Effect of 6-thioguanine and 6-thioguanosine on the area of osteolytic lesions. 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-thioguanine or 6-thioguanosine (0.5 mg/kg/day subcutaneously) was begun on day 15. Vertical arrows indicate the days of treatment. Values represent means ± SEM (n = 5 per group). *P < 0.05.