ATM and central nervous system cancer: Interestingly, the survival of nPIAFL/FL mice undergoing RT (Figure 3i, dashed red line) carrying tumors lacking all three functions p53, Ink4a/Arf, and ATM was comparable to that of nPAFL/+ mice (Figure 3i, solid blue line) whose tumors lacked p53 only, indicating that the ATM-defective gliomas induced by loss of p53 and Ink4a/Arf remain relatively radioresistant (Figure 3i).