Sclerostin, an osteocyte-expressed negative regulator of bone formation, is one 
of the inhibitors of Wnt signaling that is a critical pathway in the correct 
process of osteoblast differentiation. It has been demonstrated that Wnt 
signaling through the secretion of Wnt inhibitors, such as DKK1, sFRP-2, and 
sFRP-3, plays a key role in the decreased osteoblast activity associated with 
multiple myeloma (MM) bone disease. We provide evidence that sclerostin is 
expressed by myeloma cells that are human myeloma cell lines and plasma cells 
(CD138(+) cells) obtained from the bone marrow (BM) of a large number of MM 
patients with bone disease. Moreover, we show that there are no differences in 
sclerostin serum levels between MM patients and controls. Thus, our data 
indicate that MM cells, as a sclerostin source in the BM, could create a 
microenvironment with high sclerostin concentration that could contribute toward 
inhibiting osteoblast differentiation.