CREB1 and plasma cell myeloma: Culturing MSCs with the supernatant from myeloma cells carrying non-target control shRNA (CMCtrl) clearly inhibited OB activity, but the culture supernatant from myeloma cells carrying CREB shRNA (CMCREBi) reduced the suppression of mature osteoblasts (Fig. 6b), as evidenced by measuring Alizarin Red-S staining intensity (Fig. 6c) and the activity of alkaline phosphatase (ALP) (Fig. 6d).