Introduction: Breast cancer is one of the most common neoplastic diseases. 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 mouse models of breast cancer.

Methods: From 4 weeks of age, MMTV-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 and 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. Significant reductions in pulmonary metastasis frequency were found in runners after intravenous injections of tumor cells. Metastases of running mice displayed a reduced proliferation score.

Discussion: In this aggressive breast cancer model, an average of 6 km/day of voluntary running produces little effect on tumor formation and growth. However, the findings suggest that physical activity has impact on the metastatic process.

Citation Format: Helene Rundqvist, Sara Mijwel, Emil Ahlstedt, Carolin Lindholm, Carina Strell, Pernilla Roswall, Kristian Pietras, Randall Johnson, Arne Ostman. Effect of voluntary running on metastasis in a mouse model of breast cancer. [abstract]. In: Proceedings of the Twelfth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2013 Oct 27-30; National Harbor, MD. Philadelphia (PA): AACR; Can Prev Res 2013;6(11 Suppl): Abstract nr A65.