Discoidin domain receptors 1 and 2 (DDR1 and DDR2) are structurally-related membrane protein tyrosine kinases activated by different types of a major extracellular matrix component, triple-helical collagen. Collagen is probably the most abundant protein in man, with at least 29 families of genes encoding proteins, which undergo splice variation and post-translational processing, and may exist in monomeric or polymeric forms, producing a triple-stranded, twine-like structure. DDRs participate in several processes such as cell adhesion, migration, proliferation, and matrix remodeling. DDR1 is found in highly invasive tumor cells, suggesting its involvement in tumor progression. DDR1 appears to be preferentially expressed in tumor cells (epithelial), whereas DDR2 is expressed in tumor stroma[1],[2].