In the liver, high levels of tissue inhibitor of metalloproteinases 1 (TIMP-1) secreted by hepatocytes upregulate stromal cell-derived factor 1 (SDF-1), fibronectin, TGF-β, urokinase-type plasminogen activator (uPA), and S100A, inducing homing of breast cancer cells to this distant microenvironment (Seubert et al., 2015) (Figure 2D). Here, PLAU is linked to breast cancer.