Targeting chemoresistant malignant cells is one of the current major challenges in oncology. Therefore, it is mandatory to refine the characteristics of these cells to monitor their survival and ...develop adapted therapies. This is of particular interest in acute myeloid leukemia (AML), for which the 5-year survival rate only reaches 30%, regardless of the prognosis. The role of the microenvironment is increasingly reported to be a key regulator for blast survival. In this context, we demonstrate that contact with mesenchymal stromal cells promotes a better survival of blasts in culture in the presence of anthracycline through the activation of ABC transporters. Stroma-dependent ABC transporter activation leads to the induction of a Side Population (SP) phenotype in a subpopulation of primary leukemia blasts through alpha (α)4 engagement. The stroma-promoting effect is reversible and is observed with stromal cells isolated from either healthy donors or leukemia patients. Blasts expressing an SP phenotype are mostly quiescent and are chemoresistant
and
in patient-derived xenograft mouse models. At the transcriptomic level, blasts from the SP are specifically enriched in the drug metabolism program. This detoxification signature engaged in contact with mesenchymal stromal cells represents promising ways to target stroma-induced chemoresistance of AML cells.
Following a brief look at the structure and occurrence of glycosidic flavour precursors in plants and fruits, attention is given to mechanisms of enzymatic hydrolysis, the properties of relevant ...glycosidases, as well as endogenous and exogenous glycosidases affecting flavour release in plants, in fruit juice processing and in winemaking. The constraints for technological applications and future prospects are discussed.
The nucleoside analog cytarabine, an inhibitor of DNA replication fork progression that results in DNA damage, is currently used in the treatment of acute myeloid leukemia (AML). We explored the ...prognostic value of the expression of 72 genes involved in various aspects of DNA replication in a set of 198 AML patients treated by cytarabine-based chemotherapy. We unveiled that high expression of the DNA replication checkpoint gene CHEK1 is a prognostic marker associated with shorter overall, event-free, and relapse-free survivals and determined that the expression of CHEK1 can predict more frequent and earlier postremission relapse. CHEK1 encodes checkpoint kinase 1 (CHK1), which is activated by the kinase ATR when DNA replication is impaired by DNA damage. High abundance of CHK1 in AML patient cells correlated with higher clonogenic ability and more efficient DNA replication fork progression upon cytarabine treatment. Exposing the patient cells with the high abundance of CHK1 to SCH900776, an inhibitor of the kinase activity of CHK1, reduced clonogenic ability and progression of DNA replication in the presence of cytarabine. These results indicated that some AML cells rely on an efficient CHK1-mediated replication stress response for viability and that therapeutic strategies that inhibit CHK1 could extend current cytarabine-based treatments and overcome drug resistance. Furthermore, monitoring CHEK1 expression could be used both as a predictor of outcome and as a marker to select AML patients for CHK1 inhibitor treatments.
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.
Resistance to chemotherapeutic drugs is a major cause of treatment failure in Acute Myeloid Leukemias (AML). To better characterize the mechanisms of chemoresistance, we first identified genes whose ...expression is dysregulated in AML cells resistant to daunorubicin (DNR) or cytarabine (Ara-C), the main drugs used for the induction therapy. The genes found activated are mostly linked to immune signaling and inflammation. Among them, we identified a strong up-regulation of the NOX2 NAPDH oxidase subunit genes (CYBB, CYBA, NCF1, NCF2, NCF4 and RAC2). The ensuing increase in NADPH oxidase expression and ROS production, which is particularly strong in DNR-resistant cells, participates in the acquisition and/or maintenance of resistance to DNR. Gp91phox (CYBB-encoded Nox2 catalytic sub-unit), was found more expressed and active in leukemic cells from the FAB M4/M5 subtypes patients compared to FAB M0-M2 ones. Moreover, its expression was increased at the surface of patient's chemotherapy resistant AML cells. Using a gene expression-based score we finally demonstrate that high NOX2 subunit genes expression is a marker of adverse prognosis in AML patients. The prognosis NOX score we defined is independent of the cytogenetic-based risk classification, FAB subtype, FLT3/NPM1 mutational status and age.
To get more insight into plant cell response to cadmium (Cd) stress, both proteomic and metabolomic “differential display” analyses were performed on Arabidopsis thaliana cells exposed to different ...concentrations of the toxic chemical. After a 24 h treatment, soluble proteins extracted from untreated and treated cells were separated by 2‐D‐PAGE and image analyses were performed to quantify and compare protein levels. Proteins up‐ and down‐regulated in response to Cd were identified by MS and mapped into specific metabolic pathways and cellular processes, highlighting probable activation of the carbon, nitrogen, and sulfur metabolic pathways. For some of these proteins, Northern blot and RT‐PCR analyses were performed to test transcript accumulation in response to Cd. In parallel, metabolite profiling analyses by LC coupled to ESI MS were initiated to better characterize the metabolic adaptation to the chemical stress. This study revealed that the main variation at the metabolite level came from the presence of six different families of phytochelatins, in A. thaliana cells treated with Cd, whose accumulation increases with Cd concentrations. Taken together these data provide an overview of the molecular and cellular changes elicited by Cd exposure.
Abstract
Classifications of acute myeloid leukemia (AML) patients rely on morphologic, cytogenetic, and molecular features. Here we have established a novel flow cytometry-based immunophenotypic ...stratification showing that AML blasts are blocked at specific stages of differentiation where features of normal myelopoiesis are preserved. Six stages of leukemia differentiation-arrest categories based on CD34, CD117, CD13, CD33, MPO, and HLA-DR expression were identified in two independent cohorts of 2087 and 1209 AML patients. Hematopoietic stem cell/multipotent progenitor-like AMLs display low proliferation rate, inv(3) or
RUNX1
mutations, and high leukemic stem cell frequency as well as poor outcome, whereas granulocyte–monocyte progenitor-like AMLs have
CEBPA
mutations,
RUNX1-RUNX1T1
or
CBFB-MYH11
translocations, lower leukemic stem cell frequency, higher chemosensitivity, and better outcome.
NPM1
mutations correlate with most mature stages of leukemia arrest together with
TET2
or
IDH
mutations in granulocyte progenitors-like AML or with
DNMT3A
mutations in monocyte progenitors-like AML. Overall, we demonstrate that AML is arrested at specific stages of myeloid differentiation (SLA classification) that significantly correlate with AML genetic lesions, clinical presentation, stem cell properties, chemosensitivity, response to therapy, and outcome.
Human leukemic stem cells, like other cancer stem cells, are hypothesized to be rare, capable of incomplete differentiation, and restricted to a phenotype associated with early hematopoietic ...progenitors or stem cells. However, recent work in other types of tumors has challenged the cancer stem cell model. Using a robust model of xenotransplantation based on NOD/SCID/IL2Rγc-deficient mice, we confirmed that human leukemic stem cells, functionally defined by us as SCID leukemia-initiating cells (SL-ICs), are rare in acute myelogenous leukemia (AML). In contrast to previous results, SL-ICs were found among cells expressing lineage markers (i.e., among Lin+ cells), CD38, or CD45RA, all markers associated with normal committed progenitors. Remarkably, each engrafting fraction consistently recapitulated the original phenotypic diversity of the primary AML specimen and contained self-renewing leukemic stem cells, as demonstrated by secondary transplants. While SL-ICs were enriched in the Lin-CD38- fraction compared with the other fractions analyzed, SL-ICs in this fraction represented only one-third of all SL-ICs present in the unfractionated specimen. These results indicate that human AML stem cells are rare and enriched but not restricted to the phenotype associated with normal primitive hematopoietic cells. These results suggest a plasticity of the cancer stem cell phenotype that we believe has not been previously described.
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.
Chemotherapeutic drugs used in the treatment of acute myeloid leukemias (AMLs) are thought to induce cancer cell death through the generation of DNA double-strand breaks. Here, we report that one of ...their early effects is the loss of conjugation of the ubiquitin-like protein SUMO from its targets via reactive oxygen species (ROS)-dependent inhibition of the SUMO-conjugating enzymes. Desumoylation regulates the expression of specific genes, such as the proapoptotic gene DDIT3, and helps induce apoptosis in chemosensitive AMLs. In contrast, chemotherapeutics do not activate the ROS/SUMO axis in chemoresistant cells. However, pro-oxidants or inhibition of the SUMO pathway by anacardic acid restores DDIT3 expression and apoptosis in chemoresistant cell lines and patient samples, including leukemic stem cells. Finally, inhibition of the SUMO pathway decreases tumor growth in mice xenografted with AML cells. Thus, targeting the ROS/SUMO axis might constitute a therapeutic strategy for AML patients resistant to conventional chemotherapies.
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•Chemotherapeutic drugs induce ROS-dependent desumoylation in chemosensitive AML cells•Desumoylation regulates specific transcriptional programs and participates in apoptosis•The ROS/SUMO axis is not induced in chemoresistant AML cells•Inhibition of the SUMO pathway with anacardic acid can overcome chemoresistance
In this study, Bossis et al. show that treatment of acute myeloid leukemia cells with chemotherapeutic drugs induces a ROS-dependent loss of SUMO conjugation, which is involved in the activation of specific transcriptional programs and apoptosis. In addition, chemoresistance is associated with impaired activation of this ROS/SUMO axis. However, its targeting restores the death of chemoresistant AML cells and might thus be a way to overcome chemoresistance in patients
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