<p>K562 and K562/G01 cells were incubated 6 μM XN4 or 5 mM NAC for 48 h, and 5 mM NAC pre-treated for 1 h then added 6μM XN4 for 48 h. The cells were harvested, then double-stained with PI and Annexin V-FITC, and subsequently analyzed by flow cytometry. All tests were performed three times, and the data are expressed as the mean±SD (** <i>p<</i>0.01, * <i>p<</i>0.05 vs control group, # <i>p<</i>0.01 XN4 group vs NAC+XN4 group, n = 3).</p