One-milliliter wet-digestion for inductively coupled plasma mass spectrometry (ICP-MS): determination of platinum-DNA adducts in cells treated with platinum(II) complexes

Rapid spectrophotometric determination and extraction of platinum(IV) from pharmaceuticals assisted by 2-(2-(1-(thiophene-2-yl) ethylidene) hydrazinyl) benzoic acid (TEHBA)

It has been suggested that the chelating agent 2-(2-(1-thiophene-2-yl) ethylidene) hydrazinyl) benzoic acid (TEHBA) be utilized to extract, separate and measure platinum(IV) by UV-visible spectrophotometry at the microgram level. Following 5 min of heating the reaction mixture in a water bath, Pt(IV)-TEHBA complex formed. This complex was formed in the presence of potassium iodide solution with a molar absorption coefficient 1.9 × 103 dm3 mol-1 cm-1. At 420 nm, the substance exhibited the greatest absorption. As Beer's law described, the Pt(IV)-TEHBA complex for platinum(IV) has a beer's range of 10-50 μg cm-3. It was determined that the proportion ratio of the Pt(IV)-TEHBA complex was 1:1 after its extraction. Despite the investigation of interference from various ions, it was ascertained that the method exhibited selectivity exclusively towards platinum(IV). The trace amounts of platinum(IV) were extracted and quantified from synthetic mixtures representing alloys, binaries and ternary synthetic mixtures. The process of extracting platinum(IV) from pharmaceutical samples involves the implementation of a specific method. Moreover, the procedure exhibits a progressive segregation of palladium(II), platinum(IV) and nickel(II) while also boasting its ease of operation.

Multielement analysis of single red blood cells by single cell - inductively coupled plasma tandem mass spectrometry

A method for the analysis of essential metals (Fe, Cu, Mg, and Zn) and non-metals (P, S) in single red blood cells was developed by single cell (SC)-ICP-MS. The use of a triple quadrupole configuration (MS/MS) enabled an effective elimination of polyatomic interferences, which affect the accuracy of ICP-MS analysis using a single quadrupole mass analyzer. Fixation with glutaraldehyde for at least 90 days was developed to improve the quantification of elements in a single red blood cell. The experimental conditions were optimized while special attention was paid to the residence time of analytes in the plasma. Addition of a surfactant (0.05% (v/v) Tween80®) improved quantification of elements in fixed red blood cells. The detection limits obtained by SC-ICP-MS/MS were lower than for ICP-MS, especially for S and P (3 fg and 1.7 fg. cell-1 instead of 163 and 6.3 fg. cell-1, respectively).

Time-Dependent Studies of Oxaliplatin and Other Nucleolar Stress-Inducing Pt(II) Derivatives

The properties of small molecule Pt(II) compounds that drive specific cellular responses are of interest due to their broad clinical use as chemotherapeutics as well as to provide a better mechanistic understanding of bioinorganic processes. The chemotherapeutic compound cisplatin causes cell death through DNA damage, while oxaliplatin may induce cell death through inhibition of ribosome biogenesis, also referred to as nucleolar stress induction. Previous work has found a subset of oxaliplatin derivatives that cause nucleolar stress at 24 h drug treatment. Here we report that these different Pt(II) derivatives exhibit a range of rates and degrees of global nucleolar stress induction as well as inhibition of rRNA transcription. Potential explanations for these variations include both the ring size and stereochemistry of the non-aquation-labile ligand. We observe that Pt(II) compounds containing a 6-membered ring show faster onset and a higher overall degree of nucleolar stress than those containing a 5-membered ring, and that compounds having the 1R,2R-stereoisomeric conformation show faster onset and a higher overall degree of stress than those having the 1S,2S-conformation. Pt(II) cellular accumulation and cellular Pt(II)-DNA adduct formation did not correlate with nucleolar stress induction, indicating that the effect is not due to global interactions. Together these results suggest that Pt(II) compounds induce nucleolar stress through a mechanism that likely involves one or a few key intermolecular interactions.

Functional Expression of a Mo-Cu-Dependent Carbon Monoxide Dehydrogenase (CODH) and Its Use as a Dissolved CO Bio-microsensor

Herein, we report the heterologous expression in Escherichia coli of a Mo-Cu-containing carbon monoxide dehydrogenase (Mo-Cu CODH) from Hydrogenophaga pseudoflava, which resulted in an active protein catalyzing CO oxidation to CO₂. By supplying the E. coli growth medium with Na₂MoO₄ (Mo) and CuSO₄ (Cu), the Mo-Cu CODH metal cofactors precursors, the expressed L-subunit was found to have CO-oxidation activity even without the M- and S- subunits. This successful expression of CO-oxidizing-capable single L-subunit provides direct evidence of its role as the catalytic center of Mo-Cu CODH that has not been discovered and studied before. Subsequently, we used the expressed protein to construct a CO bio-microsensor based on a newly developed fast and sensitive Clark-type CO₂ transducer using an aprotic solvent/ionic liquid electrolyte. The CO bio-microsensor exhibited a linear response to CO concentration in the 0-9 μM range, with a limit of detection (LOD) of 15 nM CO. The sensor uses a mixture of Mo-Cu CODH's L-subunit/Mo, Cu cofactors/methylene blue, confined in the enzyme chamber that is placed in front of a CO₂ transducer. The optimized sensor's sensitivity and performance were retained to levels of at least 80% for 1 week of continuous polarization and operation in an aqueous medium. We have also demonstrated the use of an alkaline front-trap solution to make a completely O₂/CO₂ interference-free microsensor. The CO bio-microsensor developed in this study is potentially useful as an analytical tool for the detection of trace CO in dissolved form for monitoring dissolved CO concentration dynamics in natural or synthetic systems.

A successful compartmental approach for the treatment of breast cancer brain metastases

BACKGROUND

Brain metastases are challenging daily practice in oncology and remain a compartmental problem since most anti-cancer drugs do not cross the blood-brain barrier at relevant pharmacological concentrations.

METHODS

In a young woman with HER2-overexpressing breast cancer resistant to standard treatments, at the time of brain metastases progression, a ventricular reservoir was implanted for intrathecal drug injections and detailed pharmacokinetic studies.

RESULTS

A first association of intrathecal trastuzumab with intravenous cisplatin was offered to the patient. For trastuzumab, the mean cerebrospinal fluid trough concentration of 53.4 mg/L reached relevant levels, enabling the stabilization of the metastases. Adding intravenous cisplatin was not beneficial, since the cerebrospinal fluid exposure was almost undetectable under 0.08 mg/L. We then offered the patient an intrathecal combination of trastuzumab and methotrexate, because of their in vitro synergic cytotoxicity. The cerebrospinal fluid peak of methotrexate was 1037 µmol/L at 2 h, and the concentrations remained above the theoretical therapeutic concentration. After 2 months of this drug combination, we obtained an excellent response on the brain metastases.

CONCLUSION

Our preliminary study supports the interest of a compartmental approach through a direct administration of drugs into the cerebrospinal fluid for the treatment of breast cancer brain metastases.

Encapsulation, controlled release, and antitumor efficacy of cisplatin delivered in liposomes composed of sterol-modified phospholipids

We employed a recently introduced class of sterol-modified lipids (SML) to produce m-PEG-DSPE containing liposome compositions with a range of cis-platinum content release rates. SML have a cholesterol succinate attached to the phosphatidylglycerol head group and a fatty acid at the 2 position. These compositions were compared to the well-studied liposome phospholipid compositions: mPEG-DSPE/Hydrogenated Soy PC/cholesterol or mPEG-DSPE/POPC/cholesterol to determine the effect of the cis-platinum release extent on C26 tumor proliferation in the BALB/c colon carcinoma mouse model. The release rates of cis-platinum from liposomes composed of SML are a function of the acyl chain length. SML-liposomes with shorter acyl chain lengths C-8 provided more rapid cisplatin release, lower in vitro IC50, and were easier to formulate compared to liposomes using traditional phospholipid compositions. Similar to other liposome cis-platinum formulations, the half-life of m-PEG-DSPE SML liposome cisplatin is substantially longer than the free drug. This resulted in a higher tumor cisplatin concentration at 48h post-dosing compared to the free drug and higher Pt-DNA adducts in the tumor. Moreover, the maximum tolerated dose of the liposome formulations where up to four fold greater than the free drug. Using X-ray fluorescence spectroscopy on tumor sections, we compared the location of platinum, to the location of a fluorescence lipid incorporated in the liposomes. The liposome platinum co-localized with the fluorescent lipid and both were non-uniformly distributed in the tumor. Non-encapsulated Cis-platinum, albeit at a low concentration, was more uniformly distributed thorough the tumor. Three liposome formulations, including the well-studied hydrogenated HSPC composition, had better antitumor activity in the murine colon 26 carcinoma model as compared to the free drug at the same dose but the SML liposome platinum formulations did not perform better than the HSPC formulation.

DNA Adducts from Anticancer Drugs as Candidate Predictive Markers for Precision Medicine

Biomarker-driven drug selection plays a central role in cancer drug discovery and development, and in diagnostic strategies to improve the use of traditional chemotherapeutic drugs. DNA-modifying anticancer drugs are still used as first line medication, but drawbacks such as resistance and side effects remain an issue. Monitoring the formation and level of DNA modifications induced by anticancer drugs is a potential strategy for stratifying patients and predicting drug efficacy. In this perspective, preclinical and clinical data concerning the relationship between drug-induced DNA adducts and biological response for platinum drugs and combination therapies, nitrogen mustards and half-mustards, hypoxia-activated drugs, reductase-activated drugs, and minor groove binding agents are presented and discussed. Aspects including measurement strategies, identification of adducts, and biological factors that influence the predictive relationship between DNA modification and biological response are addressed. A positive correlation between DNA adduct levels and response was observed for the majority of the studies, demonstrating the high potential of using DNA adducts from anticancer drugs as mechanism-based biomarkers of susceptibility, especially as bioanalysis approaches with higher sensitivity and throughput emerge.

Specific Conformational Change in Giant DNA Caused by Anticancer Tetrazolato-Bridged Dinuclear Platinum(II) Complexes: Middle-Length Alkyl Substituents Exhibit Minimum Effect

Derivatives of the highly antitumor-active compound [{cis-Pt(NH₃)₂}₂(μ-OH)(μ-tetrazolato-N2,N3)]²⁺ (5-H-Y), which is a tetrazolato-bridged dinuclear platinum(II) complex, were prepared by substituting a linear alkyl chain moiety at C5 of the tetrazolate ring. The general formula for the derivatives is [{cis-Pt(NH₃)₂}₂(μ-OH)(μ-5-R-tetrazolato-N2,N3)]²⁺, where R is (CH₂)_nCH₃ and n = 0 to 8 (complexes 1-9). The cytotoxicity of complexes 1-4 in NCI-H460 human non-small-cell lung cancer cells decreased with increasing alkyl chain length, and those of complexes 5-9 increased with increasing alkyl chain length. That is, the in vitro cytotoxicity of complexes 1-9 was found to have a U-shaped association with alkyl chain length. This U-shaped association is attributable to the degree of intracellular accumulation. Although circular dichroism spectroscopic measurement indicated that complexes 1-9 induced comparable conformational changes in the secondary structure of DNA, the tetrazolato-bridged complexes induced different degrees of DNA compaction as revealed by a single DNA measurement with fluorescence microsopy, which also had a U-shaped association with alkyl chain length that matched the association observed for cytotoxicity. Complexes 7-9, which had alkyl chains long enough to confer surfactant-like properties to the complex, induced DNA compaction 20 or 1000 times more efficiently than 5-H-Y or spermidine. A single DNA measurement with transmission electron microscopy revealed that complex 8 formed large spherical self-assembled structures that induced DNA compaction with extremely high efficiency. This result suggests that these structures may play a role in the DNA compaction that was induced by the complexes with the longer alkyl chains. The derivatization with a linear alkyl chain produced a series of complexes with unique cellular accumulation and DNA conformational change profiles and a potentially useful means of developing next-generation platinum-based anticancer drugs. In addition, the markedly high ability of these complexes to induce DNA compaction and their high intracellular accumulation emphasized the difference in mechanism of action from platinum-based anticancer drugs.

Pharmacokinetics of cisplatin in the absence or presence of zengmian yiliu granules (a traditional Chinese medicine compound) in rats determined via ICP-MS: an investigation on drug-herb interactions

CONTEXT

Cisplatin is a highly effective chemotherapeutic agent against many tumors; however, it has potent adverse effects. Zengmian Yiliu granule (ZMYL), a traditional Chinese medicine (TCM) compound, has been clinically used against platinum (Pt)-induced toxicity and to enhance the efficacy of cisplatin.

OBJECTIVE

The study was conducted to investigate the likelihood of potential pharmacokinetics drug-herbs interaction (DHI) between cisplatin and ZMYL.

MATERIALS AND METHODS

An improved ICP-MS method combined with ultrafiltration and microwave-assisted digestion was performed to determine the total and free Pt concentrations in rat plasma after intraperitoneal administration of cisplatin (9 mg/kg) or a combined administration with ZMYL (1 g/kg) by gavage.

RESULTS

ZMYL produced a potential DHI on the pharmacokinetic parameters of cisplatin, calculated from the total Pt concentration. The clearance rate decreased from 110.52 to 66.12 mLh(-1 )kg(-1), the mean residence time extended from 63.1 to 164.54 h, the area under the plasma concentration-time curve increased from 86.58 to 152.93 µg h mL(-1), the elimination half-life extended from 48.38 to 126.4 h, and the elimination rate constant decreased from 0.017 to 0.006 h, in the ZMYL combination group (p < 0.05). In terms of free Pt concentration, the apparent volume of distribution and clearance rate was statistically different (p < 0.05). The Pt plasma protein binding ratios in the early dose stages were significantly boosted by the co-administration of ZMYL (p < 0.01).

DISCUSSION AND CONCLUSION

ZMYL is a potential complementary and alternative medicine for cisplatin chemotherapy. The therapeutic benefits of ZMYL-cisplatin chemotherapy derived from pharmacokinetic interaction needs further investigation.

Oxaliplatin and its enantiomer induce different condensation dynamics of single DNA molecules

The interactions of DNA with oxaliplatin (Pt(R,R-DACH)) or its enantiomer (Pt(S,S-DACH)) were investigated using magnetic tweezers and atomic force microscope. In the process of DNA condensation induced by Pt-DACH, only diadducts and micro-loops are formed at low Pt-DACH concentrations, while at high Pt-DACH concentrations, besides the diadducts and micro-loops, long-range cross-links are also formed. The diadduct formation rate of Pt(R,R-DACH) is higher than that of Pt(S,S-DACH). However, the proportions of micro-loops and long-range cross-links for Pt(S,S-DACH) are higher than those for Pt(R,R-DACH). We propose a model to explain these differences between the effect of Pt(R,R-DACH) and that of Pt(S,S-DACH) on DNA condensation. The study has strong implications for the understanding of the effect of chirality on the interaction between Pt-DACH and DNA and the kinetics of DNA condensation induced by platinum complexes.

Personalized medicine for targeted and platinum-based chemotherapy of lung and bladder cancer

The personalized medicine revolution is occurring for cancer chemotherapy. Biomarkers are increasingly capable of distinguishing genotypic or phenotypic traits of individual tumors, and are being linked to the selection of treatment protocols. This review covers the molecular basis for biomarkers of response to targeted and cytotoxic lung and bladder cancer treatment with an emphasis on platinum-based chemotherapy. Platinum derivatives are a class of drugs commonly employed against solid tumors that kill cells by covalent attachment to DNA. Platinum-DNA adduct levels in patient tissues have been correlated to response and survival. The sensitivity and precision of adduct detection has increased to the point of enabling subtherapeutic dosing for diagnostics applications, termed diagnostic microdosing, prior to the initiation of full-dose therapy. The clinical status of this unique phenotypic marker for lung and bladder cancer applications is detailed along with discussion of future applications.

Analysis of the DNA damage produced by a platinum-acridine antitumor agent and its effects in NCI-H460 lung cancer cells

High-performance liquid chromatography in conjunction with electrospray mass spectrometry (LC-ESMS) was used to structurally characterize the adducts formed by the platinum-acridine agent [PtCl(en)(N-(2-(acridin-9-ylamino)ethyl)-N-methylpropionimidamide)](NO(3))(2) (compound 1) in cell-free DNA. Compound 1 forms monofunctional adducts exclusively with guanine, based on the fragments identified in enzymatic digests (dG*, dGMP*, dApG*, and dTpG*, where the asterisk denotes bound drug). The time course of accumulation and DNA adduct formation of compound 1 and the clinical drug cisplatin in NCI-H460 lung cancer cells at physiologically relevant drug concentrations (0.1 μM) was studied by inductively-coupled plasma mass spectrometry (ICP-MS). Compound 1 accumulates rapidly in cells and reaches intracellular levels of up to 60-fold higher than those determined for cisplatin. The hybrid agent shows unusually high DNA binding levels: while cisplatin adducts form at a maximum frequency of 5 adducts per 10(6) nucleotides, compound 1 produces 25 adducts per 10(6) nucleotides after only 3 h of continuous incubation with the lung cancer cells. The high overall levels of compound 1 in the cells and in cellular DNA over the entire 12-h treatment period translate into a rapid decrease in cell viability. Possible implications of these findings for the mechanism of action of compound 1 and the agent's potential to overcome tumor resistance to cisplatin are discussed.

Speciation of oxaliplatin adducts with DNA nucleotides

This paper describes a set of fast and selective high performance liquid chromatography (HPLC) methods coupled to electro-spray ionisation linear ion trap mass spectrometry (ESI-MS), sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) and UV detection for in vitro studies of the bifunctional adducts of oxaliplatin with mono-nucleotides, di-nucleotides and cellular DNA. The stationary phases and the optimised conditions used for each separation are discussed. Interaction of oxaliplatin with A and G mono-nucleotides resulted in the formation of five bifunctional platinum diaminocyclohexane (DACHPt) adducts. These were two isomers of the A-DACHPt-A and A-DACHPt-G adducts, and one G-DACHPt-G adduct, as confirmed by MS/MS spectra obtained by collision induced dissociation. These adducts were also characterised by UV absorption data and SF-ICP-MS elemental (195)Pt and (31)P signals. Further, interaction of oxaliplatin with AG and GG di-nucleotides resulted in the formation of three adducts: DACHPt-GG and two isomers of the DACHPt-AG adduct, as confirmed by ESI-MS and the complementary data obtained by UV and SF-ICP-MS. Finally, a very sensitive LC-ICP-MS method for the quantification of oxaliplatin GG intra-strand adducts (DACHPt-GG) was developed and used for monitoring the in vitro formation and repair of these adducts in human colorectal cancer cells. The method detection limit was 0.14 ppb Pt which was equivalent to 0.22 Pt adduct per 10(6) nucleotides based on a 10 μg DNA sample. This detection limit makes this method suitable for in vivo assessment of DACHPt-GG adducts in patients undergoing oxaliplatin chemotherapy.

The application of inductively coupled plasma mass spectrometry in clinical pharmacological oncology research

Metal-based anticancer agents are frequently used in the treatment of a wide variety of cancer types. The monitoring of these anticancer agents in biological samples is important to understand their pharmacokinetics, pharmacodynamics, and metabolism. In addition, determination of metals originating from anticancer agents is relevant to assess occupational exposure of health care personnel working with these drugs. The high sensitivity of inductively coupled plasma mass spectrometry (ICP-MS) has resulted in an increased popularity of this technique for the analysis of metal-based anticancer drugs. In addition to the quantitative analysis of the metal of interest in a sample, ICP-MS can be used as an ultrasensitive metal selective detector in combination with speciation techniques such as liquid chromatography. In the current review we provide a systematic survey of publications describing the analysis of platinum- and ruthenium-containing anticancer agents using ICP-MS, focused on the determination of total metal concentrations and on the speciation of metal compounds in biological fluids, DNA- and protein-adducts, and environmental samples. We conclude that ICP-MS is a powerful tool for the quantitative analysis of metal-based anticancer agents from multiple sample sources.

Determination of platinum in human subcellular microsamples by inductively coupled plasma mass spectrometry

A fast and robust method for the determination of platinum in human subcellular microsamples by inductively coupled plasma mass spectrometry was developed, characterized, and validated. Samples of isolated DNA and exosome fractions from human ovarian (2008) and melanoma (T289) cancer cell lines were used. To keep the sample consumption to approximately 10 microl and obtain a high robustness of the system, a flow injection sample introduction system with a 4.6-microl sample loop was used in combination with a conventional pneumatic nebulizer and a spray chamber. The system was optimized with respect to signal/noise ratio using a multivariate experimental design. The system proved to be well suited for routine analysis of large sample series, and several hundreds of samples could be analyzed without maintenance or downtime. The detection limit of the method was 0.12 pg (26 pg/g) platinum. To avoid systematic errors from nonspectral interferences, it was necessary to use reagent matched calibration standards or isotope dilution analysis. An uncertainty budget was constructed to estimate the total expanded uncertainty of the method, giving a quantification limit of 2.3 pg (0.5 ng/g) platinum in DNA samples. The uncertainty was sufficiently low to study quantitative differences in the formation of Pt-DNA adducts after treatment with cisplatin using different exposure times and concentrations.

Kinetics of carboplatin-DNA binding in genomic DNA and bladder cancer cells as determined by accelerator mass spectrometry

Cisplatin and carboplatin are platinum-based drugs that are widely used in cancer chemotherapy. The cytotoxicity of these drugs is mediated by platinum-DNA monoadducts and intra- and interstrand diadducts, which are formed following uptake of the drug into the nucleus of cells. The pharmacodynamics of carboplatin display fewer side effects than for cisplatin, albeit with less potency, which may be due to differences in rates of DNA adduct formation. We report the use of accelerator mass spectrometry (AMS), a sensitive detection method often used for radiocarbon quantitation, to measure both the kinetics of [14C]carboplatin-DNA adduct formation with genomic DNA and drug uptake and DNA binding in T24 human bladder cancer cells. Only carboplatin-DNA monoadducts contain radiocarbon in the platinated DNA, which allowed for calculation of kinetic rates and concentrations within the system. The percent of radiocarbon bound to salmon sperm DNA in the form of monoadducts was measured by AMS over 24 h. Knowledge of both the starting concentration of the parent carboplatin and the concentration of radiocarbon in the DNA at a variety of time points allowed calculation of the rates of Pt-DNA monoadduct formation and conversion to toxic cross-links. Importantly, the rate of carboplatin-DNA monoadduct formation was approximately 100-fold slower than that reported for the more potent cisplatin analogue, which may explain the lower toxicity of carboplatin. T24 human bladder cancer cells were incubated with a subpharmacological dose of [14C]carboplatin, and the rate of accumulation of radiocarbon in the cells and nuclear DNA was measured by AMS. The lowest concentration of radiocarbon measured was approximately 1 amol/10 microg of DNA. This sensitivity may allow the method to be used for clinical applications.