bims-tremyl Biomed News
on Therapy resistance biology in myeloid leukemia
Issue of 2021‒10‒03
thirty-nine papers selected by
Paolo Gallipoli
Barts Cancer Institute, Queen Mary University of London

  1. Cancer Discov. 2021 Oct 01.
      Flt3 and Npm1 mutations synergize to rewire the chromatin landscape in acute myeloid leukemia (AML).
  2. Blood Adv. 2021 Oct 01. pii: bloodadvances.2021004469. [Epub ahead of print]
      Acute myeloid leukemia (AML) with MLL-rearrangement (MLL-r) comprises approximately 10% of all AML cases and portends poor outcomes. Much remains uncovered on how MLL-r AML drives leukemia development while preventing cells from normal myeloid differentiation. Here, we identified that transcription factor MEF2D is a super-enhancer-associated, highly expressed gene in MLL-r AML. Knockout of MEF2D profoundly impaired leukemia growth, induced myeloid differentiation, and delayed oncogenic progression in vivo. Mechanistically, MEF2D loss led to robust activation of a CEBPE-centered myeloid differentiation program in AML cells. Chromatin profiling revealed that MEF2D binds to and suppresses the chromatin accessibility of CEBPE cis-regulatory regions. In human acute leukemia samples, MEF2D expression showed a strong negative correlation with the expression of CEBPE. Depletion of CEBPE partially rescued the cell growth defect and myeloid cell differentiation induced by the loss of MEF2D. Lastly, we show that MEF2D is positively regulated by HOXA9, and downregulation of MEF2D is an important mechanism for DOT1L inhibitor-induced anti-leukemia effects. Collectively, our findings suggest that MEF2D plays a critical role in human MLL-r AML and uncover the MEF2D-CEBPE axis as a crucial transcriptional mechanism regulating leukemia cell self-renewal and differentiation block.
  3. Bone Marrow Transplant. 2021 Sep 28.
      Measurable residual disease (MRD) is associated with poor prognosis in acute myeloid leukemia (AML), even after allogeneic hematopoietic cell transplantation (HCT). New next-generation sequencing (NGS) methods have emerged as a highly sensitive and specific method to detect MRD. In addition to defining the role of post-HCT MRD monitoring in FLT3-ITD mutated AML, there is great interest in the optimal use of oral FLT3 tyrosine kinase inhibitors (FLT3 inhibitors) to maintain remission following HCT. In this study, we evaluated the clinical impact of sensitive FLT3 MRD testing early after HCT and maintenance FLT3 inhibitor use at our transplant center. We found that there was a trend towards inferior progression-free survival (PFS) for patients with early post-HCT MRD, but that overall survival (OS) was not significantly impacted by MRD. The use of maintenance FLT3 inhibitors led to a significantly superior PFS and OS in our cohort, and improved PFS and OS in both MRD-negative and MRD-positive patients. Altogether, our results demonstrate the prognostic significance of NGS-based MRD monitoring for FLT3-ITD and the ability of post-HCT maintenance therapy to prevent relapse and death in FLT3-ITD mutated AML.
  4. Blood Adv. 2021 Sep 27. pii: bloodadvances.2021004668. [Epub ahead of print]
      Acquired somatic mutations are crucial for the development of the majority of cancers. We performed a comprehensive comparative analysis of the mutational landscapes and their correlation to CHIP-related (clonal hematopoiesis of indeterminate potential) mutations and patient age of 122 genes in 3096 cases with 28 different hematological malignancies. Differences were observed regarding (i) the median number of mutations (highest, median n=4: aCML, CMML, MDS/MPN-U, s-AML; lowest, n=0, CML, MLN-eo, MGUS, PPBL), (ii) specificity of certain mutations (high frequencies in e.g. aCML (ASXL1, 86%), FL (KMT2D, 87%; CREBBP, 73%), HCL (BRAF, 100%), LPL (MYD88, 98%; CXCR4, 51%), MPN (JAK2, 68%)), (iii) distribution of mutations (broad distribution within/across the myeloid/lymphoid lineage e.g. for TET2, ASXL1, DNMT3A, TP53, BCOR, ETV6), (iv) correlation of mutations to patient age (correlated to older age across entites: e.g. TET2, DNMT3A, ASXL1, TP53, EZH2, BCOR, GATA2, IDH2; younger age: e.g. KIT, POT1, RAD21, U2AF2; WT1), (v) correlation of mutation number per patient with age (total cohort (p<0.001), AML (p<0.001), B-ALL (p=0.015), CLL (0.039), MDS (p<0.001), MPN (p<0.001), T-ALL (p=0.005)). Moreover, we observed high frequencies of mutations in RUNX1, SRSF2, IDH2, NRAS, EZH2 in cases comprising at least one DTA mutation (DNMT3A, TET2, ASXL1), while in cases without DTA mutations TP53, KRAS, WT1, SF3B1 were more frequent across entities, suggesting differences in pathophysiology. These results give further insight into the complex genetic landscape and the role of DTA mutations in hematological neoplasms and define mutation-driven entities (MDS/MPN overlap, s-AML) in comparison to entities defined by chromosomal fusions (CML, MLN-eo).
  5. Blood. 2021 Sep 28. pii: blood.2021012806. [Epub ahead of print]
      Translocations involving the NUP98 gene produce NUP98-fusion proteins and are associated with a poor prognosis in acute myeloid leukemia (AML). MLL1 is a molecular dependency in NUP98-fusion leukemia, and therefore we investigated the efficacy of therapeutic blockade of the Menin-MLL1 interaction in NUP98-fusion leukemia models. Using mouse leukemia cell lines driven by NUP98-HOXA9 and NUP98-JARID1A fusion oncoproteins, we demonstrate that NUP98-fusion driven leukemia is sensitive to the Menin-MLL1 inhibitor VTP50469, with an IC50 similar to what we have previously reported for MLL-rearranged and NPM1c leukemia cells. Menin-MLL1 inhibition upregulates markers of differentiation such as CD11b and downregulates expression of pro-leukemogenic transcription factors such as Meis1 in NUP98-fusion transformed leukemia cells. We demonstrate that MLL1 and the NUP98 fusion protein itself are evicted from chromatin at a critical set of genes that are essential for maintenance of the malignant phenotype. In addition to these in vitro studies, we established patient-derived xenograft (PDX) models of NUP98-fusion driven AML to test the in vivo efficacy of Menin-MLL1 inhibition. Treatment with VTP50469 significantly prolongs survival of mice engrafted with NUP98-NSD1 and NUP98-JARID1A leukemias. Gene expression analysis revealed that Menin-MLL1 inhibition simultaneously suppresses a pro-leukemogenic gene expression program, including downregulation of the HOXA cluster, and upregulates tissue-specific markers of differentiation. These preclinical results suggest that Menin-MLL1 inhibition may represent a rational, targeted therapy for patients with NUP98-rearranged leukemias.
  6. Blood Adv. 2021 Oct 01. pii: bloodadvances.2021005038. [Epub ahead of print]
      Survival for older patients with acute myeloid leukaemia (AML) unsuitable for intensive chemotherapy is unsatisfactory. Standard non intensive therapies have low response rates and only extend life by a few months. Quizartinib is an oral Fms-like tyrosine kinase 3 (FLT3) inhibitor with reported activity in wild type patients. As part of the AML LI trial we undertook a randomised evaluation of low dose ara-C (LDAC) with or without quizartinib in patients not fit for intensive chemotherapy. Overall, survival was not improved (202 patients), but in the 27 FLT3-ITD patients the addition of quizartinib to LDAC improved response (p=0.05) with CR/CRi for quizartinib + LDAC in 5/13 (38%) v 0/14 (0%) in patients receiving LDAC alone. Overall survival (OS) in these FLT3-ITD positive patients was also significantly improved at 2 years for quizartinib + LDAC; hazard ratio 0.36 (95% confidence intervals 0.16, 0.85), (p=0.04). Median OS was 13.7 months compared to 4.2 months with LDAC alone. This is the first report of a FLT3 targeted therapy added to standard non-intensive chemotherapy that has improved survival in this population. Quizartinib merits consideration for future triplet based treatment approaches. (Clinical trial numbers: ISRCTN No: ISRCTN40571019 EUDRACT Number: 2011-000749-19).
  7. Blood Cancer Discov. 2021 Sep;2(5): 532-547
      FMS-like tyrosine kinase 3 (FLT3) is the most frequently-mutated gene in acute myeloid leukemia and a target for tyrosine kinase inhibitors (TKI). FLT3 TKI have yielded limited improvements to clinical outcomes. One reason for this is TKI inhibition by endogenous factors. We characterized plasma protein binding of FLT3 TKI, specifically staurosporine-derivatives (STS-TKI) by alpha-1-acid glycoprotein (AGP); simulating its effects upon drug efficacy. Human AGP inhibits the anti-proliferative activity of STS-TKI in FLT3-ITD-dependent cells, with IC50 shifts higher than clinically achievable. This is not seen with non-human plasma. Mifepristone co-treatment, with its higher AGP affinity, improves TKI activity despite AGP, yielding IC50s predicted to be clinically effective. In a mouse model of AGP drug inhibition, mifepristone restores midostaurin activity. This suggests combinatorial methods for overcoming plasma protein inhibition of existing TKIs for leukemia as well as providing a platform for investigating the drug-protein interaction space for developing more potent small-molecule agents.
    Keywords:  Acute myeloid leukemia; Alpha-1-acid glycoprotein; Combinatorial drug therapy; FMS-like tyrosine kinase 3; Tyrosine kinase inhibitor
  8. Cancers (Basel). 2021 Sep 16. pii: 4646. [Epub ahead of print]13(18):
      Despite considerable growth in our understanding of the heterogeneous biology and pathogenesis of acute myeloid leukemia (AML) in recent decades, for nearly forty years, little progress was gained in the realm of novel therapeutics. Since 2017, however, nine agents have been FDA-approved for patients with AML in both the upfront and relapsed/refractory (R/R) settings. Most of these compounds function as inhibitors of key cell cycle enzymatic pathways or mediators of leukemic proliferation and survival. They have been approved both as single agents and in combination with conventional or reduced-intensity conventional chemotherapeutics. In this article, we review the molecular landscape of de novo vs. R/R AML and highlight the potential translational impact of defined molecular disease subsets. We also highlight several recent agents that have entered the therapeutic armamentarium and where they fit in the AML treatment landscape, with a focus on FLT3 inhibitors, IDH1 and IDH2 inhibitors, and venetoclax. Finally, we close with a survey of two promising novel agents under investigation that are poised to enter the mainstream clinical arena in the near future.
    Keywords:  acute myeloid leukemia; relapse; targeted therapies; therapeutics; transplantation
  9. J Oncol. 2021 ;2021 3766428
      FMS-like tyrosine kinase 3 (FLT3) mutant acute myeloid leukemia (AML) occurs in approximately 30% of all AML patients and still has a poor prognosis. This study is directed to investigate gilteritinib in combination with homoharringtonine (HHT) on FLT3-ITD-mutant AML cell lines. In our study, we found that cell proliferation was dramatically suppressed by the combination of gilteritinib and HHT. This combination therapy decreased the mitochondrial membrane potential, finally inducing apoptosis. We demonstrated that gilteritinib downregulated the expression of FLT3 and downstream signaling, further decreased the mRNA level of myeloid cell leukemia-1 (Mcl-1). HHT and combination therapy could upregulate UBE2L6, which induced the degradation of Mcl-1 via ubiquitin-proteasome system. Knockdown of UBE2L6 could protect Mcl-1 from deprivation through the ubiquitin-proteasome system. These findings may provide a novel theoretical basis for the treatment of AML patients with FLT3-ITD mutations.
  10. Cell Death Dis. 2021 Sep 25. 12(10): 875
      Tyrosine kinase inhibitor (TKI) treatment has dramatically improved the survival of chronic myeloid leukemia (CML) patients, but measurable residual disease typically persists. To more effectively eradicate leukemia cells, simultaneous targeting of BCR-ABL1 and additional CML-related survival proteins has been proposed. Notably, several highly specific myeloid cell leukemia 1 (MCL1) inhibitors have recently entered clinical trials for various hematologic malignancies, although not for CML, reflecting the insensitivity of CML cell lines to single MCL1 inhibition. Here, we show that combining TKI (imatinib, nilotinib, dasatinib, or asciminib) treatment with the small-molecule MCL1 inhibitor S63845 exerted strong synergistic antiviability and proapoptotic effects on CML lines and CD34+ stem/progenitor cells isolated from untreated CML patients in chronic phase. Using wild-type BCR-ABL1-harboring CML lines and their T315I-mutated sublines (generated by CRISPR/Cas9-mediated homologous recombination), we prove that the synergistic proapoptotic effect of the drug combination depended on TKI-mediated BCR-ABL1 inhibition, but not on TKI-related off-target mechanisms. Moreover, we demonstrate that colony formation of CML but not normal hematopoietic stem/progenitor cells became markedly reduced upon combination treatment compared to imatinib monotherapy. Our results suggest that dual targeting of MCL1 and BCR-ABL1 activity may efficiently eradicate residual CML cells without affecting normal hematopoietic stem/progenitors.
  11. Cancers (Basel). 2021 Sep 19. pii: 4698. [Epub ahead of print]13(18):
      Acute myeloid leukemia (AML) is a clonal disorder resulting from acquired somatic mutations in hematopoietic progenitor cells that lead to the dysregulation of differentiation and the proliferation of hematopoietic cells [...].
  12. Blood Cancer J. 2021 Sep 29. 11(9): 162
      Acute myeloid leukemia (AML) with rearrangement of the lysine methyltransferase 2a gene (KMT2Ar) has adverse outcomes. However, reports on the prognostic impact of various translocations causing KMT2Ar are conflicting. Less is known about associated mutations and their prognostic impact. In a retrospective analysis, we identified 172 adult patients with KMT2Ar AML and compared them to 522 age-matched patients with diploid AML. KMT2Ar AML had fewer mutations, most commonly affecting RAS and FLT3 without significant impact on prognosis, except for patients with ≥2 mutations with lower overall survival (OS). KMT2Ar AML had worse outcomes compared with diploid AML when newly diagnosed and at relapse, especially following second salvage (median OS of 2.4 vs 4.8 months, P < 0.0001). Therapy-related KMT2Ar AML (t-AML) had worse outcomes compared with de novo KMT2Ar AML (median OS of 0.7 years vs 1.4 years, P < 0.0001). Allogeneic hematopoietic stem cell transplant (allo-HSCT) in first remission was associated with improved OS (5-year, 52 vs 14% for no allo-HSCT, P < 0.0001). In a multivariate analysis, translocation subtypes causing KMT2Ar did not predict survival, unlike age and allo-HSCT. In conclusion, KMT2Ar was associated with adverse outcomes regardless of translocation subtype. Therefore, AML risk stratification guidelines should include all KMT2Ar as adverse.
  13. Blood Cancer Discov. 2021 Sep;2(5): 518-531
      To understand mechanisms of response to BET inhibitors (BETi), we mined the Beat AML functional genomic dataset and performed genome-wide CRISPR screens on BETi- sensitive and BETi- resistant AML cells. Both strategies revealed regulators of monocytic differentiation, SPI1, JUNB, FOS, and aryl-hydrocarbon receptor signaling (AHR/ARNT), as determinants of BETi response. AHR activation synergized with BETi while inhibition antagonized BETi-mediated cytotoxicity. Consistent with BETi sensitivity dependence on monocytic differentiation, ex vivo sensitivity to BETi in primary AML patient samples correlated with higher expression of monocytic markers CSF1R, LILRs, and VCAN. In addition, HL-60 cell line differentiation enhanced its sensitivity to BETi. Further, screens to rescue BETi sensitivity identified BCL2 and CDK6 as druggable vulnerabilities. Finally, monocytic AML patient samples refractory to venetoclax ex vivo were significantly more sensitive to combined BETi + venetoclax. Together, our work highlights mechanisms that could predict BETi response and identifies combination strategies to overcome resistance.
  14. Metabolites. 2021 Aug 31. pii: 586. [Epub ahead of print]11(9):
      Cellular metabolic changes reflect the characteristics of patients with acute myeloid leukemia (AML) caused by genetic variations, which are important in establishing AML treatment. However, little is known about the metabolic profile of patients with genetic variation-induced AML. Furthermore, the metabolites differ with disease progression. Here, metabolites in the bone marrow serum of ten patients with AML and healthy individuals were analyzed using gas chromatography-mass spectrometry. Compared with that in healthy individuals, expression of most metabolites decreased in patients with AML; hydroxylamine, 2-hydroxybutyric acid, monomethylphosphate, and ethylphosphate expression was unusually increased in the patients. We further examined serial metabolite changes across the initial diagnosis, postremission, and relapse phases. Patients with relapse showed increased metabolite expression compared with those in the diagnostic phase, confirming that patients with AML had aggressively modified leukemic cells. However, a clear difference in metabolite distribution was not observed between the diagnosis and complete remission phases, suggesting that the metabolic microenvironment did not change significantly despite complete remission. Interestingly, metabolite profiles differed with genetic variations in leukemic cells. Our results, which were obtained using paired samples collected during AML progression, provide valuable insights for identifying vulnerable targets in the AML metabolome and developing new treatment strategies.
    Keywords:  acute myeloid leukemia; bone marrow serum; cell metabolism; metabolomics
  15. J Hematol Oncol. 2021 Sep 27. 14(1): 155
      BACKGROUND: Acute myeloid leukaemia (AML) stem cells (LSCs) cause disease relapse. The CD47 "don't eat me signal" is upregulated on LSCs and contributes to immune evasion by inhibiting phagocytosis through interacting with myeloid-specific signal regulatory protein alpha (SIRPα). Activation of macrophages by blocking CD47 has been successful, but the ubiquitous expression of CD47 on healthy cells poses potential limitations for such therapies. In contrast, CD123 is a well-known LSC-specific surface marker utilized as a therapeutic target. Here, we report the development of SIRPα-αCD123 fusion antibodies that localize the disruption of CD47/SIRPα signalling to AML while specifically enhancing LSC clearance.METHODS: SIRPα-αCD123 antibodies were generated by fusing the extracellular domain of SIRPα to an αCD123 antibody. The binding properties of the antibodies were analysed by flow cytometry and surface plasmon resonance. The functional characteristics of the fusion antibodies were determined by antibody-dependent cellular phagocytosis and antibody-dependent cellular cytotoxicity assays using primary AML patient cells. Finally, an in vivo engraftment assay was utilized to assess LSC targeting.
    RESULTS: SIRPα-αCD123 fusion antibodies exhibited increased binding and preferential targeting of CD123+ CD47+ AML cells even in the presence of CD47+ healthy cells. Furthermore, SIRPα-αCD123 fusion antibodies confined disruption of the CD47-SIRPα axis locally to AML cells. In vitro experiments demonstrated that SIRPα-αCD123 antibodies greatly enhanced AML cell phagocytosis mediated by allogeneic and autologous macrophages. Moreover, SIRPα-αCD123 fusion antibodies efficiently targeted LSCs with in vivo engraftment potential.
    CONCLUSIONS: SIRPα-αCD123 antibodies combine local CD47 blockade with specific LSC targeting in a single molecule, minimize the risk of targeting healthy cells and efficiently eliminate AML LSCs. These results validate SIRPα-αCD123 antibodies as promising therapeutic interventions for AML.
    Keywords:  Acute myeloid leukaemia; CD123; CD47; Immunotherapy; Leukemic stem cells; Phagocytosis
  16. Nat Commun. 2021 Sep 28. 12(1): 5679
      Chromosomal rearrangements are a frequent cause of oncogene deregulation in human malignancies. Overexpression of EVI1 is found in a subgroup of acute myeloid leukemia (AML) with 3q26 chromosomal rearrangements, which is often therapy resistant. In AMLs harboring a t(3;8)(q26;q24), we observed the translocation of a MYC super-enhancer (MYC SE) to the EVI1 locus. We generated an in vitro model mimicking a patient-based t(3;8)(q26;q24) using CRISPR-Cas9 technology and demonstrated hyperactivation of EVI1 by the hijacked MYC SE. This MYC SE contains multiple enhancer modules, of which only one recruits transcription factors active in early hematopoiesis. This enhancer module is critical for EVI1 overexpression as well as enhancer-promoter interaction. Multiple CTCF binding regions in the MYC SE facilitate this enhancer-promoter interaction, which also involves a CTCF binding site upstream of the EVI1 promoter. We hypothesize that this CTCF site acts as an enhancer-docking site in t(3;8) AML. Genomic analyses of other 3q26-rearranged AML patient cells point to a common mechanism by which EVI1 uses this docking site to hijack enhancers active in early hematopoiesis.
  17. Blood Adv. 2021 Sep 28. pii: bloodadvances.2021005308. [Epub ahead of print]
      Rare hematologic malignancies display evidence of both myeloid and lymphoid differentiation. Here, we describe such a novel bilineal event discovered in an adult woman with B-lymphoblastic leukemia (BLL). At the time of BLL diagnosis, the patient had a normal karyotype and a bulk sequencing panel identified pathogenic variants in BCOR, EZH2, RUNX1, and U2AF1, a genotype more typical of myeloid neoplasia. Additionally, the patient was noted to have 3-year history of cytopenias, and morphologic dyspoiesis was noted on post-treatment samples, raising the possibility of an antecedent hematologic disorder. To investigate the clonal architecture of her disease, we performed targeted sequencing on fractionated samples enriched for either B-lymphoblasts or circulating granulocytes. These studies revealed a truncal founder mutation in the spliceosome gene U2AF1 in both fractions, while distinct secondary mutations were present only in B-lymphoblasts (BCOR, NRAS) or myeloid cells (ASXL1, EZH2, RUNX1). These results indicate that both processes evolved from a common U2AF1-mutated precursor, which then acquired additional mutations during a process of divergent evolution and bilineal differentiation. Our findings highlight novel mechanisms in BLL leukemogenesis and expand the spectrum of observed bilineal neoplasms.
  18. Leuk Lymphoma. 2021 Sep 29. 1-7
      Dual targeting of TIM-3 and PD-1/PD-L1 pathways is currently under investigation for cancer immunotherapy. The interaction of these immune checkpoints remains unclear in the leukemic microenvironment of acute myeloid leukemia (AML). We performed an immunophenotypic study of bone marrow in 37 newly diagnosed AML patients. High levels of TIM-3 expression on AML blasts were correlated with first 7 + 3 induction failure (CR 16.2% vs. non-CR 36.4%, p = .038). In contrast, high TIM-3 levels on natural killer (NK) cells were associated with complete remission (CR) status after induction (CR 24.7% vs. non-CR 6.5%, p = .035). Few PD-L1 positive AML blasts and PD-1 or PD-L1 positive NK cells were observed. Although the exhausted PD-1 expressing T cells were detected in 28.3% of T cells, the double positive of PD-1 and TIM-3 T cells were rarely detected. In summary, the TIM-3 levels on AML blasts and NK cells are potentially the prognostic biomarkers in AML.
    Keywords:  Acute myeloid leukemia; T cell immunoglobulin and mucin-domain containing-3; immune checkpoint; programmed cell death 1; programmed cell death ligand 1
  19. Cancer Res. 2021 Sep 30. pii: canres.0061.2021. [Epub ahead of print]
      Acute myeloid leukemia (AML) is an aggressive hematological malignancy, exhibiting high levels of reactive oxygen species (ROS). ROS levels have been suggested to drive leukemogenesis and is thus a potential novel target for treating AML. MTH1 prevents incorporation of oxidized nucleotides into the DNA to maintain genome integrity and is upregulated in many cancers. Here we demonstrate that hematological cancers are highly sensitive to MTH1 inhibitor TH1579 (karonudib). A functional precision medicine ex vivo screen in primary AML bone marrow samples demonstrated a broad response profile of TH1579, independent of the genomic alteration of AML, resembling the response profile of the standard-of-care treatments cytarabine and doxorubicin. Furthermore, TH1579 killed primary human AML blast cells (CD45+) as well as chemotherapy resistance leukemic stem cells (CD45+Lin-CD34+CD38-),which are often responsible for AML progression. TH1579 killed AML cells by causing mitotic arrest, elevating intracellular ROS levels, and enhancing oxidative DNA damage. TH1579 showed a significant therapeutic window, was well tolerated in animals, and could be combined with standard-of-care treatments to further improve efficacy. TH1579 significantly improved survival in two different AML disease models in vivo. In conclusion, the pre-clinical data presented here support that TH1579 is a promising novel anticancer agent for AML, providing a rational to investigate the clinical usefulness of TH1579 in AML in an on-going clinical phase 1 trial.
  20. Genes (Basel). 2021 Sep 16. pii: 1426. [Epub ahead of print]12(9):
      Nucleophosmin (NPM1) mutations occurring in acute myeloid leukemia (AML) (about 50 so far identified) cluster almost exclusively in exon 12 and lead to common changes at the NPM1 mutants C-terminus, i.e., loss of tryptophans 288 and 290 (or 290 alone) and creation of a new nuclear export signal (NES), at the bases of exportin-1(XPO1)-mediated aberrant cytoplasmic NPM1. Immunohistochemistry (IHC) detects cytoplasmic NPM1 and is predictive of the molecular alteration. Besides IHC and molecular sequencing, Western blotting (WB) with anti-NPM1 mutant specific antibodies is another approach to identify NPM1-mutated AML. Here, we show that among 382 AML cases with NPM1 exon 12 mutations, one was not recognized by WB, and describe the discovery of a novel combination of two mutations involving exon 12. This appeared as a conventional mutation A with the known TCTG nucleotides insertion/duplication accompanied by a second event (i.e., an 8-nucleotide deletion occurring 15 nucleotides downstream of the TCTG insertion), resulting in a new C-terminal protein sequence. Strikingly, the sequence included a functional NES ensuring cytoplasmic relocation of the new mutant supporting the role of cytoplasmic NPM1 as critical in AML leukemogenesis.
    Keywords:  NPM1; acute myeloid leukemia; exportin-1/XPO1; nuclear export signal (NES); nucleophosmin
  21. Int J Mol Sci. 2021 Sep 18. pii: 10105. [Epub ahead of print]22(18):
      Targeting TP53 mutated myelodysplastic syndromes and acute myeloid leukemia remains a significant unmet need. Recently, new drugs have attempted to improve the outcomes of this poor molecular subgroup. The aim of this article is to review all the current knowledge using active agents including hypomethylating agents with venetoclax, eprenetapopt or magrolimab. We include comprehensive analysis of clinical trials to date evaluating these drugs in TP53 myeloid neoplasms as well as discuss future novel combinations for consideration. Additionally, further understanding of the unique clinicopathologic components of TP53 mutant myeloid neoplasms versus wild-type is critical to guide future study. Importantly, the clinical trajectory of patients is uniquely tied with the clonal burden of TP53, which enables serial TP53 variant allele frequency analysis to be a critical early biomarker in investigational studies. Together, significant optimism is now possible for improving outcomes in this patient population.
    Keywords:  AML; MDS; TP53; eprenetapopt; magrolimab
  22. Blood Cancer J. 2021 Oct 01. 11(10): 163
      VIALE-C compared the safety and efficacy of venetoclax or placebo plus low-dose cytarabine (+LDAC) in patients with untreated AML ineligible for intensive chemotherapy. Overall, 211 patients were enrolled (n = 143, venetoclax; n = 68, placebo). At the primary analysis, the study did not meet its primary endpoint of a statistically significant improvement in overall survival (OS), however, ~60% of patients had been on study for ≤6-months. Here, we present an additional 6-months of follow-up of VIALE-C (median follow-up 17.5 months; range 0.1-23.5). Median OS was (venetoclax +LDAC vs. placebo +LDAC) 8.4 vs. 4.1 months (HR = 0.70, 95% CI 0.50,0.99; P = 0.040); a 30% reduction in the risk of death with venetoclax. Complete response (CR)/CR with incomplete hematologic recovery (CRi) rates were 48.3% vs. 13.2%. Transfusion independence rates (RBC) were 43% vs.19% and median event-free survival was 4.9 vs. 2.1 months (HR = 0.61; 95% CI 0.44,0.84; P = 0.002). These results represent improved efficacy over the primary analysis. Incidence of grade ≥3 adverse events were similar between study arms and overall safety profiles were comparable to the primary analysis. These data support venetoclax +LDAC as a frontline treatment option for patients with AML ineligible for intensive chemotherapy.This trial was registered at as #NCT03069352.
  23. Clin Lymphoma Myeloma Leuk. 2021 Sep 09. pii: S2152-2650(21)02017-6. [Epub ahead of print]
      BACKGROUND: Achievement of initial remission remains the most important clinical factor predicting long term survival in acute myeloid leukemia (AML) patients treated with intensive chemotherapy. Yet, whether the patient subset in need of a second cycle of intensive induction chemotherapy to reach remission experiences inferior outcomes compared to patients reaching remission after a single cycle of therapy, remains uncertain.PATIENTS AND METHODS: Retrospective analysis of 302 consecutive AML patients treated with intensive induction chemotherapy in our institution in 2007-2020.
    RESULTS: Median patient age was 55 years with a median follow-up duration of 23 months. In terms of European LeukemiaNet (ELN) 2017 classification, 122 patients (40%) were designated as favorable risk disease, 108 patients (36%) were intermediate risk, and 71 patients (24%) were adverse risk. A hundred and seventy-seven patients (60%) attained remission following initial chemotherapy while 58 patients (20%) required an additional cycle of intensive chemotherapy for remission. Patients requiring 2 cycles to reach remission were less likely to be NPM1 mutated (33% versus 51%; P=.025) or be in the ELN 2017 favorable risk category (25% versus 57%; P<.001). In multivariate analysis achievement of remission following 2 cycles of intensive compared with a single cycle resulted in significantly inferior survival [hazard ratio (HR)=1.67, 95% CI, 1.07-2.59; P=.025] whereas leukemia-free survival was not significantly impacted (HR=1.26, 95% CI, 0.85-1.85) (P=.23). Relapse rates also did not differ to a significant degree between groups (45% versus 47%, P=.8).
    CONCLUSION: Attainment of an early remission significantly impacts long term survival in AML patients.
    Keywords:  Acute myeloid leukemia; Chemotherapy; ELN 2017; Remission; Survival
  24. Blood Adv. 2021 Oct 01. pii: bloodadvances.2021004999. [Epub ahead of print]
      Central nervous system (CNS) involvement in newly diagnosed acute myeloid leukemia (AML) patients is rare and systematic data regarding outcome are scarce. This retrospective study summarized data from 11 consecutive ECOG-ACRIN clinical trials for newly diagnosed AML patients. 3240 patients with AML were analyzed and 36 (1.11%) were found to have CNS involvement at diagnosis. The incidence of CNS disease among the 5 studies with per protocol mandatory lumbar puncture (LP) was similar to the incidence among studies where LP was done at the discretion of the investigator (0.86% vs. 1.41%, p=0.18). There was no significant difference in the complete remission (CR) rate between patients with CNS involvement and those with other extramedullary disease (EMD) sites or those with no EMD (52.8% vs. 59.3-60%). The median overall survival (OS) of CNS-positive patients, other EMD or no EMD was 11.4, 11.3 and 12.7 months, respectively. There was no difference in OS between patients with CNS involvement and those with other EMD (HR 0.96, adjusted p=0.84) or no EMD (HR 1.19, adjusted p=0.44). In conclusion, the reported incidence of CNS involvement of newly diagnosed AML is low (1.1%), irrespective of whether an LP is mandatory or not. The presence of CNS disease at diagnosis does not appear, in and of itself, to portend for a poor prognosis for either achieving an initial CR or OS.
  25. Int J Mol Sci. 2021 Sep 17. pii: 10055. [Epub ahead of print]22(18):
      Histone methyltransferases (HMTs) have attracted considerable attention as potential targets for pharmaceutical intervention in various malignant diseases. These enzymes are known for introducing methyl marks at specific locations of histone proteins, creating a complex system that regulates epigenetic control of gene expression and cell differentiation. Here, we describe the identification of first-generation cell-permeable non-nucleoside type inhibitors of SETD2, the only mammalian HMT that is able to tri-methylate the K36 residue of histone H3. By generating the epigenetic mark H3K36me3, SETD2 is involved in the progression of acute myeloid leukemia. We developed a structure-based virtual screening protocol that was first validated in retrospective studies. Next, prospective screening was performed on a large library of commercially available compounds. Experimental validation of 22 virtual hits led to the discovery of three compounds that showed dose-dependent inhibition of the enzymatic activity of SETD2. Compound C13 effectively blocked the proliferation of two acute myeloid leukemia (AML) cell lines with MLL rearrangements and led to decreased H3K36me3 levels, prioritizing this chemotype as a viable chemical starting point for drug discovery projects.
    Keywords:  AML; SETD2 inhibitor; histone methyltransferase; virtual screening
  26. Sci Rep. 2021 Sep 27. 11(1): 19174
      Current classes of cancer therapeutics have negative side effects stemming from off-target cytotoxicity. One way to avoid this would be to use a drug delivery system decorated with targeting moieties, such as an aptamer, if a targeted aptamer is available. In this study, aptamers were selected against acute myeloid leukemia (AML) cells expressing the MLL-AF9 oncogene through systematic evolution of ligands by exponential enrichment (SELEX). Twelve rounds of SELEX, including two counter selections against fibroblast cells, were completed. Aptamer pools were sequenced, and three candidate sequences were identified. These sequences consisted of two 23-base primer regions flanking a 30-base central domain. Binding studies were performed using flow cytometry, and the lead sequence had a binding constant of 37.5 + / - 2.5 nM to AML cells, while displaying no binding to fibroblast or umbilical cord blood cells at 200 nM. A truncation study of the lead sequence was done using nine shortened sequences, and showed the 5' primer was not important for binding. The lead sequence was tested against seven AML patient cultures, and five cultures showed binding at 200 nM. In summary, a DNA aptamer specific to AML cells was developed and characterized for future drug-aptamer conjugates.
  27. Leukemia. 2021 Sep 30.
      TET2 loss-of-function mutations are recurrent events in a wide range of hematological malignancies and a physiologic occurrence in blood cells of healthy older adults. It is currently unknown what determines if a person harboring a somatic TET2 mutation will progress to myelodysplastic syndrome or acute myeloid leukemia. Here we develop a zebrafish tet2 mutant through which we show that tet2 loss leads to restricted hematopoietic differentiation combined with a modest upregulation of p53, which is also characteristic of many inherited bone marrow failure syndromes. Uniquely in the context of emergency hematopoiesis by external stimuli, such as infection or cytokine stimulation, lack of tet2 leads hematopoietic stem cells to undergo excessive proliferation, resulting in an accumulation of immature cells, which are poised to become leukemogenic following additional genetic/epigenetic perturbations. This same phenomenon observed in zebrafish extends to human hematopoietic stem cells, identifying TET2 as a critical relay switch in the context of stress hematopoiesis.
  28. Proc Natl Acad Sci U S A. 2021 Oct 05. pii: e2114227118. [Epub ahead of print]118(40):
      Human malignant hematopoietic stem and progenitor cells (HSPCs) reside in bone marrow (BM) niches, which remain challenging to explore due to limited in vivo accessibility and constraints with humanized animal models. Several in vitro systems have been established to culture patient-derived HSPCs in specific microenvironments, but they do not fully recapitulate the complex features of native bone marrow. Our group previously reported that human osteoblastic BM niches (O-N), engineered by culturing mesenchymal stromal cells within three-dimensional (3D) porous scaffolds under perfusion flow in a bioreactor system, are capable of maintaining, expanding, and functionally regulating healthy human cord blood-derived HSPCs. Here, we first demonstrate that this 3D O-N can sustain malignant CD34+ cells from acute myeloid leukemia (AML) and myeloproliferative neoplasm patients for up to 3 wk. Human malignant cells distributed in the bioreactor system mimicking the spatial distribution found in native BM tissue, where most HSPCs remain linked to the niches and mature cells are released to the circulation. Using human adipose tissue-derived stromal vascular fraction cells, we then generated a stromal-vascular niche and demonstrated that O-N and stromal-vascular niche differentially regulate leukemic UCSD-AML1 cell expansion, immunophenotype, and response to chemotherapy. The developed system offers a unique platform to investigate human leukemogenesis and response to drugs in customized environments, mimicking defined features of native hematopoietic niches and compatible with the establishment of personalized settings.
    Keywords:  3D perfusion bioreactors; AML/MPN; engineering stem cell niches; osteoblastic niche; stromal-vascular niche
  29. Blood Cancer Discov. 2021 Sep;2(5): 500-517
      Clonal hematopoiesis results from somatic mutations in cancer driver genes in hematopoietic stem cells. We sought to identify novel drivers of clonal expansion using an unbiased analysis of sequencing data from 84,683 persons and identified common mutations in the 5-methylcytosine reader, ZBTB33, as well as in YLPM1, SRCAP, and ZNF318. We also identified these mutations at low frequency in myelodysplastic syndrome patients. Zbtb33 edited mouse hematopoietic stem and progenitor cells exhibited a competitive advantage in vivo and increased genome-wide intron retention. ZBTB33 mutations potentially link DNA methylation and RNA splicing, the two most commonly mutated pathways in clonal hematopoiesis and MDS.
    Keywords:  clonal hematopoiesis; hematologic malignancies; hematopoietic stem cells; myeloid neoplasia; somatic driver gene discovery
  30. Blood Adv. 2021 Sep 28. pii: bloodadvances.2021005035. [Epub ahead of print]
      We report results of our prospective pilot trial (NCT02917096) evaluating safety/feasibility of peri-transplant administration of ruxolitinib for myelofibrosis treatment. Primary objectives were to determine the safety and identify maximum tolerated dose (MTD) of ruxolitinib. Ruxolitinib was given at two dose levels (DL) of 5 and 10mg twice daily, with fludarabine/melphalan conditioning regimen and tacrolimus/sirolimus GVHD prophylaxis. We enrolled 6 and 12 patients in DL-1 and DL-2, respectively. Median age at transplant was 65 years (range:25-73) for all patients. Per DIPSS, 4 patients were at high and 14 were at intermediate risk. PBSCs was the graft source from a matched sibling (n=5) or unrelated (n=13) donor. At each DL one patient developed DLTs: Grade 3 cardiac and GI with Grade 4 pulmonary in DL-1 and Grade 3 kidney injury in DL-2. All patients achieved engraftment. Cumulative incidence (CI) of acute GVHD grade 2-4 and 3-4 were 17% (95% CI: 6-47) and 11% (95% CI: 3-41), respectively. CI of 1-year chronic GVHD was 42% (95% CI: 24-74). With the median follow-up of 22.6 months (range:6.2-25.8) in surviving patients the 1-year overall and progression free survival were 77% (95% CI: 50-91) and 71% (95% CI: 44-87), respectively. Causes of death (n=4) were cardiac arrest, GVHD, respiratory failure, and refractory GVHD of liver. Our results showed that peri-HCT ruxolitinib was safe and well-tolerated with the MTD determined as 10 mg BID, associated with dose-dependent PK and cytokine profile. The early efficacy data are highly promising in this group of high-risk older patients with MF.
  31. Blood Adv. 2021 Sep 30. pii: bloodadvances.2021004755. [Epub ahead of print]
      The differential diagnosis of myeloid malignancies is challenging and subject to inter-observer variability. We used clinical and next-generation sequencing (NGS) data to develop a machine learning model for the diagnosis of myeloid malignancies independent of bone marrow biopsy data based on a three institution, international cohort of patients. The model achieves high performance, with model interpretations indicating that it relies on factors similar to those used by clinicians. Additionally, we describe associations between NGS findings and clinically important phenotypes, and introduce the use of machine learning algorithms to elucidate clinico-genomic relationships.
  32. Mol Cancer Ther. 2021 Sep 28. pii: molcanther.0367.2021. [Epub ahead of print]
      The protein arginine methyltransferase 5 (PRMT5) methylates a variety of proteins involved in splicing, multiple signal transduction pathways, epigenetic control of gene expression, and mechanisms leading to protein expression required for cellular proliferation. Dysregulation of PRMT5 is associated with clinical features of several cancers including lymphomas, lung cancer, and breast cancer. Here, we describe the characterization of JNJ-64619178, a novel, selective, and potent PRMT5 inhibitor, currently in clinical trials for patients with advanced solid tumors, non-Hodgkin's lymphoma, and lower risk myelodysplastic syndrome. JNJ-64619178 demonstrated a prolonged inhibition of PRMT5 and potent anti-proliferative activity in subsets of cancer cell lines derived from various histologies, including lung, breast, pancreatic, and hematological malignancies. In primary acute myeloid leukemia samples, the presence of splicing factor mutations correlated with a higher ex vivo sensitivity to JNJ-64619178. Furthermore, the potent and unique mechanism of inhibition of JNJ-64619178, combined with highly optimized pharmacological properties, led to efficient tumor growth inhibition and regression in several xenograft models in vivo, with once-daily or intermittent oral dosing schedules. An increase in splicing burden was observed upon JNJ-64619178 treatment. Overall, these observations support the continued clinical evaluation of JNJ-64619178 in patients with aberrant PRMT5 activity driven tumors.
  33. Leukemia. 2021 Sep 25.
      Spred1 is highly expressed in normal hematopoietic stem cells (HSCs). Lack of Spred1 function has been associated with aberrant hematopoiesis and acute leukemias. In chronic myelogenous leukemia (CML), Spred1 is reduced in patients with accelerated phase (AP) or blast crisis (BC) CML, thereby suggesting that deficit of this protein may contribute to disease transformation. In fact, Spred1 knockout (KO) in SCLtTA/BCR-ABL CML mice either globally, or restricted to hematopoietic cells (i.e., HSCs) or to endothelial cells (ECs), led to transformation of chronic phase (CP) CML into AP/BC CML. Upon BCR-ABL induction, all three Spred1 KO CML models showed AP/BC features. However, compared with global Spred1 KO, the AP/BC phenotypes of HSC-Spred1 KO and EC-Spred1 KO CML models were attenuated, suggesting a concurrent contribution of Spred1 deficit in multiple compartments of the leukemic bone marrow niche to the CML transformation. Spred1 KO, regardless if occurred in HSCs or in ECs, increased miR-126 in LSKs (Lin-Sca-1+c-Kit+), a population enriched in leukemic stem cells (LSCs), resulting in expansion of LSCs, likely through hyperactivation of the MAPK/ERK pathway that augmented Bcl-2 expression and stability. This ultimately led to enhancement of Bcl-2-dependent oxidative phosphorylation that supported homeostasis, survival and activity of LSCs and drove AP/BC transformation.
  34. Blood Adv. 2021 Sep 30. pii: bloodadvances.2021004438. [Epub ahead of print]
      Chronic non-resolving inflammatory syndrome is a major disease feature in myeloproliferative neoplasms (MPNs). Systemic inflammation promotes the growth of the JAK2-V617F positive hematopoietic stem cell clone and is associated with constitutive symptoms (e.g., fever, cachexia, fatigue). Therefore, it is currently being discussed whether anti-inflammatory therapy in addition to the well-established JAK-inhibitor therapy may be beneficial in control of constitutive symptoms. Moreover, effective control of the inflammatory microenvironment may contribute to prevent transformation into secondary myelofibrosis and acute leukemia. Given the pivotal role of TNFα in MPN and the distinct roles of TNFR1 and TNFR2 in inflammation, we investigated the therapeutic effects of αTNFR1 and αTNFR2 antibody treatment in MPN-like disease employing the JAK2+/VF knock-in mouse model. Peripheral blood counts, bone marrow/spleen histopathology and inflammatory cytokine levels in serum were investigated. αTNFR2 antibody treatment decreased WBC and modulated the serum levels of several cytokines (CXCL2, CXCL5, IL12(p40) and of M-CSF but lacked efficacy to ameliorate hematocrit and splenomegaly. αTNFR1 antibody treatment exhibited mild suppression of elevated hematocrit of -10.7%-points and attenuated splenomegaly (22% reduction in spleen weight). In conclusion, our studies show that TNFR1 and TNFR2 play different roles in biology of JAK2-V617F induced disease which may be of relevance in future therapeutic settings.
  35. Cancers (Basel). 2021 Sep 11. pii: 4566. [Epub ahead of print]13(18):
      Acute myeloid leukemia (AML) is a complex hematological malignancy characterized by genetic and clinical heterogeneity and high mortality. Despite the recent introduction of novel pharmaceutical agents in hemato-oncology, few advancements have been made in AML for decades. In the last years, the therapeutic options have rapidly changed, with the approval of innovative compounds that provide new opportunities, together with new challenges for clinicians: among them, on 1 September, 2017 the Food and Drug Administration granted approval for Gemtuzumab Ozogamicin (GO) in combination with daunorubicin and cytarabine for the treatment of adult patients affected by newly diagnosed CD33+ AML. Benefits of GO-based regimens were also reported in the pre- and post-transplantation settings. Moreover, several biomarkers of GO response have been suggested, including expression of CD33 and multidrug resistance genes, cytogenetic and molecular profiles, minimal residual disease and stemness signatures. Among them, elevated CD33 expression on blast cells and non-adverse cytogenetic or molecular risk represent largely validated predictors of good response.
    Keywords:  CD33; acute myeloid leukemia; biomarkers; gemtuzumab ozogamicin
  36. Blood Adv. 2021 Sep 29. pii: bloodadvances.2021005280. [Epub ahead of print]
      Acute myeloid leukemia (AML) with t(4;12)(q12;p13) translocation is rare, and often associated with an aggressive clinical course and poor prognosis. Previous reports based on fluorescence in-situ hybridization (FISH) analysis have suggested that ETV6-PDGFRA fusions are present in these patients despite the absence of eosinophilia, which is typically found in other hematopoietic malignancies with PDGFRA¬-containing fusions. We first detected an ETV6-SCFD2 fusion by targeted RNA sequencing in a patient with t(4;12)(q12;p13) who had previously been diagnosed with an ETV6-PDGFRA fusion by FISH analysis but failed to respond to imatinib. We then retrospectively identified four additional AML patients with t(4;12)(q12;p13) with apparent ETV6-PDGFRA fusions using chromosome and FISH analysis and applied targeted RNA sequencing to archival material. We again detected rearrangements between ETV6 and non-PDGFRA 4q12 genes including SCFD2, CHIC2 and GSX2. None of the three patients who received imatinib based on the incorrect assumption of an ETV6-PDGFRA fusion responded. Our findings highlight the importance of using a sequencing-based assay to confirm the presence of targetable gene fusions, particularly in genomic regions such as 4q12 with many clinically relevant genes that are too close to resolve by chromosome or FISH analysis. Finally, combining our data and review of the literature, we show that sequence-confirmed ETV6-PDGFRA fusions are typically found in eosinophilic disorders (3 of 3 cases), and patients with t(4;12)(q12;p13) without eosinophilia are found to have other 4q12 partners on sequencing (17 of 17 cases).