted in a twofold decrease of ruthenium binding to Tf. Interestingly, the introducing of low-molecular-mass components of serum dramatically increased the ruthenation of Tf. Intermolecular competition binding studies between transferrin and albumin showed that both proteins bound similar amount of ruthenium species. Investigation of NAMI-A binding to Tf in human serum showed that this protein was not the major binding partner for Ru complex. However, in spite of many competing proteins still the ruthenation of Tf was observed. The lack of free Ru species (protein unbounded) after incubation with human serum allowed to make an assumption of high affinity of NAMI-A towards serum proteins.