Skin tumor-promoting potential and systemic effects of pentachlorophenol and its major metabolite tetrachlorohydroquinone in CD-1 mice

The mouse skin carcinogenesis model provides a conceptual framework to study the carcinogenesis process. It has been used extensively to assess whether a chemical or physical agent carries a carcinogenic hazard to humans and to define the mechanism involved with the carcinogenic effects. We conducted a study to evaluate whether the tumor-promoting activity of pentachlorophenol (PCP) is mainly from its major metabolite tetrachlorohydroquinone (TCHQ). We applied the mouse skin model to CD-1 mice and the results showed that PCP and TCHQ are much weaker promoters than 12-O-tetradecanoylphorbol-13-acetate (TPA) in mouse skin during a 25-wk experiment. Both PCP and TCHQ could induce mice skin epidermal hyperplasia and proliferating cell nuclear antigen (PCNA) labeling index in the epidermis. However, TCHQ caused a more significant induction of epidermal hyperplasia and PCNA positive cells than PCP. Topical application of PCP, but not TCHQ, induced significant organ enlargement and lymphoma in mice, whereas short-term treatment of TCHQ increased tumor necrosis factor-α (TNF-α) gene expression in mouse skin. We did not observe a significant association between the carcinogenic process and serum TNF-α or interleukin-1β (IL-1β) levels in mice.