Quantitation of benzo[a]pyrene-DNA adducts by postlabeling with C-14-acetic anhydride and accelerator mass spectrometry

Quantitation of carcinogen-DNA adducts provides an estimate of the biologic ally effective dose of a chemical carcinogen reaching the target tissue. In order to improve exposure-assessment and cancer risk estimates, we are dev eloping an ultrasensitive procedure for the detection of carcinogen-DNA add ucts. The method is based upon postlabeling of carcinogen-DNA adducts by ac etylation with C-14-acetic anhydride combined with quantitation of C-14 by accelerator mass spectrometry (AMS). For this purpose, adducts of benzo[a]p yrene-r-7,t-8-dihydrodiol-t-9,10-epoxide (BPDE) with DNA and deoxyguanosine (dG) were synthesized. The most promutagenic adduct of BPDE, 7R,8S,9X-trih ydroxy-10S-(N-2-deoxyguanosyl)-7,8,9,10-tetrahydrobenzo[a]pyrene (BPdG). wa s HPLC purified and structurally characterized. Postlabeling of the BPdG ad duct with acetic anhydride yielded a major product with a greater than 60% yield. The postlabeled adduct was identified by liquid chromatography-mass spectrometry as pentakis(acetyl) BPdG (AcBPdG). Postlabeling of the BPdG ad duct with C-14-acetic anhydride yielded a major product coeluting with an A cBPdG standard. Quantitation of the C-14-postlabeled adduct by AMS promises to allow detection of attomolar amounts of adducts. The method is now bein g optimized and validated for use in human samples. (C) 2000 Elsevier Scien ce Ireland Ltd. All rights reserved.