bims-tremyl Biomed News
on Therapy resistance biology in myeloid leukemia
Issue of 2024–10–06
forty-five papers selected by
Paolo Gallipoli, Barts Cancer Institute, Queen Mary University of London



  1. Leukemia. 2024 Oct 01.
      Acute myeloid leukemia (AML) shows variable clinical outcome. The normal hematopoietic cell of origin impacts the clinical behavior of AML, with AML from hematopoietic stem cells (HSCs) prone to chemotherapy resistance in model systems. However, the mechanisms by which HSC programs are transmitted to AML are not known. Here, we introduce the leukemogenic MLL-AF9 translocation into defined human hematopoietic populations, finding that AML from HSCs is enriched for leukemic stem cells (LSCs) compared to AML from progenitors. By epigenetic profiling, we identify a putative inherited program from the normal HSC that collaborates with oncogene-driven programs to confer aggressive behavior in HSC-AML. We find that components of this program are required for HSC-AML growth and survival and identify RNA polymerase (RNAP) II-mediated transcription as a therapeutic vulnerability. Overall, we propose a mechanism as to how epigenetic programs from the leukemic cell of origin are inherited through transformation to impart the clinical heterogeneity of AML.
    DOI:  https://doi.org/10.1038/s41375-024-02428-y
  2. J Clin Invest. 2024 Oct 01. pii: e180065. [Epub ahead of print]134(19):
      Clonal hematopoiesis (CH), the expansion of hematopoietic stem cells and their progeny driven by somatic mutations in leukemia-associated genes, is a common phenomenon that rises in prevalence with advancing age to affect most people older than 70 years. CH remains subclinical in most carriers, but, in a minority, it progresses to a myeloid neoplasm, such as acute myeloid leukemia, myelodysplastic syndrome, or myeloproliferative neoplasm. Over the last decade, advances in our understanding of CH, its molecular landscape, and the risks associated with different driver gene mutations have culminated in recent developments that allow for a more precise estimation of myeloid neoplasia risk in CH carriers. In turn, this is leading to the development of translational and clinical programs to intercept and prevent CH from developing into myeloid neoplasia. Here, we give an overview of the spectrum of CH driver mutations, what is known about their pathophysiology, and how this informs the risk of incident myeloid malignancy.
    DOI:  https://doi.org/10.1172/JCI180065
  3. Blood Adv. 2024 Sep 30. pii: bloodadvances.2024013758. [Epub ahead of print]
      Measurable residual disease (MRD) monitoring in acute myeloid leukemia (AML) with FLT3 internal tandem duplication (FLT3-ITDpos) was hampered by the broad heterogeneity of ITD mutations. Using our recently developed FLT3-ITD paired-end next-generation sequencing (NGS)-based MRD assay with a limit of detection of 10-4 to 10-5, we evaluated the prognostic impact of MRD at different time-points in 157 FLT3-ITDpos AML patients enrolled in the AMLSG16-10 trial (NCT01477606) combining intensive chemotherapy with midostaurin followed by midostaurin maintenance. Achievement of MRD negativity (MRDneg) after two cycles of chemotherapy (Cy2) observed in 111/142 (78%) patients predicted for superior 4-year rates of cumulative incidence of relapse (CIR) (4y-CIR, 26% vs 46%; P=.001) and overall survival (OS) (4y-OS, 70% vs 44%; P=.012). This survival advantage was also seen for patients undergoing allogeneic hematopoietic-cell transplantation in first complete remission (4y-CIR, 14% vs 39%; P=.001; 4y-OS, 71% vs 49%; P=.029). Multivariate models for CIR and OS after Cy2 revealed FLT3-ITD MRDneg as the only consistent favorable variable for CIR (HR, 0.29; P=.006) and OS (HR, 0.39; P=.018). NPM1 co-mutation correlated with deeper molecular response as reflected by stronger MRD reduction and higher rate of FLT3-ITD MRDneg after Cy2. During follow-up, conversion from MRDneg to MRDpos was a strong, independent factor for inferior CIR (HR, 16.64; P<.001) and OS (HR, 4.05; P<.001). NGS-based FLT3-ITD MRD monitoring allows for the identification of patients at high risk of relapse and death following intensive chemotherapy plus midostaurin. Using NGS-based technology, FLT3-ITD emerges as a novel, clinically highly relevant target for MRD monitoring.
    DOI:  https://doi.org/10.1182/bloodadvances.2024013758
  4. Leukemia. 2024 Sep 28.
      Myeloproliferative neoplasms (MPN) are a heterogeneous group of clonal disorders characterized by aberrant hematopoietic proliferation and an intrinsic risk of progression to blast phase. The WHO classification 2022 identifies chronic myeloid leukemia and the BCR::ABL1 negative MPNs polycythemia vera, primary myelofibrosis and essential thrombocythemia as individual entities. However, overlaps, borderline findings or transitions between MPN subtypes occur and incomplete clinical data often complicates diagnosis. By conducting a thorough genetic analysis, we've developed a model that relies on 12 genetic markers to accurately stratify MPN patients. The model can be simplified into a decision tree for routine use. Comparing samples at chronic and blast phase revealed, that one third of patients lost their MPN driver-gene mutation, while mutations in splicing and chromatin modifying genes were stable, indicating a shared founder clone of chronic and blast phase with different driver mutations and therefore different progressing capacities. This was further supported by gain of typical de novo AML gene mutations, accompanied by gain of complex karyotypes and RAS pathway gene mutations. Our data suggest to perform a broader genetic screening at diagnosis and also at clinical progression, as driver mutations may change and the MPN-driver mutations present at diagnosis may disappear.
    DOI:  https://doi.org/10.1038/s41375-024-02425-1
  5. Blood. 2024 Oct 02. pii: blood.2024024968. [Epub ahead of print]
      The BCL2 inhibitor venetoclax has shown promise for treating acute myeloid leukemia (AML). However, identifying patients likely to respond remains a challenge, especially for those with relapsed/refractory (R/R) disease. We evaluated the utility of ex vivo venetoclax sensitivity testing to predict treatment responses to venetoclax-azacitidine in a prospective, multicenter, phase 2 trial conducted by the Finnish AML Group (VenEx, NCT04267081). The trial recruited 104 participants with previously untreated (n=48), R/R (n=39) or previously treated secondary AML (sAML) (n=17). The primary endpoint was complete remission or complete remission with incomplete hematologic recovery (CR/CRi) rate in ex vivo sensitive trial participants during the first three therapy cycles. The key secondary endpoints included the correlations between ex vivo drug sensitivity, responses, and survival. Venetoclax sensitivity was successfully assessed in 102/104 participants, with results available within a median of three days from sampling. In previously untreated AML, ex vivo sensitivity corresponded to an 85% (34/40) CR/CRi rate, with a median overall survival (OS) of 28.7 months, compared to 5.5 months for ex vivo resistant patients (p = 0.002). For R/R/sAML, ex vivo sensitivity resulted in a 62% CR/CRi rate (21/34) and median OS of 9.7 versus 3.3 months for ex vivo resistant patients (p < 0.001). In univariate and multivariate analysis, ex vivo venetoclax sensitivity was the strongest predictor for a favorable treatment response and survival. The VenEx trial demonstrates the feasibility of integrating ex vivo drug testing into clinical practice to identify AML patients, particularly in the R/R setting, who benefit from venetoclax.
    DOI:  https://doi.org/10.1182/blood.2024024968
  6. Haematologica. 2024 Oct 03.
      We evaluated response to VEN/HMA in 46 patients with acute myeloid leukemia (AML) characterized by extramedullary disease (EMD). Median age was 65 (range, 19-81) years. Patients had a median of two EMD sites (range, 1-5) and 35 (76%) patients had concurrent bone marrow involvement. Twenty (43%) patients had highrisk genetic features according to the European Leukemia Net 2022 classification. Twenty-nine (63%) were relapsed or refractory after intensive chemotherapy (CTX) including 13 (28%) with prior allogeneic hematopoietic cell transplantation (allo-HCT). Patients received a median of 2 cycles of VEN/HMA (range, 1-31). Twenty (43%) patients achieved complete remission (CR) or CR with incomplete hematological recovery (CRi) after VEN/HMA and five (11%) achieved a partial remission (PR). Six patients were subsequently consolidated with allo-HCT (CR/CRi, n=4; PR, n=2). Median follow-up was 49.1 months (95%-CI, 26.1 months - not reached) and median overall survival (OS) 6.4 months (95%-CI, 5.1-11 months). One-year and 2-years OS rates were 29.3% (95%-CI, 18.6-46.2%) and 12.3% (95%-CI, 5.5-27.6%), respectively. Age with a cut-off of 60 years had no impact on OS (P=0.90). Relapse occurred in 12 of 20 (60%) patients who achieved CR/CRi after VEN/HMA treatment. Of those, all except one succumbed to their disease. Six (30%) patients were in CR/CRi at last follow-up and 2 (10%) died in CR. In our cohort of patients with AML with EMD with high-risk features, treatment with VEN/HMA resulted in an encouraging ORR of 54% with a CR/CRi rate of 43.5%. However, VEN/HMA alone may not be effective in maintaining disease control.
    DOI:  https://doi.org/10.3324/haematol.2024.285985
  7. Lancet Oncol. 2024 Oct;pii: S1470-2045(24)00386-3. [Epub ahead of print]25(10): 1310-1324
       BACKGROUND: Ziftomenib (KO-539) is an oral selective menin inhibitor with known preclinical activity in menin-dependent acute myeloid leukaemia models. The primary objective of this study was to determine the recommended phase 2 dose in patients with relapsed or refractory acute myeloid leukaemia based on safety, pharmacokinetics, pharmacodynamics, and preliminary activity.
    METHODS: KOMET-001 is a multicentre, open-label, multi-cohort, phase 1/2 clinical trial of ziftomenib in adults with relapsed or refractory acute myeloid leukaemia. Results of the phase 1 study, conducted at 22 hospitals in France, Italy, Spain, and the USA, are presented here and comprise the dose-escalation (phase 1a) and dose-validation and expansion (phase 1b) phases. Eligible patients were aged 18 years or older, had relapsed or refractory acute myeloid leukaemia, and had an Eastern Cooperative Oncology Group performance status of 2 or less. For phase 1a, patients (all molecular subtypes) received ziftomenib (50-1000 mg) orally once daily in 28-day cycles. For phase 1b, patients with NPM1 mutations or with KMT2A rearrangements were randomly assigned (1:1) using third-party interactive response technology to two parallel dose cohorts (200 mg and 600 mg ziftomenib). Primary endpoints were maximum tolerated dose or recommended phase 2 dose in phase 1a, and safety, remission rates, and pharmacokinetics supporting recommended phase 2 dose determination in phase 1b. Analyses were performed in all patients who received at least one dose of ziftomenib (modified intention-to-treat population). Phase 1a/1b is complete. This trial is registered with ClinicalTrials.gov, NCT04067336, and the EU Clinical Trials register, EudraCT 2019-001545-41.
    FINDINGS: From Sept 12, 2019, to Aug 19, 2022, 83 patients received 50-1000 mg ziftomenib (39 [47%] were male and 44 [53%] were female). Median follow-up was 22·3 months (IQR 15·4-30·2). Of 83 patients, the most common grade 3 or worse treatment-emergent adverse events were anaemia (20 [24%]), febrile neutropenia (18 [22%]), pneumonia (16 [19%]), differentiation syndrome (12 [15%]), thrombocytopenia (11 [13%]), and sepsis (ten [12%]). Overall, 68 of 83 patients had serious adverse events, with two reported treatment-related deaths (one differentiation syndrome and one cardiac arrest). Differentiation syndrome rate and severity influenced the decision to halt enrolment of patients with KMT2A rearrangements. In Phase 1b, no responses were reported in patients treated at the 200 mg dose level. At the recommended phase 2 dose of 600 mg, nine (25%) of 36 patients with KMT2A rearrangement or NPM1 mutation had complete remission or complete remission with partial haematologic recovery. Seven (35%) of 20 patients with NPM1 mutation treated at the recommended phase 2 dose had a complete remission.
    INTERPRETATION: Ziftomenib showed promising clinical activity with manageable toxicity in heavily pretreated patients with relapsed or refractory acute myeloid leukaemia. Phase 2 assessment of ziftomenib combination therapy in the upfront and relapsed or refractory setting is ongoing.
    FUNDING: Kura Oncology.
    DOI:  https://doi.org/10.1016/S1470-2045(24)00386-3
  8. Leukemia. 2024 Oct 04.
      In addition to high-molecular risk (HMR) mutations (ASXL1, EZH2, SRSF2, IDH, and U2AF1Q157), lower JAK2V617F variant allele frequencies (VAF) have been demonstrated to be associated with poor prognosis of myelofibrosis (MF) patients. Nevertheless, the relationship between JAK2V617F VAF and HMR mutations remains inconclusive. To address this, we analyzed the mutation status of 54 myeloid neoplasm-relevant genes using targeted next-generation sequencing in 124 MF patients. Three cohorts from multiple international centers were analyzed for external validation. Among JAK2-mutated patients, the presence of HMR mutations drove poor prognosis in patients with lower JAK2V617F VAF but not in those with higher JAK2V617F VAF. Survival analyses showed consistent results across validation cohorts. In multivariable analysis, concurrent HMR and a lower JAK2V617F VAF was identified as an independent adverse prognostic factor for survival, irrespective of age, MIPSS70, MIPSS70 + v2, and GIPSS risk groups. Mutation co-occurrence tests revealed no shared mutational pattern over different cohorts, excluding potential confounding effect from other concurrent mutations. Importantly, the integration of HMR/JAK2V617F VAF (≤50%) status significantly enhanced existing prognostic models, as evidenced by higher c-indexes and time-dependent ROC analyses. Single-cell studies with sequential follow-ups are warranted to decipher the clonal evolution of MF and how it relates to JAK2V617F VAF dynamics.
    DOI:  https://doi.org/10.1038/s41375-024-02422-4
  9. Blood Adv. 2024 Sep 30. pii: bloodadvances.2024013590. [Epub ahead of print]
      Acute myeloid leukemia (AML) is the most common and lethal leukemia in adults. AML consists of many genetic subtypes which limits broad applicability of targeted therapy. We discovered that the hematopoietic restricted tetraspanin CD37 is expressed on all primary AML blasts and thus may represent a common therapeutic target for AML regardless of subtype. We demonstrate that the internalization properties of CD37 are distinct in AML blasts when compared to normal blood cells, and that CD37 rapidly accumulates inside AML blasts via dynamin-dependent endocytosis. Our work revealed that the clinically relevant anti-CD37 antibody drug conjugate (ADC) Debio 1562 (αCD37-DM1) is highly cytotoxic to AML blasts, but not normal hematopoietic stem cells. We found that αCD37-DM1 improved clinical outcomes and overall survival in multiple in vivo models of AML. Together, these data demonstrate that targeting CD37 with an ADC such as αCD37-DM1 is a feasible and promising therapeutic option for the treatment of AML.
    DOI:  https://doi.org/10.1182/bloodadvances.2024013590
  10. J Hematol Oncol. 2024 Sep 27. 17(1): 87
      DNA methyltransferase 3 A mutations (DNMT3AMT) are frequent in myeloid neoplasia (MN) and mostly heterozygous. However, cases with multiple DNMT3AMT can be also encountered but their clinical and genetic landscape remains unexplored. We retrospectively analyzed 533 cases with DNMT3AMT identified out of 5,603 consecutive MNs, of whom 8.4% had multiple DNMT3AMT hits. They were most frequent in acute myeloid leukemia (AML) with R882 variant accounting for 13.3% of the multi-hits. Multiple DNMT3AMT more likely coincided with IDH2 (P = 0.005) and ETV6 (P = 0.044) mutations compared to patients with single DNMT3AMT. When the sum of variant allele frequencies (VAFs) for multiple DNMT3AMT exceeded 60%, we found a significant positive clonal burden correlation of the two DNMT3A variants (P < 0.0001) suggesting that they occurred in biallelic configuration. AML patients with biallelic DNMT3A inactivation (n = 52) presented with older age (P = 0.029), higher leukocytes (P < 0.0001) and peripheral blast counts (P = 0.0001) and significantly poorer survival rate (5.6% vs. 47.6% at 2 years; P = 0.002) than monoallelic DNMT3AMT. Multivariate analysis identified biallelic DNMT3AMT (HR 2.65; P = 0.001), male gender (HR 2.05; P = 0.014) and adverse genetic alteration according to the European LeukemiaNet 2022 classification (HR 1.84; P = 0.028) as independent adverse factors for survival, whereas intensive chemotherapy (HR 0.47; P = 0.011) favorably influenced outcomes. Longitudinal molecular analysis of 12 cases with biallelic DNMT3AMT demonstrated that such clones persisted or expanded in 9 relapsed or transformed cases (75%) suggesting the early origin of biallelic hits with strong leukemogenic potential. Our study describes the likelihood that biallelic DNMT3AMT, while rare, are indeed compatible with clonal expansion and thus questions the applicability of synthetic lethality strategies.
    Keywords:   DNMT3A mutation; Acute myeloid leukemia; Myelodysplastic syndrome; Myeloproliferative neoplasms
    DOI:  https://doi.org/10.1186/s13045-024-01607-9
  11. Cancer Discov. 2024 Oct 04. 14(10): 1768-1770
      In this issue, Waarts and colleagues developed an advanced ex vivo CRISPR screening platform to identify vulnerabilities in clonal hematopoiesis (CH). This unique system allowed the authors to identify a link between IDH2 and TET2 CH mutations, histone demethylases, and altered cytokine signaling, which enabled targeting by ruxolitinib leading to the elimination of CH clones, offering a possible path for preventing the development of malignancy. See related article by Waarts et al., p. 1860.
    DOI:  https://doi.org/10.1158/2159-8290.CD-24-1020
  12. Leukemia. 2024 Sep 30.
      Patients with TP53 aberrations comprise the highest risk subset of all myeloid malignancies. The managerial conundrum of TP53-mutant myelodysplastic neoplasms (MDS) and acute myeloid leukemia (AML) stems from refractoriness to or relapse after conventional chemotherapy, as well as the limited translational success of investigational therapies targeting TP53-mutant cells. Thus far, no targeted therapies have been commercially approved for this mutational subset. As a result, management plans for patients with TP53-mutant MDS and AML are often driven by clinical judgment and/or physician preference rather than consensus guidelines backed by a rigorous evidence basis. This clinical case-based, evidence-driven review highlights the most salient data that guides the management of commonly encountered patient prototypes. This review discusses the therapeutic menu of first-line options that derive from multi-institutional experiences as well as from disease-centric consortia and discusses how these first-line options can be optimally tailored to heterogeneous groups of patients. The debate regarding whether allogeneic stem cell transplant should be offered to these patients is summarized. Finally, this review explores the recent unfortunate news of pauses in clinical trials for the leading investigational agents - eprenetapopt, magrolimab, sabatolimab, and idasanutlin - and offers solutions toward re-invigorating the pipeline of precision therapeutics in 2025.
    DOI:  https://doi.org/10.1038/s41375-024-02417-1
  13. Blood. 2024 Oct 02. pii: blood.2024024011. [Epub ahead of print]
      Secondary acute myeloid leukemia (sAML) has traditionally been used to designate any AML disease arising from an antecedent hematologic disorder or following prior cytotoxic or radiation therapy. We now know sAML comprises multiple disease entities with distinct clinical and biological features: AML-myelodysplastic related (AML-MR), myeloproliferative neoplasm-blast phase (MPN-BP), and AML post-cytotoxic therapy (AML-pCT). These entities largely represent adverse-risk phenotypes with the majority of patients experiencing suboptimal outcomes with standard therapeutic options. Given the aging general population and the increased lifespan of individuals receiving DNA damaging agents for other medical conditions, the incidence of these diseases is steadily rising and now comprise approximately 25-30% of all new AML diagnoses. Despite the plethora of novel agents approved for AML since 2017, many are either not applicable to sAML (i.e. lacking a targetable mutation), have limited efficacy, or have not been studied in these specific entities. Furthermore, these patients are under-represented in clinical trials, and novel therapeutic options are critically needed. Here we present multiple patient cases exemplifying the new nomenclature and classification of the diseases comprising sAML and highlighting their diverse presentations. We provide our therapeutic approach for each clinical scenario and discuss the challenges of treatment with the currently available armamentarium.
    DOI:  https://doi.org/10.1182/blood.2024024011
  14. Nat Genet. 2024 Oct 04.
      Genomic profiles and prognostic biomarkers in patients with acute myeloid leukemia (AML) from ancestry-diverse populations are underexplored. We analyzed the exomes and transcriptomes of 100 patients with AML with genomically confirmed African ancestry (Black; Alliance) and compared their somatic mutation frequencies with those of 323 self-reported white patients with AML, 55% of whom had genomically confirmed European ancestry (white; BeatAML). Here we find that 73% of 162 gene mutations recurrent in Black patients, including a hitherto unreported PHIP alteration detected in 7% of patients, were found in one white patient or not detected. Black patients with myelodysplasia-related AML were younger than white patients suggesting intrinsic and/or extrinsic dysplasia-causing stressors. On multivariable analyses of Black patients, NPM1 and NRAS mutations were associated with inferior disease-free and IDH1 and IDH2 mutations with reduced overall survival. Inflammatory profiles, cell type distributions and transcriptional profiles differed between Black and white patients with NPM1 mutations. Incorporation of ancestry-specific risk markers into the 2022 European LeukemiaNet genetic risk stratification changed risk group assignment for one-third of Black patients and improved their outcome prediction.
    DOI:  https://doi.org/10.1038/s41588-024-01929-x
  15. Leukemia. 2024 Oct 02.
      Leukemias arise from recurrent clonal mutations in hematopoietic stem/progenitor cells (HSPCs) that cause profound changes in the bone marrow microenvironment (BMM) favoring leukemic stem cell (LSC) growth over normal HSPCs. Understanding the cross talk between preleukemic mutated HSPCs and the BMM is critical to develop novel therapeutic strategies to prevent leukemogenesis. We hypothesize that preleukemic-LSCs (pLSCs) induce BMM changes critical for leukemogenesis. Using our AML-murine model, we performed single-cell RNA-sequencing of preleukemic BMM (pBMM) cells. We found normal HSC (nHSC)-regulating LepR+ mesenchymal stem cells, and endothelial cells were decreased, along with increases in CD55+ fibroblasts and pericytes. Preleukemic CD55+ fibroblasts had higher proliferation rates and decreased collagen expression, suggesting extracellular matrix remodeling during leukemogenesis. Importantly, co-culture assays found preleukemic CD55+ fibroblasts expanded pLSCs significantly over nHSCs. In conclusion, we have identified a distinct pBMM and a novel CD55+ fibroblast population that is expanded in pBMM that promote fitness of pLSCs over nHSCs.
    DOI:  https://doi.org/10.1038/s41375-024-02415-3
  16. Ann Hematol. 2024 Oct 05.
      The treatment of older patients with acute myeloid leukemia (AML) considered unfit for receiving intensive chemotherapy is challenging. Based on the hypothesis that addition of the broad tyrosine kinase inhibitor (TKI) midostaurin could improve the response to hypomethylating agents, irrespective of FLT3 gene mutational status, we conducted a randomized phase II multicenter study to assess the tolerability and efficacy of the addition of midostaurin to a 10-day schedule of decitabine in unfit (i.e. Hematopoietic Cell Transplantation Comorbidity Index (HCT-CI) ≥ 3) AML and higher risk myelodysplasia (MDS) patients (HOVON155 trial). In total, 140 eligible patients were randomly (1:1) assigned to treatment with 10-days of decitabine alone (N = 70) or combined with midostaurin (50 mg bid;starting the day following the last dose of decitabine), (N = 70). Addition of midostaurin was well tolerated and the number of AEs was comparable for both treatment arms. Early death rates (< 30 days) were similar as well (10%). In the decitabine plus midostaurin arm 24% reached CR/CRi, the median OS was 4.8 months and 1-yrs OS was 31% which compared with 34% CR/CRi, median OS of 7.4 months and 1-yrs OS of 37% for the decitabine alone group (NS). Thus, while the addition of midostaurin appears safe, it does not enhance therapeutic efficacy of decitabine in unfit AML patients.
    Keywords:  AML; Decitabine; Midostaurin; Older; Phase II trial
    DOI:  https://doi.org/10.1007/s00277-024-06033-y
  17. Cell Stem Cell. 2024 Sep 26. pii: S1934-5909(24)00322-9. [Epub ahead of print]
      Mitochondrial adaptations dynamically reprogram cellular bioenergetics and metabolism and confer key properties for human cancers. However, the selective regulation of these mitochondrial responses remains largely elusive. Here, inspired by a genetic screening in acute myeloid leukemia (AML), we identify RAS effector RREB1 as a translational regulator and uncover a unique translation control system for nuclear-encoded mitochondrial proteins in human cancers. RREB1 deletion reduces mitochondrial activities and succinate metabolism, thereby damaging leukemia stem cell (LSC) function and AML development. Replenishing complex II subunit SDHD rectifies these deficiencies. Notably, inhibition of complex II re-sensitizes AML cells to venetoclax treatment. Mechanistically, a short RREB1 variant binds to a conserved motif in the 3' UTRs and cooperates with elongation factor eEF1A1 to enhance protein translation of nuclear-encoded mitochondrial mRNAs. Overall, our findings reveal a unique translation control mechanism for mitochondrial adaptations in AML pathogenesis and provide a potential strategy for targeting this vulnerability of LSCs.
    Keywords:  RREB1; SDHD; acute myeloid leukemia; leukemia stem cell; mitochondria; succinate; translation; venetoclax
    DOI:  https://doi.org/10.1016/j.stem.2024.09.008
  18. Blood. 2024 Oct 01. pii: blood.2024024962. [Epub ahead of print]
      This was a phase II trial, evaluating the safety/efficacy of high-dose IV-ascorbic acid in patients with TET2 mutant CCUS. Eight of 10 patients enrolled were eligible for response assessment. At week 20, there were no responses by IWG MDS criteria. NCT03418038.
    DOI:  https://doi.org/10.1182/blood.2024024962
  19. bioRxiv. 2024 Sep 20. pii: 2024.09.18.612239. [Epub ahead of print]
      Mutations in protein tyrosine phosphatase non-receptor type 11 ( PTPN11 ) have been considered late acquired mutations in acute myeloid leukemia (AML) development. To interrogate the ontogeny of PTPN11 mutations, we utilized single-cell DNA sequencing and identified that PTPN11 mutations can occur as initiating events in some AML patients when accompanied by strong oncogenic drivers, commonly NPM1 mutations. The co-driver role of PTPN11 mutations was confirmed in a novel murine model that exhibits an AML phenotype with early expansion of a diverse set of variably differentiated myeloid cells that engrafted into immunodeficient and immunocompetent mice. This immune diversity was reconstituted from early precursor cells when engrafted into immunodeficient mice. Moreover, immune diversity was also observed in the blast component of patient samples with NPM1 and PTPN11 mutations, providing novel antigen targets for immune based approaches in this subset of AML that is resistant to multiple targeted therapies.
    DOI:  https://doi.org/10.1101/2024.09.18.612239
  20. Br J Haematol. 2024 Sep 27.
      Patients with relapsed/refractory acute myeloid leukaemia (R/R AML), especially those who failed in novel target agents are related to dismal survival. We developed a multi-institutional, single-arm, prospective phase II trial, to investigate intensified conditioning with 'Mega-Dose' decitabine (MegaDAC) following allogeneic haematopoietic cell transplantation (allo-HCT) for R/R AML. From 2019 to 2023, 70 heavily treated R/R AML patients in active disease were consecutively enrolled. Significantly, every patient (n = 18) harbouring specific mutations exhibited no response to their best available target agents (BATs). Moreover, 74.3% of the enrolled patients did not reach remission following venetoclax-based regimens. All patients underwent intravenous decitabine (400 mg/m2) along with busulfan and cyclophosphamide. Median follow-up was 26 months (8-65) after HCT. All engrafted patients achieved MRD negativity post-HCT, with a median 3.3-log reduction in recurrent genetic abnormalities. The regimen was well tolerated, without irreversible grades III-IV toxicity peri-engraftment. The estimated 2-year CIR was 29.6% (18.4%-41.7%) and the est-2-year NRM was 15.5% (7.8%-25.5%). The est-2-year LFS, OS, and GRFS were 55.0% (43.5%-69.4%), 58.6% (47.0%-73.0%), and 42.9% (31.9%-57.6%), respectively. Multivariate analysis showed that pre-HCT drug exposures had no significant impact on primary outcomes. MegaDAC is highlighted as an effective and safe option for R/R AML in the new era of targeted therapies.
    Keywords:  R/R AML; allo‐HCT; decitabine; mDLI; relapse
    DOI:  https://doi.org/10.1111/bjh.19781
  21. J Clin Invest. 2024 Oct 01. pii: e180066. [Epub ahead of print]134(19):
      Clonal hematopoiesis of indeterminate potential (CHIP) has emerged as a previously unrecognized, potent, age-related, and common risk factor for atherosclerosis. Somatic mutations in certain known leukemia driver genes give rise to clones of mutant cells in peripheral blood. The increased risk of developing hematologic malignancy does not, on its own, explain excess mortality in individuals with CHIP. Cardiovascular disease accounts for much of this gap. Experimental evidence supports the causality of certain CHIP mutations in accelerated atherosclerosis. CHIP due to mutations in different driver genes varies in their promotion of atherosclerotic events and in the region of augmented atherosclerotic involvement. For example, CHIP due to mutations in DNMT3a appears less atherogenic than CHIP that arises from TET2 or JAK2, forms of CHIP that incite inflammation. The recognition of certain CHIP mutations as promoters of atherosclerotic risk has opened new insights into understanding of the pathophysiology of this disease. The accentuated cardiovascular risk and involvement of distinct pathways of various forms of CHIP also inform novel approaches to allocation of targeted therapies, affording a step toward personalized medicine.
    DOI:  https://doi.org/10.1172/JCI180066
  22. Leukemia. 2024 Oct 04.
      Cop1 encodes a ubiquitin E3 ligase that has been well preserved during evolution in both plants and metazoans. In metazoans, the C/EBP family transcription factors are targets for degradation by Cop1, and this process is regulated by the Tribbles pseudokinase family. Over-expression of Tribbles homolog 1 (Trib1) induces acute myeloid leukemia (AML) via Cop1-dependent degradation of the C/EBPα p42 isoform. Here, we induced rapid growth arrest and granulocytic differentiation of Trib1-expressing AML cells using a Cop1 conditional knockout (KO), which is associated with a transient increase in the C/EBPα p42 isoform. The growth-suppressive effect of Cop1 KO was canceled by silencing of Cebpa and reinforced by exogenous expression of the p42 isoform. Moreover, Cop1 KO improved the survival of recipients transplanted with Trib1-expressing AML cells. We further identified a marked increase in Trib1 protein expression in Cop1 KO, indicating that Trib1 is self-degraded by the Cop1 degradosome. COP1 downregulation also inhibits the proliferation of human AML cells in a TRIB1-dependent manner. Taken together, our results provide new insights into the role of Trib1/Cop1 machinery in the C/EBPα p42-dependent leukemogenic activity, and a novel idea to develop new therapeutics.
    DOI:  https://doi.org/10.1038/s41375-024-02430-4
  23. Br J Haematol. 2024 Oct 03.
      Ruxolitinib is a JAK1/JAK2 inhibitor approved for the treatment of myelofibrosis (MF)-related splenomegaly or symptoms. The recommended starting dose depends on platelet count, regardless of haemoglobin level at baseline. In the recent years, an overall survival (OS) advantage was reported in patients treated with ruxolitinib compared with best available therapy. We analysed a large Italian cohort of 3494 patients identified by Agenzia Italiana del Farmaco (AIFA) monitoring registries. Of them, 2337 (66.9%) started at reduced dose: these patients were older (median age 70 vs. 67), with increased incidence of large splenomegaly (longitudinal diameter 20 vs. 19.1 cm, median volume 1064 cm3 vs. 1016 cm3), with higher IPSS risk (30.9% vs. 26.1%), and worse ECOG score (more than 1 in 14.3% vs. 9.8%). After balancing for baseline characteristics, Kaplan-Meier analysis showed a median OS of 78.2 months (95% CI 65.9-89) for patients who started at full dose and 52.6 (95% CI 49-56.6) months for patients who started with reduced dose (p < 0.001). Group analysis also showed a substantial difference in patients with intermediate-2 and high IPSS risk. The majority of MF patients in real-world analysis started with a reduced dose of ruxolitinib, which is associated with less favourable outcomes.
    Keywords:  myelofibrosis; overall survival; ruxolitinib; starting dose
    DOI:  https://doi.org/10.1111/bjh.19812
  24. bioRxiv. 2024 Sep 17. pii: 2024.09.16.613227. [Epub ahead of print]
      Myeloid-biased differentiation of multipotent hematopoietic stem and progenitor cells (HSPCs) occurs with aging or exhaustion. The molecular mechanism(s) responsible for this fate bias remain unclear. Here we report that linker histone regulates HSPC fate choice at the lymphoid versus myeloid bifurcation. HSPCs expressing H1.0 from a doxycycline (dox) inducible transgene favor the lymphoid fate, display strengthened nucleosome organization and reduced chromatin accessibility at genomic regions hosting key myeloid fate drivers. The transcription factor Hlf is located in one of such regions, where chromatin accessibility and gene expression is reduced in H1.0 high HSPCs. Furthermore, H1.0 protein in HSPCs decreases in an aspartyl protease dependent manner, a process enhanced in response to interferon alpha (IFNα) signaling. Aspartyl protease inhibitors preserve endogenous H1.0 levels and promote the lymphoid fate of wild type HSPCs. Thus, our work uncovers a point of intervention to mitigate myeloid skewed hematopoiesis.
    DOI:  https://doi.org/10.1101/2024.09.16.613227
  25. Leukemia. 2024 Sep 27.
      Hematopoietic stem cells (HSCs) are vital for the differentiation of all mature blood cells, with their homeostasis being tightly regulated by intrinsic and extrinsic factors. Alternative splicing, mediated by the spliceosome complex, plays a crucial role in regulating HSC homeostasis by increasing protein diversity. This study focuses on the ATP-dependent RNA helicase DHX16, a key spliceosome component, and its role in HSC regulation. Using conditional knockout mice, we demonstrate that loss of Dhx16 in the hematopoietic system results in significant depletion of hematopoietic stem and progenitor cells, bone marrow failure, and rapid mortality. Dhx16-deficient HSCs exhibit impaired quiescence, G2-M phase cell cycle arrest, reduced protein synthesis, abnormal ribosome assembly, increased apoptosis, and decreased self-renewal capacity. Multi-omics analysis identified intron 4 retention in Emg1 mRNA in Dhx16 knockout HSCs, leading to reduced EMG1 protein expression, disrupted ribosome assembly, and nucleolar stress, activating the p53 pathway. Overexpression of Emg1 in Dhx16-deficient HSCs partially restored ribosome assembly and HSC function, suggesting Emg1 as a potential therapeutic target for ribosomopathies. Our findings reveal the critical role of Dhx16 in HSC homeostasis through the regulation of alternative splicing and ribosome assembly, providing insights into the molecular mechanisms underlying hematopoietic diseases and potential therapeutic strategies.
    DOI:  https://doi.org/10.1038/s41375-024-02423-3
  26. Leuk Res. 2024 Sep 21. pii: S0145-2126(24)00152-8. [Epub ahead of print]147 107586
      Adult acute myeloid leukemia (AML) patients under the age of 60 often receive similar intensive treatments, while outcomes between the adolescent and young adult (AYA) age group (18-39) and middle-aged adults (40-60 years) were seldom reported. We aim to study the characteristics and outcomes of AYA patients in comparison to middle-aged adults. A retrospective analysis was performed on AYA patients treated at Princess Margaret Cancer Center between 2008 and 2018. The primary outcomes include overall survival (OS), cumulative incidence of relapse (CIR), and non-relapse mortality (NRM). A total of 174 AYA patients and 176 middle-aged patients were included, with propensity score matching adjusting for potential major confounders. Comparing AYA and middle-aged patients, 5-year OS rates were similar at 54.6 % vs. 56.5 % (p=0.91), CIR rates at 29.5 % vs. 23.1 % (p=0.31), and similar NRM rates. Notably, non-transplanted AYA patients had a significantly higher CIR (39.8 %) compared to middle-aged patients (19.6 %) (p=0.0324), with more primary refractory/early relapsing disease. An observed trend toward improved OS in AYA patients post-2015 coincided with FLAG-IDA and haploidentical transplant implementations. In conclusion, the study suggests that AYA patients, particularly those not undergoing transplantation, may benefit from more intensive treatment strategies, emphasizing the need for tailored approaches in this age group.
    Keywords:  AML relapse; AML survival; Acute myeloid leukemia; Adolescence and young adult
    DOI:  https://doi.org/10.1016/j.leukres.2024.107586
  27. Leukemia. 2024 Oct 04.
      Accurate assessment of therapy response in myelodysplastic neoplasm (MDS) has been challenging. Directly monitoring mutational disease burden may be useful, but is not currently included in MDS response criteria, and the correlation of mutational burden and traditional response endpoints is not completely understood. Here, we used genome-wide and targeted next-generation sequencing (NGS) to monitor clonal and subclonal molecular disease burden in 452 samples from 32 patients prospectively treated in a clinical trial. Molecular responses were compared with International Working Group (IWG) 2006-defined response assessments. We found that myeloblast percentage consistently underestimates MDS molecular disease burden and that mutational clearance patterns for marrow complete remission (mCR), which depends on myeloblast assessment, was not different than stable disease or bone marrow aplasia, underscoring a major limitation of using mCR. In contrast, achieving a complete remission (CR) was associated with the highest level of mutation clearance and lowest residual mutational burden in higher-risk MDS patients. A targeted gene panel approach was inferior to genome-wide sequencing in defining subclones and their molecular responses but may be adequate for monitoring molecular disease burden when a targeted gene is present in the founding clone. Our work supports incorporating serial NGS-based monitoring into prospective MDS clinical trials.
    DOI:  https://doi.org/10.1038/s41375-024-02426-0
  28. J Biol Chem. 2024 Sep 27. pii: S0021-9258(24)02327-5. [Epub ahead of print] 107825
      Our understanding of acute leukemia pathology is heavily dependent on 11q23 chromosomal translocations involving the mixed lineage leukemia-1 (MLL1) gene, a key player in histone H3 lysine 4 (H3K4) methylation. These translocations result in MLL1-fusion (MLL1F) proteins that are thought to drive leukemogenesis. However, the mechanism behind increased H3K4 trimethylation in MLL1F-leukemic stem cells (MLL1F-LSCs), following loss of the catalytic SET domain of MLL1 (known for H3K4 mono- and dimethylation), remains unclear. In our investigation, we introduced a homozygous loss-of-function point mutation in MLL1 within human induced pluripotent stem cells. This mutation mimics the histone methylation, gene expression, and epithelial-mesenchymal transition (EMT) phenotypes of MLL1F-LSCs- without requiring a translocation or functional wild-type MLL1. The mutation caused a genome-wide redistribution of the H3K4 trimethyl mark and upregulated LSC-maintenance genes like HoxA9-A13, Meis1, and the HOTTIP long non-coding RNA (lncRNA). EMT markers such as ZEB1, SNAI2, and HIC-5 were also increased leading to enhanced cellular migration and invasiveness. These observations underscore the essential role of MLL1's enzymatic activity in restraining the cascade of epigenetic changes associated with the gene-activating H3K4 trimethylation mark, which we show may be catalyzed by mislocalized SETd1a H3K4 trimethyltransferase in the absence of MLL1's enzymatic activity. Challenging existing models, our findings imply that MLL1F-induced leukemias arise from a dominant-negative impact on MLL1's histone methyltransferase activity. We propose targeting SETd1a in precision medicine as a new therapeutic approach for MLL1-associated leukemias.
    Keywords:  EMT; Epigenetic plasticity; H3K4 methylation; MLL1; SETd1A; WDR5; iPS cells; leukemic stem cell; precision medicine
    DOI:  https://doi.org/10.1016/j.jbc.2024.107825
  29. Nature. 2024 Oct 02.
      Mutation of tet methylcytosine dioxygenase 2 (encoded by TET2) drives myeloid malignancy initiation and progression1-3. TET2 deficiency is known to cause a globally opened chromatin state and activation of genes contributing to aberrant haematopoietic stem cell self-renewal4,5. However, the open chromatin observed in TET2-deficient mouse embryonic stem cells, leukaemic cells and haematopoietic stem and progenitor cells5 is inconsistent with the designated role of DNA 5-methylcytosine oxidation of TET2. Here we show that chromatin-associated retrotransposon RNA 5-methylcytosine (m5C) can be recognized by the methyl-CpG-binding-domain protein MBD6, which guides deubiquitination of nearby monoubiquitinated Lys119 of histone H2A (H2AK119ub) to promote an open chromatin state. TET2 oxidizes m5C and antagonizes this MBD6-dependent H2AK119ub deubiquitination. TET2 depletion thereby leads to globally decreased H2AK119ub, more open chromatin and increased transcription in stem cells. TET2-mutant human leukaemia becomes dependent on this gene activation pathway, with MBD6 depletion selectively blocking proliferation of TET2-mutant leukaemic cells and largely reversing the haematopoiesis defects caused by Tet2 loss in mouse models. Together, our findings reveal a chromatin regulation pathway by TET2 through retrotransposon RNA m5C oxidation and identify the downstream MBD6 protein as a feasible target for developing therapies specific against TET2 mutant malignancies.
    DOI:  https://doi.org/10.1038/s41586-024-07969-x
  30. Cell Stem Cell. 2024 Sep 26. pii: S1934-5909(24)00317-5. [Epub ahead of print]
      Acute myeloid leukemia (AML) is a malignant cancer characterized by abnormal differentiation of hematopoietic stem and progenitor cells (HSPCs). While chimeric antigen receptor T (CAR-T) cell immunotherapies target AML cells, they often induce severe on-target/off-tumor toxicity by attacking normal cells expressing the same antigen. Here, we used base editors (BEs) and a prime editor (PE) to modify the epitope of CD123 on HSPCs, protecting healthy cells from CAR-T-induced cytotoxicity while maintaining their normal function. Although BE effectively edits epitopes, complex bystander products are a concern. To enhance precision, we optimized prime editing, increasing the editing efficiency from 5.9% to 78.9% in HSPCs. Epitope-modified cells were resistant to CAR-T lysis while retaining normal differentiation and function. Furthermore, BE- or PE-edited HSPCs infused into humanized mice endowed myeloid lineages with selective resistance to CAR-T immunotherapy, demonstrating a proof-of-concept strategy for treating relapsed AML.
    Keywords:  CAR-T immunotherapy; CD123; HSPCs; acute myeloid leukemia; base editing; bystander products; epitope editing; hematopoietic stem and progenitor cell; on-target off-tumor toxicity; prime editing
    DOI:  https://doi.org/10.1016/j.stem.2024.09.003
  31. Br J Haematol. 2024 Oct 03.
      Third-generation tyrosine kinase inhibitors (TKIs) have much potential for the treatment of BCR::ABL1-positive leukaemia, particularly that harbouring the ABL1 T315I mutation. Olverembatinib (HQP1351), a novel third-generation TKI, has favourable efficacy and safety profiles in chronic myeloid leukaemia. Here, we present the clinical findings from 31 BCR::ABL1-positive acute lymphoblastic leukaemia (ALL) patients who received olverembatinib. Among the 14 patients with overt relapsed/refractory (R/R) disease (including 10 with the T315I mutation), 71.4% achieved an overall response. Of the other 17 patients with minimal residual disease (MRD)-positive ALL (including 14 with the T315I mutation), 60.0% and 47.1% achieved MRD flow negativity and complete molecular remission, respectively. With a median follow-up time of 16.3 months, the median event-free survival and overall survival were 3.9 and 8.3 months respectively, in overt R/R patients, and 11.5 and 18.4 months in MRD-positive patients. Allogeneic haematopoietic stem cell transplantation further improved outcomes among responders. The safety profile was generally manageable. This study suggests that olverembatinib-based therapy is another promising option for BCR::ABL1-positive ALL in addition to ponatinib, especially for patients with MRD-positive disease and a single T315I mutation.
    Keywords:  BCR::ABL1‐positive ALL; T315I mutation; efficacy; olverembatinib; safety
    DOI:  https://doi.org/10.1111/bjh.19804
  32. Blood Adv. 2024 Sep 23. pii: bloodadvances.2024013545. [Epub ahead of print]
      Indeterminate dendritic cell histiocytosis (IDCH) is a rare and poorly understood entity characterized by accumulation of CD1a+/S100+ histiocytes (as Langerhans cell histiocytosis (LCH)), but with reduced-absent expression of Langerin/CD207. We assembled 43 cases of IDCH (defined by CD1a+/CD207<20% immunophenotypic profile) examining the clinical, pathologic, and molecular landscape. Median age at presentation was 70 years (IQR: 44-80 years) with cutaneous (31/43; 72%) and nodal (11/43; 26%) involvement predominating. Eighteen (42%) individuals had an associated non-histiocytic hematopoietic neoplasm ('secondary' IDCH) while 7 of 43 (16%) had a concurrent non-IDCH histiocytosis ('mixed' histiocytosis). Most cases exhibited morphology indistinguishable from LCH but with a CD1c+/CSF1R(CD115)-phenotype, mirroring the signature of normal indeterminate cells and conventional dendritic cell type 2. Mutational analysis revealed frequent KRAS (13/32; 41%), and BRAF p.V600E (11/36, 31%) mutations that were nearly mutually exclusive. RNAseq analysis uncovered ETV3::NCOA2 fusion in 6 other patients presenting as a sole genetic alteration without any other concurrent histiocytic or hematopoietic neoplasm. BRAF and MAP2K1 alterations were significantly associated with partial/retained (1-20%) Langerin expression (P = .005) and mixed histiocytosis (P = .002). Remarkably, myeloid alterations (DNMT3A, TET2 and SRSF2) co-occurred in IDCH tissues of several individuals. Paired sequencing of IDCH and concurrent non-IDCH hematopoietic neoplasm in four individuals revealed shared mutations. Age at diagnosis and any nodal involvement at diagnosis predicted inferior overall survival, but BRAF/RAS pathway alterations did not impact outcome. These data have implications for the diagnostic evaluation, classification, and therapeutic management of IDCH.
    DOI:  https://doi.org/10.1182/bloodadvances.2024013545
  33. bioRxiv. 2024 Sep 19. pii: 2024.09.13.612961. [Epub ahead of print]
      Gene regulatory network (GRNs) models provide mechanistic understanding of the gene regulations and interactions that control various aspects of cellular behaviors. While researchers have constructed GRNs to model specific sets of gene regulations or interactions, little work has been made to integrate or merge these models into larger, more comprehensive ones that could encompass more genes, and improve the accuracy of predicting biological processes. Here, we present a workflow for merging logical GRN models, which requires sequential steps including model standardization, reproducing, merging and evaluations, and demonstrate its application in acute myeloid leukemia (AML) study. We demonstrate the feasibility and benefits of model merging by integrating two pairs of published models. Our integrated models were able to retain similar accuracy of the original publications, while increasing the coverage and explainability of the biological system. This approach highlights the integration of logical models in advancing system biology and enhancing the understanding of complex diseases.
    Author summary: In our study, we tackle the challenges of integrating gene regulatory network (GRN) models to enhance our understanding of complex biological systems. GRNs are essential tools for understanding how genes regulate various cellular behaviors, but individual models often focus on specific sets of genes or interactions. We present a novel workflow that merges these individual logical GRN models into more comprehensive ones, providing a broader view of gene regulation. We applied this workflow to Acute Myeloid Leukemia (AML), a highly aggressive form of blood cancer. AML is challenging to treat due to its genetic complexity and the frequent occurrence of treatment-resistant mutations. Our integrated models retain the accuracy of the original models while offering improved coverage of the biological processes. This approach offers valuable insights into the disease's underlying mechanisms through a combination of models that describe different aspects of AML. We envision that the proposed workflow will improve predictions, generate deeper insights, and improve our understanding and treatment of complex diseases like AML.
    DOI:  https://doi.org/10.1101/2024.09.13.612961
  34. Nat Commun. 2024 Sep 30. 15(1): 8439
      Chimeric antigen receptor (CAR)-modified natural killer (NK) cells show antileukemic activity against acute myeloid leukemia (AML) in vivo. However, NK cell-mediated tumor killing is often impaired by the interaction between human leukocyte antigen (HLA)-E and the inhibitory receptor, NKG2A. Here, we describe a strategy that overcomes CAR-NK cell inhibition mediated by the HLA-E-NKG2A immune checkpoint. We generate CD33-specific, AML-targeted CAR-NK cells (CAR33) combined with CRISPR/Cas9-based gene disruption of the NKG2A-encoding KLRC1 gene. Using single-cell multi-omics analyses, we identified transcriptional features of activation and maturation in CAR33-KLRC1ko-NK cells, which are preserved following exposure to AML cells. Moreover, CAR33-KLRC1ko-NK cells demonstrate potent antileukemic killing activity against AML cell lines and primary blasts in vitro and in vivo. We thus conclude that NKG2A-deficient CAR-NK cells have the potential to bypass immune suppression in AML.
    DOI:  https://doi.org/10.1038/s41467-024-52388-1
  35. J Clin Invest. 2024 Oct 01. pii: e180069. [Epub ahead of print]134(19):
      Therapy-related clonal hematopoiesis (t-CH) is defined as clonal hematopoiesis detected in individuals previously treated with chemotherapy and/or radiation therapy. With the increased use of genetic analysis in oncological care, the detection of t-CH among cancer patients is becoming increasingly common. t-CH arises through the selective bottleneck imposed by chemotherapies and potentially through direct mutagenesis from chemotherapies, resulting in a distinct mutational landscape enriched with mutations in DNA damage-response pathway genes such as TP53, PPM1D, and CHEK2. Emerging evidence sheds light on the mechanisms of t-CH development and potential strategies to mitigate its emergence. Due to its unique characteristics that predominantly affect cancer patients, t-CH has clinical implications distinct from those of CH in the general population. This Review discusses the potential mechanisms of t-CH development, its mutational landscape, mutant-drug relationships, and its clinical significance. We highlight the distinct nature of t-CH and call for intensified research in this field.
    DOI:  https://doi.org/10.1172/JCI180069
  36. Blood. 2024 Oct 02. pii: blood.2023022415. [Epub ahead of print]
      The advent of JAK inhibitors (JAKi) inaugurated a novel era in the treatment of myelofibrosis (MF), a myeloproliferative neoplasm with heterogeneous clinical manifestations. Four JAKi have been approved for intermediate or high-risk MF, in the US. Regulatory approval of the first JAK1/2 inhibitor, ruxolitinib, in 2011 transformed the landscape of MF by markedly controlling splenomegaly and constitutional symptoms, improving patients' lives, and prolonging survival. Fedratinib, the second approved JAKi, is preferred in the second-line setting. Ruxolitinib and fedratinib can cause myelosuppression and are recommended for patients with myeloproliferative MF. Approval of 2 less myelosuppressive JAKi, pacritinib and momelotinib, provided essential treatment options for patients with severe thrombocytopenia and anemia, respectively. Pacritinib and momelotinib are potent ACVR1 inhibitors, resulting in significant anemia benefits. Transfusion independence was achieved with momelotinib in severely anemic patients, and association of transfusion independence with prolonged overall survival was demonstrated. Judicious treatment decisions of JAKi can be made with in-depth understanding of the pivotal clinical trials on JAKi and their therapeutic attributes and should be guided by the dominant clinical manifestations and the type/degree of cytopenia(s). This article reviews our clinical approach to treatment with JAKi and their sequencing in MF patients by presenting 3 clinical vignettes.
    DOI:  https://doi.org/10.1182/blood.2023022415
  37. Haematologica. 2024 Oct 03.
      The ubiquitination or SUMOylation of hematopoietic related factors plays pivotal roles in hematopoiesis. RNF111, known as a ubiquitin ligase (Ubl), is a newly discovered SUMO-targeted ubiquitin ligase (STUbl) involved in multiple signaling pathways mediated by TGF-β family members. However, its role in hematopoiesis remains unclear. Herein, a heritable Rnf111 mutant zebrafish line was generated by CRISPR/Cas9-mediated genome editing. Impaired hematopoietic stem and progenitor cells (HSPC) of definitive hematopoiesis was found in Rnf111 deficient mutants. Ablation of Rnf111 resulted in decreased phosphorylation of Smad2/3 in HSPC. Definitive endoderm 2 inducer (IDE2), which specifically activates TGF-β signaling and downstream Smad2 phosphorylation, can restore the definitive hematopoiesis in Rnf111-deficient embryos. Further molecular mechanism studies revealed that Gcsfr/NO signaling was an important target pathway of Smad2/3 involved in Rnf111-mediated HSPC development. In conclusion, our study demonstrated that Rnf111 contributes to the development of HSPC by maintaining Smad2/3 phosphorylation and the Gcsfr/NO signaling pathway activation. Keywords: Rnf111, Ubiquitin ligase (UbL), HSPC, Smad2/3, Gcsfr/NO.
    DOI:  https://doi.org/10.3324/haematol.2024.285438
  38. Leukemia. 2024 Sep 27.
      Hydroxyurea (HU) constitutes the first-line treatment in most patients with essential thrombocythemia (ET), but criteria for changing therapy are not clearly established. The prognostic value of complete hematological response (CHR) and resistance/intolerance to HU was assessed in 1080 patients from the Spanish Registry of ET, classified according to revised IPSET-Thrombosis stratification (Very low- n = 61, Low- n = 83, Intermediate- n = 261, and High-risk n = 675). With a median therapy duration of 5 years, CHR was registered in 720 (67%) patients (1-year probability 51%) and resistance/intolerance in 219 (20%) patients (5-years probability 13%). After correction by other risk factors, High-risk patients achieving CHR showed a reduced risk of arterial thrombosis (HR: 0.35, 95%CI: 0.2-0.6, p = 0.001) and a trend towards lower risk of venous thrombosis (HR: 0.45, 95%CI: 0.2-1.02, p = 0.06) whereas no association was observed for intermediate- or low-risk patients. In comparison with non-responders, intermediate- and high-risk patients achieving CHR had longer survival and lower myelofibrosis incidence. Development of resistance/intolerance to HU, mainly cytopenia, was associated with higher probability of myelofibrosis but no effect on survival or thrombotic risk was demonstrated. In conclusion, CHR with HU is associated with better outcomes and might be an early indicator for selecting candidates to second-line clinical trials.
    DOI:  https://doi.org/10.1038/s41375-024-02416-2
  39. bioRxiv. 2024 Sep 21. pii: 2024.09.17.613129. [Epub ahead of print]
      Haematopoietic stem cells maintain blood production throughout life. While extensively characterised using the laboratory mouse, little is known about how the population is sustained and evolves with age. We isolated stem cells and progenitors from young and old mice, identifying 221,890 somatic mutations genome-wide in 1845 single cell-derived colonies, and used phylogenetic analysis to infer the ontogeny and population dynamics of the stem cell pool. Mouse stem cells and progenitors accrue ∼45 somatic mutations per year, a rate only about 2-fold greater than human progenitors despite the vastly different organismal sizes and lifespans. Phylogenetic patterns reveal that stem and multipotent progenitor cell pools are both established during embryogenesis, after which they independently self-renew in parallel over life. The stem cell pool grows steadily over the mouse lifespan to approximately 70,000 cells, self-renewing about every six weeks. Aged mice did not display the profound loss of stem cell clonal diversity characteristic of human haematopoietic ageing. However, targeted sequencing revealed small, expanded clones in the context of murine ageing, which were larger and more numerous following haematological perturbations and exhibited a selection landscape similar to humans. Our data illustrate both conserved features of population dynamics of blood and distinct patterns of age-associated somatic evolution in the short-lived mouse.
    DOI:  https://doi.org/10.1101/2024.09.17.613129
  40. Exp Hematol. 2024 Oct 01. pii: S0301-472X(24)00517-4. [Epub ahead of print] 104652
      Functional experimentation has laid the foundation for our understanding of hematopoietic and leukemic stem cells. Yet, most recently, a flurry of descriptive studies of primary human cells, fueled by rapid technological advances in sequencing technologies, have emerged. These increasing opportunities to describe at great detail have taken precedence over rigorously interrogating functional mediators of biology, particularly in primary human cells. Here, we argue that an improved toolset of gene editing and stem cell biology technologies will allow the field to expand beyond extensive descriptive studies to more functional studies.
    Keywords:  Functional Experimentation; Human Hematopoiesis; Leukemia Research
    DOI:  https://doi.org/10.1016/j.exphem.2024.104652
  41. Clin Lymphoma Myeloma Leuk. 2024 Sep 12. pii: S2152-2650(24)01804-4. [Epub ahead of print]
      Myelofibrosis (MF) is a chronic myeloid neoplasm characterized by myeloproliferation, bone marrow fibrosis, splenomegaly, and constitutional symptoms related to pro-inflammatory cytokine signaling. Biologically, MF is characterized by constitutive activation of JAK-STAT signaling; accordingly, JAK inhibitors have been rationally developed to treat MF. Following the initial approval of ruxolitinib in 2011, three additional agents have been approved: fedratinib, pacritinib, and momelotinib. As these therapies are noncurative, allogeneic stem cell transplantation remains a key treatment modality and patients with MF who are deemed candidates should be referred to a transplant center. This potentially curative but toxic approach is typically reserved for patients with higher-risk disease, and JAK inhibitors are recommended in the pretransplant setting. JAK inhibitors have proven effective at managing splenomegaly and constitutional symptoms and should be started early in the disease course in patients presenting with these clinical manifestations; asymptomatic patients may initially be followed with close surveillance. Drug-related myelosuppression has been a challenge with initial JAK inhibitors, particularly in patients presenting with a cytopenic phenotype. However, newer agents, namely pacritinib and momelotinib, have proven more effective in this setting and are approved for patients with significant thrombocytopenia and anemia, respectively. Resistance or disease progression is clinically challenging and may be defined by several possible events, such as increasing splenomegaly or progression to accelerated or blast phase disease. However, with multiple JAK inhibitors now approved, sequencing of these agents appears poised to improve outcomes. Additionally, novel JAK inhibitors and JAK inhibitor-based combinations are in clinical development.
    Keywords:  JAK inhibitors; JAK2 V617F; Myelofibrosis; Ruxolitinib; Splenomegaly
    DOI:  https://doi.org/10.1016/j.clml.2024.09.001
  42. Commun Biol. 2024 Oct 04. 7(1): 1257
      KMT2A-rearranged acute lymphoblastic leukemia (ALL) is characterized by deregulation of the epigenome and shows susceptibility towards histone deacetylase (HDAC) inhibition. Most broad-spectrum HDAC inhibitors simultaneously target multiple human HDAC isoforms. Consequently, they often induce toxicity and especially in combination with other therapeutic agents. Therefore, more specifically targeting HDAC isoforms may represent a safer therapeutic strategy. Here we show that shRNA-mediated knock-down of the class IIA HDAC isoforms HDAC4, HDAC5, and HDAC7 results in apoptosis induction and cell cycle arrest in KMT2A-rearranged ALL cells. In concordance, the HDAC4/5 selective small molecule inhibitor LMK-235 effectively eradicates KMT2A-rearranged ALL cell lines as well as primary patient samples in vitro. However, using a xenograft mouse model of KMT2A-rearranged ALL we found that the maximum achievable dose of LMK-235 was insufficient to induce anti-leukemic effects in vivo. Similar results were obtained for the specific class IIA HDAC inhibitors MC1568 and TMP195. Finally, LMK-235 appeared to exert minimal anti-leukemic effects in vivo in combination with the BCL-2 inhibitor venetoclax, but not enough to prolong survival in treated mice. In conclusion, class IIA HDAC isoforms represent attractive therapeutic target in KMT2A-rearranged ALL, although clinical applications require the development of more stable and efficient specific HDAC inhibitors.
    DOI:  https://doi.org/10.1038/s42003-024-06916-w
  43. J Blood Disord Malig. 2024 ;pii: JBDM-2-105. [Epub ahead of print]2(1):
      Acute myeloid leukemia (AML) is a type of blood cancer of the myeloid cell lineage. Obesity is characterized by an increase in body weight that results in excessive fat accumulation. Obesity has been associated with an increased incidence of many cancers, including blood cancers. This study evaluated the role obesity in AML progression in a novel transgenic mouse model developed by crossing Flt3ITD mice with Lepob/ob mice. Leukemia burden was augmented in obese AML mice. In addition, it was determined that obesity upregulated the ceramide-mediated and ceramide-1-phosphate-mediated NADPH oxidase 2 (NOX2). Notably, increased oxidative pathways has been attributed to disease progression in AML. Taken together, this study demonstrates a direct link between obesity and the progression of AML in part by augmenting the ceramide mediated NOX2.
    Keywords:  Acid sphingomyelinase; Acute myeloid leukemia; Ceramide; Ceramide kinase; Ceramide-1-phosphate; NADPH oxidase 2; Obesity