ATM and glioblastoma: Consequently, the potential action of Mifepristone in chemo-radiation treatments of different tumors may be mediated by other mechanisms, including its participation in apoptosis, cell cycle arrest, and expression of ATM or other radiosensitizer proteins, mechanisms that have been observed in other cell types and therefore may also be contributing to the reduction in size of glioblastoma xenografts found presently (Figure 1).