Bromodomain‐containing protein 4 (BRD4) inhibitors have been clinically developed to treat acute myeloid leukemia (AML), but their application is limited by the possibility of drug resistance, which is reportedly associated with the activation of the WNT/β‐catenin pathway. Meanwhile, homoharringtonine (HHT), a classic antileukemia drug, possibly inhibits the WNT/β‐catenin pathway. In this study, we attempted to combine a novel BRD4 inhibitor (ACC010) and HHT to explore their synergistic lethal effects in treating AML. Here, we found that co‐treatment with ACC010 and HHT synergistically inhibited cell proliferation, induced apoptosis, and arrested the cell cycle in FMS‐like tyrosine kinase 3‐internal tandem duplication ( FLT3‐ITD)–positive AML cells in vitro, and significantly inhibiting AML progression in vivo. Mechanistically, ACC010 and HHT cooperatively downregulated MYC and inhibited FLT3 activation. Further, when HHT was added, ACC010‐resistant cells demonstrated a good synergy. We also extended our study to the mouse BaF3 cell line with FLT3‐inhibitor‐resistant FLT3‐ITD/tyrosine kinase domain mutations and AML cells without FLT3‐ITD. Collectively, our results suggested that the combination treatment of ACC010 and HHT might be a promising strategy for AML patients, especially those carrying FLT3‐ITD.
Co‐treatment with a novel BRD4 inhibitor (ACC010) and homoharringtonine (HHT) synergistically inhibited cell proliferation, induced apoptosis, and arrested the cell cycle in AML with FLT3‐ITD mutation. Mechanistically, ACC010 and HHT cooperatively downregulated MYC and inhibited FLT3 activation. Further, HHT could enhance the efficacy of the BRD4 inhibitor to help overcome resistance by targeting MYC and WNT/β‐catenin pathway.