Telomerase inhibition on acute myeloid leukemia stem cell induced apoptosis with both intrinsic and extrinsic pathways.

AIMS: Acute Myeloid Leukemia (AML) is an invasive and lethal blood cancer caused by a rare population of Leukemia Stem Cells (LSCs). Telomerase activation is a limitless self-renewal process in LSCs. Apart from telomerase role in telomere lengthening, telomerase (especially hTERT subunit) inhibits intrinsic-, extrinsic-, and p53- mediated apoptosis pathways. In this study, the effect of Telomerase Inhibition (TI) on intrinsic-, extrinsic-, p53-mediated apoptosis, and DNMT3a and TET epigenetic markers in stem (CD34+) and differentiated (CD34-) AML cells is evaluated. MAIN METHODS: High-purity CD34+ (primary AML and KG-1a) cells were enriched using the Magnetic-Activated Cell Sorting (MACS) system. CD34+ and CD34- (primary AML and KG-1a) cells were treated with BIBR1532 and then, MTT assay, Annexin V/7AAD, Ki-67 assay, Telomere Length (TL) measurement, and transcriptional alterations of p53, hTERT, TET2, DNMT3a were analyzed. Finally, apoptosis-related genes and proteins were studied. KEY FINDINGS: TI with the IC50 values of 83.5, 33.2, 54.3, and 24.6 µM in CD34+ and CD34- (primary AML and KG-1a) cells significantly inhibited cell proliferation and induced apoptosis. However, TI had no significant effect on TL. The results also suggested TI induced intrinsic-, extrinsic-, and p53-mediated apoptosis. It was shown that the expression levels of DNMT3a and TET2 epigenetic markers were highly increased following TI. SIGNIFICANCE: In total, it was revealed that TI induced apoptosis through intrinsic, extrinsic, and p53 pathways and increased the expression of DNMT3a and TET2 epigenetic markers.

SCP4-STK35/PDIK1L complex is a dual phospho-catalytic signaling dependency in acute myeloid leukemia.

Acute myeloid leukemia (AML) cells rely on phospho-signaling pathways to gain unlimited proliferation potential. Here, we use domain-focused CRISPR screening and identify the nuclear phosphatase SCP4 as a dependency in AML, yet this enzyme is dispensable in normal hematopoietic progenitor cells. Using CRISPR exon scanning and gene complementation assays, we show that the catalytic function of SCP4 is essential in AML. Through mass spectrometry analysis of affinity-purified complexes, we identify the kinase paralogs STK35 and PDIK1L as binding partners and substrates of the SCP4 phosphatase domain. We show that STK35 and PDIK1L function catalytically and redundantly in the same pathway as SCP4 to maintain AML proliferation and to support amino acid biosynthesis and transport. We provide evidence that SCP4 regulates STK35/PDIK1L through two distinct mechanisms: catalytic removal of inhibitory phosphorylation and by promoting kinase stability. Our findings reveal a phosphatase-kinase signaling complex that supports the pathogenesis of AML.

Impaired myelopoiesis in congenital neutropenia: insights into clonal and malignant hematopoiesis.

A common feature of both congenital and acquired forms of bone marrow failure is an increased risk of developing acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). Indeed, the development of MDS or AML is now the major cause of mortality in patients with congenital neutropenia. Thus, there is a pressing clinical need to develop better strategies to prevent, diagnose early, and treat MDS/AML in patients with congenital neutropenia and other bone marrow failure syndromes. Here, we discuss recent data characterizing clonal hematopoiesis and progression to myeloid malignancy in congenital neutropenia, focusing on severe congenital neutropenia (SCN) and Shwachman-Diamond syndrome. We summarize recent studies showing excellent outcomes after allogenic hematopoietic stem cell transplantation for many (but not all) patients with congenital neutropenia, including patients with SCN with active myeloid malignancy who underwent transplantation. Finally, we discuss how these new data inform the current clinical management of patients with congenital neutropenia.

Therapeutic targeting of the inflammasome in myeloid malignancies.

Even though genetic perturbations and mutations are important for the development of myeloid malignancies, the effects of an inflammatory microenvironment are a critical modulator of carcinogenesis. Activation of the innate immune system through various ligands and signaling pathways is an important driver of myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). The DAMPs, or alarmins, which activate the inflammasome pathway via the TLR4/NLR signaling cascade causes the lytic cell death of hematopoietic stem and progenitor cells (HSPCs), ineffective hematopoiesis, and ß-catenin-induced proliferation of cancer cells, leading to the development of MDS/AML phenotype. It is also associated with other myeloid malignancies and involved in the pathogenesis of associated cytopenias. Ongoing research suggests the interplay of inflammasome mediators with immune modulators and transcription factors to have a significant role in the development of myeloid diseases, and possibly therapy resistance. This review discusses the role and importance of inflammasomes and immune pathways in myeloid malignancies, particularly MDS/AML, to better understand the disease pathophysiology and decipher the scope of therapeutic interventions.

Intrinsic OXPHOS limitations underlie cellular bioenergetics in leukemia.

Currently there is great interest in targeting mitochondrial oxidative phosphorylation (OXPHOS) in cancer. However, notwithstanding the targeting of mutant dehydrogenases, nearly all hopeful 'mito-therapeutics' cannot discriminate cancerous from non-cancerous OXPHOS and thus suffer from a limited therapeutic index. Using acute myeloid leukemia (AML) as a model, herein, we leveraged an in-house diagnostic biochemical workflow to identify 'actionable' bioenergetic vulnerabilities intrinsic to cancerous mitochondria. Consistent with prior reports, AML growth and proliferation was associated with a hyper-metabolic phenotype which included increases in basal and maximal respiration. 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 OXPHOS limitations. Remarkably, by performing experiments across a physiological span of ATP free energy, we provide direct evidence that leukemic mitochondria are particularly poised to consume ATP. Relevant to AML biology, acute restoration of oxidative ATP synthesis proved highly cytotoxic to leukemic blasts, suggesting that active OXPHOS repression supports aggressive disease dissemination in AML. Together, these findings argue against ATP being the primary output of leukemic mitochondria and provide proof-of-principle that restoring, rather than disrupting, OXPHOS may represent an untapped therapeutic avenue for combatting hematological malignancy and chemoresistance.

Acute myeloid leukemia presenting as horizontal diplopia.

Acute myeloid leukemia (AML) accounts for 16% of all leukemias in children. Prognosis in the pediatric population is better than that of older populations, with a younger age at diagnosis being a favorable prognostic factor [1]. Diplopia is a rare first presenting sign of AML. We present a 15 year old male complaining of diplopia and unilateral orbital swelling. Workup in the emergency department found normal neuroimaging but revealed a markedly elevated leukocytosis with anemia and thrombocytopenia. Peripheral smear showed increased blast cells >10%. This patient was ultimately diagnosed with AML. This case demonstrates an atypical presentation of AML and urges a thorough work up for patients presenting with unexplained diplopia.

Acute leukemia in pregnancy: a single institutional experience with 21 cases at 10 years and a review of the literature.

INTRODUCTION: Acute leukemia (AL) occurring in pregnancy is extremely rare, and its treatment is a clinical dilemma. METHODS: We retrospectively reviewed the medical records of our hospital from 2010 to 2019. RESULTS: Twenty-one patients were diagnosed with AL during pregnancy. Of whom, eighteen had acute myeloid leukemia, and 3 had acute lymphoblastic leukemia. Six, eight and seven patients were diagnosed during the first, second, and third trimester, respectively. Six of the 21 patients experienced therapeutic abortion and 1 had spontaneous abortion, whereas 9 gave birth to healthy babies (4 through vaginal deliveries and 5 with Caesarean sections). Four babies had been exposed to chemotherapeutic agents, but no congenital malformations were observed. Sixteen patients received chemotherapy, while 4 patients died before chemotherapy and one was discharged after refusing chemotherapy. The complete remission rate of the 10 patients who began chemotherapy immediately after diagnosis was 80%, compared with 66.7% in the 6 patients who started chemotherapy after abortion or delivery. Three remain alive. CONCLUSIONS: In general, initiation of chemotherapy as early as possible may increase the CR rate. Combined with literature data, we proposed that, for patients diagnosed in early and late stages of pregnancy (>30 weeks), elective termination or induced delivery before chemotherapy may be a good choice for better maternal (and fetal) outcome.KEY MESSAGESAcute leukaemia diagnosed in pregnancy is extremely rare, and its treatment is a clinical dilemma.In general, initiation of chemotherapy as early as possible may increase the CR rate.For patients who are diagnosed in the first trimester or late stage of pregnancy (>30 weeks), elective termination or induced delivery before starting chemotherapy may be a good choice for better maternal (and fetal) outcome.

Myeloid tumors accompanying systemic mastocytosis, basophilia, and abnormal platelet-derived growth factor receptor ß: A case report.

INTRODUCTION: Myeloid neoplasms with platelet-derived growth factor receptor ß (PDGFRB) rearrangement usually present with eosinophilia in the peripheral blood and bone marrow. Here we report a case of systemic mastocytosis related myeloid neoplasms with basophilia and PRKG2-PDGFRB fusion gene. PATIENTS CONCERNS: A 53-year-old male patient felt fatigue with thrombocythemia and normal hemoglobin over 2 years. Considering the possibility of primary thrombocytosis, the patient was treated with hydroxyurea and interferon. Then the therapy was stopped due to adverse events and worsen condition. DIAGNOSIS: Acute myelogenous leukemia (AML) diagnosis was confirmed by bone marrow morphology and flow cytometry. PDGFRB rearrangement was detected by fluorescence in situ hybridization (FISH) test, with chromosome karyotype 46,XY,t(4:5)(q21:q33). PRKG2-PDGFRB fusion was observed by next generation sequencing (NGS) and verified by RT-PCR followed by Sanger sequencing. The results of bone marrow aspiration, bone marrow biopsy, and immunophenotyping showed systemic mastocytosis-related myeloid tumor with basophilia. INTERVENTIONS: Imatinib 400 mg/d was given on the day of admission. Azacitidine 75 mg/m2 was given for induction therapy for 10 days, and followed by one course of DHAG consolidating therapy. Imatinib was taken orally continuously. OUTCOMES: On the 8th day of treatment, the patient's diet and fatigue improved. The hematological and bone marrow morphological remission was achieved on the 25th day. Cytogenetic complete remission was achieved 3 months later and continued to present (December 20, 2020). PRKG2-PDGFRB fusion gene turned negative 7 months later from diagnosis. LESSONS: Patients with increased basophilic granulocyte and/or mast cells in peripheral blood and/or bone marrow should be screened for PDGFRB abnormality and myeloid or lymphatic tumor. Patients bearing PDGFRB abnormality have a good response to imatinib.

Chronic stress promotes acute myeloid leukemia progression through HMGB1/NLRP3/IL-1ß signaling pathway.

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy with poor prognosis and overall survival. Clinical investigations show that chronic stress is commonly present in the course of AML and associated with adverse outcome. However, the underlying molecular mechanisms are elusive. In the present study, a chronic restraint stress mouse model was established to evaluate the effect of stress on AML. We found that mice under chronic stress exhibited significantly increased liver and spleen infiltration of leukemic cells and poorer overall survival. This was accompanied by elevated cellular NLR family pyrin domain containing 3 (NLRP3) and interleukin-1ß (IL-1ß) in the liver or bone marrow, and secreted IL-1ß in the plasma, indicating the activation of inflammasomes under chronic restraint stress. High mobility group box 1 (HMGB1) expression was markedly increased in newly diagnosed AML patients, but reduced in complete remission AML patients. The expression level of HMGB1 was positively correlated with NLRP3 mRNA in AML patients. Knockdown of HMGB1 significantly decreased NLRP3 and IL-1ß expression in AML cell lines, and secreted IL-1ß in supernatant of AML cell culture, while HMGB1 stimulation caused contrary effects. These results implied that HMGB1 could be involved in the regulation of inflammasome activation in AML development. Mice model showed that chronic restraint stress-facilitated proliferation and infiltration of AML cells were largely abrogated by knocking down HMGB1. Knockdown of HMGB1 also ameliorated overall survival and remarkably neutralized NLRP3 and IL-1ß expression under chronic restraint stress. These findings provide evidences that chronic stress promotes AML progression via HMGB1/NLRP3/IL-1ß dependent mechanism, suggesting that HMGB1 is a potential therapeutic target for AML. KEY MESSAGES: • Chronic restraint stress promoted acute myeloid leukemia (AML) progression and mediated NLRP3 inflammasome activation in xenograft mice. • HMGB1 mediated NLRP3 inflammasome activation in AML cells. • Knockdown of HMGB1 inhibited AML progression under chronic stress in vivo.