Inductively coupled plasma mass spectrometry for metallodrug development: albumin binding and serum distribution of cytotoxic cis- and trans-isomeric platinum(II) complexes

An unexpected in-solution instability of diiodido analogue of picoplatin complicates its biological characterization

Complex cis-[PtI2(NH3)(pic)] (1; pic = 2-methylpyridine), a diiodido analogue of clinically studied picoplatin (2), is unstable in solution, which is intriguingly connected with the release of its pic ligand. This observation complicates the biological testing of e.g. cytotoxicity in human cancer cells for 1.

How versatile is the use of ultrafiltration to study biointeractions of therapeutic metallodrugs?

For a representative number of approved or investigational anticancer metallodrugs varying in lipophilicity, unspecific adsorption onto ultracentrifugal filter units was studied. It was found that for fairly hydrophilic compounds, such as cisplatin and oxaliplatin, the binding to filters does not substantially affect their amount measured (by ICP-MS) after ultrafiltration (>95%). In the case of metal complexes with moderate lipophilicity (log P > -0.1), adsorption effects turn out to be substantial. This might impede using ultrafiltration for studying the transformations of such drugs in human serum, unless they are rapidly converted into the protein adducts. The adsorption-suppressing effect of proteins was proved for indazolium trans-[tetrachloridobis(1H-indazole)ruthenate(III)] whose recovery from the filters was 61 and 14% in free and HSA-bound form, respectively.

A kinetic and mechanistic study of analogous bifunctional dialkylamine platinum(ii) complexes

A comparative substitution behaviour of isomeric cis/trans-platinum(ii) complexes.

Bacterial Cytological Profiling Reveals the Mechanism of Action of Anticancer Metal Complexes

Target identification and mechanistic studies of cytotoxic agents are challenging processes that are both time-consuming and costly. Here we describe an approach to mechanism of action studies for potential anticancer compounds by utilizing the simple prokaryotic system, E. coli, and we demonstrate its utility with the characterization of a ruthenium polypyridyl complex [Ru(bpy)₂dmbpy²⁺]. Expression of the photoconvertible fluorescent protein Dendra2 facilitated both high throughput studies and single-cell imaging. This allowed for simultaneous ratiometric analysis of inhibition of protein production and phenotypic investigations. The profile of protein production, filament size and population, and nucleoid morphology revealed important differences between inorganic agents that damage DNA vs more selective inhibitors of transcription and translation. Trace metal analysis demonstrated that DNA is the preferred nucleic acid target of the ruthenium complex, but further studies in human cancer cells revealed altered cell signaling pathways compared to the commonly administrated anticancer agent cisplatin. This study demonstrates E. coli can be used to rapidly distinguish between compounds with disparate mechanisms of action and also for more subtle distinctions within in studies in mammalian cells.

Probing the Interactions of Cytotoxic [Pt(1S,2S-DACH)(5,6-dimethyl-1,10-phenanthroline)] and Its PtIV Derivatives with Human Serum

The discrepancy between the in vitro cytotoxic results and the in vivo performance of Pt56MeSS prompted us to look into its interactions and those of its Pt^IV derivatives with human serum (HS), human serum albumin (HSA), lipoproteins, and serum-supplemented cell culture media. The Pt^II complex, Pt56MeSS, binds noncovalently and reversibly to slow-tumbling proteins in HS and in cell culture media and interacts through the phenanthroline group with HSA, with a K_d value of ∼1.5×10^-6  m. All Pt^IV complexes were found to be stable toward reduction in HS, but those with axial carboxylate ligands, cct-[Pt(1S,2S-DACH)(5,6-dimethyl-1,10-phenantroline)(acetato)₂ ](TFA)₂ (Pt56MeSS(OAc)₂ ) and cct-[Pt(1S,2S-DACH)(5,6-dimehtyl-1,10-phenantroline)(phenylbutyrato)₂ ](TFA)₂ (Pt56MeSS(PhB)₂ ), were spontaneously reduced at pH 7 or higher in phosphate buffer, but not in Tris buffer (pH 8). HS also decreased the rate of reduction by ascorbate of the Pt^IV complexes relative to the reduction rates in phosphate buffer, suggesting that for this compound class, phosphate buffer is not a good model for HS.

Amidoxime platinum(ii) complexes: pH-dependent highly selective generation and cytotoxic activity

The reaction ofcis-[PtCl₂(Me₂S̲O)₂] with amidoximes RC(NH₂)NOH results in selective generation of two types of complexes,viz.open-chain and chelated, depending on the reaction media.

Platinum(II) Iodido Complexes of 7-Azaindoles with Significant Antiproliferative Effects: An Old Story Revisited with Unexpected Outcomes

A series of platinum(II) diiodido complexes containing 7-azaindole derivatives, having the general formula cis-[PtI₂(naza)₂] (1–8), has been prepared and thoroughly characterized, including X-ray structure analysis of cis-[PtI₂(2Me4Claza)₂]∙DMF (8∙DMF; 2Me4Claza = 2-methyl-4-chloro-7-azaindole). Complexes showed high in vitro cytotoxicity against nine human cancer cell lines (IC₅₀ ranging from 0.4 to 12.8 μM), including the cisplatin-resistant ovarian cancer cell line (A2780R; IC₅₀ = 1.0–3.5 μM). The results of in vivo testing, using the L1210 lymphocytic leukaemia model, at the equimolar doses of Pt with cisplatin (2 mg/kg) confirmed the activity of complex 8 comparable to cisplatin. From the mechanistic point of view, evaluated ex vivo by Western blot analyses on the samples of isolated tumour tissues, the treatment of the animals with complex 8, contrary to cisplatin, decreased the levels of tumour suppressor p53 and increased significantly the amount of intracellular anti-apoptotic protein MCL-1_L (37 kDa). Additionally, the active form of caspase 3 was significantly elevated in the sample of tumour tissues treated with complex 8, indicating that the activation of p53-independent cell-death pathway was initiated. The light and electron microscopy observations of the cancerous tissues revealed necrosis as a dominant mechanism of cell death, followed by scarce signs of apoptosis. The additional results (e.g. in vitro interaction experiments with selected biomolecules, cell cycle perturbations, gel electrophoretic studies on pUC19 plasmid DNA) supported the hypothesis that the complexes might be involved in the mechanism of action quite different from cisplatin.

Novel enantiopure cyclopentadienyl Ti(IV) oximato compounds as potential anticancer agents

The synthesis and characterization of new enantiopure cyclopentadienyl titanium oximato compounds (S,R)-[(η(5)-C5H5)Ti{к(2)NO,(R)NH·HCl}Cl2] (R=Ph (phenyl) 1a·HCl, Bn (benzyl) 1b·HCl, 2-pic (2-picolyl) 1c·HCl), (S,R)-[(η(5)-C5H5)TiCl2{к(2)NO,(Ph)NH}] (1a) and (S,R)-[(η(5)-C5H5)2TiCl{к(2)NO,(R)NH}] (R=Ph 2a, Bn 2b, 2-pic 2c), along with studies on their behavior in D2O at different pD values are reported. The structure of previously described ammonium-oxime (2S,5R)-{NOH,(Bn)NH·HCl} (b·HCl) and novel titanium derivative 1a have been determined by single crystal X-ray crystallography. The effect of the compounds on cytotoxicity, cell adhesion and migration of the androgen-independent prostate cancer PC-3 cells has been assessed. Compounds 2b and 2c are more cytotoxic than additive doses of titanocene dichloride and free oxime proligand, probing the synergistic effect of these novel compounds. The cytotoxicity of 2b and 2c has been further evaluated against human renal Caki-1, colon DLD-1 and triple negative breast MDA-MB-231 cancer cell lines. The activity found for 2c on PC-3 and Caki-1 is higher than that of highly active Titanocene Y (bis-[(p-methoxybenzyl)cyclopentadienyl]titanium(IV) dichloride), while showing selectivity against renal cancer when compared to a non-tumorigenic human renal (HEK-293T) cell line. Compounds 2b and especially 2c are apoptotic in Caki-1 cancer cell lines. Cell adhesion and wound-healing assays confirmed that derivatives 1c·HCl, 2b and 2c affect the adhesion and migration patterns of the PC-3 cell line. Interactions of the novel compounds with plasmid (pBR322) DNA have also been studied, showing that the oximato Ti(IV) derivatives have a weak or no interaction with DNA at physiological pH.

In vivo pharmacokinetic and tissue distribution investigation of sustained-release cisplatin implants in the normal esophageal submucosa of 12 beagle dogs

PURPOSE

The aim of this study was to clarify the pharmacokinetic, tissue distribution, hematologic, and histopathologic characteristics of sustained-release cisplatin from implants [CDDP-nanoparticle (NP) implants].

METHODS

Eighteen dogs (six hybrids and twelve beagles) were divided into three groups. In Group A, the six hybrid dogs were intravenously administered 20 mg CDDP via a hind limb vein. In Groups B and C, CDDP-NP implants containing CDDP doses of 40 and 60 mg, respectively, were embedded into the esophageal submucosa of beagles via painless gastroscopy with an endoscopic booster. Graphite frameless atomic absorption spectrophotometry was used to measure total platinum in plasma and tissues at various timepoints. In addition, free platinum levels in Group B were determined using inductively coupled plasma mass spectrometry. Toxicologic evaluation was also conducted.

RESULTS

Pharmacokinetic results indicated that the CDDP-NP implant could achieve a smooth pharmacokinetic curve, with the plasma invalid concentration reached after almost 480 h, which is approximately ten times longer than that of standard CDDP (48 h). The peak time, peak concentration, clearance, elimination half-life, area under the curve, volume of distribution at steady state, and mean residence time of Groups B and C were 494 and 211, 0.39 and 0.42, 0.044 and 0.059, 80.11 and 87.70, 44 and 49, 38.8 and 57.9, and 12.29 and 12.39 times those of Group A, respectively (all P < 0.05). The ratio of free/total platinum concentration was 2.0-3.1% in plasma, 14.2% in liver tissue, and 14.3% in kidney tissue. Tissue distribution studies showed that the highest platinum concentrations were found in the esophagus, followed by the kidney and liver. Compared with pre-implantation (day 0), there were no significant differences in most hematological indicators in Groups B and C (P > 0.05). Furthermore, histopathologic examination of the kidneys of dogs from Group C revealed no significant kidney damage. Unlike the intravenous CDDP group (Group A), no animals in the implantation groups showed any clinical signs of toxicity.

CONCLUSION

CDDP-NP implants can be used to achieve a smooth pharmacokinetic curve and higher drug concentration, as well as a longer mean residence time at the implantation site, with reduced side effects compared with intravenous CDDP.

Hydrogen bonding and anticancer properties of water-soluble chiral p-cymene Ru(II) compounds with amino-oxime ligands

The investigation of the hydrogen-bonding effect on the aggregation tendency of ruthenium compounds [(η⁶-p-cymene)Ru(κNHR,κNOH)Cl]Cl (R = Ph (1a), Bn (1b)) and [(η⁶-p-cymene)Ru(κ²NH(2-pic),κNOH)][PF₆]₂ (1c), [(η⁶-p-cymene)Ru(κNHBn,κNO)Cl] (2b) and [(η⁶-p-cymene)Ru(κNBn,κ²NO)] (3b), has been performed by means of concentration dependence ¹H NMR chemical shifts and DOSY experiments. The synthesis and full characterization of new compounds 1c, [(η⁶-p-cymene)Ru(κNPh,κ²NO)] (3a) and 3b are also reported. The effect of the water soluble ruthenium complexes 1a-1c on cytotoxicity, cell adhesion and cell migration of the androgen-independent prostate cancer PC3 cells have been assessed by MTT, adhesion to type-I-collagen and recovery of monolayer wounds assays, respectively. Interactions of 1a-1c with DNA and human serum albumin have also been studied. Altogether, the properties reported herein suggest that ruthenium compounds 1a-1c have considerable potential as anticancer agents against advanced prostate cancer.

Serum metallothionein in patients with testicular cancer

PURPOSE

Metallothioneins (MTs) have been disclosed as a useful diagnostic factor for tumour progression and drug resistance in a variety of malignancies. Increased levels of MT in blood serum have been found in patients with several types of cancer, but there is no available information on serum MT levels in patients with testicular germ cell tumour (TGCT). The aim of the study was to determine MT levels in serum of patients with TGCT and to evaluate the portion of platinum (Pt) that binds to MT after cisplatin administration since MTs could be involved in drug resistance.

METHODS

Concentration of total MT was determined in serum of 25 men with newly diagnosed TGCT by differential pulse voltammetry. The fractionation of serum was carried out by size exclusion high-performance liquid chromatography (SE-HPLC), while concentration of Pt in collected fractions was determined by inductively coupled plasma mass spectrometry.

RESULTS

Concentration of serum MT was significantly higher in TGCT patients than in healthy volunteers. The results of SE-HPLC analysis showed that only a small amount of Pt was bound to proteins in the area of MT elution.

CONCLUSIONS

Significant increase in MT levels in individuals with TGCT indicates certain health problem and, in combination with other commonly used diagnostic tools, could improve early diagnosis.

Fragmentation pathways analysis for the gas phase dissociation of protonated carnosine-oxaliplatin complexes

Collision-induced dissociation (CID) experiments on the protonated carnosine-oxaliplatin complex were shown to yield nine different fragment ions. Density functional calculations were employed to probe the fragmentation mechanisms that account for all experimental data.

Recent progress of ICP-MS in the development of metal-based drugs and diagnostic agents

Critical analysis of current capabilities, limitations, and trends of ICP-MS applied to the development of metal-based medicines is conducted.