KIT and acute promyelocytic leukemia: The leukemia progenitor cells in this APL mouse have been shown to differentiationally resemble normal GMPs with granulocytic and monocytic differentiation potentials.24, 34 To characterize the lineage directions of the spontaneous differentiation, we performed RT-PCR to measure the expressional alterations of the granulocytic or monocytic-specific transcription factors and others along with the transition form c-Kit+CD11b- AA4.1++ APL cells through c-Kit+CD11b++ APL cells towards c-Kit−CD11b++ APL cells.