For this reason, myeloma cells inhibit osteoblasts through the release of distinct secretory factors such as dickkopf-related protein 1 (DKK1), secreted frizzled-related protein 2 (sFRP2) and transforming growth factor beta (TGFβ) to overcome the tumor-suppressive effects of osteoblasts (76, 81, 82). Here, DKK1 is linked to plasma cell myeloma.