Persistent Akt/mTORC1 signaling supports senescent cell survival and can be exploited to specifically promote cell death. (a and b) Senescent fibroblasts were starved of serum and amino acids overnight in the presence or absence of the mTOR kinase inhibitor 200 nM Torin1 (overnight), 50 µM autophagy inhibitor chloroquine (CQ; 4 h), or 10 µM Akt inhibitor (4 h) as indicated. Cells were incubated with fluorescent ReadyProbe Cell Viability reagents (a), and percentage cell death was quantified (b). (c) Control or senescent (20 Gy irradiation; Sen(IR)) fibroblasts were starved of serum and amino acids in the presence or absence of 200 nM Torin1 for 24 h. Cells were incubated with fluorescent ReadyProbe Cell Viability reagents, and cell viability was quantified (c). (d) Senescent fibroblasts were starved in the presence or absence of Torin1. Cells were lysed and analyzed for markers of apoptosis (PARP and cleaved caspase-3) and autophagy (p62 and LC3). (e) Senescent fibroblasts were starved in the presence or absence of Torin1 and chloroquine as indicated. Percentage cell death was analyzed by ReadyProbe cell viability reagents. Error bars represent SEM; for all experiments, n = 3 (for immunofluorescence, at least five fields of view imaged per experimental repeat). Student’s t test performed between groups: ***, P < 0.001; NS, not significant. Bar, 30 µm.