Mitochondrial metabolism recently emerged as a critical dependency in acute myeloid leukemia (AML). The shape of mitochondria is tightly regulated by dynamin GTPase proteins, which drive opposing ...fusion and fission forces to consistently adapt bioenergetics to the cellular context. Here, we showed that targeting mitochondrial fusion was a new vulnerability of AML cells, when assayed in patient-derived xenograft (PDX) models. Genetic depletion of mitofusin 2 (MFN2) or optic atrophy 1 (OPA1) or pharmacological inhibition of OPA1 (MYLS22) blocked mitochondrial fusion and had significant anti-leukemic activity, while having limited impact on normal hematopoietic cells ex vivo and in vivo. Mechanistically, inhibition of mitochondrial fusion disrupted mitochondrial respiration and reactive oxygen species production, leading to cell cycle arrest at the G
/G
transition. These results nominate the inhibition of mitochondrial fusion as a promising therapeutic approach for AML.
Therapy resistance represents a major clinical challenge in acute myeloid leukemia (AML). Here we define a 'MitoScore' signature, which identifies high mitochondrial oxidative phosphorylation in vivo ...and in patients with AML. Primary AML cells with cytarabine (AraC) resistance and a high MitoScore relied on mitochondrial Bcl2 and were highly sensitive to venetoclax (VEN) + AraC (but not to VEN + azacytidine). Single-cell transcriptomics of VEN + AraC-residual cell populations revealed adaptive resistance associated with changes in oxidative phosphorylation, electron transport chain complex and the TP53 pathway. Accordingly, treatment of VEN + AraC-resistant AML cells with electron transport chain complex inhibitors, pyruvate dehydrogenase inhibitors or mitochondrial ClpP protease agonists substantially delayed relapse following VEN + AraC. These findings highlight the central role of mitochondrial adaptation during AML therapy and provide a scientific rationale for alternating VEN + azacytidine with VEN + AraC in patients with a high MitoScore and to target mitochondrial metabolism to enhance the sensitivity of AML cells to currently approved therapies.
Autophagy (Atg) regulates cytotoxicity after proteasome inhibition in acute myeloid leukaemia (AML) cells expressing fms‐like tyrosine kinase 3 (FLT3) mutations. Here, we show that the proteasome ...inhibitor bortezomib activates proteaphagy in AML cells expressing FLT3‐internal tandem duplication (ITD), but not in cells with wild‐type FLT3. Chemical inhibition of Atg blocking autophagosome‐lysosome fusion or the Atg receptor p62 efficiently inhibits proteaphagy and enhances bortezomib‐induced apoptosis in FLT3‐ITD‐driven leukemic cells.
Acute myeloid leukaemia (AML) is a clonal disorder that affects hematopoietic stem cells or myeloid progenitors. One of the most common mutations that results in AML occurs in the gene encoding fms‐like tyrosine kinase 3 (FLT3). Previous studies have demonstrated that AML cells expressing FLT3‐internal tandem duplication (ITD) are more sensitive to the proteasome inhibitor bortezomib (Bz) than FLT3 wild‐type cells, with this cytotoxicity being mediated by autophagy (Atg). Here, we show that proteasome inhibition with Bz results in modest but consistent proteaphagy in MOLM‐14 leukemic cells expressing the FLT3‐ITD mutation, but not in OCI‐AML3 leukemic cells with wild‐type FLT3. Chemical inhibition of Atg with bafilomycin A simultaneously blocked proteaphagy and resulted in the accumulation of the p62 Atg receptor in Bz‐treated MOLM‐14 cells. The use of ubiquitin traps revealed that ubiquitin plays an important role in proteasome‐Atg cross‐talk. The p62 inhibitor verteporfin blocked proteaphagy and, importantly, resulted in accumulation of high molecular weight forms of p62 and FLT3‐ITD in Bz‐treated MOLM‐14 cells. Both Atg inhibitors enhanced Bz‐induced apoptosis in FLT3‐ITD‐driven leukemic cells, highlighting the therapeutic potential of these treatments.
AMP-activated protein kinase (AMPK) regulates the balance between cellular anabolism and catabolism dependent on energy resources to maintain proliferation and survival. Small-compound AMPK ...activators show anti-cancer activity in preclinical models. Using the direct AMPK activator GSK621, we show that the unfolded protein response (UPR) is activated by AMPK in acute myeloid leukemia (AML) cells. Mechanistically, the UPR effector protein kinase RNA-like ER kinase (PERK) represses oxidative phosphorylation, tricarboxylic acid (TCA) cycle, and pyrimidine biosynthesis and primes the mitochondrial membrane to apoptotic signals in an AMPK-dependent manner. Accordingly, in vitro and in vivo studies reveal synergy between the direct AMPK activator GSK621 and the Bcl-2 inhibitor venetoclax. Thus, selective AMPK-activating compounds kill AML cells by rewiring mitochondrial metabolism that primes mitochondria to apoptosis by BH3 mimetics, holding therapeutic promise in AML.
After intensive chemotherapy, the emergence of cells with drug resistant and/or stem cell features might explain frequent relapses and the poor outcome of patients with acute myeloid leukemia (AML). ...Herein, we first uncovered that the adrenomedullin receptor CALCRL is overexpressed in AML patients compared to normal cells and preferentially in the immature CD34+CD38- compartment. Then, we demonstrated its role in the maintenance of leukemic stem cell function in vivo (Figure A). Moreover, CALCRL depletion strongly affected leukemic growth in xenograft models and sensitized to chemotherapeutic agent cytarabine in vivo. Accordingly, we showed that ADM-CALCRL axis drove BCL2 pathway, cell cycle and DNA integrity in E2F1-dependent manner, and high OxPHOS status that we previously described as a feature of minimal residual disease after chemotherapy (Farge et al., 2017). Moreover, CALCRL expression predicted the response to chemotherapy in vivo in mice (n=10 Patient Derived Xenografts; Figure B) and in patients. Further, using the combination of limiting dilution assays, single cell RNA-seq analysis of primary AML samples at diagnosis and relapse and before and after transplantation in NSG mice, we revealed the pre-existence of a chemoresistant leukemic stem cell sub-population harboring a CALCRL gene signature (Figure C-D). All of these data highlight the critical role of CALCRL in stem cell function and metabolism. They also identify this receptor as a new druggable marker of chemoresistant leukemic stem cell population and a promising therapeutic target to specifically eradicate them and overcome relapse in AML.
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No relevant conflicts of interest to declare.
Chemotherapy-resistant human acute myeloid leukemia (AML) cells are thought to be enriched in quiescent immature leukemic stem cells (LSC). To validate this hypothesis
, we developed a clinically ...relevant chemotherapeutic approach treating patient-derived xenografts (PDX) with cytarabine (AraC). AraC residual AML cells are enriched in neither immature, quiescent cells nor LSCs. Strikingly, AraC-resistant preexisting and persisting cells displayed high levels of reactive oxygen species, showed increased mitochondrial mass, and retained active polarized mitochondria, consistent with a high oxidative phosphorylation (OXPHOS) status. AraC residual cells exhibited increased fatty-acid oxidation, upregulated CD36 expression, and a high OXPHOS gene signature predictive for treatment response in PDX and patients with AML. High OXPHOS but not low OXPHOS human AML cell lines were chemoresistant
Targeting mitochondrial protein synthesis, electron transfer, or fatty-acid oxidation induced an energetic shift toward low OXPHOS and markedly enhanced antileukemic effects of AraC. Together, this study demonstrates that essential mitochondrial functions contribute to AraC resistance in AML and are a robust hallmark of AraC sensitivity and a promising therapeutic avenue to treat AML residual disease.
AraC-resistant AML cells exhibit metabolic features and gene signatures consistent with a high OXPHOS status. In these cells, targeting mitochondrial metabolism through the CD36-FAO-OXPHOS axis induces an energetic shift toward low OXPHOS and strongly enhanced antileukemic effects of AraC, offering a promising avenue to design new therapeutic strategies and fight AraC resistance in AML.
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Mutations in IDH induce epigenetic and transcriptional reprogramming, differentiation bias, and susceptibility to mitochondrial inhibitors in cancer cells. Here, we first show that cell lines, PDXs, ...and patients with acute myeloid leukemia (AML) harboring an IDH mutation displayed an enhanced mitochondrial oxidative metabolism. Along with an increase in TCA cycle intermediates, this AML-specific metabolic behavior mechanistically occurred through the increase in electron transport chain complex I activity, mitochondrial respiration, and methylation-driven CEBPα-induced fatty acid β-oxidation of IDH1 mutant cells. While IDH1 mutant inhibitor reduced 2-HG oncometabolite and CEBPα methylation, it failed to reverse FAO and OxPHOS. These mitochondrial activities were maintained through the inhibition of Akt and enhanced activation of peroxisome proliferator-activated receptor-γ coactivator-1 PGC1α upon IDH1 mutant inhibitor. Accordingly, OxPHOS inhibitors improved anti-AML efficacy of IDH mutant inhibitors in vivo. This work provides a scientific rationale for combinatory mitochondrial-targeted therapies to treat IDH mutant AML patients, especially those unresponsive to or relapsing from IDH mutant inhibitors.
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