A rat model of bone pain from metastatic bone cancer. (A) Rats with tibia tumors after Walker 256 cells inoculation displayed both tactile allodynia and spontaneous pain. The PWL progressively decreased and the ambulatory score progressively increased on days 6 (n = 12, ANOVA2w, P < 0.05 pos-hoc Bonferroni, df = 2, F = 1.07), 9, 12, 14, 16, 18, and 21 (ANOVA2w, P < 0.01, df = 2, F = 1.13) after inoculation (AI) in the tumor-bearing group compared with sham-injected controls and normal rats. Results are given as means ± S.D, *p < 0.05 **P < 0.01 vs. normal group; ▲p < 0.05 ▲ ▲p < 0.01 vs. sham group. (B) Radiographs of the left tibiae 18 days after inoculation with Walker 256 cells and the right normal tibiae. There was bilateral cortical bone damage and large bone defects at the 18 days' tumor-bearing proximal epiphysis of the tibiae.(C) HE staining of normal (upper panel) and 18 days of tumor-bearing (lower) proximal epiphysis of the tibiae. Note that tumor cells were densely packed in the marrow cavity and induced the destruction of trabeculae. Arrows indicate tumor cells. Bar = 1 mm in B and 40 μm in C.