Coexpression of WT1 enhances colony-forming activity of AML1-ETO-expressing myeloid progenitors. (A) The number of first-generation colonies. The mean values ± SD of 5 independent assays for each group are shown. (B) Colony-replating assay. Empty-vector-transduced wild-type BM cells (□), empty-vector-transduced WT1-Tg BM cells (○), AML1-ETO-transduced wild-type BM cells (▪), AML1-ETO-transduced WT1-Tg BM cells (•). Gray squares and circles represent the numbers of blastic colonies in the AML1-ETO-transduced wild-type and WT1-Tg BM cell cultures, respectively. The mean values of 5 independent assays for each group are shown. (C) The eighth-generation blastic colonies from the AML1-ETO-transduced wild-type BM cells (left) and AML1-ETO-transduced WT1-Tg BM cells (right) are shown (original magnification, × 60). (D) The numbers of secondary colonies produced by a single blastic colony from the AML1-ETO-transduced wild-type BM cells and AML1-ETO-transduced WT1-Tg BM cells. Fifteen blastic colonies from each group were assayed and the mean values ± SD are shown. ^*P < .01; ^**P < .005; ^***P < .001.