IL6 and neoplasm: To determine the functional significance of IL‐6 reduction in tumor cell–induced osteoclast differentiation, we restored IL‐6 levels in  4T1.ΔC cells to levels comparable to those observed in control  4T1.V cells (e.g., added 75 pg to bring to 125 pg/ml) using recombinant murine IL‐6 and assessed osteoclast differentiation induced by tumor cells in indirect coculture assays.