bims-tremyl Biomed News
on Therapy resistance biology in myeloid leukemia
Issue of 2022‒03‒27
twenty-two papers selected by
Paolo Gallipoli
Barts Cancer Institute, Queen Mary University of London

  1. Genes Dev. 2022 Mar 01. 36(5-6): 259-277
      Despite FDA approval of nine new drugs for patients with acute myeloid leukemia (AML) in the United States over the last 4 years, AML remains a major area of unmet medical need among hematologic malignancies. In this review, we discuss the development of promising new molecular targeted approaches for AML, including menin inhibition, novel IDH1/2 inhibitors, and preclinical means to target TET2, ASXL1, and RNA splicing factor mutations. In addition, we review progress in immune targeting of AML through anti-CD47, anti-SIRPα, and anti-TIM-3 antibodies; bispecific and trispecific antibodies; and new cellular therapies in development for AML.
    Keywords:  ASXL1; IDH1; IDH2; RNA splicing; TET2; acute myeloid leukemia; menin; myelodysplastic syndromes
  2. Cancers (Basel). 2022 Mar 11. pii: 1446. [Epub ahead of print]14(6):
      It is known that 8-chloro-adenosine (8-Cl-Ado) is a novel RNA-directed nucleoside analog that targets leukemic stem cells (LSCs). In a phase I clinical trial with 8-Cl-Ado in patients with refractory or relapsed (R/R) AML, we observed encouraging but short-lived clinical responses, likely due to intrinsic mechanisms of LSC resistance. LSC homeostasis depends on amino acid-driven and/or fatty acid oxidation (FAO)-driven oxidative phosphorylation (OXPHOS) for survival. We recently reported that 8-Cl-Ado and the BCL-2-selective inhibitor venetoclax (VEN) synergistically inhibit FAO and OXPHOS in LSCs, thereby suppressing acute myeloid leukemia (AML) growth in vitro and in vivo. Herein, we report that 8-Cl-Ado inhibits ribosomal RNA (rRNA) synthesis through the downregulation of transcription initiation factor TIF-IA that is associated with increasing levels of p53. Paradoxically, 8-Cl-Ado-induced p53 increased FAO and OXPHOS, thereby self-limiting the activity of 8-Cl-Ado on LSCs. Since VEN inhibits amino acid-driven OXPHOS, the addition of VEN significantly enhanced the activity of 8-Cl-Ado by counteracting the self-limiting effect of p53 on FAO and OXPHOS. Overall, our results indicate that VEN and 8-Cl-Ado can cooperate in targeting rRNA synthesis and OXPHOS and in decreasing the survival of the LSC-enriched cell population, suggesting the VEN/8-Cl-Ado regimen as a promising therapeutic approach for patients with R/R AML.
    Keywords:  8-chloro-adenosine; acute myeloid leukemia; metabolism; rRNA synthesis; venetoclax
  3. iScience. 2022 Apr 15. 25(4): 104004
      Mutations in the gene encoding DNA methyltransferase 3A (DNMT3A) are the most common cause of clonal hematopoiesis and are among the most common initiating events of acute myeloid leukemia (AML). Studies in germline and somatic Dnmt3a knockout mice have identified focal, canonical hypomethylation phenotypes in hematopoietic cells; however, the kinetics of methylation loss following acquired DNMT3A inactivation in hematopoietic cells is essentially unknown. Therefore, we evaluated a somatic, inducible model of hematopoietic Dnmt3a loss, and show that inactivation of Dnmt3a in murine hematopoietic cells results in a relatively slow loss of methylation at canonical sites throughout the genome; in contrast, remethylation of Dnmt3a deficient genomes in hematopoietic cells occurs much more quickly. This data suggests that slow methylation loss may contribute, at least in part, to the long latent period that characterizes clonal expansion and leukemia development in individuals with acquired DNMT3A mutations in hematopoietic stem cells.
    Keywords:  Biological sciences; Epigenetics; Molecular biology
  4. J Hematol Oncol. 2022 Mar 21. 15(1): 30
      BACKGROUND: Isocitrate dehydrogenase-2 (IDH2) is a mitochondrial enzyme that catalyzes the metabolic conversion between isocitrate and alpha-ketoglutarate (α-KG) in the TCA cycle. IDH2 mutation is an oncogenic event in acute myeloid leukemia (AML) due to the generation of 2-hydroxyglutarate. However, the role of wild-type IDH2 in AML remains unknown, despite patients with it suffer worse clinical outcome than those harboring mutant type.METHODS: IDH2 expression in AML cell lines and patient samples was evaluated by RT-qPCR, western blotting and database analyses. The role of wild-type IDH2 in AML cell survival and proliferation was tested using genetic knockdown and pharmacological inhibition in AML cells and animal models. LC-MS, GC-MS, isotope metabolic tracing, and molecular analyses were performed to reveal the underlying mechanisms.
    RESULTS: We found that wild-type IDH2 was overexpressed in AML and played a major role in promoting leukemia cell survival and proliferation in vitro and in vivo. Metabolomic analyses revealed an active IDH2-mediated reductive TCA cycle that promoted the conversion of α-KG to isocitrate/citrate to facilitate glutamine utilization for lipid synthesis in AML cells. Suppression of wild-type IDH2 by shRNA resulted in elevated α-KG and decreased isocitrate/citrate, leading to reduced lipid synthesis, a significant decrease in c-Myc downregulated by α-KG, and an inhibition of AML viability and proliferation. Importantly, pharmacological inhibition of IDH2 showed significant therapeutic effect in mice inoculated with AML cells with wt-IDH2 and induced a downregulation of C-MYC in vivo.
    CONCLUSIONS: Wt-IDH2 is an essential molecule for AML cell survival and proliferation by promoting conversion of α-KG to isocitrate for lipid synthesis and by upregulating c-Myc expression and could be a potential therapeutic target in AML.
    Keywords:  Acute myeloid leukemia; Alpha-ketoglutarate; Lipid synthesis; TCA cycle; Wild-type IDH2; c-Myc
  5. Cancers (Basel). 2022 Mar 21. pii: 1593. [Epub ahead of print]14(6):
      Acute myeloid leukemia (AML) is the most common acute leukemia in adults. Patients with AML harboring a constitutively active internal tandem duplication mutation (ITDMUT) in the FMS-like kinase tyrosine kinase (FLT3) receptor generally have a poor prognosis. Several tyrosine kinase/FLT3 inhibitors have been developed and tested clinically, but very few (midostaurin and gilteritinib) have thus far been FDA/EMA-approved for patients with newly diagnosed or relapse/refractory FLT3-ITDMUT AML. Disappointingly, clinical responses are commonly partial or not durable, highlighting the need for new molecules targeting FLT3-ITDMUT AML. Here, we tested EC-70124, a hybrid indolocarbazole analog from the same chemical space as midostaurin with a potent and selective inhibitory effect on FLT3. In vitro, EC-70124 exerted a robust and specific antileukemia activity against FLT3-ITDMUT AML primary cells and cell lines with respect to cytotoxicity, CFU capacity, apoptosis and cell cycle while sparing healthy hematopoietic (stem/progenitor) cells. We also analyzed its efficacy in vivo as monotherapy using two different xenograft models: an aggressive and systemic model based on MOLM-13 cells and a patient-derived xenograft model. Orally disposable EC-70124 exerted a potent inhibitory effect on the growth of FLT3-ITDMUT AML cells, delaying disease progression and debulking the leukemia. Collectively, our findings show that EC-70124 is a promising and safe agent for the treatment of AML with FLT3-ITDMUT.
    Keywords:  AML; AML preclinical model; EC-70124 multi-kinase inhibitor; FLT3 inhibitor; FLT3-ITD mutation
  6. Blood Adv. 2022 Mar 23. pii: bloodadvances.2021006233. [Epub ahead of print]
      Monitoring of measurable residual disease (MRD) in patients with acute myleoid leukemia (AML) is predictive for disease recurrence and may identify patients who benefit from treatment intensification. Current MRD techniques rely on multicolor flow cytometry or molecular methods, but are limited in applicability or sensitivity. We evaluated the feasibility of a novel approach for MRD detection in peripheral blood (PB), which combines immunomagnetic preenrichment and fluorescence-activated cell sorting (FACS) for isolation of CD34+ cells with error-reduced targeted next-generation sequencing (NGS). For clinical validation, we retrospectively analyzed 429 PB and 55 bone marrow (BM) samples of 40 AML and high-risk MDS patients, with/without molecular relapse based on CD34+ donor chimerism (DC), in complete remission after alloHSCT. Enrichment of CD34+ cells for NGS increased the detection of mutant alleles in PB ~1000-fold (median VAF 1.27% vs 0.0046% in unsorted PB; P<0.0001). Although a strong correlation was observed for the parallel analysis of CD34+ PB cells with NGS and DC (r=0.8601), the combination of FACS and NGS improved sensitivity for MRD detection in dilution experiments ~10-fold to levels of 10-6. In both assays, MRD detection was superior using PB versus BM for CD34+ enrichment. Importantly, NGS on CD34+ PB cells enabled prediction of molecular relapse with high sensitivity (100%) and specificity (91%), and significantly earlier (median 48 days, range 0-281; P=0.0011) than by CD34+ DC or NGS of unsorted PB, providing additional time for therapeutic intervention. Moreover, panel sequencing in CD34+ cells allowed the early assessment of clonal trajectories in hematological complete remission.
  7. Nat Commun. 2022 Mar 25. 13(1): 1624
      Patient-derived xenografts (PDX) are widely used as human cancer models. Previous studies demonstrated clonal discordance between PDX and primary cells. However, in acute myeloid leukemia (AML)-PDX models, the significance of the clonal dynamics occurring in PDX remains unclear. By evaluating changes in the variant allele frequencies (VAF) of somatic mutations in serial samples of paired primary AML and their PDX bone marrow cells, we identify the skewing engraftment of relapsed or refractory (R/R) AML clones in 57% of PDX models generated from multiclonal AML cells at diagnosis, even if R/R clones are minor at <5% of VAF in patients. The event-free survival rate of patients whose AML cells successfully engraft in PDX models is consistently lower than that of patients with engraftment failure. We herein demonstrate that primary AML cells including potentially chemotherapy-resistant clones dominantly engraft in AML-PDX models and they enrich pre-existing treatment-resistant subclones.
  8. Exp Hematol. 2022 Mar 16. pii: S0301-472X(22)00125-4. [Epub ahead of print]
      Cytarabine and other chain-terminating nucleoside analogs that damage replication forks in rapidly proliferating cells are a cornerstone of leukemia chemotherapy, yet the outcomes remain unsatisfactory due to resistance and toxicity. Better understanding of DNA damage repair and downstream effector mechanisms in different disease subtypes can guide combination strategies that sensitize leukemia cells to cytarabine without increasing side effects. We have previously found that mutations in DNMT3A, one of the most commonly mutated genes in acute myeloid leukemia and associated with poor prognosis, predisposed cells to DNA damage and cell killing by cytarabine, cladribine, and other nucleoside analogs, which coincided with PARP1 dysfunction and DNA repair defect (Venugopal et al, 2021). In this perspective piece, we first overview DNA repair mechanisms that remove aberrant chain-terminating nucleotides as determinants of sensitivity or resistance to cytarabine and other nucleoside analogs. Next, we discuss PARP inhibition as a rational strategy to increase cytarabine efficacy in cells without DNMT3A mutations, while considering the implications of PARP inhibitor resistance for promoting clonal hematopoiesis. Finally, we examine the utility of p53 potentiators to boost leukemia cell killing by cytarabine in the context of mutant DNMT3A. Systematic profiling of DNA damage repair proficiency has the potential to uncover subtype-specific therapeutic dependencies in AML.
    Keywords:  DNA damage repair; DNMT3A; MDM2 inhibitors; PARP inhibitors; acute myeloid leukemia (AML); cytarabine; p53 potentiators; replication fork stalling
  9. Cancer Res. 2022 Mar 21. pii: canres.0548.2021. [Epub ahead of print]
      The protein tyrosine phosphatase SHP2 is crucial for oncogenic transformation of acute myeloid leukemia (AML) cells expressing mutated receptor tyrosine kinases (RTK). SHP2 is required for full RAS-ERK activation to promote cell proliferation and survival programs. Allosteric SHP2 inhibitors act by stabilizing SHP2 in its auto-inhibited conformation and are currently being tested in clinical trials for tumors with overactivation of the RAS/ERK pathway, alone and in various drug combinations. In this study, we established cells with acquired resistance to the allosteric SHP2 inhibitor SHP099 from two FLT3-ITD-positive AML cell lines. Label-free and isobaric labeling quantitative mass spectrometry-based phosphoproteomics of these resistant models demonstrated that AML cells can restore phosphorylated ERK (pERK) in the presence of SHP099, thus developing adaptive resistance. Mechanistically, SHP2 inhibition induced tyrosine phosphorylation and feedback-driven activation of the FLT3 receptor, which in turn phosphorylated SHP2 on tyrosine 62. This phosphorylation stabilized SHP2 in its open conformation, preventing SHP099 binding and conferring resistance. Combinatorial inhibition of SHP2 and MEK or FLT3 prevented pERK rebound and resistant cell growth. The same mechanism was observed in a FLT3-mutated B-ALL cell line and in the inv(16)/KitD816Y AML mouse model, but allosteric inhibition of Shp2 did not impair the clonogenic ability of normal bone marrow progenitors. Together, these results support the future use of SHP2 inhibitor combinations for clinical applications.
  10. Front Biosci (Schol Ed). 2022 Mar 08. 14(1): 8
      The enzymes that belong to the aldehyde dehydrogenase family are expressed in a variety of cells; yet activity of their main members characterizes stem cells, both normal and malignant. Several members of this family perform critical functions in stem cells, in general, and a few have been shown to have key roles in malignant tumors and their recurrence. In particular, ALDH1A1, which localizes to the cytosol and the nucleus, is an enzyme critical in cancer stem cells. In acute myeloid leukemia (AML), ALDH1A1 protects leukemia-initiating cells from a number of antineoplastic agents, and proves vital for the establishment of human AML xenografts in mice. ALDH2, which is located in mitochondria, has a major role in alcohol metabolism by clearing ethanol-derived acetaldehyde. Haematopoietic stem cells require ALDH2 for protection against acetaldehyde, which can cause damage to DNA, leading to insertions, deletions, chromosomal rearrangements, and translocations. Mutations compromise stem cell function, and thereby threaten blood homeostasis. We review here the potential of targeting the enzymatic activity of aldehyde dehydrogenases in acute leukemia.
    Keywords:  acute; aldehyde dehydrogenase; biomarker; drug resistance; gene expression; immunosuppression; leukemia; myeloid; neoplastic stem cells
  11. Cancers (Basel). 2022 Mar 18. pii: 1554. [Epub ahead of print]14(6):
      Cyclin-dependent kinase 6 (CDK6) represents a novel therapeutic target for the treatment of certain subtypes of acute myeloid leukaemia (AML). CDK4/6 kinase inhibitors have been widely studied in many cancer types and their effects may be limited by primary and secondary resistance mechanisms. CDK4/6 degraders, which eliminate kinase-dependent and kinase-independent effects, have been suggested as an alternative therapeutic option. We show that the efficacy of the CDK6-specific protein degrader BSJ-03-123 varies among AML subtypes and depends on the low expression of the INK4 proteins p16INK4A and p18INK4C. INK4 protein levels are significantly elevated in KMT2A-MLLT3+ cells compared to RUNX1-RUNX1T1+ cells, contributing to the different CDK6 degradation efficacy. We demonstrate that CDK6 complexes containing p16INK4A or p18INK4C are protected from BSJ-mediated degradation and that INK4 levels define the proliferative response to CDK6 degradation. These findings define INK4 proteins as predictive markers for CDK6 degradation-targeted therapies in AML.
    Keywords:  AML; CDK6; Cdkn2a; Cdkn2c; INK4; degrader; p16; p18
  12. Cancer Discov. 2022 Mar 21. pii: candisc.1145.2020. [Epub ahead of print]
      Pharmacological inhibition of epigenetic enzymes can have therapeutic benefit against hematological malignancies. In addition to affecting tumor cell growth and proliferation, these epigenetic agents may induce anti-tumor immunity. Here we discovered a novel immuno-regulatory mechanism through inhibition of histone deacetylases (HDACs). In models of AML, leukemia cell differentiation and therapeutic benefit mediated by the HDAC inhibitor panobinostat required activation of the type I interferon (IFN) pathway. Plasmacytoid dendritic cells (pDCs) produced type I IFN after panobinostat treatment, through transcriptional activation of IFN genes concomitant with increased H3K27 acetylation at these loci. Depletion of pDCs abrogated panobinostat-mediated induction of type I IFN signaling in leukemia cells and impaired therapeutic efficacy, while combined treatment of panobinostat and IFN improved outcomes in pre-clinical models. These discoveries offer a new therapeutic approach for AML and demonstrate that epigenetic rewiring of pDCs enhances anti-tumor immunity, opening the possibility of exploiting this approach for immunotherapies.
  13. Cancer Lett. 2022 Mar 20. pii: S0304-3835(22)00142-2. [Epub ahead of print]535 215659
      Adenosine monophosphate activated protein kinase (AMPK) is a master regulator of cell metabolism and is involved in cancer as both a tumor suppressor and a source of resistance to metabolic stress. The role of AMPK in response to chemotherapy has been examined in solid tumor models but remains unclear in acute myeloid leukemia (AML). To determine the role of AMPK in chemotherapy response, AML cell lines were generated lacking AMPK activity. AMPK knock out cells demonstrated significant resistance to cytarabine and doxorubicin both in vitro and in vivo. Mitochondrial mass and function were unchanged in AMPK knockout cells. Mechanistically, AMPK knock out cells demonstrated a diminished DNA damage response with significantly lower γH2AX foci, p53 and p21 induction as well as decreased apoptosis following chemotherapy exposure. Most importantly, TCGA datasets revealed that patients expressing low levels of the PRKAA1 subunit of AMPK had significantly shorter survival. Finally, AML cells were sensitized to chemotherapy with the addition of the AMPK activator AICAR. These data demonstrate that AMPK sensitizes AML cells to chemotherapy and suggests a contribution of the cellular metabolic state to cell fate decisions ultimately affecting therapy response.
  14. Exp Hematol. 2022 Mar 18. pii: S0301-472X(22)00128-X. [Epub ahead of print]
      With an overall 5-10% incident rate in AML, occurrence of TP53 mutations are low compared to solid tumors. However, when focusing on high-risk groups including secondary AML (sAML) and therapy-related AMLs, the frequency of mutations reaches up to 35%. Mutations may include loss of heterozygosity (LOH) or deletion of the 17p allele, but are mostly missense substitutions that are located in the DNA-binding domain. Despite elaborate research to the effects of TP53 mutations in solid tumors, in hematological malignancies, the effects of TP53 mutations vs. loss of TP53 is still unclear and under debate. Here, we compared the cellular effects of a TP53 mutant and loss of TP53 in human hematopoietic stem and progenitor cells (HSPCs). We found that when expressing TP53 mutant or loss of TP53 using siRNA, CD34+/CD38- cells have a significant enhanced re-plating potential which could not be demonstrated for the CD34+/CD38+ population. Using RNA-sequencing analysis we found a loss of expression of p53 target genes in cells with TP53 knock-down. In contrast, an increased expression of a large number of genes was shown when expressing TP53 mutant, resulting in an increase in expression of genes involved in megakaryocytic differentiation, plasma membrane binding and extracellular structure organization. When comparing binding of p53 wild-type and p53 mutant in cell lines, we found that mutant p53 binds to a large number of binding sites genome-wide, in contrary to wild-type p53, for which binding is restricted to genes with a p53 binding motif. These findings were verified in primary AMLs with and without mutated TP53. In conclusion, in our models, we identified overlapping effects between TP53 mutant and loss of TP53 on in-vitro stem cell properties but distinct effects on DNA binding and gene expression.
  15. Clin Infect Dis. 2022 Mar 23. pii: ciac230. [Epub ahead of print]
      BACKGROUND: Multiple factors influence the choice of primary antifungal prophylaxis (PAP) in patients with acute myeloid leukemia (AML) undergoing remission induction chemotherapy (RIC) given the recent incorporation of targeted leukemia therapies into these regimens.METHODS: We evaluated the incidence and characteristics of breakthrough IFI (bIFI) in 277 adult patients with newly diagnosed AML undergoing RIC with high-intensity, or low-intensity venetoclax-containing therapy. Patients receiving posaconazole (PCZ), voriconazole (VCZ), or isavuconazole (ISA) for > 5 days as PAP during RIC were included. Echinocandin use prior to, but not concomitantly with, the PAP azole was allowed. IFI (modified EORTC/MSG criteria) occurring after > 5 days of continuous azole exposure or within 14 days of discontinuation were considered bIFI.
    RESULTS: Proven or probable bIFI were observed in 11 patients (4%). The incidence of bIFI was 2.9% for PCZ, 4.8% for VCZ, and 5.7% for ISA (p=0.55). 161 patients (58%) received echinocandin prophylaxis prior to azole initiation. Neither echinocandin exposure nor chemotherapy intensity impacted bIFI rate. Patients with bIFI had a lower rate of absolute neutrophil count recovery >1000 cells/µL (64% vs 90%, p=0.021) or complete remission (CR; 18% vs 66%, p=0.002) after RIC. Thirty-eight patients (14%) discontinued PAP due to toxicity, most often hepatotoxicity. Discontinuation due to hepatotoxicity was similar among azoles (PCZ: 13%; VCZ: 15%; ISA: 13%).
    CONCLUSIONS: The rate of bIFI is low during RIC in patients with newly diagnosed AML receiving any of the mold-active triazoles as PAP. Neutrophil recovery and achievement of CR are important for bIFI risk.
    Keywords:  acute myeloid leukemia; breakthrough invasive fungal infections; venetoclax
  16. Cancers (Basel). 2022 Mar 12. pii: 1459. [Epub ahead of print]14(6):
      The Notch signaling pathway is fundamental to early fetal development, but its role in acute myeloid leukemia is still unclear. It is important to elucidate the function that contains Notch, not only in acute myeloid leukemia, but in leukemic stem cells (LSCs). LSCs seem to be the principal cause of patient relapse. This population is in a quiescent state. Signaling pathways that govern this process must be understood to increase the chemosensitivity of this compartment. In this review, we focus on the conserved Notch signaling pathway, and its repercussions in hematopoiesis and hematological neoplasia. We found in the literature both visions regarding Notch activity in acute myeloid leukemia. On one hand, the activation of Notch leads to cell proliferation, on the other hand, the activation of Notch leads to cell cycle arrest. This dilemma requires further experiments to be answered, in order to understand the role of Notch not only in acute myeloid leukemia, but especially in LSCs.
    Keywords:  AML; LSCs; Notch; crosstalk; quiescence
  17. Expert Rev Hematol. 2022 Mar 25. 1-12
      INTRODUCTION: FLT3 inhibitors have been recently introduced as novel treatment targets in patients with FLT3-mutated acute myeloid leukemia (AML). Midostaurin is an oral multikinase inhibitor that targets multiple receptor tyrosine kinases including FLT3 and has been approved for the treatment of AML with FLT3 mutations in patients candidates for intensive chemotherapy. This article presents an updated overall overview of the use of midostaurin in clinical practice.AREAS COVERED: Tests and examinations to be performed before the use of midostaurin, antifungal and antimicrobial treatment, as well as antifungal and antimicrobial prophylaxis are discussed. Practical tips for the treatment of QTc interval prolongation and heart failure are also presented.
    EXPERT OPINION: Midostaurin is the first agent showing significant survival benefit when combined with chemotherapy in FLT3-mutated AML patients. Optimal use of midostaurin should be a priority, being essential to know the interactions with other drugs like strong CYP3A4 inhibitors or inducers, which are particularly used in the concomitant treatment of AML patients and may increase toxicity or decrease therapeutic benefit. The active role of hematologists and nursing teams is crucial to ensure patient adherence to midostaurin treatment and to minimize adverse effects by administrating the optimal dose for each situation.
    Keywords:  AML; CYP3A4; FLT3 mutation; expert opinion; midostaurin management
  18. Chemotherapy. 2022 Mar 18. 1-5
      B/myeloid mixed-phenotype acute leukemia (MPAL) is an uncommon and aggressive leukemia without well-established treatment guidelines and has an inferior outcome. Relapsed/refractory (R/R) acute myeloid leukemia (AML) that is ineligible for aggressive chemotherapy regimens and allogeneic hematopoietic stem-cell transplantation has an extremely poor prognosis. The novel regimen of venetoclax (VEN) combined with hypomethylating agents (HMAs) has a synergistic therapeutic effect and a tolerable safety profile, which has been officially approved by the US Food and Drug Administration (FDA) for newly diagnosed AML in adults who are 75 years or older or patients precluding intensive induction chemotherapy. For R/R and other rare types of AML, no consensus has been reached on the efficacy of VEN-HMA. In addition, there is no available report on treatment-naive B/myeloid MPAL with VEN-HMA. Herein, we present 3 cases of VEN-HMA in treatment-naive B/myeloid MPAL and R/R AML. Its potential efficacy is worthy of further exploration in future researches.
    Keywords:  Acute myeloid leukemia; Hypomethylating agents; Mixed-phenotype acute leukemia; Relapsed/refractory acute myeloid leukemia; Venetoclax
  19. Clin Cancer Res. 2022 Mar 24. pii: clincanres.4525.2021. [Epub ahead of print]
      On September 1, 2020, the FDA granted approval for oral azacitidine (Onureg, CC-486) for continued treatment of adult patients with acute myeloid leukemia (AML) who achieved complete remission (CR) or complete remission with incomplete blood count recovery (CRi) following intensive induction chemotherapy and who are not able to complete intensive curative therapy. Approval was based on improvement in overall survival using CC-486 300 mg daily in a two weeks on/two weeks off schedule in comparison to placebo (HR 0.69 [95% CI: 0.55, 0.86], p = 0.0009) in the randomized trial CC‑486-AML-001 (QUAZAR) in adults {greater than or equal to} 55 years old with AML in CR/CRi who did not complete standard intensive induction and post-remission therapy. Of note, the study was not designed to test CC-486 as maintenance after standard post-remission therapy nor as an alternative to standard post-remission therapy. Gastrointestinal toxicities, fatigue, and pneumonia were more common in patients treated with CC-486 compared to placebo. Additional studies are needed to establish safe dosing for patients with hepatic impairment. The pharmacokinetic parameters, recommended dose, and recommended schedule of CC-486 differ substantially from those of other azacitidine formulations; therefore, inappropriate substitutions between formulations pose a considerable risk for harm.
  20. Nat Commun. 2022 Mar 24. 13(1): 1584
      Hematopoietic stem cells (HSCs) develop from hemogenic endothelium within embryonic arterial vessels such as the aorta of the aorta-gonad-mesonephros region (AGM). To identify the signals responsible for HSC formation, here we use single cell RNA-sequencing to simultaneously analyze the transcriptional profiles of AGM-derived cells transitioning from hemogenic endothelium to HSCs, and AGM-derived endothelial cells which provide signals sufficient to support HSC maturation and self-renewal. Pseudotemporal ordering reveals dynamics of gene expression during the hemogenic endothelium to HSC transition, identifying surface receptors specifically expressed on developing HSCs. Transcriptional profiling of niche endothelial cells identifies corresponding ligands, including those signaling to Notch receptors, VLA-4 integrin, and CXCR4, which, when integrated in an engineered platform, are sufficient to support the generation of engrafting HSCs. These studies provide a transcriptional map of the signaling interactions necessary for the development of HSCs and advance the goal of engineering HSCs for therapeutic applications.
  21. Cancer Res. 2022 Mar 23. pii: canres.3376.2021. [Epub ahead of print]
      The majority of TP53 missense mutations identified in cancer patients are in the DNA-binding domain and are characterized as either structural or contact mutations. These missense mutations exhibit inhibitory effects on wild-type p53 activity. More importantly, these mutations also demonstrate gain-of-function (GOF) activities characterized by increased metastasis, poor prognosis, and drug resistance. To better understand the activities by which TP53 mutations, identified in Li-Fraumeni syndrome, contribute to tumorigenesis, we generated mice harboring a novel germline Trp53R245W allele (contact mutation) and compared them to existing models with Trp53R172H (structural mutation) and Trp53R270H (contact mutation) alleles. Thymocytes from heterozygous mice showed that all three hotspot mutations exhibited similar inhibitory effects on wild-type Trp53 transcription in vivo, and tumors from these mice had similar levels of loss of heterozygosity. However, the overall survival of Trp53R245W/+ and Trp53R270H/+ mice, but not Trp53R172H/+ mice, was significantly shorter than that of Trp53+/- mice, providing strong evidence for p53 mutant-specific GOF contributions to tumor development. Furthermore, Trp53R245W/+ and Trp53R270H/+ mice had more osteosarcoma metastases than Trp53R172H/+ mice, suggesting that these two contact mutants have stronger GOF in driving osteosarcoma metastasis. Transcriptomic analyses using RNA-sequencing data from Trp53R172H/+, Trp53R245W/+, and Trp53R270H/+ primary osteosarcomas in comparison to Trp53+/- indicated that GOF of the three mutants was mediated by distinct pathways. Thus, both the inhibitory effect of mutant over WT p53 and GOF activities of mutant p53 contributed to tumorigenesis in vivo. Targeting p53 mutant-specific pathways may be important for therapeutic outcomes in osteosarcoma.