DDR2 and breast cancer: Although the roles of DDR2 in the regulation of cell homeostasis, migration or cell cycle remain controversial, a growing number of reports have implicated DDR2 as a key driver of cell proliferation in fibroblasts [50, 51], chondrocytes [50, 52, 53], hepatic stellate cells [54], lung squamous cancer cell lines [55], osteoblasts [53], and breast cancer cell lines [56].