(color online) Schematic diagram of interactions between bone cells and myeloma cells, showing (1) pre-osteoclasts differentiating into osteoclasts; (2) osteoclasts autocrine regulation; (3) osteoclast-derived factors stimulating osteoblasts production; (4) myeloma cell-derived factors affecting osteoclasts (PTHrP, TGF-β, IL-8, among others); (5) osteoclast-derived factors affecting myeloma cells; (6) pre-osteoblasts differentiating into osteoblasts; (7) osteoblasts autocrine regulation; (8) osteoblast-derived factors inhibiting osteoclasts production; (9) myeloma cells derived factors inhibiting osteoblasts production (DKK1, BMP, IGFs, among others).