Upregulation of ALDH1 as an adaptive epigenetic response to anthracyclines in acute myeloid leukemia.

Acute myeloid leukemia (AML) is a genetically heterogeneous malignancy characterized by the clonal proliferation of undifferentiated myeloid precursors in the bone marrow. Although standard induction regimens based on anthracyclines often achieve initial remission, up to 25% of patients exhibit primary refractory disease and nearly 50% relapse, underscoring the urgent need to overcome therapy resistance. Aldehyde dehydrogenase 1 (ALDH1) contributes to leukemic cell survival by maintaining stemness, proliferation, and chemoresistance through aldehyde detoxification and retinoic acid synthesis. Here, we identify two enhancer elements, ALDH1A1-E3 and ALDH1A2-E1-A, that mediate transcriptional activation of ALDH1A1 and ALDH1A2 in response to the anthracycline daunorubicin. These enhancers are regulated by STAT3 and FOS/JUN transcription factors, which cooperatively link drug response to ALDH1 induction. Functional validation in AML cell lines, primary samples, and xenograft models shows that ALDH1 upregulation is part of an adaptive stress response and may contribute to reduced anthracycline sensitivity. Co-treatment with the ALDH1A1/1A2 inhibitor DIMATE synergistically enhances daunorubicin efficacy across in vitro and in vivo resistant models. Consistently, high ALDH1 expression is associated with adverse genetic risk, prior anthracycline exposure, and inferior OS, particularly in relapsed/refractory AML. These findings uncover a novel enhancer-mediated mechanism of ALDH1 induction in the context of anthracycline exposure and support the rationale for future clinical trials combining standard treatments with ALDH1-targeted approaches, including the clinical-stage inhibitor DIMATE.