More recently, Krause and colleagues reported that MOS-J osteosarcoma cells engineered to constitutively overexpress DKK-1 are impaired in their ability to differentiate, both in vitro and in vivo, and that these cells are more proliferative and form larger, more destructive tumors upon orthotopic implantation [19]. This evidence concerns the gene DKK1 and osteosarcoma.