TGFB1 and breast cancer: We demonstrate that cysteine cathepsin activity contributes to invasion of the TGFβ-1 treated breast cancer cells, but not of NMuMG cells, in two ways: Firstly, the proteases support the acquisition of a TGFβ-1 induced invasive cell phenotype and secondly directly contribute to invasion of TGFβ-1 transformed cells.