DDR1 and cancer: Interestingly, the epithelial-to-mesenchymal transition program that endows epithelial cells with enhanced migratory, invasive and metastatic potential [98] is associated with a down-regulation of DDR1 [99] and an increased expression of MT1-MMP [100], suggesting that the opposite regulation of these two molecules is critical to allow invasive cancer cells to cope with the collagen-rich tumour microenvironment.