Mitochondria inside acute myeloid leukemia cells hydrolyze ATP to resist chemotherapy.

Despite early optimism, therapeutics targeting oxidative phosphorylation (OxPhos) have faced clinical setbacks, stemming from their inability to distinguish healthy from cancerous mitochondria. Herein, we describe an actionable bioenergetic mechanism unique to cancerous mitochondria inside acute myeloid leukemia (AML) cells. Unlike healthy cells which couple respiration to the synthesis of ATP, AML mitochondria were discovered to support inner membrane polarization by consuming ATP. Because matrix ATP consumption allows cells to survive bioenergetic stress, we hypothesized that AML cells may resist cell death induced by OxPhos damaging chemotherapy by reversing the ATP synthase reaction. In support of this, targeted inhibition of BCL-2 with venetoclax abolished OxPhos flux without impacting mitochondrial membrane potential. In surviving AML cells, sustained polarization of the mitochondrial inner membrane was dependent on matrix ATP consumption. Mitochondrial ATP consumption was further enhanced in AML cells made refractory to venetoclax, consequential to downregulations in both the proton-pumping respiratory complexes, as well as the endogenous F 1 -ATPase inhibitor ATP5IF1 . In treatment-naive AML, ATP5IF1 knockdown was sufficient to drive venetoclax resistance, while ATP5IF1 overexpression impaired F 1 -ATPase activity and heightened sensitivity to venetoclax. Collectively, our data identify matrix ATP consumption as a cancer-cell intrinsic bioenergetic vulnerability actionable in the context of mitochondrial damaging chemotherapy.

Outcomes and adverse events in older acute lymphoblastic Leukemia patients treated with a pediatric-inspired protocol with Pegylated or native Asparaginase.

This retrospective report presents the outcomes and adverse events (AEs) observed in 73 patients aged 60 years or older diagnosed with Philadelphia Chromosome-negative Acute Lymphoblastic Leukemia (Ph-negative ALL) treated with a pediatric-inspired protocol incorporating either Pegylated (PEG-ASP) or Native Asparaginase (EC-ASP). Notably, 61% of patients experienced AEs of Grade III-IV severity. The most prevalent AEs included thrombosis (35.6%), febrile neutropenia (38.4%), and transaminitis (34.2%). AEs did not translate into significant differences concerning overall survival, leukemia-free survival, or early mortality. Furthermore, we observed a reduction in early mortality rates (11% vs. 20%) and an increase in median overall survival (54 vs. 48 months) compared to our previous data. These findings suggest that the utilization of a pediatric-inspired chemotherapy protocol, with ASP, is an effective and well-tolerated therapeutic option for older patients with Ph-negative ALL. However, it emphasizes the importance of diligent monitoring and close follow-up throughout treatment.

The proteomic landscape of genotoxic stress-induced micronuclei.

Micronuclei (MN) are induced by various genotoxic stressors and amass nuclear- and cytoplasmic-resident proteins, priming the cell for MN-driven signaling cascades. Here, we measured the proteome of micronuclear, cytoplasmic, and nuclear fractions from human cells exposed to a panel of six genotoxins, comprehensively profiling their MN protein landscape. We find that MN assemble a proteome distinct from both surrounding cytoplasm and parental nuclei, depleted of spliceosome and DNA damage repair components while enriched for a subset of the replisome. We show that the depletion of splicing machinery within transcriptionally active MN contributes to intra-MN DNA damage, a known precursor to chromothripsis. The presence of transcription machinery in MN is stress-dependent, causing a contextual induction of MN DNA damage through spliceosome deficiency. This dataset represents a unique resource detailing the global proteome of MN, guiding mechanistic studies of MN generation and MN-associated outcomes of genotoxic stress.

Metformin reduces the clonal fitness of Dnmt3aR878H hematopoietic stem and progenitor cells by reversing their aberrant metabolic and epigenetic state.

Clonal hematopoiesis (CH) arises when a hematopoietic stem cell (HSC) acquires a mutation that confers a competitive advantage over wild-type (WT) HSCs, resulting in its clonal expansion. Individuals with CH are at an increased risk of developing hematologic neoplasms and a range of age-related inflammatory illnesses1-3. Therapeutic interventions that suppress the expansion of mutant HSCs have the potential to prevent these CH-related illnesses; however, such interventions have not yet been identified. The most common CH driver mutations are in the DNA methyltransferase 3 alpha (DNMT3A) gene with arginine 882 (R882) being a mutation hotspot. Here we show that murine hematopoietic stem and progenitor cells (HSPCs) carrying the Dnmt3aR878H/+ mutation, which is equivalent to human DNMT3AR882H/+, have increased mitochondrial respiration compared with WT cells and are dependent on this metabolic reprogramming for their competitive advantage. Importantly, treatment with metformin, an oral anti-diabetic drug with inhibitory activity against complex I in the electron transport chain (ETC), reduced the fitness of Dnmt3aR878H/+ HSCs. Through a multi-omics approach, we discovered that metformin acts by enhancing the methylation potential in Dnmt3aR878H/+ HSPCs and reversing their aberrant DNA CpG methylation and histone H3K27 trimethylation (H3K27me3) profiles. Metformin also reduced the fitness of human DNMT3AR882H HSPCs generated by prime editing. Our findings provide preclinical rationale for investigating metformin as a preventive intervention against illnesses associated with DNMT3AR882 mutation-driven CH in humans.

Venetoclax resistance in acute myeloid leukaemia-Clinical and biological insights.

Venetoclax, an oral BCL-2 inhibitor, has been widely incorporated in the treatment of acute myeloid leukaemia. The combination of hypomethylating agents and venetoclax is the current standard of care for elderly and patient's ineligible for aggressive therapies. However, venetoclax is being increasingly used with aggressive chemotherapy regimens both in the front line and in the relapse setting. Our growing experience and intensive research demonstrate that certain genetic abnormalities are associated with venetoclax sensitivity, while others with resistance, and that resistance can emerge during treatment leading to disease relapse. In the current review, we provide a summary of the known mechanisms of venetoclax cytotoxicity, both regarding the inhibition of BCL-2-mediated apoptosis and its effect on cell metabolism. We describe how these pathways are linked to venetoclax resistance and are associated with specific mutations. Finally, we provide the rationale for novel drug combinations in current and future clinical trials.

The Imipridone ONC213 Targets α-Ketoglutarate Dehydrogenase to Induce Mitochondrial Stress and Suppress Oxidative Phosphorylation in Acute Myeloid Leukemia.

Eradication of acute myeloid leukemia (AML) is therapeutically challenging; many patients succumb to AML despite initially responding to conventional treatments. Here, we showed that the imipridone ONC213 elicits potent antileukemia activity in a subset of AML cell lines and primary patient samples, particularly in leukemia stem cells, while producing negligible toxicity in normal hematopoietic cells. ONC213 suppressed mitochondrial respiration and elevated α-ketoglutarate by suppressing α-ketoglutarate dehydrogenase (αKGDH) activity. Deletion of OGDH, which encodes αKGDH, suppressed AML fitness and impaired oxidative phosphorylation, highlighting the key role for αKGDH inhibition in ONC213-induced death. ONC213 treatment induced a unique mitochondrial stress response and suppressed de novo protein synthesis in AML cells. Additionally, ONC213 reduced the translation of MCL1, which contributed to ONC213-induced apoptosis. Importantly, a patient-derived xenograft from a relapsed AML patient was sensitive to ONC213 in vivo. Collectively, these findings support further development of ONC213 for treating AML. SIGNIFICANCE: In AML cells, ONC213 suppresses αKGDH, which induces a unique mitochondrial stress response, and reduces MCL1 to decrease oxidative phosphorylation and elicit potent antileukemia activity. See related commentary by Boët and Sarry, p. 950.

Outcomes of intensive and nonintensive blast-reduction strategies in accelerated and blast-phase MPN.

ABSTRACT: Transformation of BCR::ABL1-negative myeloproliferative neoplasms (MPN) to an accelerated or blast phase is associated with poor outcomes. The efficacy of acute myeloid leukemia (AML)-type intensive and nonintensive hypomethylating agent-based regimens is not well studied. We therefore performed a retrospective analysis of patients with MPN-AP/BP (N = 138) treated with intensive (N = 81) and nonintensive (N = 57) blast-reduction strategies. We used clinically relatable response criteria developed at the Princess Margaret Cancer Centre. The overall best response, comprising complete remission (CR), complete remission with incomplete hematologic recovery (CRi), and reversion to chronic phase MPN (cMPN), in the intensive and nonintensive groups was 77% (62 of 81) and 39% (21 of 54), respectively. Similar overall best response rates were observed in patients receiving induction with daunorubicin combined with cytarabine arabinoside (daunorubicin + ara-C) (74% [23 of 31]) or FLAG-IDA/NOVE-HiDAC (78% [39 of 50], P = .78). However, patients receiving daunorubicin + ara-C more often required second inductions (29% [9 of 31] vs 4% [2 of 50], P = .002). Most responses in the entire cohort were reversions to cMPN (55 of 83 [66%]). CR and CRi comprised 30% (25 of 83) and 4% (3 of 83) of responses, respectively. Mutations in TP53 (overall response [OR] 8.2 [95% confidence interval [CI] 2.01, 37.1], P = .004) and RAS pathway (OR 5.1 [95%CI 1.2, 23.7], P = .03) were associated with inferior treatment response for intensively treated patients, and poorer performance status (Eastern Cooperative Oncology Group) was associated with inferior treatment response in both intensively (OR 10.4 [95% CI 2.0, 78.5], P = .009) and nonintensively treated groups (OR 12 [95% CI 2.04, 230.3], P = .02). In patients with paired samples before and after therapy (N = 26), there was a significant residual mutation burden remaining irrespective of response to blast-reduction therapy.

Mitochondrial regulation of GPX4 inhibition-mediated ferroptosis in acute myeloid leukemia.

Resistance to apoptosis in acute myeloid leukemia (AML) cells causes refractory or relapsed disease, associated with dismal clinical outcomes. Ferroptosis, a mode of non-apoptotic cell death triggered by iron-dependent lipid peroxidation, has been investigated as potential therapeutic modality against therapy-resistant cancers, but our knowledge of its role in AML is limited. We investigated ferroptosis in AML cells and identified its mitochondrial regulation as a therapeutic vulnerability. GPX4 knockdown induced ferroptosis in AML cells, accompanied with characteristic mitochondrial lipid peroxidation, exerting anti-AML effects in vitro and in vivo. Electron transport chains (ETC) are primary sources of coenzyme Q10 (CoQ) recycling for its function of anti-lipid peroxidation in mitochondria. We found that the mitochondria-specific CoQ potently inhibited GPX4 inhibition-mediated ferroptosis, suggesting that mitochondrial lipid redox regulates ferroptosis in AML cells. Consistently, Rho0 cells, which lack functional ETC, were more sensitive to GPX4 inhibition-mediated mitochondrial lipid peroxidation and ferroptosis than control cells. Furthermore, degradation of ETC through hyperactivation of a mitochondrial protease, caseinolytic protease P (ClpP), synergistically enhanced the anti-AML effects of GPX4 inhibition. Collectively, our findings indicate that in AML cells, GPX4 inhibition induces ferroptosis, which is regulated by mitochondrial lipid redox and ETC.

Preclinical characterization and clinical trial of CFI-400945, a polo-like kinase 4 inhibitor, in patients with relapsed/refractory acute myeloid leukemia and higher-risk myelodysplastic neoplasms.

CFI-400945 is a selective oral polo-like kinase 4 (PLK4) inhibitor that regulates centriole duplication. PLK4 is aberrantly expressed in patients with acute myeloid leukemia (AML). Preclinical studies indicate that CFI-400945 has potent in vivo efficacy in hematological malignancies and xenograft models, with activity in cells harboring TP53 mutations. In this phase 1 study in very high-risk patients with relapsed/refractory AML and myelodysplastic syndrome (MDS) (NCT03187288), 13 patients were treated with CFI-400945 continuously in dose escalation from 64 mg/day to 128 mg/day. Three of the 9 efficacy evaluable AML patients achieved complete remission (CR). Two of 4 AML patients (50%) with TP53 mutations and complex monosomal karyotype achieved a CR with 1 patient proceeding to allogenic stem cell transplant. A third patient with TP53 mutated AML had a significant reduction in marrow blasts by > 50% with an improvement in neutrophil and platelet counts. Responses were observed after 1 cycle of therapy. Dose-limiting toxicity was enteritis/colitis. A monotherapy and combination therapy study with a newer crystal form of CFI-400945 in patients with AML, MDS and chronic myelomonocytic leukemia (CMML) is ongoing (NCT04730258).

Extended exposure to low doses of azacitidine induces differentiation of leukemic stem cells through activation of myeloperoxidase.

Oral azacitidine (Oral-Aza; CC-486) treatment results in longer median overall survival (OS) (24.7 vs 14.8 months in placebo) in patients with acute myeloid leukemia (AML) in remission after intensive chemotherapy. The dosing schedule of Oral-Aza (14 days/28-day cycle) allows for low exposure of azacitidine for an extended duration thereby facilitating a sustained therapeutic effect. However, the underlying mechanisms supporting the clinical impact of Oral-Aza in maintenance therapy remain to be fully understood. In this preclinical work, we explore the mechanistic basis of Oral-Aza/extended exposure to azacitidine through in vitro and in vivo modeling. In cell lines, extended exposure to azacitidine results in sustained DNMT1 loss, leading to durable hypomethylation, and gene expression changes. In mouse models, extended exposure to azacitidine, preferentially targets immature leukemic cells. In leukemic stem cell (LSC) models, the extended dose of azacitidine induces differentiation and depletes CD34+CD38- LSCs. Mechanistically, LSC differentiation is driven in part by increased myeloperoxidase (MPO) expression. Inhibition of MPO activity either by using an MPO specific inhibitor or blocking oxidative stress, a known mechanism of MPO, partly reverses the differentiation of LSCs. Overall, our pre-clinical work reveals novel mechanistic insights into oral-Aza and its ability to target leukemic stem cells.

Total Synthesis of the 2,5-Disubstituted γ-Pyrone E1 UAE Inhibitor Himeic Acid A.

The first total synthesis of the E1 ubiquitin-activating enzyme inhibitor, himeic acid A, is reported. A McCombie reaction was used to form the core γ-pyrone via a 6π-electrocyclization. A dioxenone ring-opening/acyl ketene trapping reaction with a primary amide provided the unusual unsymmetrical imide functionality. Other key steps include the use of an Evans auxiliary alkylation (d.r. ≥ 95:5) to install the (S)-2-methyl succinic acid fragment and a cross-metathesis to install the unsaturated side-chain.

Venous thromboembolism incidence associated with pegylated asparaginase (ASP) compared to the native L-ASP: A retrospective analysis with an ASP-based protocol in adult patients with acute lymphoblastic leukaemia.

Venous thromboembolism (VTE) is a well-known complication in patients with acute lymphoblastic leukaemia (ALL) receiving asparaginase (ASP)-based chemotherapy, including the ASP-intensive Dana-Farber Cancer Institute (DFCI) 91-01 protocol for adults. Since 2019, native L-ASP is no longer available in Canada and was replaced by pegylated (PEG)-ASP. To determine whether the incidence of VTE has changed since switching from L-ASP to PEG-ASP, we conducted a single-centred retrospective cohort study. We included 245 adult patients with Philadelphia chromosome negative ALL between 2011 and 2021, with 175 from the L-ASP group (2011-2019) and 70 from the PEG-ASP group (2018-2021). During Induction, 10.29% (18/175) of patients who received L-ASP developed VTE, whereas 28.57% (20/70) of patients who received PEG-ASP developed VTE (p = 0.0035; odds ratio [OR] 3.35, 95% confidence interval [CI] 1.51-7.39), after adjusting for line type, gender, history of VTE, platelets at diagnosis. Similarly, during Intensification, 13.64% (18/132) of patients had VTE on L-ASP while 34.37% (11/32) of patients on PEG-ASP developed VTE (p = 0.0096; OR 3.96, 95% CI 1.57-9.96 with multivariable analysis). We found that PEG-ASP is associated with a higher incidence of VTE compared to L-ASP, both during Induction and Intensification, despite the administration of prophylactic anticoagulation. Further VTE mitigation strategies are needed in particular for adult patients with ALL receiving PEG-ASP.

Safety of re-challenging adults with acute lymphoblastic leukemia with PEG-asparaginase-induced severe hypertriglyceridemia when treated with a pediatric-inspired regimen.

PEG-asparaginase is used as a treatment for Philadelphia-negative acute lymphoblastic leukemia. In pediatric studies, triglycerides (TGs) were affected more by PEG-asparaginase than by native L-asparaginase (10.0% vs. 5.5%). We conducted a retrospective study to determine the safety of re-challenging adult patients with PEG-asparaginase after experiencing an episode of severe hypertriglyceridemia (>1000 mg/dl or 11.4 mmol/L). The incidence of hypertriglyceridemia associated with PEG-asparaginase in adult patients was high (67.5%). Therefore, checking TGs at baseline and monitoring levels while receiving PEG-asparaginase need to be considered and studied in prospective studies. However, in patients with hypertriglyceridemia not complicated by acute pancreatitis, re-challenging is safe once TG levels normalize.

Contribution of metabolic abnormalities to acute myeloid leukemia pathogenesis.

Acute myeloid leukemia (AML) is a malignant disease of myeloid precursors. Somatic mutations have long been accepted as drivers of this malignancy. Over the past decade, unique mitochondrial and metabolic dependencies of AML and AML stem cells have been identified, including a reliance on oxidative phosphorylation. More recently, metabolic enzymes have demonstrated noncanonical roles in regulating gene expression in AML, controlling cell differentiation and stemness. These mitochondrial and metabolic adaptations occur independent of underlying genomic abnormalities and contribute to chemoresistance and relapse. In this opinion article, we discuss the current understanding of AML pathogenesis and whether mitochondrial and metabolic abnormalities drive leukemogenesis or are a non-contributory phenotype.

Applying CRISPR-Cas9 screens to dissect hematological malignancies.

Bit by bit, over the last few decades, functional genomic tools have been piecing together the molecular puzzle driving tumorigenesis in human patients. Nevertheless, our understanding of the role of several genes and regulatory elements that drive critical cancer-associated physiological processes from disease development to progression to spread is very limited, which significantly affects our ability of applying these insights in the context of improved disease management. The recent advent of clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9)-based technology and its application in cancer genomics has, however, allowed the generation of a wealth of knowledge that has helped decipher several critical questions associated with translational cancer research. Precisely, the high-throughput capability coupled with a high level of technological plasticity associated with the CRISPR-Cas9 screens have expanded our horizons from a mere struggle to appreciate cancer as a genetic disease to observing the integrated genomic/epigenomic network of numerous malignancies and correlating it with our present knowledge of drugging strategies to develop innovative approaches for next-generation precision cancer medicine. Specifically, within blood cancers, current CRISPR screens have specifically focused on improving our understanding of drug resistance mechanisms, disease biology, the development of novel therapeutic approaches, and identifying the molecular mechanisms of current therapies, with an underlying aim of improving disease outcomes. Here, we review the development of the CRISPR-Cas9 genome-editing strategy, explicitly focusing on the recent advances in the CRISPR-Cas9-based screening approaches, its current capabilities, limitations, and future applications in the context of hematological malignancies.

Traumatic stress symptoms in family caregivers of patients with acute leukaemia: protocol for a multisite mixed methods, longitudinal, observational study.

INTRODUCTION: The diagnosis, progression or recurrence of cancer is often highly traumatic for family caregivers (FCs), but systematic assessments of distress and approaches for its prevention and treatment are lacking. Acute leukaemia (AL) is a life-threatening cancer of the blood, which most often presents acutely, requires intensive treatment and is associated with severe physical symptoms. Consequently, traumatic stress may be common in the FCs of patients with AL. We aim to determine the prevalence, severity, longitudinal course and predictors of traumatic stress symptoms in FCs of patients with AL in the first year after diagnosis, and to understand their lived experience of traumatic stress and perceived support needs. METHODS AND ANALYSIS: This two-site longitudinal, observational, mixed methods study will recruit 223 adult FCs of paediatric or adult patients newly diagnosed with AL from two tertiary care centres. Quantitative data will be collected from self-report questionnaires at enrolment, and 1, 3, 6, 9 and 12 months after admission to hospital for initial treatment. Quantitative data will be analysed using descriptive and machine learning approaches and a multilevel modelling (MLM) approach will be used to confirm machine learning findings. Semi-structured qualitative interviews will be conducted at 3, 6 and 12 months and analysed using a grounded theory approach. ETHICS AND DISSEMINATION: This study is funded by the Canadian Institutes of Health Research (CIHR number PJT 173255) and has received ethical approval from the Ontario Cancer Research Ethics Board (CTO Project ID: 2104). The data generated have the potential to inform the development of targeted psychosocial interventions for traumatic stress, which is a public health priority for high-risk populations such as FCs of patients with haematological malignancies. An integrated and end-of-study knowledge translation strategy that involves FCs and other stakeholders will be used to interpret and disseminate study results.