CD38 and leukemia: LSCs have a self-renewal capacity to generate large numbers of leukemia progenitor cells (CD34+CD38+) through the activation of several signaling pathways including WNT/β-catenin, Hedgehog (Hh), Notch, transforming growth factor-β (TGF-β)/Forkhead box O (FOXO), and Musashi 2 (Msi2)-Numb signaling [50].