Previous studies on the therapeutic responses-mediating mechanisms of APL cells to ATRA or ATO were largely based on analyses of PML/RARα-expressing leukemia cell lines following in vitro treatment.7, 10 To investigate how APL cells respond to ATRA or ATO in vivo, we labeled the murine APL bone marrow (BM) cells derived from hMRP8-PML/RARα transgenic mice (FVB/NJ) with GFP-expressing retroviral vector MigR1.22 This labeling did not alter APL cells’ in vivo repopulation capacity, morphology and immunophenotype (Supplementary Figure S1a; data not shown). This evidence concerns the gene RARA and acute promyelocytic leukemia.