DNA ADDUCTS, DETECTED BY P-32 POSTLABELING, IN DNA TREATED INVITRO WITH BILE FROM PATIENTS WITH FAMILIAL ADENOMATOUS POLYPOSIS AND FROM UNAFFECTED CONTROLS

Patients with familial adenomatous polyposis (FAP) have a high risk of developing duodenal adenomas and carcinomas. The distribution of thes e neoplasms resembles mucosal exposure to bile, suggesting that bile m ay play a role in adenoma development. Our previous results, using DNA adducts detected by P-32-postlabelling as an index of genotoxicity, h ave supported this hypothesis. We found significantly higher adduct la belling in the duodenum of FAP patients than in the duodenum of contro l patients and significantly higher labelling in the small bowel of ra ts gavaged with FAP bile than in rats given control bile. We have now investigated the ability of human bile to form adducts with DNA in vit ro. Bile obtained from the gallbladder of 18 FAP patients immediately before colectomy, and from 18 control patients, was incubated with sal mon sperm DNA in solution at 37-degrees-C for 1 h, after which the pur ified DNA was analysed for DNA adducts, using the nuclease Pl method o f P-32-postlabelling. Relative adduct labelling values (RAL, adducts p er 10(9) nucleotides) produced by FAP bile samples were significantly higher than RAL values produced by control bile samples (medians 197 v ersus 86, P = 0.0016, Mann - Whitney test). We found a consistent patt ern of adduct labelling, varying in intensity between samples. Adduct spots were eluted from TLC plates and analyzed by reverse-phase HPLC. Each major spot gave several peaks that were consistent between bile s amples from different patients and were similar in FAP and control bil e. These results indicate that bile from FAP and control patients cont ains similar, directly acting genotoxic compounds but that levels are higher in FAP than in control patients. This suggests that bile from F AP patients is more genotoxic than bile from control patients. Incubat ion of bile with free-radical scavengers and deconjugating enzymes fai led to influence adduct labelling in this system.