Constitutive down-regulation of Osterix in osteoblasts from myeloma patients: in vitro effect of Bortezomib and Lenalidomide.

Bortezomib and Lenalidomide have been shown to be effective in the control of multiple myeloma (MM) progression. We have investigated their role in the in vitro expression of Osterix by primary osteoblast cultures from MM patients and found that Osterix RNA was constitutively down-regulated in these cells. Treatment of osteoblasts with Bortezomib resulted in an increase of Osterix RNA and in enhanced activity of both BMP-2 and Runx2. Instead, Lenalidomide was unable to modify Osterix transcription. These findings provide additional evidence suggesting that, at least in vitro, Bortezomib promotes the osteoblast maturation whereas Lenalidomide is ineffective.