The application of immunoassays and fluorometry to the detection of polycyclic hydrocarbon-macromolecular adducts and anti-adduct antibodies in humans

Diagnostic monitoring of urine by means of synchronous fluorescence spectrum

A novel approach to clinical-biochemical analysis of urine is presented in this work. Urine composition is defined graphically as a record of synchronous fluorescence spectra (SFS). The graphical standard has been made from SFS of urine samples from healthy children. Simple comparison of a standard record with that of an analyzed urine sample will immediately reveal changes in its composition. Reproducibility of the graphical definition is very high and it maintains its characteristic shape during repeated measurements over a span of 2 years. It is possible to elaborate patients' own standard for those with chronic illness. It differs from a normal course but it is characteristic for a given patient and it enables the clinician to monitor changes or the outcome of therapy at regular medical examinations. Application of this method for monitoring of urine composition for selected cases is a new alternative with several advantages. Analysis without any added reagents very quickly detects some illnesses near onset when they may be clinically asymptomatic and classical screening methods show negative results. Computerization of spectral measuring and filing the results enables to give a likely diagnosis or a deviation from standard. This method can also serve a doctor-clinician either to confirm or to exclude a concrete diagnosis.

DNA adducts: biological markers of exposure and potential applications to risk assessment

DNA adducts have been investigated extensively during the past decade. This research has been advanced, in part, by the development of ultrasensitive analytical methods, such as 32P-postlabeling and mass spectrometry, that enable detection of DNA adducts at concentrations as low as one adduct per 10(9) to 10(10) normal nucleotides. Studies of mutations in activated oncogenes such as ras, inactivated tumor suppressor genes such as p53, and surrogate genes such as hprt provide linkage between DNA adducts and carcinogenesis. The measurement of DNA adducts, or molecular dosimetry, has important applications for cancer risk assessment. Cancer risk assessment currently involves estimating the probable effects of carcinogens in humans based on results of animal bioassays. Estimates of risk are then derived from mathematical models that fit data of tumor incidence at the high animal exposures and extrapolate to probable human exposures that may be orders of magnitude lower. Molecular dosimetry could extend the observable range of mechanistic data several orders of magnitude lower than can be achieved in carcinogenesis bioassays. This measurement also compensates automatically for individual and species differences in toxicokinetic factors, as well as any nonlinearities that affect the quantitative relationships between exposure and molecular dose. As a result, molecular dosimetry can provide a basis for conducting high- to low-dose, route-to-route, and interspecies extrapolations. The incorporation of such data into risk assessment promises to reduce uncertainties and produce more accurate estimates of risk compared to current methods.

DNA and protein adducts

Application of methods for the measurement of DNA and protein adducts in environmental studies was surveyed. The methods included the 32P-postlabelling assay, immunoassay and synchronous fluorescence spectroscopy for DNA adducts. Additionally, methods for detecting excreted urinary RNA and DNA adducts were discussed. The protein adduct techniques included both immunological and chemical assays. The techniques have been applied in occupational and environmental studies, but usually one assay at a time. As specific DNA adducts can now be assayed for, it would be important to use these methods and specific protein adduct assays in the same studies. It is important to develop further specific adduct tests. This can be done with the help of standard compounds, which also allow quantitation in the assays. An international bank of standard compounds would be a major advancement to human biomonitoring.

Detection of human exposure to carcinogens by measurement of alkyl-DNA adducts using immunoaffinity clean-up in combination with gas chromatography-mass spectrometry and other methods of quantitation

A brief overview is given of recent developments from our laboratory in the use of immunoaffinity clean-up in the determination of alkyl-DNA adducts. Compound- and group-specific antibodies have been prepared against 7-alkylguanines and 3-alkyladenines. The antibodies were attached to solid supports to make immunoaffinity columns which could then be used to selectively purify either single adducts or groups of adducts prior to quantitation by various methods. In the case of methyl adducts quantitation was achieved by ELISA (3-methyl-adenine, using a monoclonal antibody) and HPLC-electrochemical detection (7-methylguanine). For groups of adducts, quantitation of the individual compounds was effected by gas chromatography-mass spectrometry (3-alkyladenines, using deuterated analogues of each adduct as an internal standard) and HPLC-fluorescence detection (7-alkylguanines). In all of these cases efficient purification of adducts from urine or DNA hydrolysates could be easily carried out. Using these techniques human exposure to alkylating agents in tobacco smoke and from cancer chemotherapy has been studied.

Advantages and limitations of laboratory methods for measurement of carcinogen-DNA adducts for epidemiological studies

In molecular epidemiological studies, the measurement of carcinogen-DNA adducts in human tissues can provide direct evidence of current exposure to chemical carcinogens. Moreover, data on steady state DNA adduct levels and the rate of cell proliferation can be related not only to carcinogen-target tissue dosimetry but may also be useful in assessment of human cancer risk. Thus far, laboratory methods for adduct detection have primarily utilized 32P-postlabelling, immunoassays, and mass spectrometry. However, accurate quantitation of DNA adducts requires knowledge of the structural identity and chemical properties of carcinogen-base adducts, the availability of synthetic standards for recovery determinations, and the development of complementary methods to corroborate analytical findings.