Lack of effect of a 60 Hz magnetic field on biomarkers of tumor promotion in the skin of SENCAR mice

It has been proposed that extremely low frequency magnetic fields may enhan ce tumorigenesis through a co-promotional mechanism. This hypothesis has be en further tested using the two-stage model of mouse skin carcinogenesis, i .e. 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced promotion of skin ca rcinogenesis in mice initiated by a single subcarcinogenic dose of 7,12-dim ethylbenz[a]anthracene. Experimentation utilized three different doses of T PA within its dose-response range (0.85, 1.70 or 3.40 nmol) and examined th e following early biomarkers of tumor promotion after 1, 2 and 5 weeks of p romotion: increases in epidermal thickness and the labeling index of epider mal cells, induction of epidermal ornithine decarboxylase activity and down -regulation of epidermal protein kinase C activity, Mice exposed to a 60 Hz magnetic field having a flux density of 2 mT for 6 h/day for 5 days/week w ere compared with mice exposed to an ambient magnetic field. Within the sen sitivity limits of the biomarker methodology and the exposure parameters em ployed, no consistent, statistically significant effects indicative of prom otion or co-promotion by the magnetic field were demonstrated.