DKK1 and plasma cell myeloma: To determine whether targeting CREB relieves hypoxia-stimulated myeloma cell suppression of osteoblast (OB) differentiation in vitro, we knocked down CREB in myeloma cells using a lentivirus expressing shRNA, and we ensured that DKK1 expression was largely eliminated (Fig. 6a), but the MMSET protein stability was not obviously altered (Supplementary Fig. 4A).