bims-tremyl Biomed News
on Therapy resistance biology in myeloid leukemia
Issue of 2024–07–28
25 papers selected by
Paolo Gallipoli, Barts Cancer Institute, Queen Mary University of London



  1. Leukemia. 2024 Jul 20.
      Mutations in the cohesin complex components (STAG2, RAD21, SMC1A, SMC3, and PDS5B) are recurrent genetic drivers in myelodysplastic neoplasm (MDS) and acute myeloid leukemia (AML). Whether the different cohesin subunit mutations share clinical characteristics and prognostic significance is not known. We analyzed 790 cohesin-mutant patients from the Dana-Farber Cancer Institute (DFCI) and the Munich Leukemia Laboratory (MLL), 390 of which had available outcome data, and identified subunit-specific clinical, prognostic, and genetic characteristics suggestive of distinct ontogenies. We found that STAG2 mutations are acquired at MDS stage and are associated with secondary AML, adverse prognosis, and co-occurrence of secondary AML-type mutations. In contrast, mutations in RAD21, SMC1A and SMC3 share features with de novo AML with better prognosis, and co-occurrence with de novo AML-type lesions. The findings show the heterogeneous nature of cohesin complex mutations, and inform clinical and prognostic classification, as well as distinct biology of the cohesin complex.
    DOI:  https://doi.org/10.1038/s41375-024-02347-y
  2. Lancet Haematol. 2024 Jul 19. pii: S2352-3026(24)00203-5. [Epub ahead of print]
       BACKGROUND: The preplanned interim analysis of the COMMANDS trial showed greater efficacy of luspatercept than epoetin alfa for treating anaemia in erythropoiesis-stimulating agent (ESA)-naive patients with transfusion-dependent, lower-risk myelodysplastic syndromes. In this Article, we report the results of the primary analysis of the trial.
    METHODS: COMMANDS is a phase 3, open-label, randomised, controlled trial conducted at 142 sites in 26 countries. Eligible patients were those aged 18 years or older, with myelodysplastic syndromes of very low risk, low risk, or intermediate risk (as defined by the Revised International Prognostic Scoring System), who were ESA-naive and transfusion dependent, and had a serum erythropoietin concentration of less than 500 U/L. Patients were stratified by baseline red blood cell transfusion burden, serum erythropoietin concentration, and ring sideroblast status, and randomly allocated (1:1) to receive luspatercept (1·0-1·75 mg/kg body weight, subcutaneously, once every 3 weeks) or epoetin alfa (450-1050 IU/kg body weight, subcutaneously, once a week; maximum total dose 80 000 IU) for at least 24 weeks. The primary endpoint was red blood cell transfusion independence lasting at least 12 weeks with a concurrent mean haemoglobin increase of at least 1·5 g/dL (weeks 1-24), evaluated in the intention-to-treat population. The safety population included all patients who received at least one dose of treatment. This trial is registered with ClinicalTrials.gov (NCT03682536; active, not recruiting).
    FINDINGS: Between Jan 2, 2019, and Sept 29, 2022, 363 patients were screened and randomly allocated: 182 (50%) to luspatercept and 181 (50%) to epoetin alfa. Median age was 74 years (IQR 69-80), 162 (45%) patients were female, and 201 (55%) were male. 289 (80%) were White, 44 (12%) were Asian, and two (1%) were Black or African American. 23 (6%) were Hispanic or Latino and 311 (86%) were not Hispanic or Latino. Median follow-up for the primary endpoint was 17·2 months (10·4-27·7) for the luspatercept group and 16·9 months (10·1-26·6) for the epoetin alfa group. A significantly greater proportion of patients in the luspatercept group reached the primary endpoint (110 [60%] vs 63 [35%]; common risk difference on response rate 25·4% [95% CI 15·8-35·0]; p<0·0001). Median follow-up for safety analyses was 21·4 months (IQR 14·2-32·4) for the luspatercept group and 20·3 months (12·7-30·9) for the epoetin alfa group. Common grade 3-4 treatment-emergent adverse events occurring among luspatercept recipients (n=182) were hypertension (19 [10%] patients), anaemia (18 [10%]), pneumonia (ten [5%]), syncope (ten [5%]), neutropenia (nine [5%]), thrombocytopenia (eight [4%]), dyspnoea (eight [4%]), and myelodysplastic syndromes (six [3%]); and among epoetin alfa recipients (n=179) were anaemia (14 [8%]), pneumonia (14 [8%]), neutropenia (11 [6%]), myelodysplastic syndromes (ten [6%]), hypertension (eight [4%]), iron overload (seven [4%]), and COVID-19 pneumonia (six [3%]). The most common serious treatment-emergent adverse events in both groups were pneumonia (nine [5%] luspatercept recipients and 13 [7%] epoetin alfa recipients) and COVID-19 (eight [4%] luspatercept recipients and ten [6%] epoetin alfa recipients). One death (due to acute myeloid leukaemia) considered to be luspatercept-related was reported at the interim analysis.
    INTERPRETATION: Luspatercept represents a new standard of care for ESA-naive patients with transfusion-dependent, lower-risk myelodysplastic syndromes. Significantly more patients had red blood cell transfusion independence and haematological improvement with luspatercept than with epoetin alfa, with benefits observed across patient subgroups.
    FUNDING: Celgene and Acceleron Pharma.
    DOI:  https://doi.org/10.1016/S2352-3026(24)00203-5
  3. Ann Hematol. 2024 Jul 20.
      Therapy-related myeloid neoplasms (t-MN) are characterized by aggressive features and a dismal prognosis. Recent evidence suggests a higher incidence of t-MN in individuals harboring clonal hematopoiesis of indeterminate potential (CHIP). In order to gain insight into CHIP-driven malignant progression, we gathered data from ten published reports with available detailed patient characteristics at the time of primary malignancy and t-MN development. Detailed clinical and molecular information on primary malignancy and t-MN were available for 109 patients: 43% harbored at least one somatic mutation at the time of the primary malignancy. TET2 and TP53 mutations showed an increasing variant allele frequency from CHIP to t-MN. ASXL1-associated CHIP significantly correlated with the emergence of TET2 and CEBPA mutations at t-MN, as well as U2AF1-driven CHIP with EZH2 mutation and both IDH2 and SRSF2-driven CHIP with FLT3 mutation. DNMT3A-driven CHIP correlated with a lower incidence of TP53 mutation at t-MN. In contrast, TP53-driven CHIP correlated with a complex karyotype and a lower tendency to acquire new mutations at t-MN. Patients with multiple myeloma as their first malignancy presented a significantly higher rate of TP53 mutations at t-MN. The progression from CHIP to t-MN shows different scenarios depending on the genes involved. A deeper knowledge of CHIP progression mechanisms will allow a more reliable definition of t-MN risk.
    Keywords:  Clonal Hematopoiesis of Indeterminate Potential; Myeloid neoplasms post cytotoxic therapy; TP53; Therapy-related Myeloid Neoplasms
    DOI:  https://doi.org/10.1007/s00277-024-05803-y
  4. Sci Transl Med. 2024 Jul 24. 16(757): eadk1731
      Acute myeloid leukemia (AML) remains a challenging hematological malignancy with poor prognosis and limited treatment options. Leukemic stem cells (LSCs) contribute to therapeutic failure, relapse, and adverse outcome. This study investigates the role of quiescence and related molecular mechanisms in AML pathogenesis and LSC functions to identify potential therapeutic targets. Transcriptomic analysis revealed that the LSC-enriched quiescent cell population has a distinct gene signature with prognostic relevance in patients with AML. Mechanistically, quiescent blasts exhibit increased autophagic activity, which contributes to their sustained viability. Proteomic profiling uncovered differential requirements for iron metabolism between quiescent and cycling cells, revealing a unique dependence of quiescent cells on ferritinophagy, a selective form of autophagy mediated by nuclear receptor coactivator 4 (NCOA4), which regulates iron bioavailability. We evaluated the therapeutic potential of inhibiting NCOA4-mediated ferritinophagy using genetic knockdown and chemical inhibition approaches. In vitro assays showed that suppression of NCOA4 was toxic to leukemic blasts, particularly the CD34+CD38- LSC-enriched population, without affecting normal CD34+ hematopoietic progenitors. In vivo studies using murine patient-derived xenograft (PDX) models of AML confirmed that NCOA4 inhibition reduced tumor burden and impaired LSC viability and self-renewal, indicating a specific vulnerability of these cells to ferritinophagy disruption. Our findings underscore the role of NCOA4-mediated ferritinophagy in maintaining LSC quiescence and function and suggest that targeting this pathway may be an effective therapeutic strategy for AML. This study highlights the potential of NCOA4 inhibition to improve AML outcomes and paves the way for future research and clinical development.
    DOI:  https://doi.org/10.1126/scitranslmed.adk1731
  5. FEBS Lett. 2024 Jul 24.
      In the last few decades, the increasing human life expectancy has led to the inflation of the elderly population and consequently the escalation of age-related disorders. Biological aging has been associated with the accumulation of somatic mutations in the Hematopoietic Stem Cell (HSC) compartment, providing a fitness advantage to the HSCs leading to clonal hematopoiesis, that includes non-malignant and malignant conditions (i.e. Clonal Hematopoiesis of Indeterminate Potential, Myelodysplastic Syndrome and Acute Myeloid Leukemia). The Janus Kinase-Signal Transducer and Activator of Transcription (JAK-STAT) pathway is a key player in both normal and malignant hematopoiesis. STATs, particularly STAT3 and STAT5, are greatly implicated in normal hematopoiesis, immunity, inflammation, leukemia, and aging. Here, the pleiotropic functions of JAK-STAT pathway in age-associated hematopoietic defects and of STAT3 and STAT5 in normal hematopoiesis, leukemia, and inflammaging are reviewed. Even though great progress has been made in deciphering the role of STATs, further research is required to provide a deeper understanding of the molecular mechanisms of leukemogenesis, as well as novel biomarkers and therapeutic targets for improved management of age-related disorders.
    Keywords:  AML; MDS; STAT3; STAT5; aging; leukemia; myeloid malignancy; signal transducers and activators of transcription
    DOI:  https://doi.org/10.1002/1873-3468.14985
  6. Blood. 2024 Jul 24. pii: blood.2024024789. [Epub ahead of print]
      Our phase I graft-versus-host disease (GVHD) prevention trial of JAK2 inhibitor, pacritinib, (recommended phase II dose: 100mg po BID day 0 to +70) plus sirolimus and tacrolimus (PAC/SIR/TAC) demonstrated the regimen was safe and free of pan-JAK myelosuppression after allogeneic hematopoietic cell transplantation (alloHCT). PAC inhibits IL-6 receptor activity and pathogenic Th1/Th17 differentiation in preclinical models and the phase I trial. Herein we report on our completed phase II trial of PAC/SIR/TAC after 8/8-HLA matched alloHCT. This single-arm phase II trial (NCT02891603) was powered to determine if PAC/SIR/TAC suppressed %pSTAT3+ CD4+ T cells at day +21 (primary endpoint: %pSTAT3+ CD4+ T cells ≤ 35%) and estimated grade II-IV acute GVHD by day +100. The impact of PAC/SIR/TAC on T cell subsets, CD28 (pS6 and pH3ser10), and IL-2 receptor (pSTAT5) signal transduction was also evaluated. Eligible patients (n=28) received alloHCT for hematologic malignancies or myeloproliferative neoplasms. Reduced or myeloablative intensity conditioning was permitted. PAC/SIR/TAC met the primary endpoint, reducing %pSTAT3+ CD4+ T cells to 9.62% at day +21. Th1/Th17 cells were decreased at day +21, increasing the ratio of Tregs to Th1 and Th17 cells with PAC/SIR/TAC at RP2D PAC compared to dose level 1 PAC. The cumulative incidence of grade II-IV acute GVHD by day +100 with PAC/SIR/TAC was similar to historic SIR/TAC values (46 v 43%). While PAC/SIR/TAC suppressed pSTAT3 and Th1/Th17 cells, the regimen did not improve acute GVHD prevention.
    DOI:  https://doi.org/10.1182/blood.2024024789
  7. Cell Rep. 2024 Jul 23. pii: S2211-1247(24)00871-4. [Epub ahead of print]43(8): 114542
      Granulocyte colony-stimulating factor (G-CSF) is widely used to enhance myeloid recovery after chemotherapy and to mobilize hematopoietic stem cells (HSCs) for transplantation. Unfortunately, through the course of chemotherapy, cancer patients can acquire leukemogenic mutations that cause therapy-related myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). This raises the question of whether therapeutic G-CSF might potentiate therapy-related MDS/AML by disproportionately stimulating mutant HSCs and other myeloid progenitors. A common mutation in therapy-related MDS/AML involves chromosome 7 deletions that inactivate many tumor suppressor genes, including KMT2C. Here, we show that Kmt2c deletions hypersensitize murine HSCs and myeloid progenitors to G-CSF, as evidenced by increased HSC mobilization and enhanced granulocyte production from granulocyte-monocyte progenitors (GMPs). Furthermore, Kmt2c attenuates the G-CSF response independently from its SET methyltransferase function. Altogether, the data raise concerns that monosomy 7 can hypersensitize progenitors to G-CSF, such that clinical use of G-CSF may amplify the risk of therapy-related MDS/AML.
    Keywords:  CP: Immunology; CP: Stem cell research
    DOI:  https://doi.org/10.1016/j.celrep.2024.114542
  8. Br J Haematol. 2024 Jul 23.
      Our observational study analysed fungal infection frequency within cohorts with versus without antifungal prophylaxis (AFP) among newly diagnosed first-line venetoclax and azacitidine (VEN + AZA)-treated acute myeloid leukaemias in Czech, Austrian and Slovak haematology centres. Among 186 patients, 85 (46%) received antifungal prophylaxis, while 101 (54%) received no prophylaxis. Fungal infections occurred in 1/85 patients with prophylaxis (1%) and 5/101 patients without prophylaxis (5%) (p = 0.222). No significant difference was recorded between cohorts with and without AFP in terms of death rate (p = 0.296) and overall survival (p = 0.844). In conclusion, most infections were not severe, developing during the first treatment-cycle and did not affect patients' overall outcome.
    Keywords:  acute myeloid leukaemia; antifungal prophylaxis; fungal infection; venetoclax and azacitidine
    DOI:  https://doi.org/10.1111/bjh.19670
  9. Leukemia. 2024 Jul 24.
      An increasing number of older patients with acute myeloid leukemia (AML) are offered an allogeneic hematopoietic stem cell transplantation (allo-HSCT). Normally, older patients have older matched related donors (MRD). Matched unrelated donors (MUD) are an important alternative, but it remains unclear whether a younger MUD is associated with better outcomes, especially in the context of post-transplant cyclophosphamide (PTCy). We compared outcomes of patients older than 50 years with AML in first complete remission (CR1) and receiving a first HSCT from a 10/10 MUD aged younger than 40 years to those receiving a graft from a MRD aged older than 50 years, using PTCy and with well-known transplant conditioning intensity (TCI) score. A total of 345 consecutive patients were included and classified according to TCI score as low, intermediate, or high. On multivariable analysis in the TCI-intermediate/high group, MUD was associated with better graft-versus-host disease-free, relapse-free survival, lower non-relapse mortality and lower relapse incidence. For patients receiving a TCI-low regimen, outcomes are independent on the type of donor. In patients with AML in CR1, older than 50 years and receiving a TCI-intermediate/high conditioning regimen using PTCy, a MUD younger than 40 years is preferable over a MRD older than 50 years.
    DOI:  https://doi.org/10.1038/s41375-024-02359-8
  10. Cancer Med. 2024 Jul;13(14): e70028
       BACKGROUND: Mouse double minute-2 homolog (MDM2) plays a key role in downregulating p53 activity in hematologic malignancies, and its overexpression is associated with poor outcomes.
    METHODS: This phase 1 study assessed the safety and efficacy of different dosing regimens of the MDM2 inhibitor milademetan as monotherapy and in combination with azacitidine (AZA) in patients with relapsed or refractory acute myeloid leukemia or high-risk myelodysplastic syndromes.
    RESULTS: Seventy-four patients (monotherapy, n = 57; milademetan-AZA combination, n = 17) were treated. The maximum tolerated dose of milademetan was 160 mg once daily given for the first 14-21 days of 28-day cycles as monotherapy and on Days 5-14 in combination with AZA. Dose-limiting toxicities were gastrointestinal, fatigue, or renal/electrolyte abnormalities. Treatment-emergent adverse events related to milademetan occurred in 82.5% and 64.7% of participants in the monotherapy and AZA combination arms, respectively. Two participants (4.2%) in the monotherapy arm achieved complete remission (CR), and 1 (2.1%) achieved CR with incomplete blood count recovery (CRi). Two participants (13.3%) achieved CRi in the combination arm. New TP53 mutations, detected only during milademetan monotherapy, were found pre-existing below standard detection frequency by droplet digital polymerase chain reaction.
    INTERPRETATION: Milademetan was relatively well tolerated in this population; however, despite signals of activity, clinical efficacy was minimal.
    Keywords:  acute myeloid leukemia; milademetan; mouse double minute‐2 homolog; myelodysplastic syndromes
    DOI:  https://doi.org/10.1002/cam4.70028
  11. Lancet Haematol. 2024 Jul 18. pii: S2352-3026(24)00142-X. [Epub ahead of print]
       BACKGROUND: Lenalidomide is the standard of care for patients who are transfusion dependent with chromosome 5q deletion (del[5q]) myelodysplastic syndromes. In the SintraREV trial, we aimed to investigate whether an early intervention of low lenalidomide doses for 2 years could delay transfusion dependency in patients with anaemia who were not transfusion dependent.
    METHODS: This randomised, double-blind, phase 3 trial, was conducted at 22 sites (University Hospitals) in Spain, France, and Germany. Eligible patients were aged 18 years or older diagnosed with low-risk or intermediate-1-risk del(5q) myelodysplastic syndromes with non-transfusion-dependent anaemia (according to the IPSS), were erythropoietin-stimulating agents naive, and had an ECOG performance status of 2 or less. Patients were randomly assigned (2:1) by means of a telephone system to receive lenalidomide 5 mg daily in 28-day cycles versus placebo for 2 years. The primary endpoint was time to transfusion dependency based on blinded independent central review. Analysis were by intent-to-treat (ITT) and evaluable population. Safety analyses included all participants who received at least one dose of treatment. This trial is registered with ClinicalTrials.gov (NCT01243476) and EudraCT (2009-013619-36) and is complete.
    FINDINGS: Between Feb 15, 2010, and Feb 21, 2018, 61 patients were randomly assigned to receive lenalidomide (n=40; two did not receive treatment) or placebo (n=21). The median age was 72·2 (IQR 65·4-81·9) years, 50 (82%) patients were female, and 11 (18%) were male. The median follow-up time was 60·6 (IQR 32·1-73·9) months. Regarding primary endpoint, median time to transfusion dependency was not reached (95% CI not applicable) in the lenalidomide group versus 11·6 months (95% CI 0·00-30·11) in the placebo group (p=0·0027). Lenalidomide significantly reduced the risk of transfusion dependency by 69·8% (hazard ratio 0·302, 95% CI 0·132-0·692; p=0·0046). The most frequent treatment-related adverse event was neutropenia, occurring in 24 (63%) of 38 patients in the lenalidomide group (grade 3 and 4 in 17 [45%] patients and one [3%], respectively) and in four (19%) of 21 patients in the placebo group (grade 3 in one [5%] patient). Thrombocytopenia was detected in seven (18%) of 38 patients receiving lenalidomide (grade 3 in two [5%] patients). Regarding the non-haematological toxicity, skin disorders (rash nine [23%] of 38 patients) were the most frequently described toxicities among patients receiving lenalidomide, being grade 3 in one (3%) of 38 patients. 19 serious adverse events were reported in 13 patients, 18 in the lenalidomide group and one in the placebo group, five of which were potentially related to the study drug. No treatment-related deaths were identified.
    INTERPRETATION: An early approach with low doses of lenalidomide across two years delays the time to transfusion dependency and improves the rate and quality of the responses, with a manageable safety profile in patients who are non-transfusion dependent with del(5q) low-risk myelodysplastic syndromes.
    FUNDING: Bristol Myers Squibb.
    DOI:  https://doi.org/10.1016/S2352-3026(24)00142-X
  12. Biomedicines. 2024 Jul 19. pii: 1616. [Epub ahead of print]12(7):
      Gemtuzumab ozogamicin (GO), a CD33-targeting antibody drug conjugate, previously showed longer relapse-free survival when combined with induction chemotherapy in patients with favorable-risk acute myeloid leukemia (AML). In this patient population, characterized by lower relapse risk as compared to other ELN risk groups, autologous stem cell transplantation (ASCT) can be used as consolidation strategy. However, there are limited data on the impact of GO on the peripheral blood stem cell (PBSC) mobilization potential. We therefore retrospectively analyzed data from 54 AML patients with favorable-risk AML treated with (n = 17) or without (n = 37) GO during induction treatment. We observed no significant differences in the PBSC mobilization rate between patients treated with vs. without GO. The mobilization success in a first attempt directly following cycle 2 was 65% vs. 70% (p = 0.92); and the mobilization success in a subsequent second attempt after hematologic recovery and repeated stimulation procedure was 24% vs. 19% (p = 0.56). No significant impact on treatment outcome in terms of EFS (p = 0.31) or OS (p = 0.99) was observed. Thus, our results suggest that the addition of GO to induction regimens does not negatively impact PBSC mobilization in favorable-risk AML patients. To our best knowledge, this is the first study comparing the stem cell mobilization potential in favorable-risk AML patients treated with vs. without GO.
    Keywords:  acute myeloid leukemia (AML); autologous stem cell transplantation (ASCT); gemtuzumab ozogamicin (GO); peripheral blood stem cells (PBSC); stem cell mobilization
    DOI:  https://doi.org/10.3390/biomedicines12071616
  13. Blood. 2024 Jul 24. pii: blood.2023022417. [Epub ahead of print]
      The fifth edition of the WHO classification and the International Consensus Classification (ICC) both include a category "myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase (TK) gene fusions" (WHO, MLN-TK; ICC, M/LN-eo-TK). This rare group comprises phenotypically and prognostically heterogeneous disorders that present a significant diagnostic challenge. The rapid and reliable identification of patients with MLN-TK may be delayed due to genetic complexity and significant phenotypic differences, which include chronic phase and primary/secondary blast phase (BP) of myeloid, or lymphoid or mixed phenotype in the bone marrow (BP-BM) and/or at extramedullary sites (extramedullary disease, EMD). As a result, the entire armamentarium of conventional molecular genetic and cytogenetic techniques complemented by modern sequencing technologies such as RNA sequencing or whole genome sequencing are often required to identify an underlying TK fusion. TK inhibitors (TKIs) with variable efficacy are available for all fusion genes, but a long-term favorable clinical course under TKI monotherapy is currently only observed in MLN-PDGFRA/PDGFRB fusion genes on imatinib. Since primary/secondary BP-BM/EMD occur more frequently in MLN-FGFR1/JAK2/FLT3/ETV6::ABL1, a sequential combination of selective TKIs with or without prior intensive chemotherapy, rarely local local radiationradiotherapy and/or subsequent allogeneic hematopoietic cell transplantation should be considered.
    DOI:  https://doi.org/10.1182/blood.2023022417
  14. PLoS One. 2024 ;19(7): e0307662
      Promising outcomes have been reported in elder patients with acute myeloid leukemia (AML) using combined therapy of venetoclax (VEN) and azacytidine (AZA) in recent years. However, approximately one-third of patients appear to be refractory to this therapy. Vitamin K2 (VK2) shows apoptosis-inducing activity in AML cells, and daily oral VK2 (menaquinone-4, GlakayR) has been approved for patients with osteoporosis in Japan. We observed a high response rate to AZA plus VEN therapy, with no 8-week mortality in the newly diagnosed AML patients consuming daily VK2 in our hospital. The median age of the patients was 75.9 years (range 66-84) with high-risk features. Patients received AZA 75 mg/m2 on D1-7, VEN 400 mg on D1-28, and daily VK2 45 mg. The CR/CRi ratio was 94.7% (18/19), with a CR rate of 79%. Complete cytogenetic CR was achieved in 15 of 19 (79%) patients, and MRD negativity in 2 of 15 (13%) evaluable CR patients. Owing to the extremely high response rate in clinical settings, we further attempted to investigate the underlying mechanisms. The combination of VK2 and VEN synergistically induced apoptosis in all five AML cell lines tested. VK2, but not VEN, induced mitochondrial reactive oxygen species (ROS), leading to the transcriptional upregulation of NOXA, followed by MCL-1 repression. ROS scavengers repressed VK2 induced-NOXA expression and led to the cancellation of pronounced apoptosis and the downregulation of MCL-1 by VK2 plus VEN. Additionally, knockdown and knockout of NOXA resulted in abrogation of the MCL-1 repression as well as enhanced cytotoxicity by the two-drug combination, indicating that VK2 suppresses MCL-1 via ROS-mediated NOXA induction. These data suggest that the dual inhibition of BCL-2 by VEN and MCL-1 by VK2 is responsible for the remarkable clinical outcomes in our patients. Therefore, large-scale clinical trials are required.
    DOI:  https://doi.org/10.1371/journal.pone.0307662
  15. iScience. 2024 Jul 19. 27(7): 110306
      Hematopoietic aging is associated with decreased hematopoietic stem cell (HSC) self-renewal capacity and myeloid skewing. We report that culture of bone marrow (BM) HSCs from aged mice with epidermal growth factor (EGF) suppressed myeloid skewing, increased multipotent colony formation, and increased HSC repopulation in primary and secondary transplantation assays. Mice transplanted with aged, EGF-treated HSCs displayed increased donor cell engraftment within BM HSCs and systemic administration of EGF to aged mice increased HSC self-renewal capacity in primary and secondary transplantation assays. Expression of a dominant negative EGFR in Scl/Tal1+ hematopoietic cells caused increased myeloid skewing and depletion of long term-HSCs in 15-month-old mice. EGF treatment decreased DNA damage in aged HSCs and shifted the transcriptome of aged HSCs from genes regulating cell death to genes involved in HSC self-renewal and DNA repair but had no effect on HSC senescence. These data suggest that EGFR signaling regulates the repopulating capacity of aged HSCs.
    Keywords:  Human physiology; cellular physiology; functional aspects of cell biology; molecular medicine; stem cells research
    DOI:  https://doi.org/10.1016/j.isci.2024.110306
  16. Trends Cell Biol. 2024 Jul 24. pii: S0962-8924(24)00141-7. [Epub ahead of print]
      Mitochondrial metabolism plays a central role in the regulation of hematopoietic stem cell (HSC) biology. Mitochondrial fatty acid oxidation (FAO) is pivotal in controlling HSC self-renewal and differentiation. Herein, we discuss recent evidence suggesting that NADPH generated in the mitochondria can influence the fate of HSCs. Although NADPH has multiple functions, HSCs show high levels of NADPH that are preferentially used for cholesterol biosynthesis. Endogenous cholesterol supports the biogenesis of extracellular vesicles (EVs), which are essential for maintaining HSC properties. We also highlight the significance of EVs in hematopoiesis through autocrine signaling. Elucidating the mitochondrial NADPH-cholesterol axis as part of the metabolic requirements of healthy HSCs will facilitate the development of new therapies for hematological disorders.
    Keywords:  FAO; HSC self-renewal; cholesterol; exosome; hematopoiesis; mitochondrial metabolism
    DOI:  https://doi.org/10.1016/j.tcb.2024.07.003
  17. Leukemia. 2024 Jul 23.
      Hematopoiesis is a continuous process of blood cell production driven by hematopoietic stem and progenitor cells (HSPCs) in the bone marrow. Proliferation and differentiation of HSPCs are regulated by complex transcriptional networks. In order to identify transcription factors with key roles in HSPC-mediated hematopoietic reconstitution, we developed an efficient and robust CRISPR/Cas9-based in vivo genetic screen. Using this experimental system, we identified the TFDP1 transcription factor to be essential for HSPC proliferation and post-transplant hematopoiesis. We further discovered that E2F4, an E2F transcription factor, serves as a binding partner of TFDP1 and is required for HSPC proliferation. Deletion of TFDP1 caused downregulation of genes associated with the cell cycle, with around 50% of these genes being identified as direct targets of TFDP1 and E2F4. Thus, our study expands the transcriptional network governing hematopoietic development through an in vivo CRISPR/Cas9-based genetic screen and identifies TFDP1/E2F4 as positive regulators of cell cycle genes in HSPCs.
    DOI:  https://doi.org/10.1038/s41375-024-02357-w
  18. Blood Adv. 2024 Jul 23. pii: bloodadvances.2024012670. [Epub ahead of print]
      We hypothesized that inferior disease-free survival (DFS) seen in older patients undergoing αβ/CD19-T-cell depleted (AB-TCD) haploidentical hematopoietic cell transplantation (HCT) for patients with hematologic malignancies was due to excessive exposure to rabbit antithymocyte globulin (rATG; Thymoglobulin®). Between 2015-2023, 163 patients with a median age of 13 years (range, 0.4-27.4) underwent AB-TCD haploidentical HCT for treatment of ALL (n=98), AML/MDS (n=49), or other malignancies (n=16) at nine centers on two prospective trials. Exposures of rATG pre- and post-HCT were predicted with a validated pharmacokinetic (PK) model. ROC curves were used to identify optimal target windows of rATG exposure related to outcomes. We identified four quadrants of rATG exposure - quadrant 1 (n=52): high pre-HCT AUC (≥50 AU*day/mL) and low post-HCT (<12 AU*day/L); quadrant 2 (n=47): both low pre-HCT and post-HCT AUCs, quadrant 3 (n=13): low pre-HCT AUC and high post-HCT, and quadrant 4 (n=51): both high pre- and post-HCT AUCs. Quadrant 1 had a 3-year DFS of 86.5% (95% CI, 76.3-96.7%), compared to quadrant 2 (64.6%; 95% CI, 49.1-80.1%), quadrant 3 (32.9%; 95% CI, 0.1-80.5%) or quadrant 4 (48.2%; 95% CI, 22.1-63.3%) (p<0.001). Adjusted regression analysis demonstrated additional factors associated with increased hazard for worse DFS: MRD-positivity (HR=2.45; 1.36-4.41; p=0.003) and CMV R+/D- serostatus (HR=3.33; 1.8-6.16; p<0.001). Non-optimal rATG exposure exhibited the strongest effect in unadjusted (HR=4.24; 1.79-10.03; p=0.001) and adjusted (MRD status or CMV serostatus) analyses (HR=3.84, 1.63-9.05; p=0.002). High exposure to rATG post-HCT is associated with inferior DFS following AB-TCD haploidentical HCT for pediatric patients with hematologic malignancies. Model-based dosing of rATG to achieve optimal exposure may improve DFS. Clinical trials: NCT02646839 & NCT04337515.
    DOI:  https://doi.org/10.1182/bloodadvances.2024012670
  19. Nat Aging. 2024 Jul 23.
      How hematopoietic stem cells (HSCs) maintain metabolic homeostasis to support tissue repair and regeneration throughout the lifespan is elusive. Here, we show that CD38, an NAD+-dependent metabolic enzyme, promotes HSC proliferation by inducing mitochondrial Ca2+ influx and mitochondrial metabolism in young mice. Conversely, aberrant CD38 upregulation during aging is a driver of HSC deterioration in aged mice due to dysregulated NAD+ metabolism and compromised mitochondrial stress management. The mitochondrial calcium uniporter, a mediator of mitochondrial Ca2+ influx, also supports HSC proliferation in young mice yet drives HSC decline in aged mice. Pharmacological inactivation of CD38 reverses HSC aging and the pathophysiological changes of the aging hematopoietic system in aged mice. Together, our study highlights an NAD+ metabolic checkpoint that balances mitochondrial activation to support HSC proliferation and mitochondrial stress management to enhance HSC self-renewal throughout the lifespan, and links aberrant Ca2+ signaling to HSC aging.
    DOI:  https://doi.org/10.1038/s43587-024-00670-8
  20. STAR Protoc. 2024 Jul 20. pii: S2666-1667(24)00367-8. [Epub ahead of print]5(3): 103202
      Leukemia niche impacts quiescence; however, culturing patient-derived samples ex vivo is technically challenging. Here, we present a protocol for in vitro co-culture of patient-derived xenograft acute lymphoblastic leukemia (PDX-ALL) cells with human mesenchymal stem cells (MSCs). We describe steps for labeling PDX-ALL cells with CellTrace Violet dye to demonstrate MSC-primed PDX-ALL cycling. We then detail procedures to identify MSC-primed G0/quiescent PDX-ALL cells via Hoechst-33342/Pyronin Y live cell cycle analysis. For complete details on the use and execution of this protocol, please refer to Pal et al.1,2.
    Keywords:  Cell Differentiation; Cell-based Assays; Stem Cells
    DOI:  https://doi.org/10.1016/j.xpro.2024.103202
  21. Leukemia. 2024 Jul 25.
      N6-methyladenosine (m6A) is the most prevalent epitranscriptomic modification in mammalian mRNA. Recent studies have revealed m6A is involved in the pathogenesis of various malignant tumors including hematologic neoplasms. Nevertheless, the specific roles of m6A modification and m6A regulators in myelodysplastic neoplasms (MDS) remain poorly understood. Herein, we demonstrated that m6A level and the expression of m6A methyltransferase METTL14 were elevated in MDS patients with bone marrow blasts ≥5%. Additionally, m6A level and METTL14 expression were upregulated as the disease risk increased and significantly associated with adverse clinical outcomes. Knockdown of METTL14 inhibited cell proliferation and colony formation ability of MDS cells. Moreover, in vivo experiments showed METTL14 knockdown remarkably reduced tumor burden and prolonged the survival of mice. Mechanistically, METTL14 facilitated the m6A modification of SETBP1 mRNA by formation of METTL3-METTL14 complex, leading to increased stabilization of SETBP1 mRNA and subsequent activation of the PI3K-AKT signaling pathway. Overall, this study elucidated the involvement of the METTL14/m6A/SETBP1/PI3K-AKT signaling axis in MDS, highlighting the therapeutic potential of targeting METTL3-METTL14 complex-mediated m6A modification for MDS therapy.
    DOI:  https://doi.org/10.1038/s41375-024-02350-3