Using doxycycline-inducible H2B-GFPtg mice, a gold standard in vivo model to study cell quiescence of normal HSCs [136,137], Curtis and colleagues demonstrated that self-renewal, drug resistance and clonal evolution are restricted to a rare and slow-cycling population of pre-LSCs in the Lmo2-induced T-ALL model [133]. This evidence concerns the gene LMO2 and acute lymphoblastic leukemia.