DDR1 and sarcoma: Amongst the sarcoma cell lines used in this study, collagen caused apoptosis in the cell lines expressing high DDR1, low integrin β1 and relatively low MMP14, suggesting that matrix remodeling is also a central factor in the collagen‐induced apoptotic response consistent with previous reports in breast cancer.[41] Indeed, we found that overexpressing MMP14 or co‐culturing apoptotic cell lines with highly remodeling fibroblasts, enhances the survival of these cells.