MMP13 and breast cancer: Gkretsi et al.161 reported that Ras suppressor-1 (RSU-1), a cell-ECM protein, is overexpressed in breast cancer cells embedded in stiffer 3D collagen I gels, and silencing RSU-1 led to the inhibition of urokinase plasminogen activator (UPA) and MMP-13, resulting in reduced invasion activity in breast cancer cells.