bims-tremyl Biomed News
on Therapy resistance biology in myeloid leukemia
Issue of 2021‒06‒20
thirty papers selected by
Paolo Gallipoli
Barts Cancer Institute, Queen Mary University of London

  1. Leukemia. 2021 Jun 14.
      Eukaryotic initiation factor 4A (eIF4A), the enzymatic core of the eIF4F complex essential for translation initiation, plays a key role in the oncogenic reprogramming of protein synthesis, and thus is a putative therapeutic target in cancer. As important component of its anticancer activity, inhibition of translation initiation can alleviate oncogenic activation of HSF1, a stress-inducible transcription factor that enables cancer cell growth and survival. Here, we show that primary acute myeloid leukemia (AML) cells exhibit the highest transcript levels of eIF4A1 compared to other cancer types. eIF4A inhibition by the potent and specific compound rohinitib (RHT) inactivated HSF1 in these cells, and exerted pronounced in vitro and in vivo anti-leukemia effects against progenitor and leukemia-initiating cells, especially those with FLT3-internal tandem duplication (ITD). In addition to its own anti-leukemic activity, genetic knockdown of HSF1 also sensitized FLT3-mutant AML cells to clinical FLT3 inhibitors, and this synergy was conserved in FLT3 double-mutant cells carrying both ITD and tyrosine kinase domain mutations. Consistently, the combination of RHT and FLT3 inhibitors was highly synergistic in primary FLT3-mutated AML cells. Our results provide a novel therapeutic rationale for co-targeting eIF4A and FLT3 to address the clinical challenge of treating FLT3-mutant AML.
  2. Blood. 2021 Jun 14. pii: blood.2021011320. [Epub ahead of print]
      Clonal hematopoiesis of indeterminate potential (CHIP) is associated with increased risk of cancers and inflammation-related diseases. This phenomenon becomes very common in oldest-old individuals, in whom the implications of CHIP are not well defined. We performed a mutational screening in 1794 oldest-old individuals enrolled in two population-based studies and investigate the relationships between CHIP and associated pathologies. Clonal mutations were observed in one third of oldest-old individuals and were associated with reduced survival. Mutations in JAK2 and splicing genes, multiple mutations (DNMT3A, TET2, ASXL1 with additional genetic lesions) and variant allele frequency ≥0.096 had positive predictive value for myeloid neoplasms. Combining mutation profiles with abnormalities in red blood cell indices improved the ability of myeloid neoplasm prediction. On this basis, we defined a predictive model that identifies 3 risk groups with different probabilities of developing myeloid neoplasms. Mutations in DNMT3A, TET2, ASXL1 or JAK2 (most occurring as single lesion) were associated with coronary heart disease and rheumatoid arthritis. Cytopenia was a common finding in oldest-old population, the underlying cause remaining unexplained in 30% of cases. Among individuals with unexplained cytopenia, the presence of highly-specific mutation patterns was associated with myelodysplastic-like phenotype and a probability of survival comparable to that of myeloid neoplasms. Accordingly, 7.5% of oldest-old subjects with cytopenia had presumptive evidence of myeloid neoplasm. In conclusion, specific mutational patterns define different risk of developing myeloid neoplasms vs. inflammatory-associated diseases in oldest-old population. In individuals with unexplained cytopenia, mutational status may identify those subjects with presumptive evidence of myeloid neoplasms.
  3. Hemasphere. 2021 Jul;5(7): e593
      Mutations in the calreticulin (CALR) gene are seen in about 30% of essential thrombocythemia and primary myelofibrosis patients. To address the contribution of the human CALR mutants to the pathogenesis of myeloproliferative neoplasms (MPNs) in an endogenous context, we modeled the CALRdel52 and CALRins5 mutants by induced pluripotent stem cell (iPSC) technology using CD34+ progenitors from 4 patients. We describe here the generation of several clones of iPSC carrying heterozygous CALRdel52 or CALRins5 mutations. We showed that CALRdel52 induces a stronger increase in progenitors than CALRins5 and that both CALRdel52 and CALRins5 mutants favor an expansion of the megakaryocytic lineage. Moreover, we found that both CALRdel52 and CALRins5 mutants rendered colony forming unit-megakaryocyte (CFU-MK) independent from thrombopoietin (TPO), and promoted a mild constitutive activation level of signal transducer and activator of transcription 3 in megakaryocytes. Unexpectedly, a mild increase in the sensitivity of colony forming unit-granulocyte (CFU-G) to granulocyte-colony stimulating factor was also observed in iPSC CALRdel52 and CALRins5 compared with control iPSC. Moreover, CALRdel52-induced megakaryocytic spontaneous growth is more dependent on Janus kinase 2/phosphoinositide 3-kinase/extracellular signal-regulated kinase than TPO-mediated growth and opens a therapeutic window for treatments in CALR-mutated MPN. The iPSC models described here represent an interesting platform for testing newly developed inhibitors. Altogether, this study shows that CALR-mutated iPSC recapitulate MPN phenotypes in vitro and may be used for drug screening.
  4. Leukemia. 2021 Jun 15.
      Menin inhibitors are novel targeted agents currently in clinical development for the treatment of genetically defined subsets of acute leukemia. Menin has a tumor suppressor function in endocrine glands. Germline mutations in the gene encoding menin cause the multiple endocrine neoplasia type 1 (MEN1) syndrome, a hereditary condition associated with tumors of the endocrine glands. However, menin is also critical for leukemogenesis in subsets driven by rearrangement of the Lysine Methyltransferase 2A (KMT2A) gene, previously known as mixed-lineage leukemia (MLL), which encodes an epigenetic modifier. These seemingly opposing functions of menin can be explained by its various roles in gene regulation. Therefore, leukemias with rearrangement of KMT2A are predicted to respond to menin inhibition with early clinical data validating this proof-of-concept. These leukemias affect infants, children and adults, and lead to adverse outcomes with current standard therapies. Recent studies have identified novel targets in acute leukemia that are susceptible to menin inhibition, such as mutated Nucleophosmin 1 (NPM1), the most common genetic alteration in adult acute myeloid leukemia (AML). In addition to these alterations, other leukemia subsets with similar transcriptional dependency could be targeted through menin inhibition. This led to rationally designed clinical studies, investigating small-molecule oral menin inhibitors in relapsed acute leukemias with promising early results. Herein, we discuss the physiologic and malignant biology of menin, the mechanisms of leukemia in these susceptible subsets, and future therapeutic strategies using these inhibitors in acute leukemia.
  5. Blood. 2021 Jun 10. pii: blood.2021011582. [Epub ahead of print]
      Internal tandem duplication within FLT3 (FLT3-ITD) is one of the most frequent mutations in acute myeloid leukemia (AML) and correlates with poor prognosis. While FLT3 receptor tyrosine kinase is activated at the plasma membrane to transduce PI3K/AKT and RAS/MAPK signaling, FLT3-ITD resides in the endoplasmic reticulum (ER) and triggers constitutive STAT5 phosphorylation. Mechanisms underlying this aberrant FLT3-ITD subcellular localization or its impact on leukemogenesis remain poorly established. Here we discover that FLT3-ITD is S-palmitoylated by the ZDHHC6 palmitoyl acyltransferase. Disruption of palmitoylation redirected FLT3-ITD to the plasma membrane and rewired its downstream signaling by activating AKT and ERK pathways in addition to STAT5. Consequently, abrogation of palmitoylation increased FLT3-ITD-mediated leukemic progression in xenotransplanted mouse models. We further demonstrate that FLT3 proteins were palmitoylated in primary human AML cells. ZDHHC6-mediated palmitoylation restrained FLT3-ITD surface expression, signaling and colonogenic growth of primary FLT3-ITD+ AMLs. More importantly, pharmacological inhibition of FLT3-ITD depalmitoylation synergized with FDA-approved FLT3 kinase inhibitor gilteritinib in abrogating the growth of primary FLT3-ITD+ AML cells. These findings provide novel insights into lipid-dependent compartmentalization of FLT3-ITD signaling in AML and suggest targeting depalmitoylation as a new therapeutic strategy to treat FLT3-ITD+ leukemias.
  6. Blood. 2021 Jun 14. pii: blood.2021011758. [Epub ahead of print]
      Most patients with acute promyelocytic leukemia (APL) can be cured with combined All Trans Retinoic Acid (ATRA) and Arsenic Trioxide therapy, which induce the destruction of PML-RARA, the initiating fusion protein for this disease1. However, the underlying mechanisms by which PML-RARA initiates and maintains APL cells are still not clear. We therefore identified genes that are dysregulated by PML-RARA in mouse and human APL cells, and prioritized GATA2 for functional studies because 1) it is highly expressed in pre-leukemic cells expressing PML-RARA, 2) its high expression persists in transformed APL cells, and 3) spontaneous somatic mutations of GATA2 occur during APL progression in both mice and humans. These and other findings suggested that GATA2 may be upregulated to thwart the proliferative signal generated by PML-RARA, and that its inactivation by mutation (and/or epigenetic silencing) may accelerate disease progression in APL and other forms of AML. Indeed, biallelic knockout of Gata2 with CRISPR/Cas9-mediated gene editing increased the serial replating efficiency of PML-RARA-expressing myeloid progenitors (and also progenitors expressing RUNX1-RUNX1T1, or deficient for Cebpa), increased mouse APL penetrance, and decreased latency. Restoration of Gata2 expression suppressed PML-RARA-driven aberrant self-renewal and leukemogenesis. Conversely, addback of a mutant GATA2R362G protein associated with APL and AML minimally suppressed PML-RARA-induced aberrant self-renewal, suggesting that it is a loss-of-function mutation. These studies reveal a potential role for Gata2 as a tumor suppressor in AML, and suggest that restoration of its function (when inactivated) may provide benefit for AML patients.
  7. Haematologica. 2021 Jun 17.
      The retinoid receptors RARA and RXRA contribute to myeloid maturation in both mice and humans, and deletion of Rxra and Rxrb augments leukemic growth in mice. While defining the domains of RXRA that are required for anti-leukemic effects in mouse KMT2A-MLLT3 leukemia cells, we unexpectedly identified RXRA DT448/9PP as a constitutively active variant capable of inducing maturation and loss of their proliferative phenotype. RXRA DT448/9PP was associated with ligand-independent activity in reporter assays, with enhanced co-activator interactions, reduced engraftment in vivo, and activation of myeloid maturation transcriptional signatures that overlapped with cells treated with the potent RXRA agonist bexarotene, suggestive of constitutive activity that leads to leukemic maturation. Phenotypes of RXRA DT448/9PP appear to differ from two other RXRA mutations with forms of constitutive activity (F318A and S427F), in that DT448/9PP activity was resistant to mutations at critical ligand-interacting amino acids (R316A/L326A) and was resistant to pharmacologic antagonists, suggesting it may be ligand independent. These data provide further evidence that activated RXRs can regulate myeloid maturation and provide a novel constitutively active variant that may be germane for broader studies of RXR in other settings.
  8. Elife. 2021 Jun 16. pii: e63104. [Epub ahead of print]10
      Typified by oxidative phosphorylation (OXPHOS), mitochondria catalyze a wide variety of cellular processes seemingly critical for malignant growth. As such, there is considerable interest in targeting mitochondrial metabolism in cancer. However, notwithstanding the few drugs targeting mutant dehydrogenase activity, nearly all hopeful 'mito-therapeutics' cannot discriminate cancerous from non-cancerous OXPHOS and thus suffer from a limited therapeutic index. The present project was based on the premise that the development of efficacious mitochondrial-targeted anti-cancer compounds requires answering two fundamental questions: 1) is mitochondrial bioenergetics in fact different between cancer and non-cancer cells? and 2) If so, what are the underlying mechanisms? Such information is particularly critical for the subset of human cancers, including acute myeloid leukemia (AML), in which alterations in mitochondrial metabolism are implicated in various aspects of cancer biology (e.g., clonal expansion and chemoresistance). Herein, we leveraged an in-house diagnostic biochemical workflow to comprehensively evaluate mitochondrial bioenergetic efficiency and capacity in various hematological cell types, with a specific focus on OXPHOS dynamics in AML. Consistent with prior reports, clonal cell expansion, characteristic of leukemia, was universally associated with a hyper-metabolic phenotype which included increases in basal and maximal glycolytic and respiratory flux. However, despite having nearly 2-fold more mitochondria per cell, clonally expanding hematopoietic stem cells, leukemic blasts, as well as chemoresistant AML were all consistently hallmarked by intrinsic limitations in oxidative ATP synthesis (i.e., OXPHOS). Remarkably, by performing experiments across a physiological span of ATP free energy (i.e, ΔGATP), we provide direct evidence that, rather than contributing to cellular ΔGATP, leukemic mitochondria are particularly poised to consume ATP. Relevant to AML biology, acute restoration of OXPHOS kinetics proved highly cytotoxic to leukemic blasts, suggesting that active OXPHOS repression supports aggressive disease dissemination in AML. Taken together, these findings argue against ATP being the primary output of mitochondria in leukemia and provide proof-of-principle that restoring, rather than disrupting, OXPHOS and/or cellular ΔGATP in cancer may represent an untapped therapeutic avenue for combatting hematological malignancy and chemoresistance.
    Keywords:  biochemistry; cancer biology; chemical biology; human
  9. Leukemia. 2021 Jun 12.
      Leukemic stem cells (LSCs) can acquire non-mutational resistance following drug treatment leading to therapeutic failure and relapse. However, oncogene-independent mechanisms of drug persistence in LSCs are incompletely understood, which is the primary focus of this study. We integrated proteomics, transcriptomics, and metabolomics to determine the contribution of STAT3 in promoting metabolic changes in tyrosine kinase inhibitor (TKI) persistent chronic myeloid leukemia (CML) cells. Proteomic and transcriptional differences in TKI persistent CML cells revealed BCR-ABL-independent STAT3 activation in these cells. While knockout of STAT3 inhibited the CML cells from developing drug-persistence, inhibition of STAT3 using a small molecule inhibitor sensitized the persistent CML cells to TKI treatment. Interestingly, given the role of phosphorylated STAT3 as a transcription factor, it localized uniquely to genes regulating metabolic pathways in the TKI-persistent CML stem and progenitor cells. Subsequently, we observed that STAT3 dysregulated mitochondrial metabolism forcing the TKI-persistent CML cells to depend on glycolysis, unlike TKI-sensitive CML cells, which are more reliant on oxidative phosphorylation. Finally, targeting pyruvate kinase M2, a rate-limiting glycolytic enzyme, specifically eradicated the TKI-persistent CML cells. By exploring the role of STAT3 in altering metabolism, we provide critical insight into identifying potential therapeutic targets for eliminating TKI-persistent LSCs.
  10. Leukemia. 2021 Jun 15.
      Assessment of measurable residual disease (MRD) upon treatment of acute myeloid leukemia (AML) remains challenging. It is usually addressed by highly sensitive PCR- or sequencing-based screening of specific mutations, or by multiparametric flow cytometry. However, not all patients have suitable mutations and heterogeneity of surface markers hampers standardization in clinical routine. In this study, we propose an alternative approach to estimate MRD based on AML-associated DNA methylation (DNAm) patterns. We identified four CG dinucleotides (CpGs) that commonly reveal aberrant DNAm in AML and their combination could reliably discern healthy and AML samples. Interestingly, bisulfite amplicon sequencing demonstrated that aberrant DNAm patterns were symmetric on both alleles, indicating that there is epigenetic crosstalk between homologous chromosomes. We trained shallow-learning and deep-learning algorithms to identify anomalous DNAm patterns. The method was then tested on follow-up samples with and without MRD. Notably, even samples that were classified as MRD negative often revealed higher anomaly ratios than healthy controls, which may reflect clonal hematopoiesis. Our results demonstrate that targeted DNAm analysis facilitates reliable discrimination of malignant and healthy samples. However, since healthy samples also comprise few abnormal-classified DNAm reads the approach does not yet reliably discriminate MRD positive and negative samples.
  11. Sci Adv. 2021 May;pii: eabg3217. [Epub ahead of print]7(21):
      Leukemia stem cells (LSCs) sustain the disease and contribute to relapse in acute myeloid leukemia (AML). Therapies that ablate LSCs may increase the chance of eliminating this cancer in patients. To this end, we used a bioreducible lipidoid-encapsulated Cas9/single guide RNA (sgRNA) ribonucleoprotein [lipidoid nanoparticle (LNP)-Cas9 RNP] to target the critical gene interleukin-1 receptor accessory protein (IL1RAP) in human LSCs. To enhance LSC targeting, we loaded LNP-Cas9 RNP and the chemokine CXCL12α onto mesenchymal stem cell membrane-coated nanofibril (MSCM-NF) scaffolds mimicking the bone marrow microenvironment. In vitro, CXCL12α release induced migration of LSCs to the scaffolds, and LNP-Cas9 RNP induced efficient gene editing. IL1RAP knockout reduced LSC colony-forming capacity and leukemic burden. Scaffold-based delivery increased the retention time of LNP-Cas9 in the bone marrow cavity. Overall, sustained local delivery of Cas9/IL1RAP sgRNA via CXCL12α-loaded LNP/MSCM-NF scaffolds provides an effective strategy for attenuating LSC growth to improve AML therapy.
  12. J Hematol Oncol. 2021 Jun 15. 14(1): 94
      BACKGROUND: The natural course of untreated chronic myeloid leukemia (CML) is progression to an aggressive blast phase. Even in the current era of BCR-ABL1 tyrosine kinase inhibitors (TKIs), the outcomes of blast phase CML remain poor with no consensus frontline treatment approach.METHODS: We retrospectively analyzed the response rates and survival outcomes of 104 consecutive patients with myeloid blast phase CML (CML-MBP) treated from 2000 to 2019 based on 4 different frontline treatment approaches: intensive chemotherapy (IC) + TKI (n = 20), hypomethylating agent (HMA) + TKI (n = 20), TKI alone (n = 56), or IC alone (n = 8). We also evaluated the impact of TKI selection and subsequent allogeneic stem cell transplant (ASCT) on patient outcomes.
    RESULTS: Response rates were similar between patients treated with IC + TKI and HMA + TKI. Compared to treatment with TKI alone, treatment with IC/HMA + TKI resulted in a higher rate of complete remission (CR) or CR with incomplete count recovery (CRi) (57.5% vs 33.9%, p < 0.05), a higher complete cytogenetic response rate (45% vs 10.7%, p < 0.001), and more patients proceeding to ASCT (32.5% vs 10.7%, p < 0.01). With a median follow-up of 6.7 years, long-term outcomes were similar between the IC + TKI and HMA + TKI groups. Combination therapy with IC/HMA + TKI was superior to therapy with TKI alone, including when analysis was limited to those treated with a 2nd/3rd-generation TKI. When using a 2nd/3rd-generation TKI, IC/HMA + TKI led to lower 5-year cumulative incidence of relapse (CIR; 44% vs 86%, p < 0.05) and superior 5-year event-free survival (EFS; 28% vs 0%, p < 0.05) and overall survival (OS; 34% vs 8%, p = 0.23) compared to TKI alone. Among patients who received IC/HMA + TKI, EFS and OS was superior for patients who received a 2nd/3rd generation TKI compared to those who received imatinib-based therapy. In a landmark analysis, 5-year OS was higher for patients who proceeded to ASCT (58% vs 22%, p = 0.12).
    CONCLUSIONS: Compared to patients treated with TKI alone for CML-MBP, treatment with IC + TKI or HMA + TKI led to improved response rates, CIR, EFS, and OS, particularly for patients who received a 2nd/3rd-generation TKI. Combination therapy with IC + TKI or HMA + TKI, rather than a TKI alone, should be considered the optimal treatment strategy for patients with CML-MBP.
    Keywords:  Blast phase; CML; Chemotherapy; Hypomethylating agent; TKI
  13. Leuk Lymphoma. 2021 Jun 14. 1-10
      We have analyzed treatment patterns and outcomes of relapsed/refractory(R/R) FLT3mut AML adult patients registered in our institutional data base between 1998 and 2018. Overall, 147 patients were evaluable: 34 from 1998 to 2009, 113 from 2010 to 2018. Salvage treatments were intensive chemotherapy (n = 25, 74%), and supportive care (n = 9, 26%) in the 1998-2009 period, and intensive chemotherapy (n = 63, 56%), hypomethylating agent (n = 7, 6%), low-dose cytarabine-based (n = 8, 7%), clinical trial (n = 16, 14%) and supportive care (n = 19, 17%) in the 2010-2018 period. Complete remission (CR) or with incomplete recovery (CRi) rate was 44%, 49% among patients treated intensively (vs 30% with non-intensive p = 0.005). Median overall survival since first R/R was 5.8 months, and 16.3 months in subjects receiving an allo-HSCT in CR/CRi after first salvage (vs 3.8 in the remaining patients p < 0.0001). Clinical outcomes of R/R FLT3mut AML remain unsatisfactory. Inclusion in clinical trials and expanding options could lead to improved outcomes.
    Keywords:  FLT3mut AML; real-world; relapse/refractory
  14. Expert Opin Emerg Drugs. 2021 Jun 17.
      INTRODUCTION: Polycythemia vera is a chronic hematologic malignancy frequently presenting with constitutional symptoms and associated with an increased risk of thrombosis, hemorrhage, and progression to myelofibrosis or acute myeloid leukemia. Current treatment strategies reduce thrombohemorrhagic risk by controlling blood counts and inhibiting platelets, but often fail to address disease-relate symptoms or biologically modify the disease.AREAS COVERED: We review the current paradigm for treating polycythemia vera, highlight areas of unmet need, review therapeutic agents in late stage clinical development, and provide an overarching view of how these emerging agent may fit into the future armamentarium of polycythemia vera treatments.
    EXPERT OPINION: The shift from focusing solely on secondary prevention of thrombohemorrhagic events to a comprehensive treatment strategy that additionally aims to improve quality of life and prevent disease progression has resulted in a rapidly evolving therapeutic landscape that promises to move the treatment of polycythemia vera out of antiquity into the modern age.
    Keywords:  Epigenetic Modification; Hepcidin; Interferon; JAK Inhibition; JAK/STAT Pathway; MDM2 Inhibition; Myeloproliferative Neoplasms; Polycythemia Vera; Rare Disease
  15. Cell Death Discov. 2021 Jun 10. 7(1): 137
      Over the last 50 years, there has been a steady improvement in the treatment outcome of acute myeloid leukemia (AML). However, median survival in the elderly is still poor due to intolerance to intensive chemotherapy and higher numbers of patients with adverse cytogenetics. Fadraciclib (CYC065), a novel cyclin-dependent kinase (CDK) 2/9 inhibitor, has preclinical efficacy in AML. In AML cell lines, myeloid cell leukemia 1 (MCL-1) was downregulated following treatment with fadraciclib, resulting in a rapid induction of apoptosis. In addition, RNA polymerase II (RNAPII)-driven transcription was suppressed, rendering a global gene suppression. Rapid induction of apoptosis was observed in primary AML cells after treatment with fadraciclib for 6-8 h. Twenty-four hours continuous treatment further increased efficacy of fadraciclib. Although preliminary results showed that AML cell lines harboring KMT2A rearrangement (KMT2A-r) are more sensitive to fadraciclib, we found that the drug can induce apoptosis and decrease MCL-1 expression in primary AML cells, regardless of KMT2A status. Importantly, the diversity of genetic mutations observed in primary AML patient samples was associated with variable response to fadraciclib, confirming the need for patient stratification to enable a more effective and personalized treatment approach. Synergistic activity was demonstrated when fadraciclib was combined with the BCL-2 inhibitor venetoclax, or the conventional chemotherapy agents, cytarabine, or azacitidine, with the combination of fadraciclib and azacitidine having the most favorable therapeutic window. In summary, these results highlight the potential of fadraciclib as a novel therapeutic approach for AML.
  16. Leukemia. 2021 Jun 16.
      Clonal hematopoiesis (CH) is associated with older age and an increased risk of myeloid malignancies and cardiovascular complications. We analyzed donor DNA samples in patients with AML/MDS who underwent first allogeneic stem cell transplant (SCT) to investigate the association between donor CH and transplant outcomes. We performed targeted deep sequencing of 300 genes on donor blood samples and identified CH with the minimum variant allele frequency of 2%. Among 363 donors, 65 (18%) had CH. The most frequently mutated genes were DNMT3A (31 of 65; 48%), TET2 (16 of 65; 25%), PPM1D (5 of 65, 8%), and ASXL1 (7 of 65; 11%). Transplant outcomes: time to neutrophil and platelet recovery, relapse incidence, transplant-related mortality and progression-free survival, were comparable by donor CH. However, risk of grade II-IV and III-IV acute graft versus host disease (aGvHD) at 6 months after transplant was higher with donor CH vs. without donor CH (hazard ratio (HR) = 2.4, 95% Confidence Interval (CI) = 1.6-3.6, p < 0.001 and HR = 3.8, 95% CI = 1.6-8.9, p = 0.003). In this homogenous population of AML/MDS patients, donor CH was associated with increased risk of grade II-IV and III-IV aGvHD. Further studies to investigate the mechanisms of increased aGvHD and therapeutic interventions to improve aGvHD in the context of donor CH are warranted.
  17. Front Oncol. 2021 ;11 659201
      Acute myeloid leukemia (AML) refers to a heterogeneous group of hematopoietic malignancies. The well-known European Leukemia Network (ELN) stratifies AML patients into three risk groups, based primarily on the detection of cytogenetic abnormalities. However, the prognosis of cytogenetically normal AML (CN-AML), which is the largest AML subset, can be hard to define. Moreover, the clinical outcomes associated with this subgroup are diverse. In this study, using transcriptome profiles collected from CN-AML patients in the BeatAML cohort, we constructed a robust prognostic Cox model named NEST (Nine-gEne SignaTure). The validity of NEST was confirmed in four external independent cohorts. Moreover, the risk score predicted by the NEST model remained an independent prognostic factor in multivariate analyses. Further analysis revealed that the NEST model was suitable for bone marrow mononuclear cell (BMMC) samples but not peripheral blood mononuclear cell (PBMC) samples, which indirectly indicated subtle differences between BMMCs and PBMCs. Our data demonstrated the robustness and accuracy of the NEST model and implied the importance of the immune dysfunction in the leukemogenesis that occurs in CN-AML, which shed new light on the further exploration of molecular mechanisms and treatment guidance for CN-AML.
    Keywords:  biomarker; bone marrow; cytogenetically normal acute myeloid leukemia; immune dysfunction; prognosis
  18. Blood. 2021 Jun 14. pii: blood.2020010081. [Epub ahead of print]
      T-cell acute lymphoblastic leukemia (T-ALL) are aggressive hematological cancers with dismal outcomes, and are in need of new therapeutic options. Polycomb Repressor Complex 2 (PRC2) loss-of-function alterations were reported in pediatric T-ALL; yet their clinical relevance and functional consequences remain elusive. Here, we extensively analyzed PRC2 alterations in a large series of 218 adult T-ALL patients. We found that PRC2 genetic lesions are frequent events in T-ALL and are not restricted to ETP-ALL. PRC2 loss of function associates with activating mutations of the IL7R/JAK/STAT pathway. PRC2-altered T-ALL patients poorly respond to prednisone, have low bone marrow blast clearance, and persistent minimal residual disease. Furthermore, we identified that PRC2 loss of function profoundly reshapes the genetic and epigenetic landscapes, leading to the reactivation of stem cell programs that cooperate with Bromodomain and Extraterminal (BET) proteins to sustain T-ALL. This study identifies BET proteins as key mediators of the PRC2 loss of function-induced remodeling. Our data has uncovered a targetable vulnerability to BET inhibition that can be exploited to treat PRC2-altered T-ALL patients.
  19. J Clin Invest. 2021 Jun 15. pii: 141529. [Epub ahead of print]131(12):
      Cancer cells reprogram lipid metabolism during their malignant progression, but limited information is currently available on the involvement of alterations in fatty acid synthesis in cancer development. We herein demonstrate that acetyl-CoA carboxylase 1 (ACC1), a rate-limiting enzyme for fatty acid synthesis, plays a critical role in regulating the growth and differentiation of leukemia-initiating cells. The Trib1-COP1 complex is an E3 ubiquitin ligase that targets C/EBPA, a transcription factor regulating myeloid differentiation, for degradation, and its overexpression specifically induces acute myeloid leukemia (AML). We identified ACC1 as a target of the Trib1-COP1 complex and found that an ACC1 mutant resistant to degradation because of the lack of a Trib1-binding site attenuated complex-driven leukemogenesis. Stable ACC1 protein expression suppressed the growth-promoting activity and increased ROS levels with the consumption of NADPH in a primary bone marrow culture, and delayed the onset of AML with increases in mature myeloid cells in mouse models. ACC1 promoted the terminal differentiation of Trib1-COP1-expressing cells and eradicated leukemia-initiating cells in the early phase of leukemic progression. These results indicate that ACC1 is a natural inhibitor of AML development. The upregulated expression of the ACC1 protein has potential as an effective strategy for cancer therapy.
    Keywords:  Cancer; Oncology; Tumor suppressors; Ubiquitin-proteosome system
  20. Leukemia. 2021 Jun 15.
      The most frequent genetic alteration in acute myeloid leukemia (AML) is the mutation of nucleophosmin 1 (NPM1). Yet, its downstream oncogenic routes are not fully understood. Here, we report the identification of one long noncoding RNA (lncRNA) overexpressed in NPM1-mutated AML patients (named LONA) whose intracellular localization inversely reflects that of NPM1. While NPM1 is nuclear and LONA cytoplasmic in wild-type NPM1 AML cells, LONA becomes nuclear as mutant NPM1 moves toward the cytoplasm. Gain or loss of function combined with a genome-wide RNA-seq search identified a set of LONA mRNA targets encoding proteins involved in myeloid cell differentiation (including THSB1, MAFB, and ASB2) and interaction with its microenvironment. Consistently, LONA overexpression in mutant NPM1 established cell lines and primary AML cells exerts an anti-myeloid differentiation effect, whilst it exerts an opposite pro-myeloid differentiation effect in a wild type NPM1 setting. In vivo, LONA overexpression acts as an oncogenic lncRNA reducing the survival of mice transplanted with AML cells and rendering AML tumors more resistant to AraC chemotherapy.These data indicate that mutation-dependent nuclear export of NPM1 leads to nuclear retention and consequent oncogenic functions of the overexpressed lncRNA LONA, thus uncovering a novel NPM1 mutation-dependent pathway in AML pathogenesis.
  21. Sci Adv. 2021 May;pii: eabg6165. [Epub ahead of print]7(21):
      Virus-infected cells and cancers share metabolic commonalities that stem from their insatiable need to replicate while evading the host immune system. These similarities include hijacking signaling mechanisms that induce metabolic rewiring in the host to up-regulate nucleotide metabolism and, in parallel, suppress the immune response. In both cancer and viral infections, the host immune cells and, specifically, lymphocytes augment nucleotide synthesis to support their own proliferation and effector functions. Consequently, established treatment modalities targeting nucleotide metabolism against cancers and virally infected cells may result in restricted immune response. Encouragingly, following the introduction of immunotherapy against cancers, multiple studies improved our understanding for improving antigen presentation to the immune system. We propose here that understanding the immune consequences of targeting nucleotide metabolism against cancers may be harnessed to optimize therapy against viral infections.
  22. Curr Oncol Rep. 2021 Jun 14. 23(8): 91
      PURPOSE OF REVIEW: In this review, we analyzed the available data from clinical trials with new tyrosine kinase inhibitors (TKIs) under development and how to consider chronic myeloid leukemia (CML) patients who had either resistance or intolerance to current TKIs for treatment with such agents.RECENT FINDINGS: Nearly 50% of CML patients treated with TKIs frontline have required a change of therapy by 10 years. Second-line therapy is effective (by achievement of complete cytogenetic response) in only approximately 50% of patients, and available third-generation TKI has been marred by concerns of arterio-occlusive events. These facts highlight the need for additional treatment options. New TKIs have shown promising efficacy and tolerance in CML patients with resistance or intolerance to multiple available TKIs. Additional studies will determine their role in the management of CML.
    Keywords:  Chronic myeloid leukemia; New generations; Side effects; Tyrosine kinase Inhibitors
  23. BMC Cancer. 2021 Jun 17. 21(1): 713
      BACKGROUND: Acute promyelocytic leukemia (APL) is a subset of acute myeloid leukemia (AML) which is characterized by the fusion of promyelocytic leukemia PML and retinoic acid receptor- alpha (RAR-alpha) genes. All-trans retinoic acid (ATRA) and/or arsenic trioxide (ATO) have resulted in durable cytogenetic and molecular remissions in most APL patients and have altered the natural history of the disease. Most APL patients treated with ATRA and/or ATO are now anticipated to have a nearly normal life expectancy. Unfortunately, relapse and resistance to the current treatment occur in APL patients and the outcome remains dismal in these refractory patients. AXL receptor tyrosine kinase (AXL-RTK) has been shown to increase tumour burden, provide resistance to therapy and is critical to maintain cancer stem cells (CSCs) in chronic myeloid leukemia (CML) by stabilizing β-catenin in the Wnt/β-catenin signalling pathway. However, the role of AXL-RTK has not been explored in PML/RARα-positive APL. This study aimed to explore the role of AXL-RTK receptor in PML/RARα-positive APL.METHODS AND RESULTS: By using biochemical and pharmacological approaches, here we report that targeting of AXL-RTK is related to the down-regulation of β-catenin target genes including c-myc (p < 0.001), AXIN2 (p < 0.001), and HIF1α (p < 0.01) and induction of apoptosis in PML/RARα-positive APL cell line. Resistance to all-trans retinoic acid (ATRA) was also overcomed by targeting AXL-RTK with R428 in APL (p < 0.05).
    CONCLUSION: Our results provide clear evidence of the involvement of AXL-RTK in leukemogenic potential of PML/RARα-positive APL and suggest targeting of AXL-RTK in the treatment of therapy resistant APL patients.
    Keywords:  AXL; Acute promyelocytic leukemia; All-trans retinoic acid; PML/RARα; Receptor tyrosine kinase; Retinoic acid receptor-α; Wnt/β-catenin pathway
  24. J Clin Oncol. 2021 Jun 17. JCO2002864
      PURPOSE: Patients with myelofibrosis who are relapsed or refractory (R/R) to Janus-associated kinase inhibitors (JAKis) have poor clinical outcomes including dismal overall survival (OS) that ranges between 13 and 16 months. Imetelstat, a telomerase inhibitor, was evaluated in patients with intermediate-2 or high-risk myelofibrosis R/R to JAKi in a phase II multicenter study ( identifier: NCT02426086).PATIENTS AND METHODS: Patients were randomly assigned to receive either imetelstat 9.4 mg/kg or 4.7 mg/kg intravenous once every 3 weeks. Spleen response (≥ 35% spleen volume reduction) and symptom response (≥ 50% reduction in total symptom score) rates at week 24 were coprimary end points. Secondary end points included OS and safety.
    RESULTS: Study enrollment was closed early, and patients treated with 4.7 mg/kg were permitted to continue treatment with 9.4 mg/kg. At week 24, spleen and symptom response rates were 10.2% and 32.2% in the 9.4-mg/kg arm and 0% and 6.3% in the 4.7-mg/kg arm. Treatment with imetelstat 9.4 mg/kg led to a median OS of 29.9 months and bone marrow fibrosis improvement in 40.5% and variant allele frequency reduction of driver mutations in 42.1% of evaluable patients. Fibrosis improvement and variant allele frequency reduction correlated with OS. Target inhibition was demonstrated by reduction of telomerase activity and human telomerase reverse transcriptase level and correlated with spleen response, symptom response, and OS. Most common adverse events on both arms were grade 3 or 4 reversible cytopenias.
    CONCLUSION: In this phase II study of two imetelstat doses, 9.4 mg/kg once every 3 weeks demonstrated clinical benefits in symptom response rate, with an acceptable safety profile for this poor-risk JAKi R/R population. Biomarker and bone marrow fibrosis assessments suggested selective effects on the malignant clone. A confirmatory phase III study is currently underway.
  25. Haematologica. 2021 Jun 17.
      Identification of fusion genes in clinical routine is mostly based on cytogenetics and targeted molecular genetics, such as metaphase karyotyping, FISH and RT-PCR. However, sequencing technologies are becoming more important in clinical routine as processing-time and costs per sample decrease. To evaluate the performance of fusion gene detection by RNA sequencing (RNAseq) compared to standard diagnostic techniques, we analyzed 806 RNA-seq samples from acute myeloid leukemia (AML) patients using two state-of-the-art software tools, namely Arriba and FusionCatcher. RNA-seq detected 90% of fusion events that were reported by routine with high evidence, while samples in which RNA-seq failed to detect fusion genes had overall lower and inhomogeneous sequence coverage. Based on properties of known and unknown fusion events, we developed a workflow with integrated filtering strategies for the identification of robust fusion gene candidates by RNA-seq. Thereby, we detected known recurrent fusion events in 26 cases that were not reported by routine and found discrepancies in evidence for known fusion events between routine and RNA-seq in three cases. Moreover, we identified 157 fusion genes as novel robust candidates and comparison to entries from ChimerDB or Mitelman Database showed novel recurrence of fusion genes in 14 cases. Finally, we detected the novel recurrent fusion gene NRIP1-MIR99AHG resulting from inv(21)(q11.2;q21.1) in nine patients (1.1%) and LTN1-MX1 resulting from inv(21)(q21.3;q22.3) in two patients (0.25%). We demonstrated that NRIP1-MIR99AHG results in overexpression of the 3' region of MIR99AHG and the disruption of the tricistronic miRNA cluster miR-99a/let-7c/miR-125b-2. Interestingly, upregulation of MIR99AHG and deregulation of the miRNA cluster, residing in the MIR99AHG locus, are known mechanism of leukemogenesis in acute megakaryoblastic leukemia. Our findings demonstrate that RNA-seq has a strong potential to improve the systematic detection of fusion genes in clinical applications and provides a valuable tool for fusion discovery.
  26. Blood Cancer J. 2021 Jun 16. 11(6): 112
      Fusion genes (FGs) are important genetic abnormalities in acute leukemias, but their variety and occurrence in acute leukemias remain to be systematically described. Whole transcriptome sequencing (WTS) provides a powerful tool for analyzing FGs. Here we report the FG map revealed by WTS in a consecutive cohort of 1000 acute leukemia cases in a single center, including 539 acute myeloid leukemia (AML), 437 acute lymphoblastic leukemia (ALL), and 24 mixed-phenotype acute leukemia (MPAL) patients. Bioinformatic analysis identified 792 high-confidence in-frame fusion events (296 distinct fusions) which were classified into four tiers. Tier A (pathogenic), B (likely pathogenic), and C (uncertain significance) FGs were identified in 61.8% cases of the total cohort (59.7% in AML, 64.5% in ALL, and 63.6% in MPAL). FGs involving protein kinase, transcription factor, and epigenetic genes were detected in 10.7%, 48.5%, and 15.1% cases, respectively. A considerable amount of novel FGs (82 in AML, 88 in B-ALL, 13 in T-ALL, and 9 in MPAL) was identified. This comprehensively described real map of FGs in acute leukemia revealed multiple FGs with clinical relevance that have not been previously recognized. WTS is a valuable tool and should be widely used in the routine diagnostic workup of acute leukemia.
  27. Cancer Res. 2021 Jun 18. pii: canres.0590.2021. [Epub ahead of print]
      Myelofibrosis (MF) is a deadly blood neoplasia with the worst prognosis among myeloproliferative neoplasms (MPN). The JAK2 inhibitors Ruxolitinib and Fedratinib have been approved for treatment of MF, but they do not offer significant improvement of bone marrow fibrosis. CDK6 expression is significantly elevated in MPN/MF hematopoietic progenitor cells. In this study, we investigated the efficacy of CDK4/6 inhibitor Palbociclib alone or in combination with Ruxolitinib in Jak2V617F and MPLW515L murine models of MF. Treatment with Palbociclib alone significantly reduced leukocytosis and splenomegaly and inhibited bone marrow fibrosis in Jak2V617F and MPLW515L mouse models of MF. Combined treatment of Palbociclib and Ruxolitinib resulted in normalization of peripheral blood leukocyte counts, marked reduction of spleen size, and abrogation of bone marrow fibrosis in murine models of MF. Palbociclib treatment also preferentially inhibited Jak2V617F mutant hematopoietic progenitors in mice. Mechanistically, treatment with Palbociclib or depletion of CDK6 inhibited Aurora kinase, NF-κB, and TGF-β signaling pathways in Jak2V617F mutant hematopoietic cells and attenuated expression of fibrotic markers in the bone marrow. Overall, these data suggest that Palbociclib in combination with Ruxolitinib may have therapeutic potential for treatment of MF and support the clinical investigation of this drug combination in patients with MF.
  28. Nat Rev Clin Oncol. 2021 Jun 15.
      Mutations in the genes encoding the cytoplasmic and mitochondrial forms of isocitrate dehydrogenase (IDH1 and IDH2, respectively; collectively referred to as IDH) are frequently detected in cancers of various origins, including but not limited to acute myeloid leukaemia (20%), cholangiocarcinoma (20%), chondrosarcoma (80%) and glioma (80%). In all cases, neomorphic activity of the mutated enzyme leads to production of the oncometabolite D-2-hydroxyglutarate, which has profound cell-autonomous and non-cell-autonomous effects. The broad effects of IDH mutations on epigenetic, differentiation and metabolic programmes, together with their high prevalence across a variety of cancer types, early presence in tumorigenesis and uniform expression in tumour cells, make mutant IDH an ideal therapeutic target. Herein, we describe the current biological understanding of IDH mutations and the roles of mutant IDH in the various associated cancers. We also present the available preclinical and clinical data on various methods of targeting IDH-mutant cancers and discuss, based on the underlying pathogenesis of different IDH-mutated cancer types, whether the treatment approaches will converge or be context dependent.