The Dan (Differential screening-selected gene aberrative in neuroblastoma, also known as N03) gene was first identified as the putative rat tumor suppressor gene and encodes a protein structurally related to Cerberus and Gremlin in the vertebrates. It is a founding member of the DAN family of secreted proteins, acts as an inhibitor of cell cycle progression, and is closely involved in retinoic acid-induced neuroblastoma differentiation. There are at least five mammalian protein members in the evolutionarily conserved Dan family including DAN, Gremlin/DRM, Cer1 (Cerberus-related), Dante, and PRDC (protein related to DAN and Cerberus), and share the C-terminal cystine-knot motif. As a secreted glycoprotein, DAN is a member of a class of glycoproteins shown to be secreted inhibitors of the transforming growth factor-beta (TGF-beta) and bone morphogenic protein pathways. It binds to BMPs and preventing their interactions with signaling receptor complexes, and accordingly regulates the processes of embryonic development and tissue differentiation. DAN gene product may have an important role in the regulation of the entry of cells into the S phase. Besides, the DAN gene product possesses an ability to revert phenotypes of transformed rat fibroblasts and represents a candidate tumor suppressor gene for neuroblastoma.