Treatment with PJ-34 prevented the development of MCF-7 and MDA231 xenotransplants. (a) Xenotransplants of MCF-7 developed within 6 to 7 weeks in three mice that were not treated with PJ-34 (control mice; tumors are indicated by arrows; left). Tumors did not develop in any of the three mice treated with PJ-34 for 14 days by a slow release of PJ-34 from a subcutaneously implanted osmotic pump (Alzet; pump •; Methods) (Right). Tumors were not detected during 4 months after injection with the MCF-7 cells. Each female CD-1 nu/nu mouse was injected with about 107 MCF-7 cells collected from 80% to 90% confluent cell cultures. Cells were immersed in Matrigel/PBS (Methods). Cells were injected near the pump, one hour after pump implantation. (b) Each CD-1 nu/nu female mouse was injected with about 107 MDA231 cells collected from 80% to 90% confluent cell cultures and immersed in Matrigel/PBS (Methods). Cells were injected near the pump, 24 hours after pump implantation. Xenotransplants of MDA231 developed within 10 days in five female mice that were not treated with PJ-34 (untreated mice). Tumors did not develop in five female mice treated for 14 days with a slow release from a subcutaneously implanted osmotic pump (Alzet pump). Tumors were not detected in these mice during 10 weeks after injection with MDA231 cells and 8 weeks after the treatment with PJ-34. A detailed presentation of this experiment is included in Additional data file 1. (c) Kaplan-Meier survival analysis is used for presenting tumor-free survival curves of mice injected with MCF-7 cells and mice injected with MDA231 cells, without or after treatment with PJ-34, as described earlier. The significance (log-rank significance test) was P = 0.0253 for mice injected with MCF-7 cells, and P = 0.0023 for mice injected with MDA231 cells.