CD38 and leukemia: Studies from clinical data and experimental systems have shown that AML originates from a rare population of LSCs (CD34+CD38- cells) or leukemia-initiating cells (LICs) which are capable of self-renewal, proliferation, and differentiation into malignant blasts (Lapidot et al., 1994; Bonnet and Dick, 1997; Roboz and Guzman, 2009).