Restoring ARID3A expression reestablishes normal differentiation of leukemic blasts. (A) ARID3A expression (RPKM) in fetal CD34⁺ HSPCs (n = 3) and sorted pediatric AML blasts of different subtypes: TAM (n = 16), ML-DS (n = 13), and AMKL (n = 9); others include CBFB-MYH11 (n = 12), RUNX1-RUNX1T1 (n = 8), KMT2A-MLLT10 (n = 10), and KMT2A-MLLT3 (n = 8) (1-way ANOVA). (B-C) AMKL and ML-DS PDXs were transduced with doxycycline-inducible ARID3A or LUC cDNA vectors. (B) Normalized percentage of ARID3A⁺ cells after a 12-day induction with doxycycline, normalized to the LUC control. (C) Normalized percentage of ARID3A⁺ terminally differentiated megakaryocytes (CD41⁺CD61⁺CD42⁺) after an 8-day induction with doxycycline, normalized to the LUC control (n = 3 per PDX, unpaired Student t test vs the respective control). (D) Experimental design for evaluating ARID3A restoration in vivo. Leukemic blasts were transduced with ARID3A (GFP⁺) or a LUC control (GFP⁺) and mixed 1:1 with LUC control-transduced blasts (dTomato⁺), before transplantation into sublethally irradiated recipient mice. (E) Ratio of GFP⁺ to dTomato⁺ cells in input cells (IP), and in the bone marrow (BM) of mice euthanized 4 to 5 weeks after transplantation (n = 5, unpaired Student t test). (F) Probability of event-free survival (EFS) in 258 NCI-TARGET pediatric patients with AML,⁶³ with high (green; >12.0 normalized reads; cutoff determined via maximally selected rank statistics) or low ARID3A expression (black; ≤12.0 normalized reads). (G) Probability of EFS in 171 TCGA (The Cancer Genome Atlas) adult patients with AML⁶⁴ with high (green; >12.3 normalized reads; cutoff determined via maximally selected rank statistics) or low ARID3A expression (black; ≤12.3 normalized reads). (A-C,E) Data are the mean ± standard deviation. FP⁺, fluorescent protein positive; n.s., not significant.