Aggressive Leukemia Research Articles

Personalized Management Strategies in Mast Cell Disorders: ECNM-AIM User’s Guide for Daily Clinical Practice

Mastocytosis is a myeloid neoplasm defined by expansion and focal accumulation of clonal mast cells (MCs) in one or more organs. The disease exhibits a complex pathology and may be complicated by MC activation, bone abnormalities, neurological problems, gastrointestinal symptoms, and/or hematologic progression. The World Health Organization divides mastocytosis into cutaneous forms, systemic mastocytosis (SM) and MC sarcoma. In most patients with SM, somatic mutations in KIT are detected. Patients with indolent SM have a normal to near-normal life expectancy, whereas patients with advanced SM, including aggressive SM and MC leukemia, have a poor prognosis. In those with advanced SM, multiple somatic mutations and an associated hematologic neoplasm may be detected. Mediator-related symptoms can occur in any type of mastocytosis. Symptoms may be mild, severe, or even life-threatening. In patients with severe acute symptoms, an MC activation syndrome may be diagnosed. In these patients, relevant comorbidities include IgE-dependent and IgE-independent allergies. Management of patients with SM is an emerging challenge in daily practice and requires in-depth knowledge and a multidisciplinary and personalized approach with selection of appropriate procedures and interventions. In this article, we review the current knowledge on SM and MC activation syndrome, with emphasis on multidisciplinary aspects in diagnosis and patient-specific management. In addition, we provide a user's guide for application of markers, algorithms, prognostic scores, and treatments for use in daily practice.

A distinct hematopoietic differentiation state characterizes aggressive infant leukemia.

A distinct hematopoietic differentiation state characterizes aggressive infant leukemia.

Single-cell transcriptomics reveals a distinct developmental state of KMT2A-rearranged infant B-cell acute lymphoblastic leukemia

KMT2A-rearranged infant ALL is an aggressive childhood leukemia with poor prognosis. Here, we investigated the developmental state of KMT2A-rearranged infant B-cell acute lymphoblastic leukemia (B-ALL) using bulk messenger RNA (mRNA) meta-analysis and examination of single lymphoblast transcriptomes against a developing bone marrow reference. KMT2A-rearranged infant B-ALL was uniquely dominated by an early lymphocyte precursor (ELP) state, whereas less adverse NUTM1-rearranged infant ALL demonstrated signals of later developing B cells, in line with most other childhood B-ALLs. We compared infant lymphoblasts with ELP cells and revealed that the cancer harbored hybrid myeloid–lymphoid features, including nonphysiological antigen combinations potentially targetable to achieve cancer specificity. We validated surface coexpression of exemplar combinations by flow cytometry. Through analysis of shared mutations in separate leukemias from a child with infant KMT2A-rearranged B-ALL relapsing as AML, we established that KMT2A rearrangement occurred in very early development, before hematopoietic specification, emphasizing that cell of origin cannot be inferred from the transcriptional state.

Aggressive Natural Killer Cell Leukemia: A Brief Overview of Its Genomic Landscape, Histological Features, and Current Management.

Aggressive natural killer-cell leukemia (ANKL) is a rare hematological malignancy characterized by the abnormal proliferation of natural killer (NK) cells. There are currently no therapies approved by the US Food and Drug Administration (FDA) for the treatment of ANKL, but advancements in genomics are assisting in the unraveling of this rare malignancy. We selected 37 articles that contained information on genomics, immunohistochemistry, and/or current clinical trials relating to the treatment and survival of ANKL. Current therapeutic strategies have been subdivided into (1) concurrent chemoradiation, (2) sequential chemoradiation, and (3) sandwich chemoradiation. These methods have been developed to reduce toxicity while still producing a pathologic response. Concurrent chemoradiation with VIDL (etoposide, ifosfamide, dexamethasone, and L-asparaginase) produced an excellent clinical response, while sequential chemoradiation with SMILE (steroid dexamethasone, methotrexate, ifosfamide, L-asparaginase, and etoposide) showed an adequate response, but with severe hematologic toxicity. The efficacy of L-asparaginase in chemotherapeutic regimens and its association with NK-cell apoptosis have led to its inclusion in all standard regimens. Future studies are focusing on the addition of a programmed death-ligand 1 (PD-L1) inhibitor and hematopoietic stem cell transplant (HSCT).

Update on Molecular Diagnosis in Extranodal NK/T-Cell Lymphoma and Its Role in the Era of Personalized Medicine.

Natural killer (NK)/T-cell lymphoma (NKTCL) is an aggressive malignancy with unique epidemiological, histological, molecular, and clinical characteristics. It occurs in two pathological forms, namely, extranodal NKTCL (ENKTCL) and aggressive NK leukemia, according to the latest World Health Organization (WHO) classification. Epstein–Barr virus (EBV) infection has long been proposed as the major etiology of lymphomagenesis. The adoption of high-throughput sequencing has allowed us to gain more insight into the molecular mechanisms of ENKTCL, which largely involve chromosome deletion and aberrations in Janus kinase (JAK)-signal transducer and activator of transcription (STAT), programmed cell death protein-1 (PD-1)/PD-ligand 1 (PD-L1) pathways, as well as mutations in tumor suppressor genes. The molecular findings could potentially influence the traditional chemoradiotherapy approach, which is known to be associated with significant toxicity. This article will review the latest molecular findings in NKTCL and recent advances in the field of molecular diagnosis in NKTCL. Issues of quality control and technical difficulties will also be discussed, along with future prospects in the molecular diagnosis and treatment of NKTCL.

In This Issue

In This Issue

Systematic In Vitro Evaluation of a Library of Approved and Pharmacologically Active Compounds for the Identification of Novel Candidate Drugs for KMT2A-Rearranged Leukemia

Patients whose leukemias harbor a rearrangement of the Mixed Lineage Leukemia (MLL/KMT2A) gene have a poor prognosis, especially when the disease strikes in infants. The poor clinical outcome linked to this aggressive disease and the detrimental treatment side-effects, particularly in children, warrant the urgent development of more effective and cancer-selective therapeutics. The aim of this study was to identify novel candidate compounds that selectively target KMT2A-rearranged (KMT2A-r) leukemia cells. A library containing 3707 approved drugs and pharmacologically active compounds was screened for differential activity against KMT2A-r leukemia cell lines versus KMT2A-wild type (KMT2A-wt) leukemia cell lines, solid tumor cells and non-malignant cells by cell-based viability assays. The screen yielded SID7969543, an inhibitor of transcription factor Nuclear Receptor Subfamily 5 Group A Member 1 (NR5A1), that limited the viability of 7 out of 11 KMT2A-r leukemia cell lines including 5 out of 7 lines derived from infants, without affecting KMT2A-wt leukemia cells, solid cancer lines, non-malignant cell lines, or peripheral blood mononuclear cells from healthy controls. The compound also significantly inhibited growth of leukemia cell lines with a CALM-AF10 translocation, which defines a highly aggressive leukemia subtype that shares common underlying leukemogenic mechanisms with KMT2A-r leukemia. SID7969543 decreased KMT2A-r leukemia cell viability by inducing caspase-dependent apoptosis within hours of treatment and demonstrated synergy with established chemotherapeutics used in the treatment of high-risk leukemia. Thus, SID7969543 represents a novel candidate agent with selective activity against CALM-AF10 translocated and KMT2A-r leukemias that warrants further investigation.

Prognostic implication of CTLA-4, PD-1, and PD-L1 expression in aggressive adult T-cell leukemia–lymphoma

The prognosis of patients with aggressive adult T cell leukemia-lymphoma (ATLL) is dismal even with intensive chemotherapy. Allogeneic hematopoietic stem cell transplantation (HSCT) is a promising option for patients with aggressive ATLL, but the posttransplant outcome remains unsatisfactory. Hence, to further improve clinical outcomes, novel therapeutic approaches are needed. The clinical significance of immune checkpoint protein expression has not been well-established in aggressive ATLL. This study aims to identify the association between the expression profile of immune checkpoint proteins on ATLL cells and clinical outcomes. This retrospective study cohort included 65 patients with aggressive ATLL diagnosed between 2001 and 2015 at the National Cancer Center Hospital, Tokyo, Japan. Formalin-fixed paraffin-embedded tissue was used to immunohistochemically determine the expression of immune checkpoint proteins and assess the impact of expression profile on the probability of overall survival from diagnosis or HSCT. The current analysis shows that cytotoxic T lymphocyte antigen-4 (CTLA-4), programmed death-1 (PD-1), and programmed death-ligand 1 (PD-L1) expressions were adverse prognostic factors in patients with aggressive ATLL. Experiments that assess the efficacy of immune checkpoint inhibitors are warranted to alleviate the adverse impacts associated with negative immune checkpoints.

3170 – SINGLE-CELL MULTI-OMICS RESOLVES THE EVOLUTION OF TP53-MUTANT LEUKEMIA

TP53 regulates self-renewal and quiescence of hematopoietic stem cells, and its disruption leads to the development of hematological malignancies. In myeloid neoplasms, TP53 mutations define a distinct clinical entity, associated with complex cytogenetics and dismal outcomes. Understanding the cellular and molecular framework through which TP53 mutation drives clonal evolution is a crucial step towards the design of rational therapeutic strategies. Here, we carry out TARGET-seq single-cell multi-omic analysis of haematopoietic stem/progenitor cells (HSPC) from patients with a myeloproliferative neoplasm who had transformed to TP53-mutant secondary acute myeloid leukaemia (sAML), a trackable model of TP53-driven clonal evolution. We invariably identified convergent clonal evolution leading to complete loss of TP53 wild-type (WT) alleles and gain of multiple chromosomal abnormalities upon transformation. TP53-mutant leukaemia stem cells (LSC) were transcriptionally distinct from de novo AML, with evidence of inflammation-associated transcription and aberrant erythroid differentiation. We identified a TP53-mutant LSC signature which was strongly predictive of adverse outcome in both TP53-mutant (HR:3.4) and WT AML (HR:3.1). Finally, we demonstrate a hitherto unrecognised effect of chronic inflammation in promoting disease progression. Sustained inflammatory stimuli (pIpC) led to a 2.5-fold expansion of TP53-mutant cells in WT:TP53R172H/+ chimeras, whereas WT cells were depleted. This indicates that pro-inflammatory cues promote fitness advantage of TP53-mutant cells whilst suppressing antecedent clones. In summary, we present a comprehensive single-cell multi-omic analysis ofTP53-mediated transformation, providing unique insights into the evolution of chronic hematological malignancies towards an aggressive acute leukemia and of broader relevance to other cancer types. TP53 regulates self-renewal and quiescence of hematopoietic stem cells, and its disruption leads to the development of hematological malignancies. In myeloid neoplasms, TP53 mutations define a distinct clinical entity, associated with complex cytogenetics and dismal outcomes. Understanding the cellular and molecular framework through which TP53 mutation drives clonal evolution is a crucial step towards the design of rational therapeutic strategies. Here, we carry out TARGET-seq single-cell multi-omic analysis of haematopoietic stem/progenitor cells (HSPC) from patients with a myeloproliferative neoplasm who had transformed to TP53-mutant secondary acute myeloid leukaemia (sAML), a trackable model of TP53-driven clonal evolution. We invariably identified convergent clonal evolution leading to complete loss of TP53 wild-type (WT) alleles and gain of multiple chromosomal abnormalities upon transformation. TP53-mutant leukaemia stem cells (LSC) were transcriptionally distinct from de novo AML, with evidence of inflammation-associated transcription and aberrant erythroid differentiation. We identified a TP53-mutant LSC signature which was strongly predictive of adverse outcome in both TP53-mutant (HR:3.4) and WT AML (HR:3.1). Finally, we demonstrate a hitherto unrecognised effect of chronic inflammation in promoting disease progression. Sustained inflammatory stimuli (pIpC) led to a 2.5-fold expansion of TP53-mutant cells in WT:TP53R172H/+ chimeras, whereas WT cells were depleted. This indicates that pro-inflammatory cues promote fitness advantage of TP53-mutant cells whilst suppressing antecedent clones. In summary, we present a comprehensive single-cell multi-omic analysis ofTP53-mediated transformation, providing unique insights into the evolution of chronic hematological malignancies towards an aggressive acute leukemia and of broader relevance to other cancer types.

CAR-T cell Therapies for B-cell Lymphoid Malignancies: Identifying Targets Beyond CD19.

Chimeric antigen receptors (CARs) are synthetic engineered receptors with an antigen recognition domain derived from a high-specificity monoclonal antibody that can target surface molecules on tumor cells. T cells are genetically engineered to express CARs, thereby harnessing the antigen-recognition ability of antibodies and effector function of T cells. Target surface molecule selection is crucial for manufacturing CARs. Ideally, a target surface molecule should be restricted to tumor cells and minimally expressed or absent on normal tissues. Different CD19-targeted CAR-T cell therapies have been approved for the treatment of B-cell lymphoid malignancies that are refractory to other therapies, including indolent and aggressive B-cell non-Hodgkin lymphomas (NHL) and B-cell acute lymphoblastic leukemia (B-ALL). Despite impressive results, many patients with aggressive and refractory B-cell malignancies do not respond to or relapse after CD19 CAR-T cell therapies. Thus, several additional strategies are currently being evaluated to overcome these limitations. This review discusses studies on other promising CAR-T cell targets, including CD20, CD22, BAFF-R, ROR1, CD70, BCR complex, kappa/lambda light chains, multitargeted CAR-T cells, and combinations of CAR-T cell therapy with different drugs.

Intervenção odontológica prévia e subsequente ao diagnóstico de leucemia mielóide aguda: relato de caso

ABSTRACT Leukemia’s are characterized by the proliferation of immature white blood cells, called blasts, in the bone marrow and / or blood. Among them, we highlight the Monocytic Acute Myeloid Leukemia, which represents a malignant neoplasm whose unnatural monoblast proliferation results in suppression of myeloid series cells. Oral manifestations are common, arising at the onset of the disease and are also associated with chemotherapy during treatment leading to complications that compromise oncotherapy. The present study deals with a patient with this type of aggressive leukemia, with oral complications of the disease and later, oncological treatment. It also give prominence the performance of the dental surgeon in distinct phases of the treatment emphasizing the importance of maintaining oral health in cancer patients. The presence of the Dentist in the multi-professional team contributes to the reduction of manifestations that occur both due to the disease and the treatment, ensuring a better quality of life for cancer patients and avoiding higher expenses to the health system.

A human fetal liver-derived infant MLL-AF4 acute lymphoblastic leukemia model reveals a distinct fetal gene expression program

Although 90% of children with acute lymphoblastic leukemia (ALL) are now cured, the prognosis for infant-ALL remains dismal. Infant-ALL is usually caused by a single genetic hit that arises in utero: an MLL/KMT2A gene rearrangement (MLL-r). This is sufficient to induce a uniquely aggressive and treatment-refractory leukemia compared to older children. The reasons for disparate outcomes in patients of different ages with identical driver mutations are unknown. Using the most common MLL-r in infant-ALL, MLL-AF4, as a disease model, we show that fetal-specific gene expression programs are maintained in MLL-AF4 infant-ALL but not in MLL-AF4 childhood-ALL. We use CRISPR-Cas9 gene editing of primary human fetal liver hematopoietic cells to produce a t(4;11)/MLL-AF4 translocation, which replicates the clinical features of infant-ALL and drives infant-ALL-specific and fetal-specific gene expression programs. These data support the hypothesis that fetal-specific gene expression programs cooperate with MLL-AF4 to initiate and maintain the distinct biology of infant-ALL.

Molecular regulators of HOXA9 in acute myeloid leukemia.

Dysregulation of the oncogenic transcription factor HOXA9 is a prominent feature for most aggressive acute myeloid leukemia cases and a strong indicator of poor prognosis in patients. Leukemia subtypes with hallmark overexpression of HOXA9 include those carrying MLL gene rearrangements, NPM1c mutations, and other genetic alternations. A growing body of evidence indicates that HOXA9 dysregulation is both sufficient and necessary for leukemic transformation. The HOXA9 mRNA and protein regulation includes multilayered controls by transcription factors (such as CDX2/4 and USF2/1), epigenetic factors (such as MLL-menin-LEDGF, DOT1L, ENL, HBO1, NPM1c-XPO1, and polycomb proteins), microRNAs (such as miR-126 and miR-196b), long noncoding RNAs (such as HOTTIP), three-dimensional chromatin interactions, and post-translational protein modifications. Recently, insights into the dynamic regulation of HOXA9 have led to an advanced understanding of the HOXA9 regulome and provided new cancer therapeutic opportunities, including developing inhibitors targeting DOT1L, menin, and ENL proteins. This review summarizes recent advances in understanding the molecular mechanisms controlling HOXA9 regulation and the pharmacological approaches that target HOXA9 regulators to treat HOXA9-driven acute myeloid leukemia.

Therapeutic inhibition of GAS6-AS1/YBX1/MYC axis suppresses cell propagation and disease progression of acute myeloid leukemia

BackgroundAcute myeloid leukemia (AML) is the most common type of leukemia in adults. Its therapy has not significantly improved during the past four decades despite intense research efforts. New molecularly targeted therapies are in great need. The proto-oncogene c-Myc (MYC) is an attractive target due to its transactivation role in multiple signaling cascades. Deregulation of the MYC is considered one of a series of oncogenic events required for tumorigenesis. However, limited knowledge is available on which mechanism underlie MYC dysregulation and how long non-coding RNAs (lncRNAs) are involved in MYC dysregulation in AML.MethodsAML microarray chips and public datasets were screened to identify novel lncRNA GAS6-AS1 was dysregulated in AML. Gain or loss of functional leukemia cell models were produced, and in vitro and in vivo experiments were applied to demonstrate its leukemogenic phenotypes. Interactive network analyses were performed to define intrinsic mechanism.ResultsWe identified GAS6-AS1 was overexpressed in AML, and its aberrant function lead to more aggressive leukemia phenotypes and poorer survival outcomes. We revealed that GAS6-AS1 directly binds Y-box binding protein 1 (YBX1) to facilitate its interaction with MYC, leading to MYC transactivation and upregulation of IL1R1, RAB27B and other MYC target genes associated with leukemia progression. Further, lentiviral-based GAS6-AS1 silencing inhibited leukemia progression in vivo.ConclusionsOur findings revealed a previously unappreciated role of GAS6-AS1 as an oncogenic lncRNA in AML progression and prognostic prediction. Importantly, we demonstrated that therapeutic targeting of the GAS6-AS1/YBX1/MYC axis inhibits AML cellular propagation and disease progression. Our insight in lncRNA associated MYC-driven leukemogenesis may contribute to develop new anti-leukemia treatment strategies.

A Novel Aggressive NK Cell Leukemia Cell Line and Mouse Model for Evaluation of Therapeutic Candidates

Introduction: Aggressive nature killer-cell leukemia (ANKL) is a rare, highly lethal and disseminated malignancy derived from NK cells. Patients are most commonly young to middle aged adults who present with constitutional symptoms and often have organomegaly, hemophagocytosis, and multiorgan failure. Most cases are refractory to therapy and the median survival is less than 2 months despite multiagent chemotherapy. Development model systems and novel targeted therapeutic agents remains an urgent issue. In this study we established a cell line and a NOD-scid IL2Rgammanull(NSG) mouse model of ANKL, which represented the primary malignant cells. We characterized the molecular features of this model and explored new targeted agents against it.Methods: Primary tumor cells were cultured ex vivo in the presence of human IL-2 and then injected into a NSG mouse. Flow cytometry, immunohistochemistry (IHC), CISH-EBER were used to confirm the engraftment and to compare the pathologic features of engrafted tumor cells with the primary sample. Karyotyping and oligonucleotide/single nucleotide polymorphism microarray analyses were performed to compare the established cell line CCANKL with primary tumor cells. Selective inhibitors targeting anti-apoptotic BCL-2 family members and a CD6-targeted antibody drug conjugate (ADC) were tested for their treatment efficacies in this model.Results: Leukemic peripheral blood from a 31-year old woman with relapsed ANKL demonstrated a hyperleukocytosis in which NK cells accounted for 88% of cells. Immunophenotyping showed the malignant cells expressed CD2, 7, 38, 45 and 56, and lacked CD3, 4, 5, 8, 10, 11b, 13, 14, 16, 19, 20, 22, 33, 34, 57, 64, 65, 117, HLADR and Kappa or Lambda immunoglobulin light chain. IHC of an involved lymph node showed the presence of EBV (EBER in situ hybridization) and a proliferative index of 70%. Isolated PBMC were cultured ex vivo and serially passaged as a cell line (CCANKL) in the presence of human IL2. CCANKL cells successfully engrafted in NSG mice and displayed splenomegaly. IHC and Immunophenotyping data confirmed both CCANKL cells and engrafted cells in NSG mice represented primary tumor cells. Both the primary PBMC and CCANKL cells had similar, abnormal karyotypes of 46,XX,dup(1)(q21q42), del(6)(q15q25)[1]/46,idem,der(20)t(7;20)(q11.2;q13.1)[9] and 46,XX,del(6)(q15q25),der(20)t(7;20)(q11.2;q13.1),add(22)(p11.1)[10], respectively. Microarray analysis of both primary tumor cells and CCANKL confirmed some of the karyotypic findings, but also revealed additional abnormalities, in particular for the CCANKL cell line. There were also some differences for the copy number changes and regions of loss of heterozygosity observed between the primary tumor cells and CCANKL. Abnormalities involving 1q, 6q and 7p have been reported in association with aggressive NK cell leukemia.Both immunoblotting and IHC revealed expression of anti-apoptotic proteins of BCL-xL, MCL-1 and pro-apoptotic BIM in CCANKL cells and NSG-engrafted tumors, while BCL-2 was positive in cultured cells by Western blotting but not detectable in engrafted tissue via IHC. Expression level of BCL-xl was stable but there were enhanced expression of MCL-1 and BIM during 72-hour starvation of IL2 in cultured CCANKL cells. Single agent of venetoclax, BCL-xl inhibitor (A-1331852), and CDK9 inhibitor (A-1592668), at range of 1 - 1000 nM, had no detectable (BCL-2), mild (BCL-xL), and strong (CDK9) killing activities against CCANKL cells.We further confirmed expression of CD6, a surface glycoprotein expressed on most T-cells and a subset of NK cells, by IHC and flow cytometry in CCANKL and also tested a novel CD6-targeted ADC. Compared to naked anti-CD6 IgG and isotype control, CD6-ADC was capable of inducing apoptosis in CCANKL cells. Administration of either anti-CD6 IgG or CD6-ADC (4 mg/kg) on the same day as inoculation of CCANKL cells in NSG mice blocked engraftment of these malignant cells in NSG mice. The 2 nd ANKL case tested by IHC showed positive of CD6 in malignant cells.Conclusion: A novel aggressive NK cell leukemia cell line and a NSG mouse model were established. The in vitro data support further investigation of the expression features of BCL-2 family proteins in ANKL cases and in vivo evaluation for the efficiency of anti-apoptotic protein inhibitors in this aggressive disease. Further studies targeting CD6 in ANKL is warranted. DisclosuresLin: Takeda Pharma: Consultancy, Research Funding. Phillips: AbbVie Inc.: Current Employment, Current equity holder in publicly-traded company. Hsi: AbbVie Inc, Eli Lilly: Research Funding.

Hepatic Niche Leads to Aggressive Natural Killer Cell Leukemia Proliferation

Aggressive natural killer cell leukemia (ANKL) is a rare form of natural killer (NK)-cell neoplasm with median survival of less than 2 months. Recently, the genomic mutation analysis using tumor cells reveled that the mutational profile of ANKL was similar to that of extranodal NK / T-cell lymphoma, which has relatively better prognosis than ANKL, explaining no causative mutations with a dismal prognosis. Here, using patient-derived xenograft model (PDX) mouse, we show that hepatic niche plays an important role in the ANKL biology.We established PDX mouse by intravenously injecting ANKL cells derived from patient peripheral blood or bone marrow samples to immunocompromised mice, which enables comprehensive analysis for tumor cells as well as tumor microenvironment. In total, we obtained four PDX strains derived from different patients. Time series pathological and flowcytometric analyses revealed that the ANKL cells initially engrafted and proliferated in sinusoidal or peri-portal area of the liver. This sinusoid or peri-portal distribution of ANKL in the liver was also confirmed with the patient liver specimen.To further determine the feature of ANKL in the liver, we selected liver or spleen tropic cells by serial adaptive transfer from each organ to the next mice. The liver-tropic ANKL cells proliferated more rapidly than splenic ANKL cells, which was evident by the significantly shorter survival of PDX mice injected liver-tropic cells (Figure). We performed RNA-sequencing using liver-tropic ANKL cells, spleen-tropic ANKL cells and NK-cells derived from healthy donors. These three types of cells showed distinct populations in principal component analysis. To further clarify the interaction between ANKL and liver niche, we performed additional RNA sequencing using total liver of mouse with or without bearing leukemic cells. In the cell-cell interaction analysis, we used two computational methods, mixed-species RNA-seq (Komura, et al. BMC Genomics 2016), which can distinguish transcripts derived from human (cancer) with mouse (non-cancer niche cells), and NicheNet (Browaeys, et al. Nat Methods 2020), which is a computational algorithm to model intercellular communication by linking ligands to target genes. These two methods allowed us to investigate the interaction between liver niche ligands and ANKL receptors.Among the listed ligand-receptor interactions, we focused on the macrophage migration inhibitory factor (MIF) and its receptor, CD74 axis. While CD74 was upregulated in ANKL cells compared with normal NK cells, MIF was highly expressed in the liver mainly liver sinusoid and Kupffer cells. Although we failed to culture primary ANKL cells in vitro, ANKL cells treated with MIF showed improved viability in vitro compared with untreated cells. Deletion of CD74 on the ANKL cells using CRISPR-Cas9 system attenuated the tumor formation in the liver as well as in bone marrow and spleen of PDX mouse compared with the wild type ANKL cells. These findings highlight that the liver, non-canonical hematopoietic organ in adults, is a principal niche where the liver specific components are required for survival and proliferation of ANKL cells. MIF-CD74 axis might play an important role in the communication between ANKL and hepatic niche. [Display omitted] DisclosuresKanda: Otsuka Pharmaceutical: Honoraria, Research Funding; Sanofi: Research Funding; MSD: Honoraria.

Deficiency of the E3 Ligase Hoip Impairs Adult Hematopoiesis and Myeloid Leukemia

Ubiquitination is a post-translational modification that plays important roles in the regulation of various cellular processes. The linear ubiquitin chain assembly complex (LUBAC) is the only E3 ubiquitin ligase, which can specifically generate linear ubiquitin chains. LUBAC is composed of three subunits: catalytic Hoip (Rnf31), Hoil-1l (RBCK1), and Sharpin. LUBAC regulates canonical NF-κB signaling pathway and apoptosis. Several studies have shown that LUBAC is required for fetal hematopoiesis and tumorigenesis in several solid cancers, but the role of Hoip, which is the catalytic component of the LUBAC, in adult hematopoiesis and myeloid leukemia is unclear.To address whether Hoip is required for adult hematopoiesis, we used tamoxifen induced Hoip deleted mice (Hoip fl/fl; Rosa26-CreERT). Deletion of Hoip reduced the numbers of almost all cell fractions in bone marrow and peripheral blood, except for long-term hematopoietic stem cell (LT-HSC) fraction (CD34 - Flk2 - Lineage - c-Kit + Sca-1 +: LSK). Deletion of Hoip treated with tamoxifen markedly impaired colony formation of LT-HSCs in vitro. Among competitive transplantation assay using bone marrow cells from Hoip fl/fl; Rosa26-CreERT mice, deletion of Hoip treated with tamoxifen following stable reconstitution 8 weeks after transplantation led to a significant reduction of Hoip-deficient chimerism compared to control in vivo (Figure A). Deletion of Hoip induced apoptosis in bone marrow cells and increased the frequency of CD34 - LSK cells in S/G2/M phase of the cell cycle. Collectively, these data indicated that Hoip is required for adult hematopoiesis.To evaluate the consequences of Hoip deletion in myeloid leukemia propagation and maintenance, we utilized aggressive murine myeloid leukemia models driven by retroviral transduction of oncogenes: MLL-AF9 and NRAS G12V-driven acute myeloid leukemia (AML) and BCR-ABL and NUP98-HOXA9-driven blast crisis of chronic myelogenous leukemia (CML-BC) models. Deletion of Hoip in established leukemia cells treated with tamoxifen markedly impaired colony formation of leukemia cells in vitro and led to a significantly longer survival with reduced disease burden in bone marrow and spleen in vivo in both of leukemic models (Figure B,C). Deletion of Hoip also induced apoptosis in leukemia stem cells (LSCs: c-Kit + Lineage - cells) (Figure D) and increased the frequency of LSCs in S-phase of the cell cycle. Furthermore, we evaluated the contribution of HOIP to human myeloid leukemia. Knockdown of HOIP by small hairpin RNA using lentivirus in several myeloid leukemia cell lines (THP-1, SKM-1, and K562) and primary patient-derived AML cells exhibited reduced numbers of colony forming cells in vitro, and increased apoptosis. LUBAC inhibitor gliotoxin impaired the growth of murine and human leukemia cells. These results indicate that Hoip is essential for propagation and maintenance in murine and human myeloid leukemia.Because LUBAC regulates canonical NF-κB signaling pathway, we evaluated protein levels of p65 phosphorylation on Ser536 (p-p65) and IκBα in leukemia cells by flow cytometric analysis. Reduction in p-p65 and inhibition of IκBα degradation were observed in Hoip-deficient leukemia cells (Figure E), indicating that Hoip plays an important role in regulation of NF-κB signaling in myeloid leukemia.Since Hoip is the central component of LUBAC and the only catalytically active subunit of E3 ubiquitin ligase, we examined the importance of each domain of Hoip for myeloid leukemia propagation using Hoip mutant isoforms. Loss of colony-forming ability of Hoip-deficient AML cells could not be rescued by retroviral transduction of the Hoip mutants with deletion of UBA domain (which is required for interaction with the other LUBAC subunits) and with deletion of RBR domain and with mutation in C879A (which lack ligase activity) (Figure F), indicating that LUBAC ligase activity and interaction with the other LUBAC subunits are critical for leukemia propagation.Thus, our data demonstrated that Hoip is essential for adult hematopoiesis and myeloid leukemia. Given that patients with myeloid leukemia have shown increased activity of NF-κB signaling, inhibition of LUBAC ligase activity could serve as a promising strategy for treating myeloid leukemia. [Display omitted] DisclosuresJimbo: Japan Society for the Promotion of Science: Research Funding. Ito: Japan Society for the Promotion of Science: Research Funding; Institute for Frontier Life and Medical Sciences, Kyoto University: Research Funding. Iwama: Nissan Chemical Corporation: Research Funding. Nannya: Otsuka Pharmaceutical Co., Ltd.: Consultancy, Speakers Bureau; Astellas: Speakers Bureau. Konuma: Japan Society for the Promotion of Science: Research Funding; The Japanese Society of Hematology: Research Funding; SGH Foundation: Research Funding; Institute for Frontier Life and Medical Sciences, Kyoto University: Research Funding.

Single-Cell Multi-Omics Reveals the Genetic, Cellular and Molecular Landscape of TP53 Mutated Leukemic Transformation in MPN

Single-Cell Multi-Omics Reveals the Genetic, Cellular and Molecular Landscape of TP53 Mutated Leukemic Transformation in MPN

PHF6 and JAK3 Mutations Cooperatively Drive T-Cell Acute Lymphoblastic Leukemia Progression

T cell acute lymphoblastic leukemia (T-ALL) is one of the most frequent hematologic malignancies resulted from gene mutations and/or genomic rearrangements that occur in T cell progenitors. The 5-year survival rate of T-ALL patients is less than 50%. Much efforts have been dedicated to decipher the molecular events underlying TALL transformation, with the goals to identify specific therapeutic targets and develop new and more effective drugs. As a member of JAK kinase family, JAK3 mutations can be identified in 16.1% of T-ALL cases, and JAK3 M511I mutation is the most common one within all JAK3 mutations. Activating JAK3 M511I mutation induced a lympho-proliferative disorder, that followed by a T-ALL-like disease. PHF6 mutation is one of the most common co-existing gene mutations with JAK3 in T-ALL patients. Co-mutation events of JAK3 and PHF6 account for 1.89%-10.0% in T-ALL cases. However, the role(s) of PHF6 and JAK3 co-mutations in tumorigenesis is unknown.Here in this study, we first analyzed the genetic data of 449 T-ALL cases from multiple clinical centers in which JAK/STAT mutations is about 21% of the total cases. Interestingly, we found that PHF6 mutations were significantly associated with JAK3 mutations in these T-ALL cases (P<0.05), and the JAK3 and PHF6 co-mutation occurred in 7.2% of the cohort. Significantly, the average survival time of PHF6 and JAK/STAT co-mutated group was much shorter than that of the single JAK/STAT mutated group (P<0.05) or none-PHF6/JAK/STAT mutated group (P<0.001). We generated Phf6 KO+JAK3 M511I mice by transplanting JAK3M511I infected Phf6 Lin - cells into wild-type mice. All Phf6 KO+JAK3M511Imice succumbed to leukemia from 74 to 101 days after transplantation with significantly shorter survival time than that of Phf6WT+JAK3M511Imice. The Phf6 KO+JAK3M511I mice showed more aggressive phenotypes of T-ALL than Phf6WT+JAK3M511I mice, including higher counts of WBCs, neutrophils and lymphocytes in peripheral blood, as well as higher degree of extramedullary infiltration in spleen, liver, lung and brain. Extreme limiting dilution transplantation assays demonstrated a marked increase in leukemia-initiating cell activity in Phf6 KO +JAK3M511Icells when compared with Phf6WT +JAK3M511Icells, supporting a role for loss of Phf6 in promoting leukemia blast self-renewal and proliferation.To investigate the underlying molecular mechanisms of Phf6 in accelerating T-ALL development,we performed RNAseq to analyze the transcriptome programing changes associated with Phf6 in isogenic Phf6WT +JAK3M511I or Phf6KO +JAK3M511IT-ALL cells. Gene set enrichment analysis (GSEA) showed up-regulated cell cycle in Phf6 KO +JAK3 M511I leukemia cells. We then performed Chromatin immunoprecipitation sequencing (ChIP-seq) and found that PHF6 associated with BAI1 gene. qPCR and Western blot showed that the mRNA and protein expression of Bai1/BAI1 were significantly decreased in Phf6KO +JAK3M511Icells in comparison with Phf6 WT+JAK3M511I cells. BAI1 has been reported to prevent MDM2-mediated P53 ubiquitination, and loss of BAI1 reduces P53 level. We found that the protein expression of BAI1 and P53 was decreased, and the ubiquitination of P53 was significantly increased in PHF6 knockdown (KD) MOLT-4 cells (T-ALL) when compared with the control cells. BAI1 overexpression in PHF6 KD MOLT-4 cells significantly increased P53 expression in PHF6 KD+BAI1 OE MOLT-4 cells when compared with that of PHF6 KD cells. It suggested that Phf6 deficiency increased BAI1-mediated P53 degradation. To confirm this, we treated Phf6 KO + JAK3M511I mice with a JAK3 inhibitor (ruxolitinib) in combination with a MDM2 inhibitor (idasanutlin), and found a synergistic response of the treatment within a significant attenuation in leukemia burden in vivo.In conclusion, we found that PHF6 mutation frequently co-existed with JAK3 mutation in T-ALLs, and together they can drive an aggressive leukemia in mice model. Notably, PHF6 deficiency promoted JAK3-induced T-ALL progression by inhibiting BAI1-MDM2-P53 signaling pathway that is independent of JAK3-STAT signaling pathway. We further demonstrated that combination therapy by tofacitinib and idasanutlin can reduce the Phf6 KO and JAK3 M511I leukemia burden in vivo. Our study suggested that combinational usage of JAK3 inhibitors and MDM2 inhibitors may increase the drug benefit for T-ALL patients with PHF6 and JAK3 co-mutations. DisclosuresNo relevant conflicts of interest to declare.

Immunotherapeutic Targeting of TSLPR with Chimeric Antigen Receptor T Cells in AML

Adoptive transfer of T cells engineered to express chimeric antigen receptors (CARs) has achieved impressive outcomes in the treatment of refractory/relapsed B-ALL, providing potentially curative treatment options for these patients. The use of CAR T in AML, however, is still in its infancy with limitations due to the innate heterogeneity associated with AML and the lack of AML-specific targets for therapeutic development. The CRLF2 gene encodes for thymic stromal lymphopoietin receptor (TSLPR) and has previously been shown to be highly upregulated in a subset of children and adults with B-ALL. Targeting TSLPR with CAR T cells demonstrates potent anti-leukemia activity against TSLPR-positive B-ALL (PMID 26041741). Through Target Pediatric AML (TpAML), we profiled the transcriptome of nearly 3000 children and young adults with AML and identified CRLF2 (TSLPR) to be highly expressed in a subset of AML, including the majority of AML harboring KM2TA (aka MLL) fusions. TSLPR cell surface expression was validated in primary patient samples using flow cytometry, which showed uniform expression of TSLPR on AML blasts. Given that TSLPR is expressed in AML with confirmed cell surface expression, we developed TSLPR-directed CAR T for preclinical evaluation in AML.We generated a TSLPR-directed CAR using the single-chain variable fragment (scFv) derived from an anti-TSLPR binder (clone 3G1, MD Anderson), IgG4 spacer and 41-BB/CD3zeta signaling domains. The in vitro cytotoxicity of TSLPR CAR T cells was evaluated against the REH-1 cell line and primary AML specimens. TSLPR CAR T cells demonstrated anti-leukemia activity against REH-1 as well as against primary AML specimens. To evaluate the in vivo efficacy of TSLPR CAR T cells, we developed a patient-derived xenograft (PDX) model using bone marrow cells from a TSLPR-positive patient. These cells provided a robust model system to evaluate the in vivo activity of TSLPR CAR T cells, as they produced an aggressive leukemia in humanized NSG-SGM3 mice. The PDX generated from these cells died within 2 months of transplant with significant leukemia infiltration into the bone marrow, liver, and spleen. In the in vivo study, the leukemia burden was assessed by flow cytometric analysis of AML cells in the peripheral blood and bone marrow aspirates following treatment with unmodified control or TSLPR CAR T cells given at 10x10 6 T cells per mouse. After CAR T treatment, we detected a significant decrease in leukemia infiltration into the peripheral blood and bone marrow in the CAR T-treated mice compared to mice that received unmodified T cells.In this study, we report that similar to B-ALL, CRLF2 (TSLPR) is overexpressed in a subset of AML, providing a strategy to eliminate AML cells with CAR T cell therapy. We validated the cell surface expression of TSLPR and showed that the expression is uniform across AML specimens. We further demonstrate that CAR T cells targeting TSLPR were effective in eliminating AML cells in vitro and in vivo. Given that TSLPR is highly expressed in the KMT2A-rearranged AML, a subtype that is associated with poor outcomes, TSLPR-directed CAR T cells represent a promising immunotherapy for this high-risk AML subset. DisclosuresPardo: Hematologics, Inc.: Current Employment.