In quest for leukemia initiating cells in AML

Leukemic stem cells (LSC), also referred as leukemia-initiating cells (LIC), represent a rare subpopulation of leukemic cells that possess stem cell properties distinct from bulk leukemic cells. Such properties include leukemia initiation (the ability to engraft and to reconstitute the heterogeneous leukemia disease), self-renewal (the ability to transfer disease into secondary/tertiary recipients) and drug resistance. In Acute Myeloid Leukemia (AML), LSC were identified more than 20 years ago as a population of leukemic cells with the CD34+CD38？ immunophenotype [1, 2]. However, more recent studies have challenged this result and have shown that LSC are also present in other phenotypically defined compartments [3, 4]. In their study, Ng et al. have demonstrated that expression of a 17 gene signature derived from functionally defined LSC predicts the risk for relapse irrespective of CD34/CD38 expression. This suggests that leukemia initiating activity and leukemic cell chemoresistance is a cellular intrinsic property independent of cell surface phenotype