The pro-oxidant effect of L-ascorbic acid (LAA) is toxic to leukemia cells.LAA induces the oxidation of glutathione to its oxidized form (GSSG) and this is followed by a concentration-dependent H2O2 accumulation,which occurs in parallel to the induction of apoptosis.To identify early protein targets of LAA in leukemia cells,we used a differential proteomics approach in NB4 human leukemia cells treated with 0.5 mM of LAA for 30 min.This exposure was determined to efficiently block cellular proliferation and to activate oxidative stress-inducible apoptosis.