Targeting leukemic stem cells by breaking their dormancy

Transient or long-term quiescence, the latter referred to as dormancy are fundamental features of at least some adult stem cells. The status of dormancy is likely a critical mechanism for the observed resistance of normal HSCs and leukemic stem cells (LSCs) to anti-proliferative chemotherapy. Recent studies have revealed cytokines such as Interferon-alpha (IFN alpha) and G-CSF as well as arsenic trioxide (As2O3) to be efficient agents for promoting cycling of dormant HSCs and LSCs. Most interestingly, such cell cycle activated stem cells become exquisitely sensitive to killing by different chemotherapeutic agents, suggesting that dormant LSCs in patients may be targeted by a sequential two-step protocol involving an initial activation by IFNa, G-CSF or As2O3, followed by targeted chemotherapy. (C) 2010 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.