Earlier studies showed that
oral administration of
green tea or
caffeine to SKH-1 mice inhibited ultraviolet B light (UVB)-induced skin
carcinogenesis, decreased dermal fat thickness and increased locomotor activity. In the present study, the effects of voluntary running wheel exercise on thickness of dermal fat as well as on UVB-induced
tumorigenesis in SKH-1 mice were studied in UVB-initiated high-risk and UVB-induced complete
carcinogenesis models. In the high-risk model, animals were exposed to UVB (30 mJ/
cm(2)) 3 times/week for 16 weeks. For 14 weeks subsequent to UVB exposure, half of the animals had access to running wheels in their cages whereas the other half did not. In the complete
carcinogenesis model, animals were exposed to UVB (30 mJ/cm(2)) 2 times/week for 33 weeks. From the beginning, half of the animals had access to running wheels whereas the other half did not. At the conclusion of each study,
body weights were not different between groups, although animals with running wheels consumed significantly more food and water than animals without running wheels. In addition, animals with running wheels had decreases in parametrial fat pad weight and thickness of the dermal fat layer. In both UVB-initiated high-risk and complete
carcinogenesis models, voluntary running wheel exercise delayed the appearance of
tumors, decreased the number of
tumors per mouse and decreased
tumor volume per mouse. Histopathology studies revealed that running wheel exercise decreased the number of non-malignant
tumors (primarily
keratoacanthomas) by 34% and total
tumors per mouse by 32% in both models, and running wheel exercise decreased the formation of
squamous cell carcinomas in the UVB-induced complete
carcinogenesis model by 27%. In addition, the size of
keratoacanthomas and
squamous cell carcinomas were decreased substantially in both models. The effects described here indicate that voluntary running wheel exercise inhibits UVB-induced skin
tumorigenesis and may also inhibit
tumor growth.