Promotion of Skin Carcinogenesis by Dimethylarsinic Acid in Keratin (K6)/ODC Transgenic Mice

Dimethylarsinic acid (DMA) is a major metabolite of inorganic arsenicals in mammals, and arsenic exposure is associated with tumor development in a wide variety of human tissues, particularly the skin. Transgenic mice with ornithine decarboxylase (ODC) targeted to hair follicle keratinocytes are much more sensitive than littermate controls to carcinogens. In this study we investigated the promoting effect of DMA on skin carcinogenesis in such K6/ODC transgenic mice. The back skin of female C57BL/6J K6/ODC transgenic mice, 10 to 14 weeks old, was initiated with topical application of 7,12‐dimethylbenz[α]anthracene (DMBA) at a dose of 50 μg or acetone alone on day 1 of the experiment, followed by treatment with 3.6 mg of DMA, 5 μg of 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) or neutral vehicle (control) twice a week for 18 weeks. Mice were killed 1 week after the end of the treatment. Induction of skin tumors was significantly accelerated in the DMA‐treated group, as well as in the TPA‐treated group, indicating that DMA has a promoting effect on skin tumorigenesis in K6/ODC transgenic mice.