Fig. 5. Low-dose splicing modulation combined with talazoparib or chemotherapy targets PDX AML in vivo.

(A) Morphologic evaluation of bone marrow of STAG2-mutant AMl1 patient–derived xenograft shows infiltration with human leukemia blasts. images were stained using hematoxylin and eosin (H&E) (top) and hCD45-targeting antibody (bottom) and imaged at ×10 and ×40 (scale bars, 0.125 mm) original magnification. (B) Total number and directionality of significant (FDR < 0.05, ΔPSI >5%) splicing alterations differentially called in STAG2-mutant human AML1 PDX cells isolated from bone marrow of NSGS mice treated with E-7107 compared with vehicle for 5 days in vivo. Splicing events are categorized by event type and direction of regulation in E-7107 versus vehicle-treated mice. SE, skipped exon; A3SS, alternative 3′ splice site; A5SS, alternative 5′ splice site; MXE, mutually exclusive exon; RI, retained intron. N = 3 mice per condition. (C) heatmap of ΔPSI scores for H3B-8800–regulated exons called from U937 cells (Fig. 2B) that are expressed in STAG2-mutant AML PdX1 treated with E-7107 in vivo. each comparison consists of two (STAG2-KO1 and SMC3-heterozygous) or three (STAG2-KO2, wild type, and STAG2-mutant PDX) independent biological replicates compared with either DMSO or vehicle-treated controls. color bar on the left indicates the type of splicing event that was called, and column colors are labeled by genotype and drug treatment on the right. (D) Volcano plot depicting differential gene expression of DNA repair genes in STAG2-mutant human AML1 PDX cells isolated from the bone marrow of NSGS mice treated with E-7107 versus vehicle for 5 days in vivo. N = 3 mice per condition. (E) Schematic of in vivo E-7107 drug treatment and survival analysis of STAG2-mutant AML1 PDX model (other mutations include BCOR/RUNX1/U2AF1/DNMT3A). Treatment of mice assigned to two treatment arms was initiated 3 weeks after bone marrow transplantation: talazoparib only (n = 8) or E-7107 for 5 days followed by talazoparib (n = 8). Survival data were combined from two independent experiments. P < 0.005 (log-rank test). (F) Survival analysis of STAG2-mutant AML1 PDX mice treated with 3 days of E-7107 followed by combination chemotherapy (5 + 3 doxorubicin + cytarabine) or combination chemotherapy alone (n = 5 mice per arm). P < 0.005 (log-rank test).