The Hoechst 33342 negative/low staining cells rate in KG-1a cells. KG-1a cells were stained by Hoechst 33342 and the cells were observed under inverted fluorescence microscope. Three independent experiments were performed. (KG-1a +5-FU) group: KG-1a cells incubated at 50 μg/mL of 5-FU for 4 d. The enriched cells had a high percentage of negative/low staining cells *, p < 0.05. Error bars correspond to mean ± SD.