Exercise affects high-fat diet-stimulated breast cancer metastasis through irisin secretion by altering cancer stem cell properties

Background: Regular physical activities reduce the growth of breast cancer, but research on the effects of steady exercise on metastasis and its mechanisms is limited. In this study, the effects of steady exercise on breast cancer metastasis and its possible mechanism were demonstrated. Methods: Experimental metastasis was induced after 8 weeks of steady exercise using a mouse model. Furthermore, one of the myokines, irisin, was studied to elucidate the effects of metastasis-regulating protein expression, and colony and sphere formation, which are cancer stem cell properties. Results: Low- and moderate-intensity exercise significantly reduced the number and volume of metastasized tumors. Among myokines, only irisin was significantly increased by steady exercise but decreased by a high-fat diet. In vitro studies, irisin significantly decreased the number of colonies and sphere formation. Irisin also inhibited cell migration and invasion and suppressed the malignancy of breast cancer cells by reducing the expression of vimentin, MMP-2, MMP-9, and HIF-1 and by increasing the expression of TIMP-1 and TIMP-2. Conclusion: Steady exercise modulates myokine secretions and among them, irisin suppresses breast cancer metastasis by decreasing self-renewal properties and invasion regulating protein expressions. Thus, regular exercise may be beneficial in the prevention of breast tumor metastasis.