[Immunological detection of carcinogen-DNA adducts]

Antibodies raised in rabbits against DNA modified with the carcinogen 4-hydroxyaminoquinoline 1-oxide or benzo (a) pyrene have been used in combination with an avidin-biotin peroxidase complex staining method to locate DNA adducts in paraffin sections of mouse tissues. The specificity of immunostaining was confirmed in several ways. When various doses of carcinogen solution were injected s.c. into isolated portions of mouse skin clamped off with ring-shaped forceps, the immunohistochemical staining of carcinogen-DNA adducts in the nuclei of epithelial cells, fibroblasts and panniculus carnosus cells increased dose-dependently. Nuclear staining was absent in animals given injections of isotonic solution only, and the intensity of staining correlated well with the level of unscheduled DNA synthesis demonstrated autoradiographically. 4HAQO-DNA adducts were observed in all target organs of 4HAQO tumorigenesis (i.e., lung, trachea, pancreas, uterus, vagina, skin, and colon) after injection of the carcinogen. Nuclear staining was absent or low in nontarget organs, including the liver and brain. Considerable variation was found in staining levels between cell types and different anatomic locations of cells within each target organ. The intensity of immunohistochemical staining correlated well with the numbers of 4HAQO-DNA adducts measured by the radio-labeling technique.