Development and validation of a liquid chromatography tandem mass spectrometry quantification method for 14 cytotoxic drugs in environmental samples

RATIONALE

Cytotoxic drug preparation in hospital pharmacies is associated with chronic occupational exposure leading to a risk of adverse effects. The objective was to develop and validate a quantification method for the following cytotoxic drugs in environmental wipe samples: cyclophosphamide, ifosfamide, cytarabine, dacarbazine, docetaxel, paclitaxel, doxorubicin, epirubicin, etoposide, 5-fluorouracil, gemcitabine, irinotecan, methotrexate and pemetrexed.

METHODS

The quantification method was developed using liquid chromatography coupled to tandem mass spectrometry and a wiping technique using viscose swabs. Linearity, accuracy, precision, limit of quantification, specificity and stability were assessed, from swab desorbed solution, to validate the analytical method, with respect to ICH guidelines. Environmental samples were collected by wiping five work surfaces of 225 cm² with viscose swabs, during three days.

RESULTS

The quantification method was linear over the calibration range with a lower limit of quantification ranging from 0.5 to 5.0 ng mL^-1 depending on the cytotoxic drug. The intra-day and inter-day relative biases were below 1.5% and 13.5%, respectively. This method was successfully applied to surface-wipe sampling and environmental contaminations ranged from 0.7 to 1840.0 ng cm^-2 for the most contaminated areas.

CONCLUSIONS

This quantification method for 14 cytotoxic drugs was successfully applied to environmental contamination monitoring and could therefore be a useful tool for monitoring and toxicological studies.

A DNA aptamer for binding and inhibition of DNA methyltransferase 1

DNA methyltransferases (DNMTs) are enzymes responsible for establishing and maintaining DNA methylation in cells. DNMT inhibition is actively pursued in cancer treatment, dominantly through the formation of irreversible covalent complexes between small molecular compounds and DNMTs that suffers from low efficacy and high cytotoxicity, as well as no selectivity towards different DNMTs. Herein, we discover aptamers against the maintenance DNA methyltransferase, DNMT1, by coupling Asymmetrical Flow Field-Flow Fractionation (AF4) with Systematic Evolution of Ligands by EXponential enrichment (SELEX). One of the identified aptamers, Apt. #9, contains a stem-loop structure, and can displace the hemi-methylated DNA duplex, the native substrate of DNMT1, off the protein on sub-micromolar scale, leading for effective enzymatic inhibition. Apt. #9 shows no inhibition nor binding activity towards two de novo DNMTs, DNMT3A and DNMT3B. Intriguingly, it can enter cancer cells with over-expression of DNMT1, colocalize with DNMT1 inside the nuclei, and inhibit the activity of DNMT1 in cells. This study opens the possibility of exploring the aptameric DNMT inhibitors being a new cancer therapeutic approach, by modulating DNMT activity selectively through reversible interaction. The aptamers could also be valuable tools for study of the functions of DNMTs and the related epigenetic mechanisms.

A fully validated simple new method for environmental monitoring by surface sampling for cytotoxics

A wipe sampling procedure followed by a simple ultra-performance liquid chromatography - tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for simultaneous quantification of six cytotoxic drugs: 5-fluorouracil (5FU), doxorubicin (DOXO), epirubicin (EPI), ifosfamide (IF), cyclophosphamide (CP) and gemcitabine (GEM), as surrogate markers for occupational exposure. After a solid-phase extraction of wiping filter on 10 × 10 cm surface, the separation was performed within 6.5 min, using a gradient mobile phase and the analytes were detected by mass spectrometry in the multiple reaction ion monitoring mode. The method was validated according to the recommendations of the US Food and Drug Administration. The method was linear (r² > 0.9912) between 2.5 and 200 ng per wiping sample (25 to 2000 pg/cm²) for 5FU, doxorubicin and epirubicin and between 0.2 and 40 ng per wiping sample (2 to 400 pg/cm²) for cyclophosphamide, ifosfamide and gemcitabine. The lower limits of quantification were 2.5 ng (25 pg/ cm²) for 5FU, doxorubicin and epirubicin, and 0.2 ng (2 pg/cm²) for CP, IF and GEM. Within-day and between-day imprecisions were <14.0, 10.6, 11.1, 8.7, 11.2 and 10.9% for 5-fluorouracil, doxorubicin, epirubicin, ifosfamide cyclophosphamide and gemcitabine, respectively. The inaccuracies did not exceed 2.7, 10.9, 1.1, 4.5, 1.6 and 2.9% for the studied molecules, respectively. This new sensitive validated method for surface contamination studies of cytotoxics was successfully applied on different localizations in hospital. This approach is particularly suitable to assess occupational exposure risk to cytotoxic drugs.

Closed-system drug-transfer devices plus safe handling of hazardous drugs versus safe handling alone for reducing exposure to infusional hazardous drugs in healthcare staff

BACKGROUND

Occupational exposure to hazardous drugs can decrease fertility and result in miscarriages, stillbirths, and cancers in healthcare staff. Several recommended practices aim to reduce this exposure, including protective clothing, gloves, and biological safety cabinets ('safe handling'). There is significant uncertainty as to whether using closed-system drug-transfer devices (CSTD) in addition to safe handling decreases the contamination and risk of staff exposure to infusional hazardous drugs compared to safe handling alone.

OBJECTIVES

To assess the effects of closed-system drug-transfer of infusional hazardous drugs plus safe handling versus safe handling alone for reducing staff exposure to infusional hazardous drugs and risk of staff contamination.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, OSH-UPDATE, CINAHL, Science Citation Index Expanded, economic evaluation databases, the World Health Organization International Clinical Trials Registry Platform, and ClinicalTrials.gov to October 2017.

SELECTION CRITERIA

We included comparative studies of any study design (irrespective of language, blinding, or publication status) that compared CSTD plus safe handling versus safe handling alone for infusional hazardous drugs.

DATA COLLECTION AND ANALYSIS

Two review authors independently identified trials and extracted data. We calculated the risk ratio (RR) and mean difference (MD) with 95% confidence intervals (CI) using both fixed-effect and random-effects models. We assessed risk of bias according to the risk of bias in non-randomised studies of interventions (ROBINS-I) tool, used an intracluster correlation coefficient of 0.10, and we assessed the quality of the evidence using GRADE.

MAIN RESULTS

We included 23 observational cluster studies (358 hospitals) in this review. We did not find any randomised controlled trials or formal economic evaluations. In 21 studies, the people who used the intervention (CSTD plus safe handling) and control (safe handling alone) were pharmacists or pharmacy technicians; in the other two studies, the people who used the intervention and control were nurses, pharmacists, or pharmacy technicians. The CSTD used in the studies were PhaSeal (13 studies), Tevadaptor (1 study), SpikeSwan (1 study), PhaSeal and Tevadaptor (1 study), varied (5 studies), and not stated (2 studies). The studies' descriptions of the control groups were varied. Twenty-one studies provide data on one or more outcomes for this systematic review. All the studies are at serious risk of bias. The quality of evidence is very low for all the outcomes.There is no evidence of differences in the proportion of people with positive urine tests for exposure between the CSTD and control groups for cyclophosphamide alone (RR 0.83, 95% CI 0.46 to 1.52; I² = 12%; 2 studies; 2 hospitals; 20 participants; CSTD: 76.1% versus control: 91.7%); cyclophosphamide or ifosfamide (RR 0.09, 95% CI 0.00 to 2.79; 1 study; 1 hospital; 14 participants; CSTD: 6.4% versus control: 71.4%); and cyclophosphamide, ifosfamide, or gemcitabine (RR not estimable; 1 study; 1 hospital; 36 participants; 0% in both groups).There is no evidence of a difference in the proportion of surface samples contaminated in the pharmacy areas or patient-care areas for any of the drugs except 5-fluorouracil, which was lower in the CSTD group than in the control (RR 0.65, 95% CI 0.43 to 0.97; 3 studies, 106 hospitals, 1008 samples; CSTD: 9% versus control: 13.9%).The amount of cyclophosphamide was lower in pharmacy areas in the CSTD group than in the control group (MD -49.34 pg/cm², 95% CI -84.11 to -14.56, I² = 0%, 7 studies; 282 hospitals, 1793 surface samples). Additionally, one interrupted time-series study (3 hospitals; 342 samples) demonstrated a change in the slope between pre-CSTD and CSTD (3.9439 pg/cm², 95% CI 1.2303 to 6.6576; P = 0.010), but not between CSTD and post-CSTD withdrawal (-1.9331 pg/cm², 95% CI -5.1260 to 1.2598; P = 0.20). There is no evidence of difference in the amount of the other drugs between CSTD and control groups in the pharmacy areas or patient-care areas.None of the studies report on atmospheric contamination, blood tests, or other measures of exposure to infusional hazardous drugs such as urine mutagenicity, chromosomal aberrations, sister chromatid exchanges, or micronuclei induction.None of the studies report short-term health benefits such as reduction in skin rashes, medium-term reproductive health benefits such as fertility and parity, or long-term health benefits related to the development of any type of cancer or adverse events.Five studies (six hospitals) report the potential cost savings through the use of CSTD. The studies used different methods of calculating the costs, and the results were not reported in a format that could be pooled via meta-analysis. There is significant variability between the studies in terms of whether CSTD resulted in cost savings (the point estimates of the average potential cost savings ranged from (2017) USD -642,656 to (2017) USD 221,818).

AUTHORS' CONCLUSIONS

There is currently no evidence to support or refute the routine use of closed-system drug transfer devices in addition to safe handling of infusional hazardous drugs, as there is no evidence of differences in exposure or financial benefits between CSTD plus safe handling versus safe handling alone (very low-quality evidence). None of the studies report health benefits.Well-designed multicentre randomised controlled trials may be feasible depending upon the proportion of people with exposure. The next best study design is interrupted time-series. This design is likely to provide a better estimate than uncontrolled before-after studies or cross-sectional studies. Future studies may involve other alternate ways of reducing exposure in addition to safe handling as one intervention group in a multi-arm parallel design or factorial design trial. Future studies should have designs that decrease the risk of bias and enable measurement of direct health benefits in addition to exposure. Studies using exposure should be tested for a relevant selection of hazardous drugs used in the hospital to provide an estimate of the exposure and health benefits of using CSTD. Steps should be undertaken to ensure that there are no other differences between CSTD and control groups, so that one can obtain a reasonable estimate of the health benefits of using CSTD.

Cleaning Efficiencies of Three Cleaning Agents on Four Different Surfaces after Contamination by Gemcitabine and 5-fluorouracile

Occupational exposure to antineoplastic drugs has been documented for decades showing widespread contamination in preparation and administration areas. Apart from preventive measures, efficient cleaning of surfaces is indispensable to minimize the exposure risk. The aim of this study was to evaluate the efficiency of three cleaning agents after intentional contamination by gemcitabine (GEM) and 5-fluorouracile (5-FU) on four different surface types usually installed in healthcare settings. Glass, stainless steel, polyvinylchloride (PVC), and laminated wood plates were contaminated with 20 ng/μl GEM and 2 ng/μl 5-FU solutions. Wipe samples were analyzed for drug residues after cleaning with a) distilled water, b) aqueous solution containing sodium dodecyl sulfate (10 mM) and 2-propanol (SDS-2P), and c) Incides N (pre-soaked) alcoholic wipes. Quantification was performed by high-performance liquid chromatography (HPLC) for GEM and gas chromato-graphy-tandem mass spectrometry (GCMS/MS) for 5-FU. Recovery was determined and cleaning efficiency was calculated for each scenario. Mean recoveries were 77-89% for GEM and 24-77% for 5-FU and calculated cleaning efficiencies ranged between 95 and 100% and 89 and 100%, respectively. Residual drug amounts were detected in the range nd (not detected) - 84 ng GEM/sample and nd - 6.6 ng 5-FU/sample depending on surface type and cleaning agent. Distilled water and SDS-2P had better decontamination outcomes than Incides N wipes on nearly all surface types, especially for GEM. Regarding 5-FU, the overall cleaning efficiency was lower with highest residues on laminated wood surfaces. The tested cleaning procedures are shown to clean glass, stainless steel, PVC, and laminated wood with an efficiency of 89-100% after contamination with GEM and 5-FU. Nevertheless, drug residues could be verified by wipe samples. Pure distilled water and SDS in an alcoholic-aqueous solution expressed an efficient cleaning performance, especially with respect to GEM. The study results demonstrate the need to adapt cleaning procedures to the variety of drugs and surface types to develop effective decontamination strategies.

Mapping antiretroviral drugs in tissue by IR-MALDESI MSI coupled to the Q Exactive and comparison with LC-MS/MS SRM assay

This work describes the coupling of the IR-MALDESI imaging source with the Q Exactive mass spectrometer. IR-MALDESI MSI was used to elucidate the spatial distribution of several HIV drugs in cervical tissues that had been incubated in either a low or high concentration. Serial sections of those analyzed by IR-MALDESI MSI were homogenized and analyzed by LC-MS/MS to quantify the amount of each drug present in the tissue. By comparing the two techniques, an agreement between the average intensities from the imaging experiment and the absolute quantities for each drug was observed. This correlation between these two techniques serves as a prerequisite to quantitative IR-MALDESI MSI. In addition, a targeted MS(2) imaging experiment was also conducted to demonstrate the capabilities of the Q Exactive and to highlight the added selectivity that can be obtained with SRM or MRM imaging experiments.

Predicting concentrations of the cytostatic drugs cyclophosphamide, carboplatin, 5-fluorouracil, and capecitabine throughout the sewage effluents and surface waters of Europe

The present study evaluated the potential environmental concentrations of 4 cytostatic (also known as cytotoxic) drugs in rivers. The antimetabolite 5-fluorouracil (5FU) and its pro-drug capecitabine were examined based on their very high use rates, cyclophosphamide (CP) for its persistence, and carboplatin for its association with the metal element platinum. The study combined drug consumption information across European countries, excretion, national water use, and sewage removal rates to derive sewage effluent values across the continent. Results showed considerable variation in the popularity of individual cytostatic drugs across Europe, including a 28-fold difference in 5FU use and 15-fold difference in CP use. Such variations could have a major effect on the detection of these compounds in effluent or river water. Overall, capecitabine and CP had higher predicted levels in effluent than 5FU or carboplatin. Predicted effluent values were compared with measurements in the literature, and many non-detects could be explained by insufficient limits of detection. Linking the geographic based water resources model GWAVA with this information allowed water concentrations throughout 1.2 million km of European rivers to be predicted. The 90th percentile (worst case) prediction indicated that, with the exception of capecitabine, more than 99% of Europe's rivers (by length) would have concentrations below 1 ng/L for these cytostatic drugs. For capecitabine, 2.2% of river length could exceed 1 ng/L.

Influence of ambient air pollution on global DNA methylation in healthy adults: a seasonal follow-up

BACKGROUND

DNA methylation changes are potential pathways of environmentally induced health effects. We investigated whether exposure to ambient concentrations of NO2, PM10, PM2.5 and O3 and traffic parameters were associated with global DNA methylation in blood of healthy adults.

METHODS

48 non-smoking adults (25 males) with a median age of 39years were sampled in winter and summer. Global DNA methylation in whole blood (% 5-methyl-2'-deoxycytidine, %5mdC) was analyzed with HPLC. Exposure to air pollutants at the home address was assessed using interpolated NO2, PM10, PM2.5 and O3 concentrations for various exposure windows (60- to 1-day moving average exposures and yearly averages) and GIS-based traffic parameters. Associations between pollutants and %5mdC were tested with multiple mixed effects regression models.

RESULTS

Average %5mdC (SD) was 4.30 (0.08) in winter and 4.29 (0.08) in summer. Men had higher %5mdC compared to women both in winter (4.32 vs. 4.26) and summer (4.31 vs. 4.27). When winter and summer data were analyzed together, various NO2, PM10 and PM2.5 moving average exposures were associated with changes in %5mdC (95% CI) ranging from -0.04 (-0.09 to 0.00) to -0.14 (-0.28 to 0.00) per IQR increase in pollutant. NO2, PM10, PM2.5 and O3 moving average exposures were associated with decreased %5mdC (95% CI) varying between -0.01 (-0.03 to 0.00) and -0.17 (-0.27 to -0.06) per IQR increase in pollutant in summer but not in winter.

CONCLUSION

Decreased global DNA methylation in whole blood was associated with exposure to NO2, PM10, PM2.5 and O3 at the home addresses of non- adults. Most effects were observed for the 5- to 30-day moving average exposures.

The 5-methyl-deoxy-cytidine (5mdC) localization to reveal in situ the dynamics of DNA methylation chromatin pattern in a variety of plant organ and tissue cells during development

DNA methylation of cytosine residues constitutes a prominent epigenetic modification of the chromatin fiber which is locked in a transcriptionally inactive conformation leading to gene silencing. Plant developmental processes, as differentiation and proliferation, are accompanied by chromatin remodeling and epigenetic reprogramming. Despite the increasing knowledge gained on the epigenetic mechanisms controlling plant developmental processes, the knowledge of the DNA methylation regulation during relevant developmental programs in flowering plants, such as gametogenesis or embryogenesis, is very limited. The analysis of global DNA methylation levels has been frequently conducted by high performance capillary electrophoresis, and more recently also by ELISA-based assays, which provided quantitative data of whole organs and tissues. Nevertheless, to investigate the DNA methylation dynamics during plant development in different cell types of the same organ, the analysis of spatial and temporal pattern of nuclear distribution of 5-methyl-deoxy-cytidine (5mdC) constitutes a potent approach. In this work, immunolocalization of 5mdC on sections and subsequent confocal laser microscopy analysis have been applied for in situ cellular analysis of a variety of plant cells, tissues and organs with different characteristics, e.g. hardness, heterogeneity, cell accessibility, tissue compactness, etc.; the results demonstrated the versatility and feasibility of the approach for different plant samples, and revealed defined DNA methylation nuclear patterns associated with differentiation and proliferation events of various plant cell types and developmental programs. Quantification of 5mdC immunofluorescence intensity by image analysis software also permitted to estimate differences in global DNA methylation levels among different cells types of the same organ during development.

Analytical detection and method development of anticancer drug Gemcitabine HCl using gold nanoparticles

A simple, rapid, cost effective and extractive UV spectrophotometric method was developed for the determination of Gemcitabine HCl (GMCT) in bulk drug and pharmaceutical formulation. It was based on UV spectrophotometric measurements in which the drug reacts with gold nanoparticles (AuNP) and changes the original colour of AuNP and forms a dark blue coloured solution which exhibits absorption maximum at 688nm. The apparent molar absorptivity and Sandell's sensitivity coefficient were found to be 3.95×10(-5)lmol(-1)cm(-1) and 0.060μgcm(-2) respectively. Beer's law was obeyed in the concentration range of 2.0-40μgml(-1). This method was tested and validated for various parameters according to ICH guidelines. The proposed method was successfully applied for the determination of GMCT in pharmaceutical formulation (parental formulation). The results demonstrated that the procedure is accurate, precise and reproducible (relative standard deviation <2%). As it is simple, cheap and less time consuming, it can be suitably applied for the estimation of GMCT in dosage forms.

Photochemical stability of 4'-azido-2'-deoxy-2'-methylcytidine hydrochloride: structural elucidation of major degradation products by LC-MS and NMR analysis

The photochemical stability of (1'R,2'S,3'S,4'R)-4'-azido-2'-deoxy-2'-methylcytidine hydrochloride, a new anti-HCV agent, was investigated. Aqueous solutions and bulk drug powder of the drug candidate were exposed to UV-visible light, complying with ICH requirements. The nucleoside analog decomposed via loss of nitrogen to yield products derived from a highly reactive azide intermediate. Major photolysis products were identified by LC-MS and NMR analysis, revealing three main photodegradation pathways. The first one led to the formation of a ring-expanded imidate ester. The other degradation pathways involved exocyclic or endocyclic bond cleavage with imine or imino lactone formation. The latter were prone to rapid hydrolysis, eventually resulting in the release of cytosine, 2-methyl malonaldehyde and (E)-cytosyl-2-methylpropenal.

Concentrations of tenofovir and emtricitabine in breast milk of HIV-1-infected women in Abidjan, Cote d'Ivoire, in the ANRS 12109 TEmAA Study, Step 2

The aim was to evaluate emtricitabine (FTC) and tenofovir (TFV) neonatal ingestion through breast milk. Median TFV and FTC breast milk doses represented 0.03% and 2%, respectively, of the proposed oral infant doses. Neonatal simulated plasma concentrations were extremely low for TFV but between the half-maximal inhibitory concentration and the adult minimal expected concentration for FTC. The rare children who will acquire HIV despite TDF-FTC therapy will need to be monitored for viral resistance acquisition.

Simultaneous determination of 8-hydroxy-2'-deoxyguanosine and 5-methyl-2'-deoxycytidine in DNA sample by high performance liquid chromatography/positive electrospray ionization tandem mass spectrometry

8-Hydroxy-2'-deoxyguanosine (8-OHdG) and 5-methyl-2'-deoxycytidine (5-mdC) are utilized as useful biomarkers not only for early diagnosis but also for the detection and assessment of high-risk individuals. In the present study, a sensitive and specific method was developed for simultaneous determination of 8-OHdG and 5-mdC in DNA by high performance liquid chromatography/positive electrospray ionization tandem mass spectrometry. The limits of quantification for 8-OHdG and 5-mdC were 80 and 40pg/ml, respectively. The calibration curves of 8-OHdG and 5-mdC were linear over the concentration range of 0.02-100ng/ml and the correlation coefficients were higher than 0.9990. The intra-day and inter-day relative standard derivative values were in the range of 0.70-7.47% for 8-OHdG and 1.07-7.06% for 5-mdC, respectively. The recoveries were 93.4-108.5% for 8-OHdG and 87.4-104.9% for 5-mdC, respectively. This method was validated by determination of the background levels of 8-OHdG and 5-mdC in calf thymus DNA, and satisfactory results were obtained.

Combined environmental risk assessment for 5-fluorouracil and capecitabine in Europe

An environmental risk assessment (ERA) was made for the old cytostatic active pharmaceutical ingredient 5-fluorouracil (5-FU) and for capecitabine (CAP), which is a prodrug of 5-FU. This ERA is based on published and company internal data as well as new test results for physicochemical, human metabolism, biodegradability, environmental partitioning and fate, and acute and chronic ecotoxicity properties of the active substance 5-FU as well as on use sales data for 5-FU and CAP in Europe. Predicted environmental concentrations (PECs) were extrapolated following the EMEA 2006 Guideline on ERA for human pharmaceuticals and the European Union 2003 Technical Guidance Document (TGD) for risk assessment as well as the TGD-based application EUSES v2.0. Actual amounts sold were taken from IMS Health Databases, in order to refine the default use and EMEA penetration factor as well as the PECs. Moreover, available measured environmental concentrations (MECs) were used to supplement PECs. A predicted no-effect concentration (PNEC) for 5-FU was derived from chronic ecotoxicity data. Except for the simplistic EMEA Phase I default PEC, the risk characterization by PEC:PNEC and MEC:PNEC ratios for various environmental compartments resulted in no significant risk. As the EMEA Phase I PEC does not integrate documented human metabolism and environmental degradation, in contrast to refined PEC derivations, it is inferred that the current use of CAP and 5-FU does not present any evident risk to the environment. An additional evaluation of persistence, bioaccumulation, and toxicity (PBT) properties supports the conclusion of no significant environmental risk for 5-FU and CAP.

Quantitative DNA-methylation in Daphnia magna and effects of multigeneration Zn exposure

Little research on the epigenetic phenomenon of DNA methylation has been performed with invertebrates. However, a few studies have shown that effects of transient chemical exposure can be transferred to non-exposed generations through epigenetic inheritance. If this is a wide-spread phenomenon it may have major consequences for current ecological risk assessments. The presence of DNA methylation in Daphnia magna has only very recently been demonstrated, although not quantified. In the present study, the overall content of 5-methyl-2'-deoxycytidine (5 mdC) in the DNA of D. magna was determined. Additionally, the effect of transgenerational Zn exposure on the 5 mdC content was assessed. An optimized LC-MS-MS method proved to be very suitable for measuring overall levels of 5 mdC in relatively small samples of D. magna DNA. The average [5 mdC]/[dG] ratio ranged from 0.13% to 0.81%. A slight but significant decrease in DNA methylation was found in the offspring (F1) of Zn exposed daphnids in the parental generation. However, this effect did not propagate into the next generation (F2). The presence of DNA methylation in D. magna and the finding that different exposure histories can entail different levels of methylation, open the way for further investigations on the implications of epigenetics in aquatic toxicology.

Mass flows of X-ray contrast media and cytostatics in hospital wastewater

Little is known about the significance of hospitals as point sources for emission of organic micropollutants into the aquatic environment. A mass flow analysis of pharmaceuticals and diagnostics used in hospitals was performed on the site of a representative Swiss cantonal hospital. Specifically, we analyzed the consumption of iodinated X-ray contrast media (ICM) and cytostatics in their corresponding medical applications of radiology and oncology, respectively, and their discharge into hospital wastewater and eventually into the wastewater of the municipal wastewater treatment plant. Emission levels within one day and over several days were found to correlate with the pharmacokinetic excretion pattern and the consumed amounts in the hospital during these days. ICM total emissions vary substantially from day to day from 255 to 1259 g/d, with a maximum on the day when the highest radiology treatment occurred. Parent cytostatic compounds reach maximal emissions of 8-10 mg/d. A total of 1.1%, 1.4%, and 3.7% of the excreted amounts of the cytostatics 5-fluorouracil, gemcitabine, and 2',2'-difluorodeoxyuridine (main metabolite of gemcitabine), respectively, were found in the hospital wastewater, whereas 49% of the total ICM was detected, showing a high variability among the compounds. These recoveries can essentially be explained by the high amount administered to out-patients (70% for cytostatics and 50% for ICM); therefore, only part of this dose is expected to be excreted on-site. In addition, this study emphasizes critical issues to consider when sampling in hospital sewer systems. Flow proportional sampling over a longer period is crucial to compute robust hospital mass flows.

Intraperitoneal gemcitabine pharmacokinetics: a pilot and pharmacokinetic study in patients with advanced adenocarcinoma of the pancreas

BACKGROUND

The pyrimidine analogue gemcitabine (2', 2'-difluorodeoxycitidine, dFdC) is active against pancreatic cancer, and its high clearance (CL(tb)) and low incidence of local toxicity make it an excellent candidate for evaluation as intraperitoneal (IP) therapy. We designed a dosing schema that used multiple sequential exchanges of a peritoneal dialysate containing dFdC in an effort to produce prolonged IP dFdC exposure.

METHODS

As part of a study involving multi-modality therapy for advanced pancreatic adenocarcinoma, patients were treated with four 6-h IP dwells of dFdC (50 mg/m(2) in 2 l) over a 24-h period. A second 24-h cycle of IP dFdC therapy was repeated 1 week later. Each exchange of dialysate contained 50 mg/m(2) dFdC in 2 l of commercial 1.5% dextrose dialysis solution. Plasma and peritoneal fluid were analyzed by HPLC to determine concentrations of dFdC and its inactive metabolite 2', 2' difluorodeoxyuridine (dFdU). Clinical data were recorded to note drug toxicity and response.

RESULTS

Nine patients underwent IP dFdC therapy, and eight were able to receive two cycles. There were no recorded significant toxicities. Low plasma dFdC concentrations (<1 microg/ml) were present transiently in seven of nine patients, and dFdC was not detectable in the plasma of the other two. Plasma dFdU concentrations were low but increased gradually until 12 h and then declined little if any. IP dFdC concentrations declined rapidly, and dFdC was seldom measurable prior to administration of the next scheduled 6-h dwell. dFdU concentrations in peritoneal fluid were very low (<0.5 microg/ml) throughout treatment. The mean area under the concentration versus time curve (AUC) for dFdC in peritoneal fluid was 182 microg/ml x h, which was approximately 70x the AUC of dFdC reported in the ascites of a patient undergoing systemic dFdC therapy.

CONCLUSIONS

IP dFdC was well tolerated, and no significant toxicities were noted. The rapid decrease in peritoneal dFdC concentrations and low concentrations of IP dFdU imply almost total absorption of IP-administered dFdC. Little, if any, dFdC could be detected in plasma, but the steady-state plasma dFdU concentrations also imply absorption and inactivation of virtually all IP-administered dFdC. These findings are consistent with the known high CL(tb) and low incidence of local toxicity of dFdC and argue for its further evaluation as a drug for IP therapy.

Etheno-DNA adduct formation in rats gavaged with linoleic acid, oleic acid and coconut oil is organ- and gender specific

Intake of linoleic acid (LA) increased etheno-DNA adducts induced by lipid peroxidation (LPO) in white blood cells (WBC) of female but not of male volunteers [J. Nair, C.E. Vaca, I. Velic, M. Mutanen, L.M. Valsta, H. Bartsch, High dietary omega-6 polyunsaturated fatty acids drastically increase the formation of etheno-DNA adducts in white blood cells of female subjects, Cancer Epidemiol. Biomarkers Prev. 6 (1997) 597-601]. Etheno-adducts were measured in rats gavaged with LA, oleic acid (OA) and saturated fatty acid rich coconut oil for 30 days. DNA from organs and total WBC was analyzed for 1, N(6)-ethenodeoxyadenosine (varepsilondA) and 3, N(4)-ethenodeoxycytidine (varepsilondC) by immunoaffinity/(32)P-postlabeling. Colon was the most affected target with LA-treatment, where etheno-adducts were significantly elevated in both sexes. In WBC both adducts were elevated only in LA-treated females. Unexpectedly, OA treatment enhanced etheno-adduct levels in prostate 3-9 fold. Our results in rodents confirm the gender-specific increase of etheno-adducts in WBC-DNA, likely due to LPO induced by redox-cycling of 4-hydroxyestradiol. Colon was a target for LPO-derived DNA-adducts in both LA-treated male and female rats, supporting their role in omega-6 PUFA induced colon carcinogenesis.

Rapid determination of gemcitabine in plasma and serum using reversed-phase HPLC

Gemcitabine (2'2'-difluorodeoxycytidine) is a pyrimidine analog used in the treatment of a variety of solid tumors. After intravenous (i.v.) administration, it is rapidly inactivated to 2'-deoxy-2',2'-difluorouridine (dFdU). A sensitive analytical method for the quantitation of gemcitabine is required for the assessment of alternative dosage and treatment schemes. A rapid and robust RP-HPLC assay for analysis of gemcitabine in human and animal plasma and serum was developed and validated using 2'-deoxyuridine (dU) and 5-fluoro-2'-deoxyuridine (5FdU) as internal standards. It is based on protein precipitation, the use of an Atlantis dC18 column of 100 mm length (inner diameter, 4.6 mm; particle size, 3 microm) and isocratic elution using a 10 mM phosphate buffer, pH 3.0, followed by isocratic elution with the same buffer containing 3% of ACN. For gemcitabine, RSD values for intraday and interday precision were < 4.4 and 5.3%, respectively, the LOQ was 20 ng/mL, and the assay was linear in the range of 0.020-20 microg/mL with an accuracy of > or =89%. The recovery for gemcitabine, dU and 5FdU was 86-98%. The assay was applied to determine gemcitabine levels in plasma samples of patients collected during and shortly after conventional infusion of 25-30 mg/kg body mass (levels: 2.0-18.9 microg/mL) and rats that received lower doses (1.5 mg/kg) via i.v., subcutaneous and oral drug administration (levels: 0.20-2.60 microg/mL). It could also be applied to estimate dFdU levels in human plasma.

Column selection for pharmaceutical analyses based on a column classification using four test parameters

This paper focuses on the usability of a previously developed column classification system, applied to pharmaceutical analyses. The separation of two drugs from their respective related substances was investigated on 65 new reversed-phase liquid chromatographic columns. The chromatographic procedure for fluoxetine hydrochloride was performed according to the method prescribed in the European Pharmacopoeia monograph while the separation of gemcitabine hydrochloride was carried out according to the United States Pharmacopeia monograph. It was shown that the column ranking system is a helpful tool in the selection of a suitable column.

Development and validation of a stability-indicating liquid chromatographic method for determination of emtricitabine and related impurities in drug substance

A novel stability-indicating high-performance liquid chromatographic (HPLC) method was developed and validated for assay and determination of impurities of emtricitabine in drug substance. Emtricitabine was found to be degraded under acidic, alkaline, and oxidative stress conditions and to be more labile under oxidative conditions. The drug proved to be stable to dry heat and photolytic degradation. Resolution of major and minor degradation impurities was achieved on an Intersil ODS-3V column utilizing 10 mM sodium phosphate buffer and methanol (85:15) as mobile phase. Detection was at 280 nm. Validation studies were performed as per ICH recommended conditions. The developed method was found to be linear, accurate, specific, selective, precise, and robust.

Characterization of in vitro and in vivo hypomethylating effects of decitabine in acute myeloid leukemia by a rapid, specific and sensitive LC-MS/MS method

DNA hypermethylation is a common finding in malignant cells and has been explored as a therapeutic target for hypomethylating agents (e.g., decitabine). Detection of changes in DNA methylation might serve as a pharmacodynamic endpoint to establish the biological activity of these agents and predict clinical response. We developed and validated a rapid, sensitive and specific LC-MS/MS method for determination of global DNA methylation (GDM) in vitro and in vivo. Ratios of 5-methyl-2'-deoxycytidine (5mdC) to the internal standard 2-deoxyguanosine (2dG) in mass signal were used to quantify GDM levels. The assay was validated in a linear range from 40 fmol to 200 pmol 5mdC. The intra-day precision values ranged from 2.8 to 9.9% and the inter-day values from 1.1 to 15.0%. The accuracy of the assay varied between 96.7 and 109.5%. This method was initially applied for characterization of decitabine-induced GDM changes in in-vitro-treated leukemia cells. Following exposure to 2.5 microM decitabine, GDM decreased to approximately 50% of the baseline value. The clinical applicability of this method was then demonstrated in bone marrow samples from patients with acute myeloid leukemia treated with decitabine. Our data support the use of our LC-MS/MS method for clinical pharmacodynamic determination of changes in GDM in vivo.

Rapid and simultaneous determination of capecitabine and its metabolites in mouse plasma, mouse serum, and in rabbit bile by high-performance liquid chromatography

A rapid high-performance liquid chromatography method has been developed for simultaneous determination of capecitabine and its metabolites: 5'-deoxy-5-fluorocytidine (5'-DFCR), 5'-deoxy-5-fluorouridine (5'-DFUR) and 5-fluorouracil (5-FU). 5'-DFCR was synthesized by hydrolyzing capecitabine using commercially available carboxyl esterase (CES) and characterized by NMR, mass spectrometry and elemental analysis. Base-line separations between capecitabine, 5'-DFCR, 5'-DFUR and 5-FU were found with symmetrical peak shapes on a Discovery RP-amide C16 column using 10 mM ammonium acetate at pH 4.0 and methanol as the mobile phase. The retention times of capecitabine, 5'-DFCR, 5'-DFUR and 5-FU were 8.9, 5.0, 5.3 and 3.0 min, respectively. Linear calibration curves were obtained for each compound across a range from 1 to 500 microg ml(-1). The intra- and inter-day relative standard deviations (%RSD) were <5%. A single-step protein precipitation method was employed for separation of the analytes from bio-matrices. Greater than 85% recoveries were obtained for capecitabine, 5'-DFCR, 5'-DFUR and 5-FU from bio-fluids including mouse plasma, mouse serum and rabbit bile.

Quantitative analysis of gemcitabine triphosphate in human peripheral blood mononuclear cells using weak anion-exchange liquid chromatography coupled with tandem mass spectrometry

Gemcitabine triphosphate (dFdCTP) is a highly active metabolite of gemcitabine. It is formed intra-cellularly via the phosphorylation of gemcitabine by deoxycytidine kinase. The monitoring of dFdCTP in human peripheral blood mononuclear cells (PBMCs), in addition to plasma concentrations of gemcitabine and its metabolite 2',2'-difluorodeoxyuridine, is considered very useful in determining pharmacokinetic-pharmacodynamic relationships. We describe a novel sensitive assay for the quantification of dFdCTP in human PBMCs. The method is based on weak anion-exchange liquid chromatography and detection with tandem mass spectrometry (LC-MS/MS). The assay has been validated from 1 ng/ml (lower limit of quantification, LLOQ) to 25 ng/ml (upper limit of quantification, ULOQ) using 180 microl aliquots of PBMC extracts containing approximately 0.648 mg protein or 3.8 x 10(6) lysed PBMCs. The LLOQ is equivalent to 94 fmol/10(6) cells (1 ng/ml = 0.18 ng/180 microl or 0.18 ng/0.648 mg protein = 0.047 ng/10(6) cells or 94 fmol/10(6) cells). This highly sensitive assay is capable of quantifying about 200-fold lower concentrations of dFdCTP in human PBMCs than currently available methods.

A new, simple method for quantifying gemcitabine triphosphate in cancer cells using isocratic high-performance liquid chromatography

A deoxycytidine analog, gemcitabine (dFdC), is effective for treating solid tumors and hematological malignancies. After being transported into cancer cells, dFdC is phosphorylated to dFdC triphosphate (dFdCTP), which is subsequently incorporated into the DNA strand, thereby inhibiting DNA synthesis. Intracellular dFdCTP is the critical determinant for dFdC cytotoxicity, so therapeutic drug monitoring or in vitro testing of the capability of cancer cells to accumulate dFdCTP may be informative for optimizing dFdC administration. We have developed a new isocratic-elution high-performance liquid chromatography method for quantifying dFdCTP in cancer cells. Samples (500 microL) were eluted isocratically using 0.06 M Na(2)HPO(4) (pH 6.9) containing 20% acetonitrile, at a constant flow rate of 0.7 mL/min and at ambient temperature. Separation was carried out using an anion-exchange column (TSK gel DEAE-2SW; 250 mm x 4.6 mm inside diameter, particle size 5 microL) and monitored at 254 nm. The standard curve was linear with low within-day and interday variability. The lower detection limit (20 pmol) was as sensitive as that of the previous gradient-elution method. dFdCTP was well separated from other nucleoside triphosphates. The method could measure dFdCTP in cultured or primary leukemic cells treated in vitro with dFdC. The method was also applicable to simultaneous determination of dFdCTP and cytarabine triphosphate, the results of which demonstrated ara-CTP production augmented by dFdC pretreatment. Thus, our isocratic high-performance liquid chromatography assay method will be of great use because of its sensitivity and simplicity as well as its applicability to biological materials.

The determination of gemcitabine and 2'-deoxycytidine in human plasma and tissue by APCI tandem mass spectrometry

A fast, sensitive and accurate method for the determination of gemcitabine (difluorodeoxycytidine; dFdC) and deoxycytidine (CdR) in human plasma/tissue was developed using LC-MS/MS techniques. Effectiveness of the method is illustrated with the analysis of plasma from a phase I trial of dFdC administered as a 24h infusion. The method was developed using (15)N(3) CdR as an internal standard across the concentration range of 1-500ng/ml, using a cold alcohol-protein precipitation followed by desorption with freeze drying. Sample clean-up for LC-MS/MS analysis was performed by an innovative liquid/liquid back extraction with ethyl acetate and water. Chromatography was performed using a Chrompak-spherisorb-phenyl-column (3.1mmx200mm, 5microm) with a 50mM formic acid: acetonitrile (9:1) mobile phase eluted at 1ml/min. Extracted samples were observed to be stable for a minimum of 48h after extraction when kept at 4 degrees C. Detection was performed using an atmospheric pressure chemical ionization (APCI) source and mass spectrometric positive multi-reaction-monitoring-mode (+MRM) for dFdC (264 m/z; 112 m/z), CdR (228 m/z; 112 m/z), and (15)N(3) CdR (231 m/z; 115 m/z) at an ion voltage of +3500V. The accuracy, precision and limit-of-quantitation (LOQ) were as follows: dFdC: 99.8%, +/-7.9%, 19nM; CdR: 100.0%, +/-5.3%, 22nM, linear range LOQ to 2microM. During 24h infusion dFdC levels were detected with no interference from either CdR or difluorodeoxyuridine (dFdU). CdR co-eluted with dFdC but selectivity demonstrated no "crosstalk" between the compounds. In conclusion the analytical assay was very sensitive, reliable and robust for the determination of plasma and tissue concentrations of dFdC and CdR.

Modified approach of administering cytostatics to the lung: more efficient isolated lung perfusion

BACKGROUND

Isolated lung perfusion (ILuP) is an experimental technique for the treatment of pulmonary metastases. We hypothesized that part of the drug taken up by the lung during ILuP is washed out during the flush procedure. Therefore, we investigated gemcitabine uptake at different inflow concentrations, and the effect of delayed clamp release after ILuP on lung levels was studied.

METHODS

Thirty rats had ILuP during 30 minutes using gemcitabine perfusate levels of 1.3, 2.7, 4.0, 5.3, and 6.7 mg/mL. Another 37 rats underwent ILuP with gemcitabine perfusate levels of 6.7 mg/mL during 6 minutes followed by a 5-minute flush and 30 or 60 minutes of reperfusion, while two other groups had ILuP and delayed clamp release for 30 or 60 minutes followed by a 5-minute flush. All effluent and lung samples were stored for later analysis. Results were evaluated using Friedmann two-way analysis and two-way analysis of variance.

RESULTS

At 6 minutes, steady-state of gemcitabine uptake was achieved for all inflow concentrations and a linear relation (r = 0.933, p < 0.0001) between effluent and lung levels was observed. Delayed clamp release resulted in significantly higher lung levels compared with immediate restoration of blood circulation after ILuP (456% at 30 minutes and 828% at 60 minutes).

CONCLUSIONS

Effective gemcitabine lung levels are already achieved after 6 minutes of ILuP with 6.7 mg/mL followed by delayed clamp release during 30 minutes instead of the clinically applied 30 minutes ILuP.

Ascorbate and H2O2 induced oxidative DNA damage in Jurkat cells

The effect of vitamin C (ascorbate) on oxidative DNA damage was examined by first incubating cells with dehydroascorbate, which boosts the intracellular concentration of ascorbate, and then exposing cells to H(2)O(2). Oxidative DNA damage was estimated by the analysis of 5-hydroxy-2'-deoxycytidine (oh(5)dCyd) and 8-oxo-7,8-dihydro-2'-deoxyguanosine (oxo(8)dGuo). The presence of a high concentration of ascorbate (30 mM), compared to the absence of ascorbate in cells, when exposed to H(2)O(2) (200 microM), resulted in a remarkable sensitization of oh(5)dCyd from 2.7 +/- 0.6 to 40.8 +/- 6.1 lesions /10(6) dCyd (15-fold). In contrast, the level of oxo(8)dGuo increased from 8.4 +/- 0.4 to 12.1 +/- 0.5 lesions/10(6) dGuo (50%). The formation of oh(5)dCyd was also observed at lower concentrations of intracellular ascorbate and exogenous H(2)O(2). Additional studies showed that replacement of H(2)O(2) with tert-butyl hydroperoxide completely abolished damage, and that preincubation with iron and desferroxamine increased and decreased this damage, respectively. The latter studies suggest that a Fenton reaction is involved in the mechanism of damage. In conclusion, we report a novel model system in which ascorbate sensitizes H(2)O(2)-induced oxidative DNA damage in cells, leading to elevated levels of oh(5)dCyd and oxo(8)dGuo, with a strong bias toward the formation of oh(5)dCyd.

Evaluation of early DNA damage in healthcare workers handling antineoplastic drugs

OBJECTIVES

This study evaluates by comet assay the induction of early DNA damage in healthcare workers of an oncology hospital regularly handling antineoplastic drug mixtures. The aim was to identify a suitable biomarker of DNA damage by exposure to low levels of such drugs.

METHODS

We studied 12 day hospital nurses and 13 oncology ward nurses who performed up to 300 and up to 35 drug administrations per week, respectively, and five pharmacy employees who regularly prepared mixtures of antineoplastic agents. Thirty healthy subjects were selected as controls. For exposure evaluation, we performed environmental monitoring of 5-fluorouracil, cytarabine, gemcitabine, cyclophosphamide, and ifosfamide in selected work areas of pharmacy and day hospital units and biological monitoring of urine for the 5-fluorouracile metabolite, alpha-fluoro-beta-alanine. We evaluated early DNA damage in lymphocytes and exfoliated buccal cells by comet assay measuring tail moment (TM) parameter that indirectly indicates the presence of DNA damage.

RESULTS

Environmental monitoring detected cyclophosphamide, 5-fluorouracil and ifosfamide, with higher levels of contamination in day hospital unit. The biological monitoring measured detectable levels of alpha-fluoro-beta-alanine only in three nurses. Comet assay showed an increase on exfoliated buccal cells, even if not statistically significant, of mean TM with respect to controls in day hospital nurses (43.2 vs. 28.6, respectively) while ward nurses and pharmacy technicians did not show differences. Comet assay performed on lymphocytes did not show appreciable differences between exposed and controls.

CONCLUSIONS

The employment of the sensitive comet assay, which is able to detect early the effects of a recent exposure to genotoxic substances, allowed us to find a slight DNA damage, only on exfoliated buccal cells of day hospital nurses, the group handling the highest amount of drugs during the administration process. This finding suggests that comet assay on exfoliated buccal cells could represent a useful tool to evaluate early and still repairable genotoxic effects of exposure to antineoplastic drug mixtures and then contribute to the improvement of the hospital safety practices.

Simultaneous determination of gemcitabine di- and triphosphate in human blood mononuclear and cancer cells by RP-HPLC and UV detection

A reverse-phase HPLC method based on ion-pair formation with UV detection was set up for the simultaneous determination of gemcitabine diphosphate (dFdCDP) and triphosphate (dFdCTP) in human cells. The separation was achieved on a Tracer Excel ODSA column (100 mm x 4.6mm i.d., 3 microm particle size) at room temperature. Nine nucleotides were separated by isocratic elution in 26 min. Accuracy, linearity, sensitivity and precision studies for dFdCDP, dFdCTP, adenosine diphosphate (ADP) and triphosphate (ATP) validated this method. This assay was used to provide data from gemcitabine treated patients and in vitro grown human cancer cells.

High-performance liquid chromatographic method for the determination of gemcitabine and 2′,2′-difluorodeoxyuridine in plasma and tissue culture media

Gemcitabine, a pyrimidine antimetabolite undergoes metabolism by plasma and liver cytidine deaminase to form the inactive compound, 2',2'-difluorodeoxyuridine (dFdU). The parent molecule is activated by intracellular phosphorylation. To evaluate the population pharmacokinetics in patients receiving gemcitabine, and to test the relation between gemcitabine infusion rate and antitumor activity in an in vitro bioreactor cell culture system, we developed and validated a sensitive and specific HPLC-UV method for gemcitabine and dFdU. Deproteinized plasma is vortexed, centrifuged, and 25 microL of the acidified extract sample is injected onto a Waters Spherisorb 4.6 mm x 250 mm, 5 microm C18 column at 40 degrees C. The mobile phase (flow rate, 1.0 mL/min) consists of 10:90 (v/v) acetonitrile-aqueous buffer (50 mM sodium phosphate and 3.0 mM octyl sulfonic acid, pH 2.9). Gemcitabine, dFdU, and the internal standard, 2'-deoxycytidine (2'dC) were detected with UV wavelength set at 267 nm. The standard curves for gemcitabine in both matrices ranged from 2 to 200 microM, and for dFdU in plasma, from 2 to 100 microM. Within-run and between-run component precision (CV%) was <or=6.1 and 5.7%, respectively for both human plasma and tissue culture media, and for dFdU, 2.3 and 2.7%. Total accuracy ranged from 98.7 to 106.2% for human plasma and from 96.9 to 99.2% for tissue culture media, respectively, and for dFdU, from 96.5 to 99.6%. Tetrahydrouridine (THU), an inhibitor of cytidine deaminase is used to prevent breakdown in human plasma. With one method we can measure gemcitabine in both plasma and tissue culture media. Utility is demonstrated by evaluation of the disposition of gemcitabine in an in vitro bioreactor cell culture system.

Analysis of mannitol in pharmaceutical formulations using hydrophilic interaction liquid chromatography with evaporative light-scattering detection

This study demonstrates the use of hydrophilic interaction liquid chromatography (HILIC) for the separation of both active and inactive ingredients in pharmaceuticals from a single injection. Excipients commonly used in parenteral formulations were separated using a gradient method employing increasing aqueous composition. An evaporative light-scattering detector (ELSD) provided direct detection of inactive excipients and inorganic salts lacking UV chromophores. Analyses of Gemzar parenteral formulations using optimized isocratic HILIC-ELSD method conditions were performed based on retention time screening from the gradient assay. All of the components were efficiently separated using a TSK-Gel Amide 80 column including gemcitabine, mannitol, and sodium cation demonstrating the qualitative capability of the technique. The method was thoroughly validated for mannitol content to access the quantitative potential of the technique. Validation parameters included linearity, accuracy, specificity, solution stability, repeatability, and intermediate precision. Overall, the method described in this report proved to be very robust and represents a novel technique to conveniently separate and detect the active and inactive components in pharmaceuticals both quickly and accurately.

Procainamide is a specific inhibitor of DNA methyltransferase 1

CpG island hypermethylation occurs in most cases of cancer, typically resulting in the transcriptional silencing of critical cancer genes. Procainamide has been shown to inhibit DNA methyltransferase activity and reactivate silenced gene expression in cancer cells by reversing CpG island hypermethylation. We report here that procainamide specifically inhibits the hemimethylase activity of DNA methyltransferase 1 (DNMT1), the mammalian enzyme thought to be responsible for maintaining DNA methylation patterns during replication. At micromolar concentrations, procainamide was found to be a partial competitive inhibitor of DNMT1, reducing the affinity of the enzyme for its two substrates, hemimethylated DNA and S-adenosyl-l-methionine. By doing so, procainamide significantly decreased the processivity of DNMT1 on hemimethylated DNA. Procainamide was not a potent inhibitor of the de novo methyltransferases DNMT3a and DNMT3b2. As further evidence of the specificity of procainamide for DNMT1, procainamide failed to lower genomic 5-methyl-2'-deoxycytidine levels in HCT116 colorectal cancer cells when DNMT1 was genetically deleted but significantly reduced genomic 5-methyl-2'-deoxycytidine content in parental HCT116 cells and in HCT116 cells where DNMT3b was genetically deleted. Because many reports have strongly linked DNMT1 with epigenetic alterations in carcinogenesis, procainamide may be a useful drug in the prevention of cancer.

Detection of chlorinated DNA and RNA nucleosides by HPLC coupled to tandem mass spectrometry as potential biomarkers of inflammation

Upon inflammation, activated neutrophils secrete myeloperoxidase, an enzyme able to generate hypochlorous acid (HOCl) from hydrogen peroxide and chloride ions. An analytical method, involving HPLC coupled to electrospray tandem mass spectrometry, has been set-up to detect low levels of HOCl-induced nucleic acids lesions, including both ribo and 2'-deoxyribonucleoside derivatives of 8-chloroguanine, 8-chloroadenine and 5-chlorocytosine. Validation of the developed method was achieved using isolated cells treated with HOCl. The method was found to be sensitive enough to allow the measurement of background levels of 5-chloro-2'-deoxycytidine in the DNA of human white blood cells isolated from 7 mL of blood.

Simultaneous determination of capecitabine and its metabolites by HPLC and mass spectrometry for preclinical and clinical studies

A reverse-phase high-performance liquid chromatography method with electrospray ionization and detection by mass spectrometry is described for the simultaneous determination of capecitabine, its intermediate metabolites (DFCR, DFUR) and the active metabolite 5-fluorouracil in mouse plasma, liver and human xenograft tumours. The method was also cross-validated in human plasma and human tumour for clinical application. The method has greater sensitivity than previously published methods with an equivalent accuracy and precision. It uses less biological material (plasma, tissue) and should therefore be applicable to biopsies in patients treated with capecitabine.

Automated nanospray using chip-based emitters for the quantitative analysis of pharmaceutical compounds

An automated nanospray system based on chip technology (the NanoMate) was successfully interfaced to a modified Particle Discriminator Interface on a triple quadrupole mass spectrometer. A number of the interface parameters were optimized to improve the sampling efficiency for ions from the chip-based system. Analytical performance was assessed using a number of biochemicals as well as via a methodology for a pharmaceutical that passed validation as required by Good Laboratory Practices. Infusion analyses in flow rates <1 microL/min provided advantages in terms of throughput and sample consumption when compared to other methodologies based on liquid chromatography.

Specific Method for the Determination of Genomic DNA Methylation by Liquid Chromatography-Electrospray Ionization Tandem Mass Spectrometry

Herein we report a novel method for determining genomic DNA methylation that utilizes liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) to measure 5-methyl-2'-deoxycytidine levels following enzymatic hydrolysis of genomic DNA. LC separation of 5-methyl-2'-deoxycytidine from the four deoxyribonucleosides, the four ribonucleosides, and 5-methyl-2'-cytidine, a RNA methylation product, has been achieved within 15 min. In combination with ESI-MS/MS detection, the reported method is highly specific and extremely sensitive with a limit of detection (LOD) of 0.2 fmol and a quantification linearity range from 1 fmol to 20 pmol. Genomic DNA methylation was expressed as the ratio of 5-methyl-2'-deoxycytidine to 2'-deoxyguanosine and was determined directly using 2'-deoxyguanosine as the internal standard. Because deoxycytidine methylation typically ranges from 2 to 6% in mammalian genomes, and pharmacological or genetic manipulations have not achieved levels lower than 0.1%, we validated the assay for methylation levels ranging from 0.05 to 10%. Importantly, both RNA contamination and incomplete DNA hydrolysis had no appreciable effect on 5-methyl-2'-deoxycytidine quantification. LOD studies indicate that only 4 ng of DNA is required for this assay. This LOD should permit the use of this method for applications having limiting amounts of DNA that were not previously candidates for global genomic DNA methylation analysis, e.g., clinical trial samples, or cells collected by laser capture microdissection.

Simultaneous determination of capecitabine and its metabolite 5-fluorouracil by column switching and liquid chromatographic/tandem mass spectrometry

A liquid chromatographic/tandem mass spectrometric method was developed and validated for the quantitation of capecitabine and its metabolite 5-fluorouracil in human plasma. The simultaneous determination of both analytes was achieved by a column switching method using a trapping column and two analytical columns with different stationary phases. Isocratic elution was used for the separation of capecitabine on a C18 column whereas 5-fluorouracil was separated using gradient elution on an non-polar carbon phase. The calibration curves were linear for both compounds with a correlation factor (R2) > 0.9993 for 5-fluorouracil and >0.9942 for capecitabine. The assay was validated in the concentration range 5.00-1000 ng ml(-1) for both compounds. The intra-day precision was better than 10% for 5-fluorouracil and better than 11% for capecitabine whereas the inter-day precision was better than 8% for 5-fluorouracil and better than 14% for capecitabine.

Identification of the cytosolic carboxylesterase catalyzing the 5'-deoxy-5-fluorocytidine formation from capecitabine in human liver

Capecitabine, a prodrug of 5-fluorouracil, is first metabolized to 5'-deoxy-5-fluorocytidine (5'-DFCR) by carboxylesterase (CES), which is mainly expressed in microsomes. Recently, we clarified that 5'-DFCR formation was catalyzed by the enzyme in cytosol as well as microsomes in human liver. In the present study, the cytosolic enzyme involved in 5'-DFCR formation from capecitabine was identified. This enzyme was purified in the cytosolic preparation by ammonium sulfate precipitation, Sephacryl S-300 gel filtration, Mono P chromatofocusing, and Superdex 200 gel filtration. The purified enzyme was identified by the amino acid sequence analysis to be CES1A1 or a CES1A1 precursor. Based on the result of the N-terminal amino acid sequence analysis, the purified enzyme has no putative signal peptide, indicating that it was CES1A1. The apparent Km and Vmax values of 5'-DFCR formation were 19.2 mM and 88.3 nmol/min/mg protein, respectively. The 5'-DFCR formation catalyzed by the purified enzyme was inhibited by both diisopropylfluorophosphate and bis(p-nitrophenyl)phosphate in a concentration-dependent manner. 7-Ethyl-10-hydroxycamptothecin (SN-38) formation from irinotecan also occurred in the purified enzyme, cytosol, and microsomes. In conclusion, the cytosolic enzyme involved in 5'-DFCR formation from capecitabine would be CES1A1. It is suggested that the cytosolic CES has significant hydrolysis activity and plays an important role as the microsomal CES in drug metabolism. It is worthy to investigate the metabolic enzyme in cytosol involved in the activation of ester-type prodrugs such as capecitabine.

Comparison of zero- and second-order derivative spectrophotometric and HPLC methods for the determination of gemcitabine in human plasma

Zero- and second-order derivative spectrophotometric and high-performance liquid chromatography (HPLC) methods were developed and validated for the determination of gemcitabine in human plasma. Spectrophotometrically, gemcitabine was determined by means of zero-order derivative absorbance values (A) at 288 nm and from values from the second-order derivative absorbance values (2D) at 285 nm. Beer's Law was obeyed in the range 0.50-15.0 microg ml(-1). The proposed other method, normal-phase HPLC method for determination of gemcitabine in human plasma was described. Calibration curve was linear over the concentration range 0.20-15.0 microg ml(-1). Quantitation was achieved by diode array detection at 272 nm using 2'-deoxycytidine as internal standard. Results obtained by spectrophotometric and HPLC methods for determination of gemcitabine in human plasma described in this paper showed adequate accuracy, precision and repeatability. No interference was found in plasma at the selected derivative wavelength and chromatographic conditions. According to the statistical comparison, there is no significant difference between the three methods. This is suggested that the three methods are equally applicable.

Polysaccharide-based chiral phase under polar organic mode of elution in the determination of the enantiomeric purity of emtricitabine an anti-HIV analogue nucleoside

This work reports the separation of FTC enantiomers using an amylose tris[(S)-1-phenylethylcarbamate] coated onto APS-Nucleosil (7 microm particle size, 500 A pore size, 20% w/w, 15 x 0.46 cm ID) chiral column under polar organic elution mode. Good enantioselectivity (alpha=1.9) with excellent enantioresolution (R(S)=3.3) was achieved by the use of methanol with 0.02% of triethylamine acetate as mobile phase. The method allows the accurate determination of as low as 0.2% of each enantiomer as an impurity. The validated method proved to be reliable and sensitive for the quantification of both enantiomers as impurity in different batches of emtricitabine and beta-D-(+)-FTC.

Characterization of 2'-deoxycytidine adducts derived from 4-oxo-2-nonenal, a novel lipid peroxidation product

Analysis of the reaction between 2'-deoxycytidine and 4-oxo-2-nonenal by LC/MS revealed the presence of three major products (adducts A(1), A(2), and B; [M + H](+) = 364). Adducts A(1) and A(2) were isomeric, and each dehydrated to form adduct B. The structure of adduct B was shown by LC/MS and NMR spectroscopy to be an etheno-2'-deoxycytidine adduct 1' '-[1-(2'-deoxy-beta-d-erythro-pentofuranosyl)-1H-imidazo[2,1-c]pyrimidin-2-oxo-4-yl]heptane-2' '-one. A time course experiment performed at 65 degrees C (pH 5-8) showed that the transformation of both A(1) and A(2) was pH-dependent. In acidic conditions, adducts A(1) and A(2) dehydrated primarily to adduct B. In contrast, in basic conditions, adducts A(1) and A(2) hydrolyzed primarily to dCyd. The data are consistent with adducts A(1) and A(2) being substituted ethano adducts that dehydrate to adduct B, a substituted 3,N(4)-etheno-2'-deoxycytidine adduct.

Identification and quantification of mutagenic halogenated cytosines by gas chromatography, fast atom bombardment, and electrospray ionization tandem mass spectrometry

Oxidative modification of nucleic acids has been implicated in carcinogenesis. One potential mechanism involves halogenation by the myeloperoxidase and eosinophil peroxidase systems of phagocytes. In the current studies, three mass spectrometric methods for the in vitro and in vivo analysis of halogenated cytosines and deoxycytidines were compared: gas chromatography-electron ionization-mass spectrometry (GC-EI-MS) with a quadrupole instrument, fast atom bombardment or electrospray ionization (ESI) tandem MS with a four-sector magnetic instrument, and liquid chromatography ESI tandem MS (HPLC-ESI-MS/MS) with an ion-trap instrument. GC-EI-MS with selected ion monitoring of dimethyl-tert-butylsilyl derivatives of nucleobases was the most sensitive method. High-energy collisionally induced dissociation MS/MS analysis with a four-sector magnetic instrument yielded detailed structural information about halogenated nucleoside adducts but required relatively large amounts of material. The most sensitive analysis of intact halogenated deoxycytidine was achieved with extracted ion chromatograms using HPLC-ESI-MS/MS with an ion-trap instrument. Our results indicate that GC-EI-MS is the methodology of choice for ultrasensitive analysis of halogenated cytosines. HPLC-ESI-MS/MS provides greater structural detail for these compounds and may rival GC-EI-MS in sensitivity with more advanced liquid chromatography applications. The mass spectrometric methods we have developed should be useful for evaluating the role of phagocyte-derived oxidants in halogenating nucleobases, nucleosides, and DNA at sites of inflammation.

Comparison of multiple DNA adduct types in tumor adjacent human lung tissue: effect of cigarette smoking

Cigarette smokers inhale a broad range of carcinogens derived from tobacco and its pyrolysis products, including free radicals, which induce oxidative stress and subsequent lipid peroxidation (LPO). Miscoding carcinogen-DNA adducts are formed by cigarette smoke constituents and are thought to initiate lung carcinogenesis. The presence of various types of DNA damage was therefore analyzed in tumor adjacent uninvolved lung tissues of 13 smoking and 11 non-smoking operated lung cancer patients. O(4)-ethylthymidine (O(4)etT), 1,N(6)-ethenodeoxyadenosine ( epsilon dA) and 3,N(4)-ethenodeoxycytidine ( epsilon dC) were determined by immuno-enriched (32)P-postlabeling. Polycyclic aromatic hydrocarbon (PAH)-DNA adducts were measured as diagonal radioactive zones after nuclease P1 enriched (32)P-postlabeling. Mean O(4)etT and PAH-DNA adduct levels were higher in lung DNA of smokers than of non-smokers (O(4)etT/10(8) thymidine: 3.8 versus 1.6, P < 0.01; PAH-DNA adducts/10(8) nucleotides: 11.2 versus 2.2, P < 0.01). Pulmonary etheno-DNA adduct levels did not differ between smokers and non-smokers, but large inter-individual variations were observed (80- and 250-fold differences for epsilon dA and epsilon dC, respectively). As all smokers (except one) refrained from smoking at least for 1 week before surgery, our results demonstrate the persistence of O(4)etT and PAH-DNA adducts in human lung. A positive correlation obtained between O(4)etT and PAH-DNA adducts (R = 0.65, P < 0.01) suggests that both adducts are formed from cigarette smoke as the main exposure source. We conclude that in addition to the DNA adducts derived from PAH and tobacco-specific nitrosamines, miscoding O(4)etT lesions are formed by cigarette smoke that contribute to the increased genomic instability and increased lung cancer risk in smokers.

Analytical and pharmacokinetic studies with 5-chloro-2'-deoxycytidine

5-Chloro-2'-deoxycytidine (NSC 371331, CDC) is in development as a possible radiosensitizing agent for cancer treatment. Previous studies have been done to demonstrate the in vivo efficacy of CDC with various modulators of its metabolism. This paper describes our preclinical studies to determine the pharmacokinetic properties of CDC and the disposition of the drug, both alone and in the presence of the metabolic modulator tetrahydrouridine (THU), a cytidine deaminase inhibitor. Detection of the drug in biological fluids was performed by HPLC analysis using a C-18 column, gradient elution with solvents composed of aqueous trifluoroacetic acid and acetonitrile, and ultraviolet absorbance at 290 nm. Samples were processed by treatment with ammonium sulfate prior to injection into the HPLC system. CDC was stable in aqueous solution and in mouse plasma. High doses of CDC (100mg/kg) were given i.v. or i.p. to mice for the determination of CDC plasma half-life (10 min). CDC was not detectable in plasma after oral administration. It was converted rapidly to 5-chloro-2'-deoxyuridine (CDU) by cytidine deaminase, and CDU was readily discernable in plasma and urine samples collected after i.v. and i.p. administration of CDC. When CDC in doses ranging from 5 to 100mg/kg was given with 100mg/kg of THU, increased plasma levels of CDC were seen. CDC was eliminated through the kidneys, as well as by enzymatic deamination, and did not bind to plasma proteins. The initial steps of the CDC metabolic pathway were determined in vitro with isolated enzymes. Cytidine deaminase from mouse kidney converted CDC into CDU; thymidine phosphorylase converted CDU into 5-chlorouracil (5-CU). The conclusions of these studies are: (a) CDC is a drug with a short half-life and (b) it is excreted through the kidney, mainly in metabolite form. Administration of THU substantially increased the concentrations of CDC in mouse plasma, supporting proposals that the combination of THU with CDC should be evaluated in clinical trials.

A method to assess genomic DNA methylation using high-performance liquid chromatography/electrospray ionization mass spectrometry

Eukaryotic DNA is methylated at some cytosine residues, and this epigenetic feature performs critical functions. We developed a method for quantitative determination of 5-methyl-2'-deoxycytidine in human DNA using liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS). The DNA was enzymatically hydrolyzed by sequential digestion with three enzymes. DNA hydrolyzates were subsequently separated by reversed-phase high-performance liquid chromatography in isocratic mode. The four major DNA bases and 5-methyl-2'-deoxycytidine were resolved and eluted in 13 min. Identification of 2'-deoxycytidine and 5-methyl-2'-deoxycytidine was obtained by combined diode array UV spectra analysis and mass spectra of chromatographic peaks. The isotopomers [15N3]-2'-deoxycytidine and (methyl-d3,ring-6-d1)-5-methyl-2'-deoxycytidine were used as internal standards. Ions of m/z 126 and 130 were used to detect 5-methyl-2'-deoxycytidine and its isotopomer, and ions of m/z 112 and 115 were used to detect 2'-deoxycytidine and its stable isotopomer, respectively. The DNA methylation status was calculated on the basis of the amount of 5-methyl-2'-deoxycytidine per microgram of DNA with percent relative standard deviations (%RSD) for a method precision of 7.1 (within-day) and 5.7 (day-to-day). This method also allows the measurement of 5-methyl-2'-deoxycytidine expressed as a percentage of total deoxycytidine residues in genomic DNA with %RSD for method precision of 1.9 (within-day) and 1.7 (day-to-day). This LC/MS method for quantitative determination of genomic DNA methylation status is rapid, sensitive, selective, and precise.

Quantification of 2'-fluoro-2'-deoxyuridine and 2'-fluoro-2'-deoxycytidine in DNA and RNA isolated from rats and woodchucks using LC/MS/MS

Apatmers are synthesized using 2'-fluoropyrimdines in place of normal pyrmidines to stabilize them against enzymatic degradation, and thereby improve their therapeutic efficacy. Despite this stabilizing effect, the apatmers can still be degraded by nucleases in the blood. Primer template extension studies have demonstrated that mammalian DNA polymerases can incorporate these 2'-fluoropyrimidines into growing strands of DNA. The toxicologic effects of these compounds have been examined in rats and woodchucks, animals known to be susceptible to the toxic effects of other modified pyrimidines. Whether these nucleosides can be incorporated into DNA in vivo has not been established. These studies report the development of methodologies and the results of studies designed to determine if and to what extent 2'-fluoropyrimidines are incorporated into tissue DNA following long-term treatment. Rats were dosed intravenously with either 2'-fluorouridine (2'-FU) or 2'-fluorocytidine (2'-FC) at doses of 5, 50, and 500 mg/kg/day for 90 days. Woodchucks were dosed intravenously with either 2'-FU or 2'-FC at doses of 0.75 or 7.5 mg/kg/day for 90 days. The amounts of 2'-FU or 2'-FC in DNA and RNA were quantified using newly developed LC/MS/MS methodologies. Administration of 2'-FU to rats and woodchucks resulted in incorporation of the compound into DNA from liver, spleen, testis, muscle, and kidney. Incorporation also occurred in RNA from rat liver (only tissue examined). Similarly, administration of 2'-FC to rats and woodchucks resulted in incorporation into liver DNA (only tissue examined). These data demonstrate that 2'-fluoropyrimidines are incorporated into DNA and RNA of various tissues of rats and woodchucks following long-term administration.

High-performance capillary electrophoretic method for the quantification of 5-methyl 2'-deoxycytidine in genomic DNA: application to plant, animal and human cancer tissues

A new approach to the evaluation of the relative degree of genomic DNA methylation through the quantification of 2'-deoxynucleosides is proposed. Detection and quantification of 5-methyl 2'-deoxycytidine in genomic DNA has been performed using micellar high-performance capillary electrophoresis (HPCE) with UV-Vis detection. This approach has been demonstrated to be more sensitive and specific than other HPCE methods for the quantification of DNA methylation degree and also to be faster than other HPLC-based methods. The detection and quantification of nucleosides through enzymatic hydrolyses notably increases the specificity of the technique and allows its exploitation in the analysis of poorly purified and/or concentrated DNA samples such as those obtained from meristematic plant regions and paraffin-embedded tissues.

Quantitative analysis of etheno-2'-deoxycytidine DNA adducts using on-line immunoaffinity chromatography coupled with LC/ES-MS/MS detection

Etheno DNA adducts, including 3,N4-etheno-2'-deoxycytidine (etheno-dC), are promutagenic lesions present in normal animal and human tissues. These DNA adducts are believed to be important in the etiology of cancer. Existing methods for quantifying etheno-dC use 32p. postlabeling. Although highly sensitive, postlabeling requires the use of an energetic radioisotope and considerable time and effort. The new methodology reported here permits automated quantification of trace levels of etheno-dC in crude DNA hydrolysates on the order of 5 adducts in 10(8) normal nucleotides from 100-microg samples of DNA. This was accomplished by using on-line immunoaffinity chromatography, a reverse-phase LC separation on graphitized carbon, tandem mass spectrometric detection, and an isotopically labeled internal standard. The automated procedures permitted analysis of 4 DNA hydrolysates/hr. The sensitivity using immunoaffinity cleanup was approximately 100-fold greater than that observed when using a silica-based trapping system. The validated method was applied to the analysis of etheno-dC in commercial calf thymus DNA, untreated mouse liver, and untreated rat liver DNA. The demonstrated level of performance suggests future applicability of this method in studies of cancer in humans and experimental animals.