RESUMEN
Rearrangements of the MLL (KMT2A) locus are associated with aggressive leukaemia of both myeloid and lymphoid lineages, that present profound therapeutic challenges in pediatric and adult patient populations. MLL-fusion genes resulting from these rearrangements function as driving oncogenes and have been the focus of research aimed at understanding mechanisms underlying their leukemogenic activity and revealing novel therapeutic opportunities. Inspired by the paradigm of depleting the PML-RARA fusion protein in acute promyelocytic leukemia using all-trans retinoic acid and arsenic trioxide, we conducted a screen to identify FDA-approved drugs capable of depleting MLL-fusion protein expression in leukemia cells. Previously, we reported potent anti-leukemia effects of disulfiram (DSF), identified through this screen. In the present study, we demonstrate that another hit compound, niclosamide (NSM), is also able to deplete MLL-fusion proteins derived from a range of different MLL-fusion genes in both acute myeloid (AML) and acute lymphoid (ALL) leukemias. Loss of MLL-fusion protein appeared to result from inhibition of global protein translation by NSM. Importantly, combination of DSF with NSM enhanced MLL-fusion protein depletion. This led to more profound inhibition of downstream transcriptional leukemogenic programs regulated by MLL-fusion proteins and more effective killing of both MLL-rearranged AML and ALL cells. In contrast, DSF/NSM drug combination had little impact on normal hematopoietic progenitor cell differentiation. This study demonstrates that two FDA-approved drugs with excellent safety profiles can be combined to increase the efficacy of MLL-fusion protein depletion and elimination of MLL-rearranged leukaemia.
RESUMEN
Acute leukemia continues to be a major cause of death from disease worldwide and current chemotherapeutic agents are associated with significant morbidity in survivors. While better and safer treatments for acute leukemia are urgently needed, standard drug development pipelines are lengthy and drug repurposing therefore provides a promising approach. Our previous evaluation of FDA-approved drugs for their antileukemic activity identified disulfiram, used for the treatment of alcoholism, as a candidate hit compound. This study assessed the biological effects of disulfiram on leukemia cells and evaluated its potential as a treatment strategy. We found that disulfiram inhibits the viability of a diverse panel of acute lymphoblastic and myeloid leukemia cell lines (n = 16) and patient-derived xenograft cells from patients with poor outcome and treatment-resistant disease (n = 15). The drug induced oxidative stress and apoptosis in leukemia cells within hours of treatment and was able to potentiate the effects of daunorubicin, etoposide, topotecan, cytarabine, and mitoxantrone chemotherapy. Upon combining disulfiram with auranofin, a drug approved for the treatment of rheumatoid arthritis that was previously shown to exert antileukemic effects, strong and consistent synergy was observed across a diverse panel of acute leukemia cell lines, the mechanism of which was based on enhanced ROS induction. Acute leukemia cells were more sensitive to the cytotoxic activity of disulfiram than solid cancer cell lines and non-malignant cells. While disulfiram is currently under investigation in clinical trials for solid cancers, this study provides evidence for the potential of disulfiram for acute leukemia treatment. KEY MESSAGES: Disulfiram induces rapid apoptosis in leukemia cells by boosting oxidative stress. Disulfiram inhibits leukemia cell growth more potently than solid cancer cell growth. Disulfiram can enhance the antileukemic efficacy of chemotherapies. Disulfiram strongly synergises with auranofin in killing acute leukemia cells by ROS induction. We propose testing of disulfiram in clinical trial for patients with acute leukemia.