Synergistic efficacy of homoharringtonine and venetoclax on acute myeloid leukemia cells and the underlying mechanisms

BACKGROUND: To evaluate whether homoharringtonine (HHT) combined with venetoclax could produce a synergistic anti-acute myeloid leukemia (AML) effect and determine the underlying mechanisms. METHODS: The effect of HHT and venetoclax combination on cell viability, apoptosis, and mitochondrial membrane potential was investigated in vitro using AML cell lines and primary cells. High-throughput mRNA sequencing was used to analyze mRNA level changes after the application of HHT and venetoclax on OCI-AML3 cells. Western blotting was used to verify the changes in protein expression within the mitogen-activated protein kinases/extracellular signal-regulated kinase (MAPK/ERK), phosphatidylinositiol 3-kinase (PI3K)/AKT and p53 pathway. The efficacy of HHT and venetoclax in vivo and their effects on survival time were evaluated in a xenograft model established in severe immunodeficiency (NOD/SCID) mice. RESULTS: Venetoclax and HHT synergistically inhibited the proliferation of AML cells, decreased the mitochondrial membrane potential, and promoted AML cell apoptosis in a time- and concentration-dependent manner. Venetoclax combined with HHT increased the expression of the caspase-3, Poly (ADP-ribose) polymerase (PARP), and γH2AX proteins. HHT enhanced the proapoptotic effect of venetoclax by reducing the expression of myeloid cell leukemia sequence 1 (Mcl-1). HHT arrested AML cells in G1 phase of the cell cycle. HHT enhanced the proapoptotic effect of venetoclax by inhibiting the activation of the MAPK/ERK and PI3K/AKT pathways and activating the p53 pathway. In vivo experiments confirmed that the combination of HHT and venetoclax could inhibit the growth of tumors in AML xenotransplanted mice and prolong the survival time of tumor-bearing mice. CONCLUSIONS: HHT combined with venetoclax synergistically promoted apoptosis in AML cell lines and primary cells by inhibiting the activation of the MAPK/ERK and PI3K/AKT pathways and activating the p53 pathway.