Chemical Screening Identified Compounds That Trigger Differentiation and Augment ATRA-Induced Myeloid Cell Differentiation

Acute myeloid leukemia (AML) is a blood cancer characterized by abnormal proliferation and differentiation arrest of myeloid progenitor cells. Clinical treatment of AMLs remains challenging. Promoting AML cell differentiation is a valid therapeutic strategy. But most AMLs lack effective differentiation drugs. In this study, we generated Tg(drl:hoxa9) zebrafish, which drives hoxa9 overexpression in hematopoietic cells and exhibits myeloid differentiation arrest. Using Tg(drl:hoxa9) embryos, we performed a chemical screen and identified four FDA-approved drugs, ethacrynic acid, khellin, oxcarbazepine and alendronate, that efficiently restored myeloid differentiation in embryos. The four drugs also induced the differentiation of AML cells, with ethacrynic acid being the most effective. By RNA-seq analysis, we found that during induction of differentiation, ethacrynic acid activates the IL-17 and MAPK signaling pathways, which are known to promote granulopoiesis. Furthermore, we found that ethacrynic acid enhances all-trans retinoic acid (ATRA)-induced myeloid differentiation, and the two signaling are convergent on the IL-17/MAPK pathways. Inhibition of IL-17 /MAPK pathways impairs ethacrynic acid and ATRA-induced differentiation. In addition, we showed that ethacrynic acid is less toxic to embryonic development and less disruptive to normal hematopoietic processes than ATRA. Thus, the combination of ethacrynic acid and ATRA may have a broader clinical application. In conclusion, through zebrafish-aided screening, our study identified four drugs repurposed to induce AML differentiation and provided new agents for AML therapy.