In addition, membrane-bound matrix metalloproteinase membrane-type-1 matrix metalloproteinase (MT1-MMP) is highly expressed in invasive cells, including fibroblasts and invasive cancer cells, and promotes breast cancer tumorigenesis by inhibiting the apoptosis induced by the collagen/DDR1/BIK signaling axis (Liu et al., 2014). Here, DDR1 is linked to breast cancer.