Oral and dermal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces cutaneous papillomas and squamous cell carcinomas in female hemizygous Tg.AC transgenic mice.
Tg.AC mice develop epidermal papillomas in response to treatment with dermally applied nongenotoxic and complete carcinogens. The persistent environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a multi-site rodent carcinogen and tumor promoter that induces the formation of papillomas in Tg.AC mice. To examine the dose-response relationship and compare dermal and oral routes of exposure for TCDD-induced skin papillomas, female Tg.AC mice were exposed dermally to average daily doses of 0, 2.1, 7.3, 15, 33, 52, 71, 152, and 326 ng TCDD/kg/day or 0, 75, 321, and 893 ng TCDD/kg body weight by gavage for 26 weeks. The incidence of cutaneous papillomas was increased in a dose-dependent manner, and tumors developed earlier with higher exposure to TCDD regardless of route of administration. Increased incidences of cutaneous squamous cell carcinomas were observed in mice exposed to dermal (> or =52 ng/kg) and oral (893 ng/kg) TCDD. Higher gavage doses than dermal exposure doses were required to induce papillomas and squamous cell carcinomas. Despite a linear correlation between administered dose and terminal skin concentrations, the incidence of tumor formation was lower in the gavage study than in the dermal study with respect to mean terminal skin TCDD concentrations. These studies demonstrate that, although Tg.AC mice are less responsive to TCDD by gavage than by dermal exposure, the induction of skin neoplasms is a response to systemic exposure and not solely a local response at the site of dermal application. Differences in response between the routes of exposure may reflect pharmacokinetic differences in the delivery of TCDD to the skin over the duration of the study.
National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
Michael E
ME
Wyde
Angelique P J M
AP
Braen
Milton
M
Hejtmancik
Jerry D
JD
Johnson
John D
JD
Toft
James C
JC
Blake
Stephen D
SD
Cooper
Joel
J
Mahler
Molly
M
Vallant
John R
JR
Bucher
Nigel J
NJ
Walker
D000279:Administration, Cutaneous; D000284:Administration, Oral; D000818:Animals; D015197:Carcinogenicity Tests / Q000379:methods*; D002273:Carcinogens / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000633:toxicity*; D002294:Carcinoma, Squamous Cell / Q000139:chemically induced* / Q000473:pathology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004785:Environmental Pollutants / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000633:toxicity*; D005260:Female; D006579:Heterozygote; D051379:Mice; D008822:Mice, Transgenic; D010212:Papilloma / Q000139:chemically induced* / Q000473:pathology; D000072317:Polychlorinated Dibenzodioxins / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000633:toxicity*; D012867:Skin / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D012878:Skin Neoplasms / Q000139:chemically induced* / Q000473:pathology; D014018:Tissue Distribution
D002273:Carcinogens; D004785:Environmental Pollutants; D000072317:Polychlorinated Dibenzodioxins