Decorin inhibits myeloma cell-induced tube formation and osteoclastogenesis. HUVECs were seeded on Matrigel for 3 to 4 hours with the indicated media and conditions. (A) Medium containing a cocktail of growth factors (see “Tube-formation assay”) or 48-hour conditioned medium from culture of myeloma cells from 2 patients induced tube formation by HUVECs, an effect that was completely abrogated by decorin (DCN, 10 μg/mL). (B) Photomicrographs show representative tube formation after incubation with medium lacking growth factors (control medium) and with myeloma cell-conditioned medium in the absence or presence of decorin (original magnification ×10). (C,D) Osteoclast (OC) precursors were incubated with osteoclast medium in the absence or presence of decorin. The number of TRAP-expressing multinucleate osteoclasts shown in panel C (; original magnification ×20) was counted and plotted in panel D.