Blood vessels supply tumors with nutrients and, on the other hand, enable cancer cells to spread throughout the body. The settlement of circulating tumor cells in a distant organ is promoted by factors whose production is induced by the primary tumor itself. Scientists from the German Cancer Research Center (DKFZ) and the Medical Faculty Mannheim, Heidelberg University, have now identified a new growth factor produced by blood vessels that enables tumor cells to metastatically colonize organs.