Tumor-bearing Tax mice have decreased bone mineral density and enhanced osteoclastogenesis. (A-B) Bone mineral density (BMD) of Tax⁺ mice measured by dual-energy x-ray absorptiometry (DEXA) is depicted as the mean ± SEM. One-month-old Tax⁺ mice have normal BMD on tails, tibias, and femurs as compared with their wild-type littermates (P > .05, n = 10). Tumor-bearing Tax⁺ mice have significantly decreased BMD on tails, tibias, and femurs as compared with the wild-type littermates (^*P < .05, n = 10). (C) Whole bone marrow cells from a 1-month-old Tax⁺ mouse and a wild-type littermate were cultured in low-dose M-CSF (12 ng/mL) and GST-RANKL (10 ng/mL and 30 ng/mL) for 5 days; cells were fixed and TRAP stained. Three independent experiments were repeated. Multinucleated TRAP-positive osteoclasts of Tax⁺ mice and wild-type mice were counted and depicted as the mean ± SEM. There was not a significant difference (P > .05), indicating similar osteoclast formation between 1-month-old Tax⁺ and wild-type mice. (D) Representative TRAP staining of 1-month-old wild-type and Tax⁺ whole bone marrow–derived osteoclast cultures at day 5 (× 20). (E) Whole bone marrow cells from a 7-month-old Tax⁺ tumor-bearing mouse and a wild-type littermate cultured under low M-CSF (12 ng/mL) and GST-RANKL (10 ng/mL and 30 ng/mL) for 5 days; cells were fixed and TRAP stained. Three independent experiments were repeated. Multinucleated TRAP-positive osteoclasts of Tax⁺ mice were more abundant compared with wild-type mice, indicating enhanced osteoclast formation in tumor-bearing Tax⁺ mice (^*P < .01). (F) Representative TRAP staining of 7-month-old wild-type and Tax⁺ whole bone marrow osteoclast cultures at day 5 (× 20).