The majority of DNA lesions resulting from interactions of carcinogens with DNA are usually either single strand breaks or lesions which are converted to single strand breaks by treatment of DNA with alkaline solutions. A sensitive method of detecting DNA single strand breaks is the alkaline filter elution of DNA. We started to test this method for biomonitoring occupational exposure with sensitive experimental conditions using pH 12.6, where most alkali-labile DNA lesions are converted to single strand breaks. Under our conditions statistically significant differences can be detected between the elution rates of untreated V79 cells and cells treated with [3H]-thymidine 24 h prior to the elution. Statistically significant increases were detected in the elution rates of male smoking automobile mechanics and male smoking painters compared to non-smoking controls. No statistically significant differences were detected in the elution rates of male non-smoking automobile mechanics and male workers with a suspected exposure to halogenated aromatics compared to male controls. No statistically significant differences were observed in the elution rates of female smoking dry-cleaning workers compared to female smoking controls. Our experience showed that the alkaline elution technique can be a valuable tool for monitoring DNA damage in peripheral lymphocytes in man.

After metabolic activation of benzo[a]pyrene to the 7,8-dihydrodiol-9,10-epoxide, this ultimate carcinogen preferentially binds to the exocyclic amino group of guanine. In order to investigate possible interindividual differences in the capacity of repair of the DNA adducts formed from benzo[a]pyrene 7,8-dihydrodiol 9,10-epoxide, their persistence in freshly isolated lymphocytes of several donors was studied. The results show a surprisingly large interindividual variation in DNA adduct formation and their persistence in freshly isolated lymphocytes. This range included several individuals with an apparent complete lack of repair capability for these adducts. Compared with controls, smokers showed on average a lower initial extent of the DNA adducts formed from benzo[a]pyrene-7,8-dihydrodiol 9,10-epoxide, suggesting induction of inactivating enzymes. However, one of the smokers was an individual with apparent complete lack of repair for the DNA adducts formed from benzo[a]pyrene-7,8-dihydrodiol 9,10-epoxide, combining exposure to benzo[a]pyrene with a long persistence of the DNA adducts formed from benzo[a]pyrene-7,8-dihydrodiol 9,10-epoxide. The investigation of the DNA repair of methylnitrosourea-induced lesions showed significant interindividual differences in the adaptive response triggered by repeated exposure to the carcinogen, whereas the interindividual variations after single doses were low.

[3H]Benzo[a]pyrene (BP) and salmon sperm DNA were incubated with hepatocytes from 5,6-benzo-flavone-treated rats. The cellular DNA and the exogenously added DNA were separately isolated, hydrolyzed and chromatographed on a Sephadex LH-20 column. The extracellular DNA yielded 3 peaks of radioactivity in the chromatographic eluate. The cellular DNA contained an additional peak suggesting the formation of a DNA adduct from a metabolite that does not leave the cell.

Etheno adducts can be formed by the reaction of vinyl chloride metabolites with DNA and may play a role in the carcinogenicity of this chemical. These adducts are highly fluorescent and may be quantitated by sensitive photometric methods in conjunction with high-performance liquid chromatographic (HPLC) separation. Three HPLC systems were evaluated on the basis of maximal fluorescence intensity and resolution of two etheno adducts, ethenodeoxycytidine and ethenodeoxyadenosine. Analyses were conducted with enzymatically digested DNA that had been incubated with chloroacetaldehyde, a vinyl chloride metabolite which may cause etheno adduct formation in vivo. All three known etheno adducts of DNA were tentatively identified in DNA reacted in vitro. The sensitivity of the method was highest for the ethenodeoxyadenosine adduct, with the limit of detection (1 pmol per injection in the HPLC system) being similar to that for O6-methylguanine, another promutagenic DNA adduct for which quantitation by HPLC with fluorescence detection has been reported. The method described here may be useful for the analysis of DNA from animals or humans exposed to vinyl chloride.

We describe the interfacing of a fluorometer to a desk-top computer by means of a commercially available interface box, for the purpose of generating three-dimensional fluorescence spectra. The important features of a self-designed program in BASIC are discussed in detail.

After incubation of chloroacetaldehyde-treated DNA with cell-free homogenates, the excision of N2,3-ethenoguanine and 1,N6-ethenoadenine was observed with a rat brain tumour cell line. The repair mechanism was that of an N-glycosylase. The high specificity of all known DNA N-glycosylases and some unique properties of the enzymatic reaction indicate the existence of N-glycosylases specific for the repair of etheno, or similar, adducts.

Epidemiologic studies of human carcinogenesis have demonstrated that exposure to certain chemicals significantly increases cancer risks. Additionally, the carcinogenic effects of chemicals have been observed in many animal experiments. As a result of these studies, strong regulations have been imposed worldwide to limit exposure to chemical carcinogens, primarily during occupational, and industrial exposure as well as restricting the use of potentially hazardous pharmaceutical products and dangerous food additives. Despite the efforts to minimize human exposure to chemical carcinogens, the abundance of these carcinogens in our natural environment implies that exposure to chemical carcinogens is not only a problem of industrialized civilization but is in fact inevitably associated with normal food consumption etc. The ubiquitous distribution of cancer-causing chemicals makes imperative the study of the biochemical mechanisms of chemical carcinogenesis.

Human microsomal epoxide hydrolase (mEH) catalyzes a key step in the biotransformation of benzo[a]pyrene that yields the highly mutagenic (+)-anti-7,8-diol-9,10 epoxide (BPDE). Two polymorphisms have been described in the coding region of the mEH gene (EPHX1) that produce two protein variants: 113Tyr→113His (exon 3) and 139His→139Arg (exon 4). We performed a case-control study among Northwestern Mediterranean Caucasians to investigate a possible association between these EPHX1 variants and lung cancer risk. Both EPHX1 polymorphisms were analyzed in a group of lung cancer patients (n=176) and in a control group of healthy smokers (n=187). The results showed a significantly decreased risk for the rare homozygous 113His/113His (adjusted odds ratio (OR): 0.44, 95% confidence interval (CI): 0.27–0.71) and 139Arg/139Arg (adjusted OR: 0.55, 95% CI: 0.33–0.91) compared with the major wild-types 113Tyr/113Tyr and 139His/139His, respectively, as the references. Thereafter, we analyzed the EPHX1 variants in combination with three glutathione S-transferase polymorphic genes (GSTM1, GSTT1, and GSTP1) and we found a significant overepresentation of cancer patients with a combination of exon 3 113Tyr/113Tyr EPHX1 and exon 5 105Ile/105Ile GSTP1 (adjusted OR: 2.34, 95% CI: 1.21–4.52). The polymorphic site within the exon 5 of GSTP1 results in a Ile→Val substitution, and the isoleucine GSTpi isoform has been found in vitro to be less active than the valine isoform towards the conjugation of BPDE. The 113 Tyr/Tyr EPHX1 encodes for a high-activity mEH. Our results agree with these observations in vitro and suggest that a genetically determined combination of a high-activity mEH and a low-activity GSTpi may increase lung cancer risk among smokers.

Annals of the New York Academy of SciencesVolume 381, Issue 1 p. 290-303 DNA MODIFICATION AND REPAIR IN THE EXPERIMENTAL INDUCTION OF NERVOUS SYSTEM TUMORS BY CHEMICAL CARCINOGENS* Paul Kleihues, Corresponding Author Paul Kleihues Abteilung Neuropathologie, Pathologisches Institut, Universität Freiburg, 78 Freiburg Federal Republic of Germany Isotopenlaboratorium Biokinetik, Bayer AG, 56 Wuppertal, Federal Republic of Germany†Address for correspondence: Pathologisches Institut, Albert Str. 19, 78 Freiburg, West Germany.Search for more papers by this authorKarl Patzschke, Karl Patzschke Abteilung Neuropathologie, Pathologisches Institut, Universität Freiburg, 78 Freiburg Federal Republic of Germany Isotopenlaboratorium Biokinetik, Bayer AG, 56 Wuppertal, Federal Republic of GermanySearch for more papers by this authorGerhard Doerjer, Gerhard Doerjer Abteilung Neuropathologie, Pathologisches Institut, Universität Freiburg, 78 Freiburg Federal Republic of Germany Isotopenlaboratorium Biokinetik, Bayer AG, 56 Wuppertal, Federal Republic of GermanySearch for more papers by this author Paul Kleihues, Corresponding Author Paul Kleihues Abteilung Neuropathologie, Pathologisches Institut, Universität Freiburg, 78 Freiburg Federal Republic of Germany Isotopenlaboratorium Biokinetik, Bayer AG, 56 Wuppertal, Federal Republic of Germany†Address for correspondence: Pathologisches Institut, Albert Str. 19, 78 Freiburg, West Germany.Search for more papers by this authorKarl Patzschke, Karl Patzschke Abteilung Neuropathologie, Pathologisches Institut, Universität Freiburg, 78 Freiburg Federal Republic of Germany Isotopenlaboratorium Biokinetik, Bayer AG, 56 Wuppertal, Federal Republic of GermanySearch for more papers by this authorGerhard Doerjer, Gerhard Doerjer Abteilung Neuropathologie, Pathologisches Institut, Universität Freiburg, 78 Freiburg Federal Republic of Germany Isotopenlaboratorium Biokinetik, Bayer AG, 56 Wuppertal, Federal Republic of GermanySearch for more papers by this author First published: April 1982 https://doi.org/10.1111/j.1749-6632.1982.tb50393.xCitations: 10 * This work was supported by the Deutsche Forschungsgemeinschaft (SFB 31). AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume381, Issue1Brain Tumors in the Chemical IndustryApril 1982Pages 290-303 RelatedInformation

The reaction of chloroacetaldehyde, a reactive metabolic of the carcinogen vinyl chloride, with DNA produces in addition to the hitherto known adducts, 1,N6-ethenoadenine and 3,N4-ethenocytosine, an ethenoguanine adduct, namely N2,3-ethenoguanine. This adduct is formed in the reaction of chloroacetaldehyde with the free base as well. After DNA hydrolysis followed by isolation of this new adduct by h.p.l.c., its mass spectrum and fluorescence spectrum are identical with those published in the literature for the chemically synthesized N2,3-ethenoguanine. The formation of only this guanine derivative out of several theoretically possible reaction products allows the formulation of a reaction scheme. The absence of 7-(2-oxoethyl)-guanine, another recently detected DNa adduct of vinyl chloride, in chloroacetaldehyde-treated DNA suggests its origin from the other reactive metabolic of vinyl chloride, chloroethylene oxide. The potential of N2,3-ethenoguanine to lead to misincorporation of deoxythymidine monophosphate opposite of guanine and the high fluorescence of this adduct provide it with potentially high biological significance and ease of analytical monitoring.