PLAU and breast cancer: The Tcf-4/β-catenin signalling pathway has an important role in expression of urokinase plasminogen activator (Mann et al, 1999), metalloproteinase 1 (MMP-1; Takahashi et al, 2002) as well as MMP-7 (Brabletz et al, 1999), which have an important function in breast cancer metastatic progression.