Voluntary exercise and experimental mammary cancer

Area of Science:

• Oncology
• Exercise Physiology
• Nutritional Science

Background:

• High-fat diets are prevalent in Western societies and linked to increased cancer risk.
• Voluntary physical activity is a modifiable lifestyle factor with potential cancer-preventive benefits.

Purpose of the Study:

• To investigate the suppressive effects of voluntary physical activity on primary mammary tumor development in rodents fed high-fat diets.
• To examine the influence of physical activity on body fat composition and metastasis.
• To explore the dose-dependent effects of carcinogens and activity levels on tumor outcomes.

Main Methods:

• Rodents (rats and mice) were fed high-fat (40% calories) or low-fat (10% calories) diets.
• Chemically (DMBA, NMU) and virally (MMTV) induced mammary tumors were studied.
• Voluntary activity levels and body fat composition were monitored.
• Tumor incidence, multiplicity, time to first tumor, and lung metastases were assessed.

Main Results:

• Voluntary activity suppressed primary mammary tumor development in rodents on high-fat diets.
• Activity showed a trend toward decreased body fat, significantly in female Fischer F-344 rats.
• Carcinogen dose influenced outcomes: low-DMBA extended tumor latency, high-DMBA reduced multiplicity.
• NMU model showed an inverse association between activity and tumor incidence, unlike DMBA.
• Activity enhanced lung metastases volume in high-fat fed rats, with most active animals showing greatest metastases.

Conclusions:

• Voluntary activity can suppress mammary tumor development, particularly in the context of high-fat diets.
• The relationship between physical activity, diet, and cancer prevention is complex, with potential for increased metastases at high activity levels.
• Dietary fat and the quantity of voluntary activity are critical variables in both primary and secondary cancer prevention.