Combined inhibition of DOT1L and BCL-2 induces synergistic anti-leukemic effects in MLL-rearranged acute myeloid leukemia via suppression of the PI3K/AKT pathway.

MLL-rearranged acute myeloid leukemia (AML) is a high-risk hematological malignancy driven by aberrant epigenetic regulation. MLL fusion proteins recruit the DOT1L methyltransferase, causing dysregulated histone H3K79 methylation and sustained leukemogenic gene expression (HOXA10, MLLT10), while BCL-2 overexpression contributes to apoptosis resistance. This study evaluated the synergistic efficacy of combining the DOT1L inhibitor EPZ004777 with the BCL-2 inhibitor ABT-737. THP-1 cells were treated with EPZ004777 and ABT-737 alone or in combination. Cell proliferation, apoptosis, H3K79 methylation, target gene expression, and PI3K/AKT signaling were assessed. An in vivo xenograft mouse model (C-NKG mice) validated therapeutic effects. Combined treatment exhibited potent synergistic cytotoxicity. Dual inhibition reduced H3K79 di- and tri-methylation, downregulated HOXA10 and MLLT10, and blocked PI3K/AKT phosphorylation. In vivo, combination therapy prolonged survival, restored bone marrow function, and alleviated organ infiltration. These findings demonstrate that dual targeting of DOT1L and BCL-2 exerts synergistic anti-leukemic activity via PI3K/AKT suppression in MLL-rearranged AML, providing a pharmacological rationale for this innovative combination strategy.