DKK1 and plasma cell myeloma: For example, transgenic mice overexpressing DKK-1 exhibit osteopenia, whereas reduction of DKK-1 expression increases bone mass.(45,46) Also, antibodies to DKK-1 have been shown to reduce osteolytic lesions and tumor burden in animal models of myeloma, thereby confirming the important negative regulatory effect that DKK-1 has on osteoblastogenesis.(47,48)