Cooperative Effect Of Chidamide And MI-3 Induce Apoptosis By DNA Damage Accumulation In Acute Myeloid Leukemia Cells With MLL Transduced

As aberrant translocation of the mixed lineage leukemia(MLL)gene drives the pathogenesis of acute myeloid leukemia(AML),it represents an independent predictor for poor prognosis of adult AML patients.Hence,small molecule inhibitors of Menin-MLL fusion protein interaction have been emerging for the treatment of MLL-rearranged AML.As both histone deacetylase(HDAC)and Menin-MLL interaction inhibitors target the transcription machinery via epigenetic regulation of chromatin remodeling to govern expression of genes involved in tumorigenesis,it is hypothesized that these two classes of agents might interact to kill MLL-rearranged AML cells.Here,we report that subtoxic doses of the HDAC inhibitor chidamide and the Menin-MLL interaction inhibitor MI-3 displayed a highly synergistic anti-tumor activity against human AML cells carrying MLL rearrangement in vitro and in vivo.Mechanistically,co-exposure to chidamide and MI-3 induced robust apoptosis,in association with loss of mitochondrial membrane potential and a sharp increase in ROS generation.Combined treatment also disrupted DNA damage checkpoint at CHKl and CHK2 kinases,rather than their upstream kinases ATR and ATM,as well as DNA repair likely via homologous recombination(HR)but not non-homologous end joining(NHEJ).Genome-wide RNA-seq revealed several potential signaling pathways(e.g.,MAPK,NF-KB)and targets(e.g.,SULT1A3)that might account for or contribute to the mechanisms of action for anti-leukemia activity of chidamide and MI-3 as single agent or in combination in MLL-rearranged AML.Collectively,these findings provide a preclinical basis for further clinical investigation of this novel targeted strategy combining HDAC and Menin-MLL interaction inhibitors to improve therapeutic outcomes in the poor-prognostic subset of patients with MLL-rearranged leukemia.