DNA adduct measurements and tumor incidence during chronic carcinogen exposure in rodents.

In an attempt to elucidate the relationship between DNA adduct formation and tumorigenesis, DNA adducts were measured in the livers and bladders of mice during chronic exposure to several different doses of 2-acetylaminofluorene (2-AAF) and 4-aminobiphenyl (4-ABP). Continuous oral administration of these compounds for 4 weeks produced an increase in DNA adduct formation during the first 2 weeks, followed by a plateau, which presumably occurred because the rate of adduct removal offset the rate of adduct formation. The quantity of DNA adducts present at equilibrium correlated directly with the carcinogen concentration; therefore, when exposure was continued for 4 weeks, DNA adducts that reflected the plateau level at each dose could be expressed as a function of dose. Liver and bladder DNA adduct profiles thus obtained during administration of multiple doses of 2-AAF (to female mice) and 4-ABP (to male and female mice) were compared to profiles for tumor incidences obtained during lifetime exposures to the same doses. These experiments demonstrated similar profiles for DNA adduct formation and tumorigenesis in liver. In the bladder, DNA adducts were linear, but tumors only appeared at the higher doses in conjunction with cell proliferation. In addition to these aromatic amines, similar data are available for aflatoxin B1, diethylnitrosamine, and (methylnitrosamino)-1-(3-pyridyl)-1-butanone (also known as nicotine-derived nitrosoketone). Of the nine different biological situations (carcinogen/species/sex/organ) for which data are available, correlations between steady-state DNA adduct levels and tumorigenic response at the different doses were linear in five of the nine biological models.(ABSTRACT TRUNCATED AT 250 WORDS)