Wnt3A stimulates bone formation and attenuates primary MM growth in SCID-hu mice. SCID-hu mice engrafted with MM cells from 5 patients were daily injected with Cont-CM and Wnt3a-CM into the surrounding area of the implanted bones (patients 1 and 2) or treated with rWnt3a using Alzet pumps. (A,B) Changes in circulating human kappa Ig level (A) and in the BMD of the implanted bones (B) from pretreatment level. (C,D) X-ray radiographs showing changes in myelomatous bone mass of hosts treated with Cont-CM and Wnt3a-CM (C) and rWnt3a (D). Note that osteolytic lesions were evident before initiation of treatment (pre-Rx) and that, although in control hosts bone loss continued to increase (white arrows), Wnt3a treatment resulted in increased bone mass (white arrows).