Ornithine Decarboxylase Expression in Cutaneous Papillomas in SENCAR Mice Is Associated with Altered Expression of Keratins 1 and 10

The study investigated the effects of multiple exposures to 12-O-tetradecanoylphorbol-13-acetate (TPA), mezerein, and ethyl phenylpropriolate (EPP) on murine epidermal cells, focusing on the induction of ornithine decarboxylase (ODC) activity. While single applications of these agents caused similar hyperplasia and ODC induction, multiple treatments revealed significant differences in ODC activity, with TPA and mezerein inducing more than EPP. Immunocytochemical analysis showed distinct patterns of ODC-positive cells, with TPA prominently affecting perifollicular cells, mezerein affecting both interfollicular and perifollicular areas, and EPP affecting only interfollicular cells. Flow cytometry identified three keratinocyte subpopulations, with TPA causing the expansion of an intermediate-sized subpopulation not seen with EPP or mezerein. The findings suggested that TPA, a potent tumor promoter, selectively expanded a keratinocyte subpopulation hyperinducible for ODC, potentially important for neoplastic transformation, while mezerein and EPP were less effective in this regard.

The study investigated the expression of ornithine decarboxylase (ODC) in mouse skin treated with the tumor promoter TPA. It was found that ODC expression was heterogeneous, with high levels predominantly in suprabasal cells around hair follicles shortly after TPA treatment. This expression was transient, disappearing within 16 to 24 hours, but persisted in some cells within benign papillomas a week after TPA application. Pretreatment with retinoic acid or cycloheximide inhibited ODC expression. The findings suggested that both normal and tumor tissues in mice exhibited varied ODC expression.