**3.1 LSCs are mostly in the G0 quiescent phase**

Dean et al. showed that 96% of LSCs are in the G0 phase of the cell cycle [33]. Chemotherapeutic drugs acting on the cell cycle or on rapidly differentiating cells can inhibit only differentiated mature leukemia cells, while LSCs in the G0 phase cannot be completely inhibited because they do not divide. Once they are properly stimulated to re-enter the cell cycle, they will continue to proliferate and differentiate into daughter leukemia cells, thus causing recurrence. According to some studies, LSCs are much less sensitive to daunorubicin and cytarabine than differentiated leukemia cells.
