Monitoring Human Exposure to Environmental Carcinogens

Details

• Personal Author:
  Lee BM ; Lu XQ ; Santella RM ; Young TL ; Zhang YJ
• Description:
  One of the long range goal of research in chemical carcinogenesis is the identification of individuals at increased risk of cancer development. Cancer is a multistep, multistage process in which many factors effect ultimate risk. The initiating event in the process of chemical carcinogenesis is the binding of the reactive electrophilic species of the carcinogen to nucleophilic sites in DNA. The extent of this reaction is influenced by a number of factors including metabolism to the active species or less toxic metabolites, detoxification of reactive intermediates and repair of adducts once formed. Thus, individuals with the same exposure may be at very different risk for cancer development because of differences in these processes due to genetic susceptibility. Suggestive evidence for this genetic susceptibility has come from epidemiologic studies demonstrating a higher proportion of individuals with a specific phenotype (e.g. poor metabolizers of debrisoquin or lacking specific glutathione transferase activity) among cancer cases than controls (Ayesh et al. 1984, Seidegard et al. 1986). By measuring levels of carcinogen-DNA adducts in humans we may be able to obtain information directly related to that individuals risk for cancer development. Measurement of carcinogen-DNA adducts in the target tissue, termed biologically effective dose, is believed to be a more relevant arker of exposure than measurement of the chemical itself either in the environment or in body fluids (Perera and Weinstein 1982). Such assays take into account individual differences in absorption and metabolism of carcinogens as well as repair of adducts. Methods are now available for the sensitive detection and quantitation of carcinogen-DNA adducts which do not depend upon radiolabeled carcinogens. These methods are essential for the measurement of adducts in humans with exposure to environmental and occupational carcinogens. Immunologic methods for measurement of DNA adducts have utilized monoclonal and polyclonal antibodies recognizing a number of specific carcinogen-DNA adducts (Poirier 1984, Santella 1988). Antibodies can be developed against either the carcinogen-nucleoside adduct covalently coupled to carrier protein or the modified DNA electrostatically complexed to methylated bovine serum albumin. These antibodies can be used in highly sensitive competitive enzyme-linked immunosorbent assays (ELISA) with color- or fluorescence-endpoint detection. Since femtomole (10-15) sensitivities are readily attainable, DNA adduct levels in the range of 1/108 nucleotides can be measured. With monoadduct-specific antibodies, higher sensitivities may be obtainable if large amounts of DNA are available and the adduct is isolated by various chromatographic procedures before quantitation in the ELISA. A major advantage of immunologic methods for adduct detection in humans is that once a sensitive and specific method has been developed it can easily be applied to the large number of samples that are collected in epidemiologic studies. However, before an immunoassay can be developed the structure of the adduct of interest must be known and it must be possible to systhesize the adduct for development of the antibody. Table 1 lists some of the available polyclonal and monoclonal antisera recognizing carcinogen-DNA adducts. In addition, we have recently developed monoclonal antibodies to 8-oxoguanosine, 4- aminobiphenyl-guanosine and 7-hydroxyethylguanosine (unpublished studies). A number of the antibodies listed in Table 1, including those recognizing alkylation, aflatoxin, benzo(a)pyrene diol epoxide, cisplatinum and 8-methoxypsoralen-DNA adducts, have been applied to adduct detection in humans (reviewed in Farmer et al. 1987, Santella 1988). An alternate method for adduct detection utilizes [32p] posUabeling of adducts after enzymatic digestion of the DNA to 3'monophosphates (Randerath et al. 1981). Very small amounts of DNA are required (1-50ug) and prior knowledge of the identity of the adducts, essential for the immunologic approach, is not necessary. Four dimensional thin layer chromatography of the labeled nucleoside bisphosphates, followed by autoradiography allows separation of the normal nucleotides and visualization of adduct spots. Quantitative data is obtained by counting areas of the chromatogram containing adducts. Adducts cannot be identified but because of the limitations of the thin layer chromatography system, must result from the binding of bulky hydrophobic carcinogens. While the alkylated adducts would be lost with the normal nucleotides in the standard assay, HPLC methods have been developed for their quantitation (Reddy et al. 1984, Wilson et al. 1988). Several methods have also been developed to give high sensitivity (up to a reported 1 adduct/l0 9- 10nucleotides) including butanol extraction of adducts (Gupta and Earley 1988) and nuclease PI digestion of normal nucleotides (Reddy and Randerath 1986) before labeling to enrich the sample in adducts. The advantages of the method, including high sensitivity, small sample size and ability to detect a broad range of adducts, make it ideal for studying individuals with exposure to complex mixtures. The major disadvantages are the utilization of [32p], the complexity of the assay and the inability to measure some adducts by standard procedures. The method has been applied to the detection of adducts in placental (Everson et al. 1986, Everson et al. 1988) and lung (Phillips et al. 1988a) DNA of smokers and nonsmokers and white blood cell DNA of roofers (Herberts et al. in press) and foundry workers (Phillips et al. 1988b). Several other methods have been developed for quantiation of DNA adducts but have not been as extensively applied to human adduct detection as have immunoassays and postlabeling. They include synchronous fluorescence spectroscopy (Harris et al. 1985) and gas chromatography/ mass spectroscopy (Weston et al. 1989). While DNA is believed to be the critical target, chemical carcinogens also bind to RNA and proteins. Quantitation of protein adducts on either hemoglobin or albumin, has been used as an alternate marker of exposure to environmental carcinogens. Large amounts of protein can be obtained from blood samples (6mg albumin and 140mg hemoglobin/ml of whole blood). This can be contrasted with the 500-700ug of DNA normally obtained from 30-35ml of blood. Thus, much smaller amounts of blood are required for protein adduct measurement making these methods more generally applicable to routine occupational monitoring. In addition, a number of studies have demonstrated a correlation between DNA and protein adduct levels suggesting that it is an appropriate surrogate for DNA adduct measurement (Neumann 1984). No repair occurs on protein thus, chronic low levels of exposure may be measurable. Red blood cells have an average lifespan of 4 months while albumin has a half life of 21 days indicating that only recent exposure will be detectable. [Description provided by NIOSH]
• Subjects:
  Carcinogens Environmental Exposure Occupational Health Safety
• Keywords:
  Carcinogenesis Chemicals DNA Adducts DNA Damage Environmental Exposure Exposure Levels Genetic Factors Humans
• ISBN:
  9781468458770
• ISSN:
  0065-2598
• Publisher:
  Plenum Press
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  New York ; OSHA Region 2
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  165-181
• Volume:
  283
• NIOSHTIC Number:
  nn:20059130
• Citation:
  Adv Exp Med Biol, Biological Reactive Intermediates IV: Molecular and Cellular Effect and Their Impact on Human Health, Proceedings of the Fourth International Symposium on Biological Reactive Intermediates, January 14-17, 1990, Tucson, Arizona. Witmer CM, Snyder RR, Jollow DJ, Kalf GF, Kocsis JJ, Sipes IG eds. NY: Plenum Press, 1991 Feb; 283:165-181
• Editor(s):
  Witmer CM; Snyder RR; Jollow DJ; Kalf GF; Kocsis JJ; Sipes IG
• Federal Fiscal Year:
  1991
• Performing Organization:
  Columbia University, New York
• Peer Reviewed:
  True
• Start Date:
  19890101
• Source Full Name:
  Advances in Experimental Medicine and Biology. Biological Reactive Intermediates IV: Molecular and Cellular Effect and Their Impact on Human Health, Proceedings of the Fourth International Symposium on Biological Reactive Intermediates, January 14-17, 1990, Tucson, Arizona
• End Date:
  19921231
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:aca2fe3cdccbc3fb7550581a8bc501f3d5980db1f0a7ef9a1709bb0cbcff0f3d6b5a3fc6e5b3f46c87ae0053844c878359c539acbf99b557198766c0f8d7f607
• Download URL:
  https://stacks.cdc.gov/view/cdc/223442/cdc_223442_DS1.pdf
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  [PDF - 974.57 KB ]