(a) Effect of 6-thioguanosine on the area of osteolytic lesions in mice bearing MDA-MB-231 cells after intracardiac injection. Osteolytic-lesion area was assessed by Faxitron (model 43855A, Faxitron X-ray Corp.) and computerized image analysis of hindlimb radiographs. MDA-MB-231 tumor cells were inoculated on day 0. Treatment with 6-thioguanosine (0.1 mg/kg/day subcutaneously) was begun on the following day. Vertical arrows indicate the days of treatment. Values represent means ± SEM (n = 5 per group). *P < 0.05. (b) Representative radiographs of hindlimbs from mice bearing MDA-MB-231 tumors 28 days after tumor inoculation with and without treatment with 6-thioguanosine (Figure 7a). Arrows indicate osteolytic lesions.