TNFRSF11B and neoplasm: TRAP staining of bone lesions showed that the density of osteoclasts on the bone surface facing the tumor was significantly reduced in PC3-OPG-injected mice (19.9±5.8 per mm bone) compared to PC3-mock-injected mice (32.7±9.3 per mm bone; P<0.05, Fig. 2C).