Senescence Effects of Angelica sinensis Polysaccharide on Human AML Stem and Progenitor Cells

Acute myelogenous leukemia (AML) arises from a rare population of leukemia stem cells (LSC), which were initially characterized based on their CD34+CD38immunophenotype and xenotransplantation in NOD/SCID mice (Bonnet et al., 1997). LSC are largely quiescent and refractory to traditional cell cycle-dependent agents contributing to poor long-term survival and continuous relapse. They share properties with normal hematopoietic stem or progenitor cells, such as CD34+, CD38-, CD71and HLA-DR-, that make them difficult to exclusively target while sparing normal hematopoietic cells (Blair et al., 1997; Jordan et al., 2000). However, emerging studies demonstrated that LSC can be selectively targeted by some chemical agents or major active constituents of traditional Chinese medicine (Guzman et al., 2005; Guzman et al., 2007; Zhang et al., 2013). As a consequence of these constituents’ effects, LSC were exclusively diminished with or without affecting normal cells. Features such as these suggest that LSC-specific targeted therapy has the promise to eradicate AML. Consistent with normal stem cell, LSC are largely retained in a quiescent state. This allows them to maintain refractory to common drugs such as arabinoside and daunorubicin that interfere with DNA replication and induce cells apoptosis. Moreover, substantial damage to