CEBP Frontiers in Cancer Prevention Research - 2008 Cancer Health Disparities Conference 2009
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Cancer Research Clinical Cancer Research
Cancer Epidemiology Biomarkers & Prevention Molecular Cancer Therapeutics
Molecular Cancer Research Cancer Prevention Research
Cancer Prevention Journals Portal Cancer Reviews Online
Annual Meeting Education Book Meeting Abstracts Online
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Scholl, P. F.
Right arrow Articles by Wild, C. P.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Scholl, P. F.
Right arrow Articles by Wild, C. P.
Cancer Epidemiology Biomarkers & Prevention Vol. 15, 823-826, April 2006
© 2006 American Association for Cancer Research

Short Communication

Quantitative Comparison of Aflatoxin B1 Serum Albumin Adducts in Humans by Isotope Dilution Mass Spectrometry and ELISA

Peter F. Scholl1, Paul C. Turner2, Anne E. Sutcliffe2, Abdoulaye Sylla3, Momadou S. Diallo3, Marlin D. Friesen1, John D. Groopman1 and Christopher P. Wild2

1 Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland; 2 Molecular Epidemiology Unit, Centre for Epidemiology and Biostatistics, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds, United Kingdom; and 3 Institut Pasteur de Guinée, Kindia, Republic of Guinea

Requests for reprints: Peter F. Scholl, Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205-2103. Phone: 410-955-4235; Fax: 410-955-0617. E-mail: pscholl{at}jhsph.edu.


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Metabolic activation of the hepatocarcinogenic mycotoxin aflatoxin B1 (AFB1) results in the covalent attachment of AFB1 to serum albumin. Digestion of adducted albumin releases AFB1-lysine, a biomarker of exposure status. AF-albumin adducts have been most frequently measured in precipitated serum albumin using an immunoassay (ELISA); however, a sensitive and specific isotope dilution mass spectrometric (IDMS) assay for measurement of AFB1-lysine in serum has recently been developed. The ELISA and IDMS methods were compared using 20 human sera collected in Guinea, West Africa, where AF exposure is endemic. Measurement of AFB1-lysine adduct concentrations by IDMS in serum and albumin precipitated from the same sample revealed that precipitation has no effect on the measured adduct levels. The concentration of AF-albumin adducts measured by ELISA and AFB1-lysine measured by IDMS in 2 mg of albumin were well correlated (R = 0.88, P < 0.0001); however, AF-albumin adduct concentrations measured by ELISA were on average 2.6-fold greater than those of the AFB1-lysine adduct. Although these data suggest that the ELISA is measuring other AF adducts in addition to AFB1-lysine, these biomarkers are comparable in their ability to assess AF exposure at AF-albumin concentrations ≥3 pg AFB1-lysine equivalents/mg albumin. Identification of other adducts may clarify the mechanistic basis for using AF-protein biomarkers to assess exposure status in future epidemiologic studies of liver cancer. (Cancer Epidemiol Biomarkers Prev 2006;15(4):823–6)


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
Aflatoxins (AF) are a major risk factor for hepatocellular cancer in Asia and sub-Saharan Africa (1). AB1 is the most carcinogenic AF, and an understanding of AFB1 metabolism and subsequent development of blood and urinary biomarkers played an essential role in the molecular epidemiology studies that established this relationship (2, 3). AFB1 is oxidized by cytochrome P450s to yield a variety of metabolites, and its toxicology has been reviewed (4). The major reactive metabolite is the exo-AFB1 8,9-epoxide, which if not detoxified, can bind to double-stranded DNA to form the promutagenic AFB1-N7-guanine adduct or, following hydrolysis to the AFB1-dihydrodiol, with proteins such as albumin (5-8). Both urinary AFB1-N7-guanine and serum AF-albumin levels are correlated with dietary intake of AFs (8-13).

AF-albumin accounts for ~2% of a single AFB1 dose in rat (3-1,200 µg AFB1/kg body weight) and human studies (8-10). However, because the half-life of human albumin is ~20 days, AF-albumin may theoretically accumulate following chronic exposure to reach levels 30-fold higher than that found after a single dose (8, 14, 15). In contrast, urinary AFB1-N7-guanine excretion will tend to parallel intake over the previous few days (16). Therefore, due to its correlation with dietary AF exposure, DNA adduct formation, and the integration of exposure over time, the AF-albumin adduct has been widely applied to assess exposure in epidemiologic studies, including intervention studies (17, 18). The only AFB1 adduct structurally identified to date in enzymatically digested plasma albumin is AFB1-lysine (AF-lysine; refs. 14, 19, 20). This adduct has been measured by ELISA, high-performance liquid chromatography (HPLC) with fluorescence detection and more recently by isotope dilution mass spectrometry (IDMS; refs. 10, 21-24). To date, the high-throughput, relatively inexpensive equipment needs and robust performance of the ELISA have made it the method of choice. The sensitivities of the ELISA (~3 pg AF-lysine equivalents/mg albumin) and HPLC fluorescence assays are comparable, whereas the IDMS method is about 10-fold more sensitive. The ELISA, HPLC fluorescence, and IDMS methods all involve the release of AF residues from digested albumin, but whereas the latter two chromatographic approaches selectively detect AF-lysine, the ELISA will probably measure a broader range of AF adducts.

AF-albumin adduct levels measured by ELISA and AF-lysine adducts measured by HPLC fluorescence in the same human serum samples showed an excellent correlation, but the ELISA indicated ~11-fold higher adduct burdens (9, 13). Because the ELISA uses AF-lysine to generate the standard curve in a competitive binding technique, the assay metric is pg AF-lysine equivalent/mg albumin and not pg AF-lysine/mg albumin, as used in the more chemically specific HPLC fluorescence and IDMS assays. These methods, therefore, measure closely related but analytically distinct biomarkers of AF and AFB1 exposure. Here, we directly measure the concentration of AF-lysine and AF-albumin adducts in the same human samples by IDMS and ELISA. This provides an opportunity to compare these assays qualitatively and quantitatively. This is important both to permit comparisons between epidemiology studies using different methodologies and to investigate the contribution of the AF-lysine adduct to the total AF-albumin residues in human blood samples.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Chemicals
AFB1, bromocreosol purple, human serum, and albumin were purchased from Sigma-Aldrich Chemical Co. (St. Louis, MO). The Coomassie protein assay was purchased from Bio-Rad (Hercules, CA). Pronase (120 KPUK/g, nuclease free) was purchased from Calbiochem-Novabiochem (La Jolla, CA). Sep-pak (C18) and mixed-mode, solid-phase extraction cartridges (Oasis MAX) were obtained from the Waters Corp. (Cambridge, MA).

Preparation of AF-Lysine and D4-AF-Lysine Standards
AF-lysine and the tetra-deuterated (D4) internal standard AF-D4-lysine (ISTD) were prepared for mass spectrometric assays and chromatographically purified as previously described (25, 26).

Human Sample Collection and Preparation
Twenty serum samples from a previous study in West Africa (18) were used in the current study to compare the ELISA and IDMS methodologies. First, immunoglobulins were precipitated from serum using ammonium sulfate, and albumin was precipitated from the resulting supernatant using acetic acid (23). The concentrations of AF-albumin and AF-lysine in precipitated albumin were respectively measured by ELISA (University of Leeds) and IDMS (Johns Hopkins University). IDMS was additionally used to measure the concentration of AF-lysine in whole sera.

ELISA
The concentration of AF-albumin adducts was measured as previously described (23). Albumin (2 mg) was digested overnight using Pronase, and AF-albumin adducts were isolated by solid-phase extraction using a Sep-pak cartridge. Samples were analyzed in quadruplicate by ELISA on two occasions on separate days.

IDMS Determination of AF-Lysine
The concentration of albumin in serum samples was measured using the bromocreosol purple assay (27). The average albumin concentration in serum samples (n = 20) was 52.5 ± 7.1 mg/mL (range, 42.4-72.3 mg/mL). Serum and albumin precipitated from the same serum sample were analyzed using a minor variation of the method reported by McCoy et al. (24). Serum (60 µL, ~ 2 mg albumin) was mixed with PBS (149 µL), ISTD (100 µL x 2 ng AF-D4-lysine/mL), and Pronase solution (350 µL, 13 mg/mL PBS) and incubated for 4.5 hours at 37°C. Precipitated albumin solution volumes that provided 2 mg of albumin were mixed with PBS such that the combined volume was 209 µL. Precipitated albumin was otherwise processed in the same way as serum. Mixed-mode, solid-phase extracted samples were analyzed by HPLC with mass spectrometric detection using a ThermoElectron TSQ Quantum Ultra operated in the positive electrospray ionization selected reaction monitoring mode as previously described (24). The ISTD parent molecular ion [(M + H)+, m/z 461.3] underwent fragmentation to yield an ion at m/z 398.2. The AF-lysine molecular ion (m/z 457.2) fragmented to yield an ion at m/z 394.1. A 10-point isotopic dilution standard curve was generated by triplicate injection of AF-D4-lysine (200 pg) mixed with varying amounts of AF-lysine (0-29 ng/mL) prepared as 3-fold serial dilutions. The data were fitted using the method of least squares with a 1/x weighting factor.


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
AF-Lysine Mass Spectrometric Standard Curve
The isotope dilution standard curve was linear over the range 1.3 to 2.9 ng injected onto the column in 100 µL (R2 = 0.9998). The coefficient of variation was 3% when 1.3 pg AF-lysine was injected and increased to 45% for 0.5 pg AF-lysine.

Mass Spectrometric Measurement of AF-Lysine in Precipitated Albumin and Serum Samples
Examples of chromatograms from the IDMS assay are presented in Fig. 1 . AF-lysine concentrations measured by IDMS in serum and albumin precipitated from the same serum sample are presented in Fig. 2 . AF-lysine was detected in all samples from Guinea but not in the negative control human serum. AF-lysine concentrations in precipitated albumin and serum samples in Fig. 2 are described by the equation y = 0.981x + 0.295 (R = 0.982, P < 0.001). The apparent recoveries of the ISTD in serum and precipitated albumin were respectively 90 ± 16% and 83 ± 16% (average ± {sigma}, n = 20). Extensive hemolysis was indicated in one serum sample by its brick red to tan color that carried over into the precipitated albumin. This serum sample exhibited the highest AF-lysine concentration (see Fig. 3 ). The adduct concentration in this sample decreased by 19% (3.7 pg AF-lysine/mg albumin) in the corresponding precipitated albumin. The average difference between the precipitated albumin and serum sample concentration measured by IDMS was –0.14 ± 1.24 pg AF-lysine/mg albumin.


Figure 1
View larger version (19K):
[in this window]
[in a new window]
  		Figure 1. Chromatographic separation and selected reaction monitoring of AF-lysine in equivalent amounts of albumin from precipitated albumin and serum samples. The albumin in (A) was precipitated from the serum sample (4 pg AF-lysine/mg albumin) in (B). A. Precipitated albumin (2 mg). B. Serum. C. Human serum–negative control. Top, AF-lysine selected reaction monitoring (m/z 457-394); 100% relative abundance = 5.5 x 103. Bottom, AF-D4-lysine ISTD selected reaction monitoring 461(m/z 461-398); 100% relative abundance = 4.6 x 104.

 

Figure 2
View larger version (8K):
[in this window]
[in a new window]
  		Figure 2. Comparison of the AF-lysine (AF-lys) adduct concentration measured by IDMS in matched serum and precipitated albumin samples.

 

Figure 3
View larger version (9K):
[in this window]
[in a new window]
  		Figure 3. Comparison of ELISA and IDMS measurement of AF-albumin and AF-lysine (AF-lys) concentrations, respectively. The AF-albumin concentration measured by ELISA was compared with IDMS measured values in serum (•) and in albumin ({circ}) precipitated from the same serum sample. ELISA measurements are exclusively made using precipitated albumin.

 
Comparison of ELISA and Mass Spectrometric Measurements of AF-Albumin Adducts in Precipitated Albumin and Serum Samples
AF-albumin and AF-lysine adduct concentrations, measured respectively by ELISA and IDMS in precipitated albumin and serum from the same individual, are presented in Fig. 3. AF-albumin and AF-lysine concentration metrics in precipitated albumin samples are described by the equation y = 0.392x + 0.021 (R = 0.856, P < 0.0001). AF-albumin concentration metrics in precipitated albumin samples and AF-lysine concentrations in serum samples are described by the equation y = 0.379x + 0.426 (R = 0.885, P < 0.0001).


   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
The ELISA for AF-albumin adduct is the most widely used assay for measuring human AF exposure in molecular epidemiology studies (23). The AF-albumin levels measured by ELISA correlate well with dietary AF intake and are reduced when intervention strategies are employed that diminish AF exposure (13, 18). Alternative assays for measuring AF exposure include HPLC with fluorescence detection and the recently developed IDMS assay (9, 10, 24). These chromatographic assays specifically measure the AF-lysine adduct; in the case of IDMS, the assay uses an AF-D4-lysine internal standard and detects a parent molecular fragment ion uniquely obtained from AF-lysine (24-26). This improved specificity over the HPLC fluorescence approach means that a more direct comparison with ELISA is now possible. This is important to be able to interpret data both in a qualitative and quantitative fashion across molecular epidemiology studies of AF exposure and disease.

The direct correlation of AF-lysine concentrations measured by IDMS in serum and in albumin precipitated from the same serum sample indicated that precipitation does not degrade AF-lysine or affect the extent of protein digestion. The high recoveries of ISTD in precipitated albumin and serum samples support this interpretation and further indicate that Pronase does not degrade AF-lysine. Low sample recovery and degradation of AF-lysine during precipitation or digestion could have contributed to the lower adduct levels reported by HPLC fluorescence compared with ELISA (9, 10). It is difficult to generalize about the effect of hemolysis on IDMS measurements from the single observation of the 19% lower AF-lysine concentration in precipitated albumin relative to the matched serum sample in an extensively hemolyzed sample because other hemolyzed samples did not exhibit this effect. Thus, the concordance between the analyses of albumin in serum and precipitated albumin provides context for the comparison of ELISA and IDMS data.

The concentration of AF-albumin measured by ELISA was well correlated with the IDMS analysis of AF-lysine in paired samples but the former assay gave consistently higher levels than the latter, by on average 2.6-fold. The measurement of higher adduct concentrations by ELISA relative to IDMS is qualitatively consistent with the previous reports of rat and human ELISA and HPLC fluorescence data, in which the ELISA yielded ~5-fold and 10-fold higher concentrations than the HPLC fluorescence method in matched rat and human plasma samples, respectively (9, 10, 13). The incomplete digestion of albumin leading to adducted peptides rather than the monoadduct, AF-lysine, was one suggested cause (9). The presence of AF adducts in addition to AF-lysine is an alternative potential cause of the difference in adduct levels measured by ELISA and IDMS.

Unlike laboratory animals treated only with AFB1, humans can be simultaneously exposed to several AFs, including AFB1, AFB2, AFG1, AFG2, and AFM1. Knowledge of AFB1 metabolism suggests that additional protein adducts should be formed, and the differences in AF-albumin adduct concentration measured by ELISA and IDMS are therefore likely to be due to the presence of uncharacterized AF adducts. Spontaneous formation of the hemiacetal AFB2a from AFB1 or AFB2 can be expected to yield protein adducts through reactions similar to that producing AF-lysine (19, 20, 28). Although significant human exposure to AFG1 occurs, and this toxin can form both DNA and albumin adducts in rats (29), AFG1-lysine adduct formation has not been shown in humans. AFM1 is produced by the hydroxylation of AFB1 and the terminal furofuran ring can be further oxidized to yield AFM1-epoxide. AFM1-guanine adducts have been detected in the liver DNA and urine of shrews treated with AFB1 (30); however, AFM1 protein adducts were not assayed, and AFM1-lysine adduct formation has not been shown in humans. AFP1, AFQ1, and the series of AF toxicols could similarly undergo oxidation at the unsaturated 8,9-position to yield hemiacetals, epoxides, or dihydrodiols that could be further sources of protein adducts.

These hypothetical and known compounds would not be detected in the IDMS assay for AF-lysine but would likely be detected by the ELISA. It is notable that the HPLC fluorescence analysis of Pronase digested human serum revealed the presence of several uncharacterized fluorescent peaks in addition to AF-lysine (10). Chromatographic analysis of Pronase digests of serum protein from rats treated with 3H-AFB1 revealed more than six fluorescent peaks, and AF-lysine accounts for <10% of the detected 3H (21).

Although HPLC fluorescence and IDMS data suggest that the ELISA is measuring other AF adducts in addition to AF-lysine, these closely related but analytically distinct approaches to assessment of AF exposure provide extremely similar classification of individuals with regard to their exposure status. This suggests that the additional adducts do not greatly skew the relationship between AF exposure and measured levels of the biomarkers AF-albumin and AF-lysine. Identification of unknown AF-albumin adducts would further clarify the mechanistic basis for using these biomarkers to assess exposure status in future epidemiologic studies. Because the sensitivity of the ELISA is good, and it requires less expensive instrumentation, it is more generally applicable than IDMS. However, the greater sensitivity and specificity of the IDMS assay can be used to detect AF-lysine adducts at lower levels and thereby potentially reduce exposure misclassification error. Ultimately, each investigator must evaluate their budget and instrumentation resources as well as perform statistical power calculations appropriate to their unique study population to determine which of these complementary analytic methods best serves their needs.


   Footnotes
 
Grant support: NIH grants P01 ES06052 and P30 ES 03819 (all authors).

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Received 11/25/05; revised 1/25/06; accepted 2/ 7/06.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. IARC. Aflatoxins. In: Evaluation of carcinogenic risks in humans. Vol. 82. Lyon (France): IARC Scientific Publication; 2002. p. 171–274.
  2. Ross RK, Yuan JM, Yu MC, et al. Urinary aflatoxin biomarkers and risk of hepatocellular carcinoma. Lancet 1992;339:943–6.[CrossRef][Medline]
  3. Wang LY, Hatch M, Chen CJ, et al. Aflatoxin exposure and risk of hepatocellular carcinoma in Taiwan. Int J Cancer 1996;67:620–5.[CrossRef][Medline]
  4. Wild CP, Turner PC. The toxicology of aflatoxins as a basis for public health decisions. Mutagenesis 2002;17:471–81.[Abstract/Free Full Text]
  5. Essigmann JM, Croy RG, Nadzan AM, et al. Structural identification of the major DNA adduct formed by aflatoxin B1 in vitro. Proc Natl Acad Sci U S A 1977;74:1870–4.[Abstract/Free Full Text]
  6. Baertschi SW, Raney KD, Stone MP, Harris TM. Preparation of the 8,9-epoxide of the mycotoxin aflatoxin B1: the ultimate carcinogenic species. J Am Chem Soc 1988;110:7929–31.[CrossRef]
  7. Johnson WW, Harris TM, Guengerich FP. Kinetics and mechanism of hydrolysis of aflatoxin B1 exo-8,9-oxide and rearrangement of the dihydrodiol. J Am Chem Soc 1996;18:8213–20.
  8. Wild CP, Garner RC, Montesano R, Tursi F. Aflatoxin B1 binding to plasma albumin and liver DNA upon chronic administration to rats. Carcinogenesis 1986;7:853–8.[Abstract/Free Full Text]
  9. Wild CP, Jiang Y, Sabbioni G, Chapot B, Montesano R. Evaluation of methods for quantitation of aflatoxin albumin adducts and their application to human exposure assessment. Cancer Res 1990;50:245–51.[Abstract/Free Full Text]
  10. Sabbioni G, Ambs S, Wogan GN, Groopman JD. The aflatoxin-lysine adduct quantified by high-performance liquid chromatography from human plasma albumin samples. Carcinogenesis 1990;11:2063–6.[Abstract/Free Full Text]
  11. Groopman JD, Zhu ZQ, Donahue PR, et al. Molecular dosimetry of urinary aflatoxin-DNA adducts in people living in Guangxi Autonomous Region, People's Republic of China. Cancer Res 1992;52:45–52.[Abstract/Free Full Text]
  12. Groopman JD, Hall A, Whittle H, et al. Molecular dosimetry of aflatoxin-N7-guanine in human urine obtained in The Gambia, West Africa. Cancer Epidemiol Biomarkers Prev 1992;1:221–7.[Abstract/Free Full Text]
  13. Wild CP, Hudson GJ, Sabbioni G, et al. Dietary intake of aflatoxins and the level of albumin-bound aflatoxin in peripheral blood in The Gambia, West Africa. Cancer Epidemiol Biomarkers Prev 1992;1:229–34.[Abstract/Free Full Text]
  14. Sabbioni G, Skipper PL, Büchi G, Tannenbaum SR. Isolation and characterization of the major plasma albumin adduct formed by aflatoxin B1 in vivo in rats. Carcinogenesis 1987;8:819–24.[Abstract/Free Full Text]
  15. Wild CP, Hasegawa R, Barraud L, et al. Aflatoxin-albumin adducts: a basis for the comparative carcinogenesis between animals and humans. Cancer Epidemiol Biomarkers Prev 1996;5:179–89.[Abstract/Free Full Text]
  16. Groopman JD, Wild CP, Hasler J, Junshi C, Wogan GN, Kensler TW. Molecular epidemiology of aflatoxin exposures: validation of aflatoxin N7-guanine levels in urine as a biomarker in experimental rat models and humans. Environ Health Perspect 1993;99:107–13.[Medline]
  17. Kensler TW, Qian GS, Chen JG, Groopman JD. Translational strategies for cancer prevention in liver. Nat Rev Cancer 2003;3:321–9.[CrossRef][Medline]
  18. Turner PC, Sylla A, Gong Y, et al. Reduction in exposure to carcinogenic aflatoxins by post-harvest intervention measures in west Africa: a community-based intervention study. Lancet 2005;365:1950–6.[CrossRef][Medline]
  19. Sabbioni G. Chemical and physical properties of the major albumin adduct of aflatoxin B1 and their implications for the quantification in biological samples. Chem Biol Interact 1990;75:1–15.[CrossRef][Medline]
  20. Guengerich FP, Arneson KO, Williams KM, Deng Z, Harris TM. Reaction of aflatoxin B1 oxidation products with lysine. Chem Res Toxicol 2002;15:780–92.[Medline]
  21. Sheabar FZ, Groopman JD, Qian GS, Wogan GN. Quantitative analysis of aflatoxin-albumin adducts. Carcinogenesis 1993;14:1203–8.[Abstract/Free Full Text]
  22. Wang JS, Qian G, Zarba A, et al. Temporal patterns of aflatoxin-albumin adducts in hepatitis B surface antigen positive and antigen-negative residents of Daxin, Qidong Country, People's Republic of China. Cancer Epidemiol Biomarkers Prev 1996;5:252–61.
  23. Chapot B, Wild CP. ELISA for quantification of aflatoxin-albumin adducts and their application to human exposure assessment. In: Warthol M, van Velzer D, Bullock GR, editors. Techniques in diagnostic pathology. Vol. 2. London: Academic Press Ltd.; 1991. p. 135–55.
  24. McCoy L, Scholl PF, Schleicher R, Groopman JD, Powers C, Pfeiffer CM. Analysis of aflatoxin B1-lysine adduct in serum using isotope-dilution liquid chromatography/tandem mass spectrometry. Rapid Commun Mass Spectrom 2005;19:2203–10.[CrossRef][Medline]
  25. Scholl PF, Groopman JD. Synthesis of 4,4,5,5,-D4-L-lysine-aflatoxin B1 for use as a mass spectrometric internal standard. J Label Compd Radiopharam 2004;47:807–15.
  26. Scholl PF, McCoy L, Kensler TK, Groopman JD. Quantitative analysis and chronic dosimetry of aflatoxin B1 plasma albumin adducts in rats by HPLC-electrospray mass spectrometry. Chem Res Toxicol 2006;19:44–9.[CrossRef][Medline]
  27. Hill PG, Wells TNC. Bromocreosol purple and the measurement of albumin. Ann Clin Biochem 1983;20:264–70.
  28. Eaton DL, Monroe DH, Bellamy G, Kellman DA. Identification of a novel dihydroxy metabolite of aflatoxin B1 produced in vitro and in vivo in rats and mice. Chem Res Toxicol 1988;1:108–14.[Medline]
  29. Sabbioni G, Wild CP. Identification of an aflatoxin G1 serum albumin adducts and its relevance to the measurement of human exposure to aflatoxins. Carcinogenesis 1990;12:97–103.
  30. Egner PA, Yu X, Johnson JK, et al. Identification of aflatoxin M1-N7-guanine in liver and urine of tree shrews and rats following administration of aflatoxin B1. Chem Res Toxicol 2003;16:1174–80.[CrossRef][Medline]



This article has been cited by other articles:


Home page
 Cancer Epidemiol. Biomarkers Prev.Home page
L. F. McCoy, P. F. Scholl, A. E. Sutcliffe, S. M. Kieszak, C. D. Powers, H. S. Rogers, Y. Y. Gong, J. D. Groopman, C. P. Wild, and R. L. Schleicher
Human Aflatoxin Albumin Adducts Quantitatively Compared by ELISA, HPLC with Fluorescence Detection, and HPLC with Isotope Dilution Mass Spectrometry
Cancer Epidemiol. Biomarkers Prev., July 1, 2008; 17(7): 1653 - 1657.
[Abstract] [Full Text] [PDF]

Home page
 Cancer Epidemiol. Biomarkers Prev.Home page
P. F. Scholl and J. D. Groopman
Long-term Stability of Human Aflatoxin B1 Albumin Adducts Assessed by Isotope Dilution Mass Spectrometry and High-Performance Liquid Chromatography-Fluorescence
Cancer Epidemiol. Biomarkers Prev., June 1, 2008; 17(6): 1436 - 1439.
[Abstract] [Full Text] [PDF]

Home page
 CarcinogenesisHome page
L. Tang, M. Tang, L. Xu, H. Luo, T. Huang, J. Yu, L. Zhang, W. Gao, S. B. Cox, and J.-S. Wang
Modulation of aflatoxin biomarkers in human blood and urine by green tea polyphenols intervention
Carcinogenesis, February 1, 2008; 29(2): 411 - 417.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Scholl, P. F.
Right arrow Articles by Wild, C. P.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Scholl, P. F.
Right arrow Articles by Wild, C. P.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Cancer Research Clinical Cancer Research
Cancer Epidemiology Biomarkers & Prevention Molecular Cancer Therapeutics
Molecular Cancer Research Cancer Prevention Research
Cancer Prevention Journals Portal Cancer Reviews Online
Annual Meeting Education Book Meeting Abstracts Online