Intracellular AA (iAA) protects HL60, U266, and RPMI-8226 cells from As₂O₃ cytotoxicity. Cell viability of HL60 (A) and U266 (D) cells loaded with vitamin C using DHA and exposed to As₂O₃ for 48 hours. Cloning efficiency of HL60 (B) and U266 (E) cells loaded with vitamin C and treated with 2 and 1 μMAs₂O₃, respectively. (C) HL60 cells were loaded with 4 mM iAA, treated with 3 μMAs₂O₃ for 24 or 48 hours, and apoptotic cells were stained using annexin V–FITC assay (left panel) or a TUNEL assay (right panel), respectively. (F) Cell viability of RPMI-8226 cells loaded with 4 mM AA and exposed to 1 μMAs₂O₃ for 48 hours. (A-F) Data are expressed as the mean ± SD of 3 independent experiments.