SIRT1 and breast cancer: Based on findings regarding the roles of SIRT1 and FoxOs in tumor growth and apoptosis, as well as their roles on metastasis, the aim of the present study was to investigate expression and regulation of SIRT1 and FoxO and their related pathways in tumor growth and metastasis in primary tumors and distant organs using both benign and highly metastatic breast cancer cells under in vitro and in vivo conditions.