Introduction: Emerging evidence states that regular physical exercise provides a risk reduction for breast cancer by approximately 25%. In addition, recent studies suggest that physical activity may also have an effect on recurrence and mortality. Mouse models are suitable tools to study anti-neoplastic mechanisms.

Aim: to evaluate the effect of voluntary running on tumor initiation, growth and metastasis in the Polyoma Middle T (PyMT) model of breast cancer.

Methods: PyMT mice were housed with access either to wirelessly recording running wheels or locked control wheels. Running distances and tumor volumes were recorded. At 12 weeks, mice were sacrificed. Mammary glands were histologically staged and pulmonary metastases were quantified. In a follow up study, pre-trained mice were injected intravenously with tumor cells derived from the PyMT model and after an additional 10 weeks of voluntary running, pulmonary metastases were quantified.

Results: PyMT mice ran significantly more than wildtype mice (6.4 vs 3.4 km/day). No significant effects of voluntary running on tumor- initiation, volume or stage were found. However, a trend for reduced metastasis was observed. After intravenous injections of tumor cells, runners had a significantly lower pulmonary metastasis frequency than non-runners.

Conclusion: In this aggressive breast cancer model, an average of 6 km/day of voluntary running did not induce any effect on tumor formation or growth. However, the findings suggest that physical activity has impact on the metastatic process.

Citation Format: Sara Mijwel, Helene Rundqvist, Carolin Lindholm, Carina Strell, Pernilla Roswall, Kristian Pietras, Randall S. Johnson, Arne Östman. Effect of voluntary running on metastasis in a mouse model of breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 836.