Daniel H. Wiseman

Mutations in TRNT1 cause congenital sideroblastic anemia with immunodeficiency, fevers, and developmental delay (SIFD)

Mutations in genes encoding proteins that are involved in mitochondrial heme synthesis, iron-sulfur cluster biogenesis, and mitochondrial protein synthesis have previously been implicated in the pathogenesis of the congenital sideroblastic anemias (CSAs). We recently described a syndromic form of CSA associated with B-cell immunodeficiency, periodic fevers, and developmental delay (SIFD). Here we demonstrate that SIFD is caused by biallelic mutations in TRNT1, the gene encoding the CCA-adding enzyme essential for maturation of both nuclear and mitochondrial transfer RNAs. Using budding yeast lacking the TRNT1 homolog, CCA1, we confirm that the patient-associated TRNT1 mutations result in partial loss of function of TRNT1 and lead to metabolic defects in both the mitochondria and cytosol, which can account for the phenotypic pleiotropy.

Reversible inhibitors of LSD1 as therapeutic agents in acute myeloid leukemia: clinical significance and progress to date

In the 10 years since the discovery of lysine‐specific demethylase 1 (LSD1), this epigenetic eraser has emerged as an important target of interest in oncology. More specifically, research has demonstrated that it plays an essential role in the self‐renewal of leukemic stem cells in acute myeloid leukemia (AML). This review will cover clinical aspects of AML, the role of epigenetics in the disease, and discuss the research that led to the first irreversible inhibitors of LSD1 entering clinical trials for the treatment of AML in 2014. We also review recent achievements and progress in the development of potent and selective reversible inhibitors of LSD1. These compounds differ in their mode of action from tranylcypromine derivatives and could facilitate novel biochemical studies to probe the pathways mediated by LSD1. In this review, we will critically evaluate the strengths and weaknesses of published series of reversible LSD1 inhibitors. Overall, while the development of reversible inhibitors to date has been less fruitful than that of irreversible inhibitors, there is still the possibility for their use to facilitate further research into the roles and functions of LSD1 and to expand the therapeutic applications of LSD1 inhibitors in the clinic.

A novel syndrome of congenital sideroblastic anemia, B-cell immunodeficiency, periodic fevers, and developmental delay (SIFD)

Congenital sideroblastic anemias (CSAs) are a heterogeneous group of inherited disorders identified by pathological erythroid precursors with perinuclear mitochondrial iron deposition in bone marrow. An international collaborative group of physicians and laboratory scientists collated clinical information on cases of CSA lacking known causative mutations, identifying a clinical subgroup of CSA associated with B immunodeficiency, periodic fevers, and development delay. Twelve cases from 10 families were identified. Median age at presentation was 2 months. Anemia at diagnosis was sideroblastic, typically severe (median hemoglobin, 7.1 g/dL) and markedly microcytic (median mean corpuscular volume, 62.0 fL). Clinical course involved recurrent febrile illness and gastrointestinal disturbance, lacking an infective cause. Investigation revealed B-cell lymphopenia (CD19⁺ range, 0.016-0.22 × 10⁹/L) and panhypogammaglobulinemia in most cases. Children displayed developmental delay alongside variable neurodegeneration, seizures, cerebellar abnormalities, sensorineural deafness, and other multisystem features. Most required regular blood transfusion, iron chelation, and intravenous immunoglobulin replacement. Median survival was 48 months, with 7 deaths caused by cardiac or multiorgan failure. One child underwent bone marrow transplantation aged 9 months, with apparent cure of the hematologic and immunologic manifestations. We describe and define a novel CSA and B-cell immunodeficiency syndrome with additional features resembling a mitochondrial cytopathy. The molecular etiology is under investigation.

CD86 expression as a surrogate cellular biomarker for pharmacological inhibition of the histone demethylase lysine-specific demethylase 1.

There is a lack of rapid cell-based assays that read out enzymatic inhibition of the histone demethylase LSD1 (lysine-specific demethylase 1). Through transcriptome analysis of human acute myeloid leukemia THP1 cells treated with a tranylcypromine-derivative inhibitor of LSD1 active in the low nanomolar range, we identified the cell surface marker CD86 as a sensitive surrogate biomarker of LSD1 inhibition. Within 24h of enzyme inhibition, there was substantial and dose-dependent up-regulation of CD86 expression, as detected by quantitative polymerase chain reaction, flow cytometry, and enzyme-linked immunosorbent assay. Thus, the use of CD86 expression may facilitate screening of compounds with putative LSD1 inhibitory activities in cellular assays.

The variety of leukemic stem cells in myeloid malignancy

Human acute myeloid leukemias (AMLs) are sustained by leukemic stem cells (LSCs) that generate through aberrant differentiation the blast cells that make up the bulk of the malignant clone. LSCs were first identified as rare cells with an immunophenotype shared with normal hematopoietic stem cells (HSCs). However, refinements of xenotransplantation assays, alternative methods of quantitation and syngeneic murine models have all led to an appreciation that LSCs display marked variability in frequency, immunophenotype and differentiation potential, both between and even within leukemias. Insights from next-generation sequencing efforts have dramatically extended understanding of the mutational landscape and clonal organization of AML and have added an additional layer of complexity to the biology of LSCs: a requirement to consider the effect of the various recurrently occurring genetic lesions in AML on the initiation and maintenance of leukemic subclones. Despite these advances, cure rates in AML remain substantially unchanged in recent years. A renewed focus on the biological properties of chemotherapy-resistant LSCs, a cellular entity of prime clinical importance, will be required to develop additional therapeutic strategies to enhance patient outcomes.

Bullous pyoderma gangrenosum in acute myeloid leukaemia.

A 68-yr-old man with relapsed acute myeloid leukaemia (FAB M5) presented with small, tender, erythematous papules on the dorsal aspects of both wrists, at sites of recent intravenous cannulation. These were initially diagnosed as infective and flucloxacillin was commenced. Subsequently he developed fever and constitutional symptoms. Despite antibiotic escalation the lesions developed into large, exquisitely tender, concentric plaques with well-demarcated, violaceous, serpinginous borders and central necrosis. Similar lesions developed on his left thigh, upper lip and left ear. Microbiology investigations were normal and despite clinical concern that the lesions might represent leukaemic infiltration, recognition of the apparent central necrosis indicated the diagnosis as superficial bullous pyoderma gangrenosum (PG). Punch biopsy revealed inflammatory changes with fat necrosis compatible with PG. Oral prednisolone 1 mg/kg daily was commenced with dramatic regression of the lesions. The association between PG and myeloid malignancy is well established. Typical lesions rapidly enlarge, are tender and violaceous with a well-defined edge and necrotic/ulcerated centre. Histology is non-diagnostic but may exclude doi:10.1111/j.1600-0609.2007.00845.x European Journal of Haematology ISSN 0902-4441

Direct comparison of quantitative digital PCR and 2-hydroxyglutarate enantiomeric ratio for IDH mutant allele frequency assessment in myeloid malignancy.

Direct comparison of quantitative digital PCR and 2-hydroxyglutarate enantiomeric ratio for IDH mutant allele frequency assessment in myeloid malignancy

Elevated plasma 2-hydroxyglutarate in acute myeloid leukaemia: association with the IDH1 SNP rs11554137 and severe renal impairment.

Tobias Menne Fiona Keenan Jontha P. Wallis Haemostasis Research Unit, Department of Haematology, University College London, London, Department of Haematology, Newcastle upon Tyne Hospitals NHS Foundation Trust, Department of Microbiology, Newcastle upon Tyne Hospitals NHS Foundation Trust, Department of Haematology, University of Newcastle, Newcastle, and Department of Haematology, County Durham and Darlington NHS Foundation Trust, Darlington, UK. E-mail: Jonathan.Wallis@nuth.nhs.uk

Discovery and Optimization of Allosteric Inhibitors of Mutant Isocitrate Dehydrogenase 1 (R132H IDH1) Displaying Activity in Human Acute Myeloid Leukemia Cells

A collaborative high throughput screen of 1.35 million compounds against mutant (R132H) isocitrate dehydrogenase IDH1 led to the identification of a novel series of inhibitors. Elucidation of the bound ligand crystal structure showed that the inhibitors exhibited a novel binding mode in a previously identified allosteric site of IDH1 (R132H). This information guided the optimization of the series yielding submicromolar enzyme inhibitors with promising cellular activity. Encouragingly, one compound from this series was found to induce myeloid differentiation in primary human IDH1 R132H AML cells in vitro.

Donor cell leukemia following unrelated donor bone marrow transplantation for primary granulocytic sarcoma of the small intestine

Granulocytic sarcoma (GS) in the absence of bone marrow involvement at diagnosis is unusual. Treatment of primary (aleukemic) GS should follow intensive acute myeloid leukemia (AML)-style chemotherapy protocols, as patients otherwise appear destined to rapidly declare frank medullary disease. However, the role of hematopoietic stem cell transplantation (HSCT) is less clear. Here we present an unusual case of isolated primary GS involving small bowel treated with chemotherapy consolidated by HSCT from an unrelated donor. Full donor chimerism was achieved and maintained, without relapse of the original disease. However, 28 months post-transplant our patient developed a distinct and rapidly progressive medullary AML, apparently derived from transplanted cells of donor origin. Donor cell leukemia (DCL) is a fascinating and increasingly recognized phenomenon, with at least 50 cases reported to date. Our case adds to this growing literature and highlights the ethical dilemmas concerning notification of unrelated donors in such cases, since there is little evidence that they are at increased risk of developing leukemia themselves. This also represents the first case of DCL reported after transplantation for primary GS.