CHARACTERIZATION OF THE TUMOR-PROMOTING ACTIVITY OF M-CHLOROPEROXYBENZOIC ACID IN SENCAR MOUSE SKIN AND ITS INHIBITION BY GALLOTANNIN, OLIGOMERIC PROANTHOCYANIDIN, AND THEIR MONOMERIC UNITS

m-Chloroperoxybenzoic acid (CPBA),which induces ornithine decarboxylas e activity as much as 12-O-tetradecanoylphorbol-13-acetate (TPA), was tested for its ability to induce DNA synthesis, hydroperoxide (HPx) pr oduction, and tumor promotion in mouse epidermis in vivo. After an ear ly inhibition, CPBA stimulates DNA synthesis, a response which is main tained between 16 and 72 h and maximal after two treatments. CPBA at 0 .6-5 mg stimulates DNA synthesis more than other organic peroxides, an d nearly as much as TPA. The HPx-producing activity of the epidermis i s maximally stimulated 48 h after two CPBA treatments at a 24-h interv al. However, the HPx response to CPBA is much smaller than that to TPA . Aleppo gall tannic acid (AGTA) and loblolly pine bark condensed tann in (LPCT) inhibit both the DNA and HPx responses to CPBA. In contrast, their respective monomeric units, gallic acid (GA) and catechin (Cat) inhibit the DNA response to CPBA but fail to alter CPBA-stimulated HP x production. Although it is more potent than benzoyl peroxide, CPBA i s a complete tumor promoter much weaker than TPA and even less effecti ve than mezerein (MEZ). CPBA in stage 1 cannot enhance like TPA the tu mor-promoting activity of MEZ in stage 2. And in contrast to that of M EZ, the very weak tumor-promoting activity of CPBA is not enhanced aft er stage 1 treatment with TPA. At equal mg doses, AGTA, GA, LPCT, and Cat pretreatments all remarkably inhibit complete skin tumor promotion by CPBA. In spite of their antioxidant activities, AGTA post-treatmen ts have no or very little inhibitory effects on the development of ski n tumors by CPBA during 2-stage or complete tumor promotion.