Background

The anti-diabetic drug metformin has been shown to affect cancer cell metabolism [1,2] and to display anti-tumoral properties in numerous cancers [3,4], however, its role in the formation of metastases remains poorly docu-mented. Cell migration is a critical step in the progression of prostate cancer to the metastatic state, the lethal form of the disease. Results We show here that metformin reduces the occurrence of metastases in an orthotopic metastatic prostate cancer cell model established in nude mice. As predicted, metformin hampers cell motility in PC3 and DU145 prostate cancer cells and triggers a radical reorganization of the cell cytos-keleton. The small GTPase Rac1 is a master regulator of cytoskeleton organization and cell migration. We repor