Osteoclasts promote the survival of cytokine-dependent myeloma cell lines. (A) XG-19 and XG-20 myeloma cells were cultured at 10⁵ cells/mL without cytokine, or with IL-6 (2 ng/mL), or with 10⁴ osteoclasts with or without anti–IL-6 (BE8) mAb (10 μg/mL), TACI-Fc (20 μg/mL), anti–IGF-1R mAb (4 μg/mL), anti–IL-10 mAb (10 μg/mL), or anti-CCR2 mAb (10 μg/mL). Cells were recovered after 3 days of culture, and apoptotic cells were detected by annexin V staining. Results are those of one experiment representative of 5. (B) Purified MMCs of patients were cultured at 10⁵ cells/mL without cytokine or in the presence of osteoclasts (1 osteoclast for 4 MMC) or IL-6 (2 ng/mL). Cells were recovered after 2, 5, and 6 days of culture, and apoptotic cells were detected by annexin V staining.