Carcinogenesis Advance Access originally published online on January 18, 2007
Carcinogenesis 2007 28(7):1582-1588; doi:10.1093/carcin/bgm001
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Pro/antioxidant status and AP-1 transcription factor in murine skin following topical exposure to cumene hydroperoxide
1 Department of Physiology and Pharmacology, West Virginia University, Morgantown, WV 26505, USA
2 Pathology and Physiology Research Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, m/s 2015, 1095 Willowdale Road, Morgantown, WV 26505, USA
* To whom correspondence should be addressed. Tel: +1 304 285 5826; Fax: +1 304 285 5938; Email: zsk1{at}cdc.gov
Organic peroxides, widely used in the chemical and pharmaceutical industries, can act as skin tumor promoters and cause epidermal hyperplasia. They are also known to trigger free radical generation. The present study evaluated the effect of cumene hydroperoxide (Cum-OOH) on the induction of activator protein-1 (AP-1), which is linked to the expression of genes regulating cell proliferation, growth and transformation. Previously, we reported that topical exposure to Cum-OOH caused formation of free radicals and oxidative stress in the skin of vitamin E-deficient mice. The present study used JB6 P+ mouse epidermal cells and AP-1-luciferase reporter transgenic mice to identify whether exposure to Cum-OOH caused activation of AP-1, oxidative stress, depletion of antioxidants and tumor formation during two-stage carcinogenesis. In vitro studies found that exposure to Cum-OOH reduced the level of glutathione (GSH) in mouse epidermal cells (JB6 P+) and caused the induction of AP-1. Mice primed with dimethyl-benz[a]anthracene (DMBA) were topically exposed to Cum-OOH (82.6 µmol) or the positive control, 12-O-tetradecanoylphorbol-13-acetate (TPA, 17 nmol), twice weekly for 29 weeks. Activation of AP-1 in skin was detected as early as 2 weeks following Cum-OOH or TPA exposure. No AP-1 expression was found 19 weeks after initiation. Papilloma formation was observed in both the DMBA–TPA- and DMBA–Cum-OOH-exposed animals, whereas skin carcinomas were found only in the DMBA–Cum-OOH-treated mice. A greater accumulation of peroxidative products (thiobarbituric acid-reactive substances), inflammation and decreased levels of GSH and total antioxidant reserves were also observed in the skin of DMBA–Cum-OOH-exposed mice. These results suggest that Cum-OOH-induced carcinogenesis is accompanied by increased AP-1 activation and changes in antioxidant status.
Abbreviations: AAPH, 2,2'-azobis(2-aminodinopropane)-dihydrochloride; AP-1, activator protein-1; Cum-OOH, cumene hydroperoxide; DMBA, dimethyl-benz[a]anthracene; FBS, fetal bovine serum; GSH, glutathione; MEM, minimum essential medium; MPO, myeloperoxidase; OP, organic peroxide; TBARS, thiobarbituric acid-reactive substance; TPA, 12-O-tetradecanoylphorbol-13-acetate
Received August 18, 2006; revised December 18, 2006; accepted January 4, 2007.