Figure 4.

Sirtuin-1-dependent autophagy favors stress resistance in human cancer cells. (a, b) Metabolic stress-induced cell death is increased by the knockdown or inhibition of Sirtuin-1 (Sirt-1). Wild-type (WT) HCT 116 cells were transfected with the indicated siRNAs (a) or treated with 100 μM EX527 and/or 1 μM rapamycin (Rapa) (b) and subjected to metabolic stress (cultured in nutrient-free, hypoxic conditions) for 48 h. Cells were then stained with the mitochondrial transmembrane potential (Δψ_m)-sensitive dye DiOC₆(3) and the vital dye propidium iodide (PI). Black and white columns illustrate the percentage (mean±S.E.M., n=3, ^*P<0.05) of DiOC₆(3)^low/PI⁻ (dying) and DiOC₆(3)^low/PI⁺ (dead) cells, respectively