DKK1 and plasma cell myeloma: As Sostdc1 and Dkk1 both target the LRP/Frz-Wnt receptors and regulate Wnt-BMP crosstalk in OB progenitors, either molecule may be active at various stages in the development of myeloma-induced lytic bone disease: Dkk1 having a role in targeting mature OB cells, while Sostdc1 affects the maturation of OB progenitors.