Heterogeneity of ornithine decarboxylase expression in 12-O-tetradecanoylphorbol-13-acetate-treated mouse skin and in epidermal tumors

One of the earliest events after treatment of mouse skin with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) is the induction of ornithine decarboxylase (ODC). Using an immunoperoxidase technique with a rabbit antiserum specific for ODC, the localization of cells containing high levels of ODC following TPA treatment was determined. CD-1 female mice treated with multiple topical applications of TPA and killed 4.5 h after the last TPA treatment exhibited a heterogeneous localization of ODC in this hyperplastic epidermis. The cells which exhibited intense immunostaining were found predominantly in the suprabasal cells lining the hair follicles. This specific ODC staining in cells surrounding hair follicles was inhibited by pretreatment of mice with either retinoic acid or cycloheximide 1 h before TPA treatment. The induction of ODC-specific staining after TPA treatment in hyperplastic mouse skin was transient, since no staining was observed 16 or 24 h after TPA treatment. In contrast, benign papillomas produced by two-stage tumorigenesis contained some cells demonstrating high levels of ODC a week after the last TPA application. These results indicate that both normal mouse epidermal cells as well as tumor tissue display cellular heterogeneity of ODC expression.