Effects of voluntary exercise on tumorigenesis in the C3(1)/SV40Tag transgenic mouse model of breast cancer

Epidemiologic studies suggest an association between physical activity (PA) and breast cancer risk. We examined the relationship between voluntary wheel running and breast cancer in C3(1)/SV40Tag mice. Female FVB/N and C3(1)/SV40Tag mice were assigned to either PA [C3(1)-PA] (n=12) or sedentary (Sed) [C3(1)-Sed] (n=15) treatment and were placed in a cage with access to a running wheel (PA) or without (Sed) from 4 to 24 weeks of age (sacrifice). Physical activity data were analyzed for running distance, time and speed. Body composition was examined at 12 weeks of age. Tumors were counted twice weekly and at sacrifice to assess multiplicity. Tumor volume was calculated using external calipers [0.52 x (largest diameter) x (smallest diameter)2]. Heart and body weight were also recorded at sacrifice. Results showed that voluntary wheel running reduced tumor volume per tumor [C3(1)-Sed, 422.3±89.9 mm(3); C3(1)-PA, 260.2±61.7 mm(3)] (P