DUX4-r ALL cells are dependent on the PI3K/AKT pathway. (A) Volcano plot representing genes significantly overexpressed in DUX4-r blast cells (green) and normal progenitor B cells (yellow). Top genes based on fold changes are indicated with a label. P value cutoff is 0.01 (B) Chromatin accessibility of the gene regions of AGAP1, ANGPT2, GATA3, S100A16, and MCAM, the top 5 expressed genes based on fold change in DUX4-r blast cells. (C) Top 10 cell-type marker gene sets from GSEA of differentially expressed genes between DUX4-r blast cells and normal progenitor B cells. (D) Network plot visualizing GSEA of reactome pathways when comparing DUX4-r blast cells and progenitor B cells. (E) In vitro viability of BCP-ALL cell lines treated with a selective p110α (PIK3CA) inhibitor, alpelisib, with half-maximal inhibitory concentration (IC50) and 95% CI. (F) Experimental design for in vivo treatment of the DUX4-r-13 PDX sample in immunodeficient mice using alpelisib (35 mg/kg, 5 days on/2 days off for 3 weeks). (G) Number of human DUX4-r blast cells (ALL cells) in the BM after treatment. (H) Phosphorylation of AKT (pS473) in human DUX4-r blast cells in the mouse BM after treatment. (I) Phosphorylation of mammalian target of rapamycin (mTOR) (pS2448) in human DUX4-r blast cells in the mouse BM after treatment. CI, confidence interval.