Comparison between capillary and nano liquid chromatography-electrospray mass spectrometry for the analysis of minor DNA-melphalan adducts

Effects of GSTT1 Genotype on the Detoxification of 1,3-Butadiene Derived Diepoxide and Formation of Promutagenic DNA-DNA Cross-Links in Human Hapmap Cell Lines

Smoking is a leading cause of lung cancer, accounting for 81% of lung cancer cases. Tobacco smoke contains over 5000 compounds, of which more than 70 have been classified as human carcinogens. Of the many tobacco smoke constituents, 1,3-butadiene (BD) has a high cancer risk index due to its tumorigenic potency and its abundance in cigarette smoke. The carcinogenicity of BD has been attributed to the formation of several epoxide metabolites, of which 1,2,3,4-diepoxybutane (DEB) is the most toxic and mutagenic. DEB is formed by two oxidation reactions carried out by cytochrome P450 monooxygenases, mainly CYP2E1. Glutathione-S-transferase theta 1 (GSTT1) facilitates the conjugation of DEB to glutathione as the first step of its detoxification and subsequent elimination via the mercapturic acid pathway. Human biomonitoring studies have revealed a strong association between GSTT1 copy number and urinary concentrations of BD-mercapturic acids, suggesting that it plays an important role in the metabolism of BD. To determine the extent that GSTT1 genotype affects the susceptibility of individuals to the toxic and genotoxic properties of DEB, GSTT1 negative and GSTT1 positive HapMap lymphoblastoid cell lines were treated with DEB, and the extent of apoptosis and micronuclei (MN) formation was assessed. These toxicological end points were compared to the formation of DEB-GSH conjugates and 1,4-bis-(guan-7-yl)-2,3-butanediol (bis-N7G-BD) DNA-DNA cross-links. GSTT1 negative cell lines were more sensitive to DEB-induced apoptosis as compared to GSTT1 positive cell lines. Consistent with the protective effect of GSH conjugation against DEB-derived apoptosis, GSTT1 positive cell lines formed significantly more DEB-GSH conjugate than GSTT1 negative cell lines. However, GSTT1 genotype did not affect formation of MN or bis-N7G-BD cross-links. These results indicate that GSTT1 genotype significantly influences BD metabolism and acute toxicity.

Applying Tobacco, Environmental, and Dietary-Related Biomarkers to Understand Cancer Etiology and Evaluate Prevention Strategies

Many human cancers are caused by environmental and lifestyle factors. Biomarkers of exposure and risk developed by our team have provided critical data on internal exposure to toxic and genotoxic chemicals and their connection to cancer in humans. This review highlights our research using biomarkers to identify key factors influencing cancer risk as well as their application to assess the effectiveness of exposure intervention and chemoprevention protocols. The use of these biomarkers to understand individual susceptibility to the harmful effects of tobacco products is a powerful example of the value of this type of research and has provided key data confirming the link between tobacco smoke exposure and cancer risk. Furthermore, this information has led to policy changes that have reduced tobacco use and consequently, the tobacco-related cancer burden. Recent technological advances in mass spectrometry led to the ability to detect DNA damage in human tissues as well as the development of adductomic approaches. These new methods allowed for the detection of DNA adducts in tissues from patients with cancer, providing key evidence that exposure to carcinogens leads to DNA damage in the target tissue. These advances will provide valuable insights into the etiologic causes of cancer that are not tobacco-related.See all articles in this CEBP Focus section, "Environmental Carcinogenesis: Pathways to Prevention."

Interindividual Differences in DNA Adduct Formation and Detoxification of 1,3-Butadiene-Derived Epoxide in Human HapMap Cell Lines

Smoking-induced lung cancer is a major cause of cancer mortality in the US and worldwide. While 11-24% of smokers will develop lung cancer, risk varies among individuals and ethnic/racial groups. Specifically, African American and Native Hawaiian cigarette smokers are more likely to get lung cancer as compared to Caucasians, Japanese Americans, and Latinos. It is important to identify smokers who are at the greatest risk of developing lung cancer as they should be candidates for smoking cessation and chemopreventive intervention programs. Among 60+ tobacco smoke carcinogens, 1,3-butadiene (BD) is one of the most potent and abundant (20-75 μg per cigarette in mainstream smoke and 205-361 μg per cigarette in side stream smoke). BD is metabolically activated to 3,4-epoxy-1-butene (EB), which can be detoxified by glutathione S-transferase theta 1 (GSTT1)-mediated conjugation with glutathione, or can react with DNA to form 7-(1-hydroxy-3-buten-2-yl)guanine (EB-GII) adducts. In the present study, we employed EBV-transformed human lymphoblastoid cell lines (HapMap cells) with known GSTT1 genotypes to examine the influence of the GSTT1 gene on interindividual variability in butadiene metabolism, DNA adduct formation/repair, and biological outcomes (apoptosis). We found that GSTT1- HapMap cells treated with EB in culture produced lower levels of glutathione conjugates and were more susceptible to apoptosis but had similar numbers of EB-GII adducts as GSTT1+ cells. Our results suggest that GSTT1 can influence an individual's susceptibility to butadiene-derived epoxides.

Characterization of nitrogen mustard formamidopyrimidine adduct formation of bis(2-chloroethyl)ethylamine with calf thymus DNA and a human mammary cancer cell line

A robust, quantitative ultraperformance liquid chromatography ion trap multistage scanning mass spectrometric (UPLC/MS(3)) method was established to characterize and measure five guanine adducts formed by reaction of the chemotherapeutic nitrogen mustard (NM) bis(2-chloroethyl)ethylamine with calf thymus (CT) DNA. In addition to the known N7-guanine (NM-G) adduct and its cross-link (G-NM-G), the ring-opened formamidopyrimidine (FapyG) monoadduct (NM-FapyG) and cross-links in which one (FapyG-NM-G) or both (FapyG-NM-FapyG) guanines underwent ring-opening to FapyG units were identified. Authentic standards of all adducts were synthesized and characterized by NMR and mass spectrometry. These adducts were quantified in CT DNA treated with NM (1 μM) as their deglycosylated bases. A two-stage neutral thermal hydrolysis was developed to mitigate the artifactual formation of ring-opened FapyG adducts involving hydrolysis of the cationic adduct at 37 °C, followed by hydrolysis of the FapyG adducts at 95 °C. The limit of quantification values ranged between 0.3 and 1.6 adducts per 10(7) DNA bases when the equivalent of 5 μg of DNA hydrolysate was assayed on column. The principal adduct formed was the G-NM-G cross-link, followed by the NM-G monoadduct; the FapyG-NM-G cross-link adduct; and the FapyG-NM-FapyG was below the limit of detection. The NM-FapyG adducts were formed in CT DNA at a level ∼20% that of the NM-G adduct. NM-FapyG has not been previously quanitified, and the FapyG-NM-G and FapyG-NM-FapyG adducts have not been previously characterized. Our validated analytical method was then applied to measure DNA adduct formation in the MDA-MB-231 mammary tumor cell line exposed to NM (100 μM) for 24 h. The major adduct formed was NM-G (970 adducts per 10(7) bases), followed by G-NM-G (240 adducts per 10(7) bases), NM-FapyG (180 adducts per 10(7) bases), and, last, the FapyG-NM-G cross-link adduct (6.0 adducts per 10(7) bases). These lesions are expected to contribute to NM-mediated toxicity and genotoxicity in vivo.

Advanced nanoscale separations and mass spectrometry for sensitive high-throughput proteomics

Recent developments in combined separations with mass spectrometry for sensitive and high-throughput proteomic analyses are reviewed herein. These developments primarily involve high-efficiency (separation peak capacities of approximately 10(3)) nanoscale liquid chromatography (flow rates extending down to approximately 20 nl/min at optimal liquid mobile-phase separation linear velocities through narrow packed capillaries) in combination with advanced mass spectrometry and in particular, high-sensitivity and high-resolution Fourier transform ion cyclotron resonance mass spectrometry. Such approaches enable analysis of low nanogram level proteomic samples (i.e., nanoscale proteomics) with individual protein identification sensitivity at the low zeptomole level. The resultant protein measurement dynamic range can approach 10(6) for nanogram-sized proteomic samples, while more abundant proteins can be detected from subpicogram-sized (total) proteome samples. These qualities provide the foundation for proteomics studies of single or small populations of cells. The instrumental robustness required for automation and providing high-quality routine performance nanoscale proteomic analyses is also discussed.

Separation and identification of trinucleotide-melphalan adducts from enzymatically digested DNA using HPLC-ESI-MS

Melphalan is a bifunctional alkylating agent that covalently binds to the nucleophilic sites present in DNA. In this study we investigated oligonucleotides prepared enzymatically from DNA modified with melphalan. Calf thymus DNA was incubated in-vitro with melphalan and the resulting modifications were enzymatically cleaved by means of benzonase and nuclease S1. Efficient sample preconcentration was achieved by solid-phase extraction, in which phenyl phase cartridges resulted in better recovery of the modified species than C(18). The applied enzymatic digestion time resulted in production of trinucleotide adducts which were efficiently separated and detected by use of reversed-phase HPLC coupled to an ion-trap mass spectrometer with electrospray ionization. It was assumed that melphalan could act as both a monofunctional and bifunctional alkylating agent. Mono-alkylated adducts were much more abundant, however, and the alkylation site was located on the nucleobases. On the other hand, we unequivocally identified cross-link formation in DNA, even though at low abundance and only a few adduct types were detected.

Recent applications in nanoliquid chromatography

Since its first introduction by Karlsson and Novotny in 1988 nano-LC has emerged as a complementary and/or competitive separation method to conventional HPLC, offering several advantages such as higher efficiency, ability to work with minute sample sizes and lower consumption of mobile phases, and better compatibility with MS, etc. Although its use was not so extended initially, in the last years new and interesting applications have appeared which deserve to be carefully considered. The aim of this review is therefore to provide an updated and critical survey of different nano-LC applications in analytical chemistry.

Identification of the adduct between a 4-Aza-3-ene-1,6-diyne and DNA using electrospray ionization mass spectrometry

The interactions between a novel enediyne [1-methyl-2-(phenylethynyl)-3-(3-phenylprop-2-ynyl)-3H-benzimidazolium] (1) and various cytosine-containing oligonucleotides were studied using electrospray ionization mass spectrometry (ESI-MS) in a flow injection analysis mode useful for small volumes. This enediyne ligand, developed as a potential alternative to the highly cytotoxic natural enediynes, some of which have been successfully used as anti-tumor agents, has previously been shown to interact with DNA through frank strand scission as well as via the formation of adducts that lead to 2'-deoxycytidine-specific cleavage. Through ESI-MS, the structures of these adducts were examined and a sequence dependence of the 2'-deoxycytidine-specific cleavage was noted. Collisionally activated dissociation of the observed adducts confirmed the strength of the interactions between the enediyne and DNA and supports a direct linkage between the enediyne and the cytosine nucleobase, likely the result of a nucleophilic attack of the phenylethynyl group by the cytosine amine.

Quantitative determination of melphalan DNA adducts using HPLC - inductively coupled mass spectrometry

For the quantification of Melphalan DNA adducts, an analytical approach based on the detection of phosphorus using liquid chromatography combined with inductively-coupled-plasma mass spectrometry (ICP-MS) was developed. In reaction mixtures of native 2'-deoxynucleotides-5'-monophosphates and Melphalan, which were separated using reversed phase chromatography, phosphate adducts were found as the most abundant modifications. Besides the phosphate adducts, several base alkylated adducts were observed. In calf thymus DNA incubated with Melphalan and enzymatically digested using Nuclease P1, the phosphate adducts as well as monoalkylated dinucleotides were found. The most abundant single Melphalan adduct observed in DNA was a ring-opened adenosine monophosphate. Some dinucleotide adducts and the adenosine adduct were identified using electrospray ionization mass spectrometry (ESI-MS).

Analysis of nucleic acid constituents by on-line capillary electrophoresis-mass spectrometry

This review is focused on the capillary electrophoresis-mass spectrometric (CE-MS) analysis of nucleic acid constituents in the broadest sense, going from nucleotides and adducted nucleotides over nucleoside analogues to oligonucleotides. These nucleic acid constituents play an important role in a variety of biochemical processes. Hence, their isolation, identification, and quantification will undoubtedly help reveal the process of life and disease mechanisms, such as carcinogenesis, and can also be useful for antitumor and antiviral drug research to provide valuable information about mechanism of action, pharmacokinetics, pharmacodynamics, toxicity, therapeutic drug level monitoring, and quality control related to this substance class. Fundamental investigations into their structure, the search for modifications, the occurrence and biochemical impact of structural variation amongst others, are therefore of great value. In view of the related bioanalytical procedures, the coupling of CE to MS has emerged as a powerful tool for the analysis of the complex mixtures of nucleic acid constituents: CE confers rapid analysis and efficient resolution, while MS provides high selectivity and sensitivity with structural characterization of minute amounts of compound. After an introduction about the biochemical and analytical perspectives on the nucleic acid constituents, the different modes of CE used in this field of research as well as the relevant CE-MS interfaces and the difficulties associated with quantitative CE-MS are briefly discussed. A large section is finally devoted to field-oriented applications.

Detection and quantification of N-(deoxyguanosin-8-yl)-4-aminobiphenyl adducts in human pancreas tissue using capillary liquid chromatography-microelectrospray mass spectrometry

Cigarette smoking has been associated with various cancers including bladder and pancreas. 4-Aminobiphenyl has been isolated as a constituent of cigarette smoke and has been established as a carcinogen in various animal models and humans. In rodents and humans, 4-aminobiphenyl is N-hydroxylated and forms adducts to DNA, the predominant one being N-(deoxyguanosin-8-yl)-4-aminobiphenyl (dG-C8-ABP). In this study, we report a micro-electrospray mass spectrometric (muESI-MS) isotope dilution method for the detection and quantification of dG-C8-ABP in human pancreatic tissue. A reverse phase capillary column (320 microm ID) was connected to a triple quadrupole mass spectrometer via a commercially available micro-ESI source. The system was operated in the selected reaction monitoring mode transmitting the [M + H]+ --> [M + H - 116]+ transitions for both the analyte and the isotopically labeled internal standard. Twelve human pancreas samples were analyzed, where six were current smokers (three male and three female) and six were considered nonsmokers (three female and three male). Of the samples analyzed, six showed dG-C8-ABP levels above the limit of quantification for the method, five were considered to have levels that were undetectable, and one was discarded due to inconsistent internal standard signal. The age of the human subjects ranged from 17 to 63, and, in samples where adduct was present, levels ranged anywhere from 1 to 60/10(8) nucleotides. Although no correlation between smoking preference, age, or gender was proven with this particular sample pool, this report demonstrates that capillary LC-muESI-MS can provide a sensitive and definitive method for DNA adduct analysis in human tissue.

Implications of enzymatic, acidic and thermal hydrolysis of DNA on the occurrence of cross-linked melphalan DNA adducts

Calf thymus DNA was treated with melphalan, a nitrogen mustard, and the formation of melphalan cross-linked DNA adducts was investigated. These cross-linked adducts could not be detected either in the enzymatically or in the thermally generated DNA hydrolysates. However, a search for DNA cross-linked adducts in the hydrolysates obtained under acidic conditions revealed the presence of different types of cross-links, mainly containing an adenine moiety. These results are very important because they show that the detection of cross-links is dependent on the hydrolytic procedure used and that these cross-linked adducts are formed under totally different reaction conditions from those in in vivo situations. This can explain the very low abundance or even the absence of cross-linked adducts in nitrogen mustard treated animals. The generally accepted theory that the anti-cancer activity of bifunctional mustards such as melphalan is due to cross-linking of DNA strands remains therefore from our point of view questionable.

Structural characterization of melphalan modified 2'-oligodeoxynucleotides by miniaturized LC-ES MS/MS

In this study a miniaturized LC coupled to electrospray tandem mass spectrometry was used to analyze modifications originating from the interaction between the chemotherapeutic agent melphalan and 2'-oligodeoxynucleotides. Low energy CAD product ion spectra gave information about the specificity of melphalan alkylation with regard to certain DNA sequences. These data can be very useful to estimate the risk in the development of secondary leukaemia as a result of a melphalan cure. In the study of the interaction between melphalan and d(GG), differentiation could be made between alkylation on the 5'-side and alkylation on the 3'-side, because of the presence or absence of the alkylated w1 fragment in the low energy CAD spectra. In the other di-mers alkylation specificity for the different bases could be observed. Melphalan alkylation occurs in the sequence G > A > C > T. The study of the alkylated d(GGGG) revealed the presence of mainly 5'-end alkylation. Furthermore studies were performed which investigated other melphalan treated di-, tetra-, hepta-, and octa-mers.

High-Efficiency On-Line Solid-Phase Extraction Coupling to 15−150-μm-i.d. Column Liquid Chromatography for Proteomic Analysis

The ability to manipulate and effectively utilize small proteomic samples is important for analyses using liquid chromatography (LC) in combination with mass spectrometry (MS) and becomes more challenging for very low flow rates due to extra column volume effects on separation quality. Here we report on the use of commercial switching valves (150-microm channels) for implementing the on-line coupling of capillary LC columns operated at 10,000 psi with relatively large solid-phase extraction (SPE) columns. With the use of optimized column connections, switching modes, and SPE column dimensions, high-efficiency on-line SPE-capillary and nanoscale LC separations were obtained demonstrating peak capacities of approximately 1000 for capillaries having inner diameters between 15 and 150 microm. The on-line coupled SPE columns increased the sample processing capacity by approximately 400-fold for sample solution volume and approximately 10-fold for sample mass. The proteomic applications of this on-line SPE-capillary LC system were evaluated for analysis of both soluble and membrane protein tryptic digests. Using an ion trap tandem MS it was typically feasible to identify 1100-1500 unique peptides in a 5-h analysis. Peptides extracted from the SPE column and then eluted from the LC column covered a hydrophilicity/hydrophobicity range that included an estimated approximately 98% of all tryptic peptides. The SPE-capillary LC implementation also facilitates automation and enables use of both disposable SPE columns and electrospray emitters, providing a robust basis for automated proteomic analyses.

Detection of estrogen DNA-adducts in human breast tumor tissue and healthy tissue by combined nano LC-nano ES tandem mass spectrometry

For the first time estrogen DNA-adducts were identified in DNA human breast tumor tissue using nano-LC coupled to nano-Electrospray Tandem Mass Spectrometry. Normal breast tissue was analyzed analogously. The data obtained in the five breast tumor and five adjacent normal tissue samples were compared qualitatively, but no straightforward difference was observed. Prior to LC-MS analysis the DNA was enzymatically hydrolyzed to a nucleoside pool. The DNA-hydrolysates were directly injected onto a column switching system developed for on-line sample clean-up and subsequent analysis of the DNA-adducts. In four patients using Premarin, DNA-adducts of 4-hydroxy-equilenin (4OHEN) were detected. All except three samples contained DNA-adducts from 4-hydroxy-estradiol or 4-hydroxy-estrone. Also DNA isolated from eight alcohol fixed and paraffin embedded breast tumor tissue showed the presence of different estrogen DNA-adducts. Worthwhile mentioning is the presence of adducts responding to m/z 570 > m/z 454 transition. This is a well-known SRM-transition indicative for the presence of the 2'-deoxyguanosine (dGuo) adduct of Benzo[a]pyrene.

Capillary liquid chromatography/electrospray mass spectrometry for analysis of steroid sulfates in biological samples

A new procedure for capillary liquid chromatography-electrospray (CLC-ES) mass spectrometry is described. Using this procedure, coupling of a CLC column to a low-flow-rate ES interface is made simple. A 5-cm precolumn and a 35-cm analytical column, both fused-silica capillaries with an i.d. of 100 microm and packed with 3-microm octadecylsilane-bonded material, are coupled in series to a sheathless ES emitter. One solvent splitter is positioned between the loop injector and the precolumn, and a second, between the precolumn and the analytical column. By opening and closing the splitters in the appropriate order, this arrangement permits the injection of 1-20 microL of sample solution with analyte focusing onto the top of the precolumn, followed by isocratic or gradient elution at a flow rate of 0.2-0.3 microL/min through the analytical column. The relative standard deviation of the retention times of reference compounds was <3.5% (n = 5). The potential of the system in metabolome analysis, in which numerous isomeric compounds will require identification, is illustrated by the application of the system to the analysis of steroid sulfates in plasma.

Hyphenated techniques in anticancer drug monitoring. II. Liquid chromatography-mass spectrometry and capillary electrophoresis-mass spectrometry

High-performance liquid chromatography has become the separation technique of choice for the monitoring of generally thermolabile anticancer agents. With the introduction of electrospray mass spectrometry, the coupling of liquid chromatogaphy and mass spectrometry has opened the way to widely and routinely applied anticancer drug monitoring. Real-time metabolism versus degradation can now be distinguished, since derivatization is no longer obligatory. This is important for the monitoring of the anabolic and catabolic pathways of the same agent, such as 5-fluorouracil. Detection limits almost equal to those obtained with capillary gas chromatography-mass spectrometry are realistic with the latest generation of mass spectrometers, enabling quantitative analysis of various anticancer agents and their metabolites down to the low ng/ml level. Furthermore, sample clean-up and chromatography can be downscaled markedly using the latest column technologies, such as the generally applied 10 cm x 2.8 mm I.D. RP 18 columns. The coupling of capillary electrophoresis to mass spectrometry is today far from a routine application in anticancer drug monitoring. Nevertheless, interesting applications have been reported and are selected for the present review.

Applications of mass spectrometry for quantitation of DNA adducts

DNA adducts are formed when electrophilic molecules or free radicals attack DNA. 32P-postlabeling has been the most commonly used assay for quantitation of DNA adducts due mainly to its excellent sensitivity that allows quantitation at concentrations as low as approximately 1 adduct per 10(9) normal bases. Such methods, however, do not have the specificity desired for accurate and reliable quantitation, and are prone to produce false positives and artifacts. In the last decade, mass spectrometry in combination with liquid and gas chromatography has presented itself as a good alternative to these techniques since it can satisfy the need for specificity and reliability through the use of stable isotope-labeled internal standards and highly specific detection modes such as selected reaction monitoring and high-resolution mass spectrometry. In this article, the contribution of mass spectrometry to the quantitation of DNA adducts is reviewed with special emphasis on unique applications of mass spectrometry in the area of DNA adduct quantitation and recent applications with improvements in sensitivity.

Determination of hydroxyalkyl derivatives of cobalamin (vitamin B12) using reversed phase high performance liquid chromatography with electrospray tandem mass spectrometry and ultraviolet diode array detection

Electrospray ionization tandem mass spectrometry (ESI-MS/MS) and ultraviolet diode array detection (UV-DAD), coupled on-line to reversed phase high performance liquid chromatography (HPLC), was used for the characterization of hydroxyalkyl derivatives of cob(I)alamin. The reduced form of vitamin B12, cob(I)alamin, denoted a supernucleophile due to its high nucleophilic strength, has shown promise as an analytical tool in studies of electrophilically reactive compounds in vitro and in vivo. A method for analysis of DNA-phosphate adducts was developed earlier utilizing the supernucleophilicity of cob(I)alamin to transfer alkyl groups from the phosphotriester configuration in DNA, with the formation of a Co-substituted alkyl-cobalamin (alkyl-Cbl) complex. For the purpose of identification and quantification of alkyl-Cbls at high sensitivity, an MS/MS method has been developed with application to a number of 2-hydroxyalkyl-cobalamins (OHalkyl-Cbls). The precursor oxiranes were reacted with cob(I)alamin, followed by clean-up and mass spectrometric analysis of the resulting OHalkyl-Cbls. It was found that ionization was highly dependent on solvent composition. By using acetonitrile/water/trifluoroacetic acid (TFA) (eluent I), the base peak was the doubly protonated molecule [M + 2H](2+), whereas acetonitrile/water/1-methylpiperidine (eluent II) yielded the singly protonated molecule [M + H](+) as the base peak. Excellent separation was obtained with eluent II, with good separation between stereoisomers, thus enabling the characterization of these by means of UV spectra. Limits of quantitation for 2-hydroxypropyl-cobalamin (OHPr-Cbl) were 0.2 and 2 pg/microL (or 0.1 and 1 fmol/microL) using selected ion recording (SIR) with eluent I and II, respectively. The obtained detection level should be sufficient for analysis of alkyl-Cbls from a wide range of toxicological applications.

Analysis of urinary nucleosides. II. Comparison of mass spectrometric methods for the analysis of urinary nucleosides

Qualitative and quantitative analyses of urinary nucleosides have diagnostic potential as tumour markers. We have developed separation techniques linked to mass spectrometric detection in order to overcome the problems associated with past identification and quantitation methods. The three methods of analysis utilised were: gas chromatography/mass spectrometry (GC/MS), high-performance liquid chromatography/ion-trap mass spectrometry (HPLC/ITMS) and capillary liquid chromatography/triple quadrupole mass spectrometry (CapLC/TQMS). Here we compare the relative effectiveness of each of the techniques for subsequent application in the systematic study of urinary nucleoside profiles in cancer patients. All three methods proved to be valuable techniques for such urinary nucleoside analyses, and a combination rather than one single choice is concluded as the ideal.