RAC1 and cancer: As a paradigm, the silence of matrix proteolysis or ROCK could mute myosin II and Rac1-mediated protrusive activity of cancer cells within the collagen-based 3D matrix.274 Tang et al. have reported that β1-integrin activation was necessary for the membrane-anchored metalloproteinase MT1-MMP (Mmp14)-induced proteolysis of the surrounding matrix.275 Specifically, MT1-MMP+/+ SSC cells displayed a spreading morphology with activated β1-integrin and FAK in degradable PEG-based hydrogels compared to the non-degraded one (Fig. 7b–d).