Sally Killick

Coexistence of LMPP-like and GMP-like Leukemia Stem Cells in Acute Myeloid Leukemia

The relationships between normal and leukemic stem/progenitor cells are unclear. We show that in ∼80% of primary human CD34+ acute myeloid leukemia (AML), two expanded populations with hemopoietic progenitor immunophenotype coexist in most patients. Both populations have leukemic stem cell (LSC) activity and are hierarchically ordered; one LSC population gives rise to the other. Global gene expression profiling shows the LSC populations are molecularly distinct and resemble normal progenitors but not stem cells. The more mature LSC population most closely mirrors normal granulocyte-macrophage progenitors (GMP) and the immature LSC population a previously uncharacterized progenitor functionally similar to lymphoid-primed multipotential progenitors (LMPPs). This suggests that in most cases primary CD34+ AML is a progenitor disease where LSCs acquire abnormal self-renewal potential.

Guidelines for the diagnosis and management of aplastic anaemia

King’s College Hospital, St Mary’s Hospital, Barts and The London Hospital, London, Birmingham Children’s Hospital, Birmingham, Barts and The London School of Medicine and Dentistry, St George’s Hospital, London, Queen Elizabeth Hospital, King’s Lynn, Norfolk, Ashford Hospital, Middlesex, London, Patient representative, St Helier Hospital, Carshalton, Surrey, Royal Bournemouth Hospital, Dorset, Chesterfield Royal Hospital, Derbyshire, and Manchester Royal Infirmary, Manchester, UK.

Remission in acute refractory and relapsing thrombotic thrombocytopenic purpura following rituximab is associated with a reduction in IgG antibodies to ADAMTS-13

Thrombotic thrombocytopenic purpura (TTP) is a life‐threatening disorder and plasma exchange (PEX) remains the primary treatment modality. Twenty‐five patients with acute refractory/relapsing idiopathic TTP received rituximab in conjunction with PEX because of progressive clinical disease or deterioration in laboratory parameters, despite intensive standard therapy. In relapsing TTP, rituximab was started if antibody to ADAMTS‐13 (a disintegrin and metalloproteinase with thrombospondin motif‐13) was demonstrated during previous episodes. All 25 patients attained complete clinical and laboratory remission in a median of 11 d after initiating rituximab. In 21 cases, ADAMTS‐13 activity was within the normal range following rituximab. Inhibitors were detected in 24/25 patients by mixing studies and/or immunoglobulin G (IgG) antibodies to ADAMTS‐13 pre‐rituximab. There was no evidence of inhibitors and/or IgG activity <10% in 23/25 patients following rituximab. In acute refractory cases, the median number of PEX pre‐rituximab and following the first rituximab infusion was 13 and 9, respectively. There have been no infectious complications, despite low CD 19 levels and no relapses. In patients with acute refractory/relapsing idiopathic TTP, rituximab appears to be a safe, effective, targeted therapy with a significant reduction in the requirement for PEX.

Frequent mutation of the polycomb-associated gene ASXL1 in the myelodysplastic syndromes and in acute myeloid leukemia

Frequent mutation of the polycomb-associated gene ASXL1 in the myelodysplastic syndromes and in acute myeloid leukemia

The effect of treatment with Campath‐1H in patients with autoimmune cytopenias

We describe 21 patients with severe and life‐threatening autoimmune cytopenias resistant to standard immunosuppression who were treated with the monoclonal antibody Campath‐1H. Four patients had autoimmune neutropenia, four had autoimmune haemolytic anaemia, four had pure red cell aplasia, one had immune thrombocytopenia purpura (ITP), three had autoimmune haemolytic anaemia and ITP (Evans syndrome), three had autoimmune pancytopenia (ITP, autoimmune neutropenia and autoimmune haemolytic anaemia), one had ITP (associated with acquired Glanzmanns disease) and autoimmune neutropenia, and one had ITP and red cell aplasia. Campath‐1H was administered at a dose of 10 mg/d as an intravenous infusion for 10 d. Responses were seen in 15 patients, which were sustained in six. Relapse occurred in eight patients after Campath‐1H treatment. Patients entering the study later, received cyclosporine after Campath‐1H in an attempt to reduce the incidence of relapse. Three patients received a second course of Campath‐1H; all responded but later relapsed. Fourteen patients are alive at a median of 12 months (range 4–61) after Campath‐1H. Campath‐1H represents an alternative therapeutic option for severe, refractory autoimmune cytopenias.

Deregulated gene expression pathways in myelodysplastic syndrome hematopoietic stem cells.

To gain insight into the molecular pathogenesis of the myelodysplastic syndromes (MDS), we performed global gene expression profiling and pathway analysis on the hematopoietic stem cells (HSC) of 183 MDS patients as compared with the HSC of 17 healthy controls. The most significantly deregulated pathways in MDS include interferon signaling, thrombopoietin signaling and the Wnt pathways. Among the most significantly deregulated gene pathways in early MDS are immunodeficiency, apoptosis and chemokine signaling, whereas advanced MDS is characterized by deregulation of DNA damage response and checkpoint pathways. We have identified distinct gene expression profiles and deregulated gene pathways in patients with del(5q), trisomy 8 or −7/del(7q). Patients with trisomy 8 are characterized by deregulation of pathways involved in the immune response, patients with −7/del(7q) by pathways involved in cell survival, whereas patients with del(5q) show deregulation of integrin signaling and cell cycle regulation pathways. This is the first study to determine deregulated gene pathways and ontology groups in the HSC of a large group of MDS patients. The deregulated pathways identified are likely to be critical to the MDS HSC phenotype and give new insights into the molecular pathogenesis of this disorder, thereby providing new targets for therapeutic intervention.

Gene expression profiling of CD34+ cells in patients with the 5q− syndrome

The transcriptome of the CD34+ cells was determined in a group of 10 patients with the 5q− syndrome using a comprehensive array platform, and was compared with the transcriptome of CD34+ cells from 16 healthy control subjects and 14 patients with refractory anaemia and a normal karyotype. The majority of the genes assigned to the commonly deleted region (CDR) of the 5q− syndrome at 5q31–q32 showed a reduction in expression levels in patients with the 5q− syndrome, consistent with the loss of one allele. Candidate genes showing haploinsufficiency in the 5q− syndrome included the tumour suppressor gene SPARC and RPS14, a component of the 40S ribosomal subunit. Two genes mapping to the CDR, RBM22 and CSNK1A1, showed a >50% reduction in gene expression, consistent with the downregulation of the remaining allele. This study identified several significantly deregulated gene pathways in patients with the 5q− syndrome and gene pathway analysis data supports the proposal that SPARC may play a role in the pathogenesis of the 5q− syndrome. This study suggests that several of the genes mapping to the CDR of the 5q− syndrome play a role in the pathogenesis of this disorder.

A pilot study of antithymocyte globulin (ATG) in the treatment of patients with ‘low‐risk’ myelodysplasia

Summary. We report 30 ‘low‐risk’ patients with myelodysplasia (MDS) (defined as < 10% bone marrow blasts) who were treated with antithymocyte globulin (ATG). In total, 20 patients were evaluable at the study end‐point (response to treatment at 6 months). The diagnosis in these 20 patients was refractory anaemia (RA) in 13, RA with excess blasts in four, and RA with ringed sideroblasts in three. Median age was 54·5 years (range, 31–73 years). There were two cases of secondary MDS. The bone marrow was hypocellular in eight cases and cytogenetics were abnormal in four cases. All patients received lymphoglobuline (horse ATG; Sangstat, France) at a dose of 1·5 vials/10 kg/day for 5 d. The treatment was well tolerated. Three patients in the study died (disease progression, invasive aspergillosis and lung carcinoma respectively); 10 out of 20 evaluable patients (50%) responded to treatment and became transfusion independent; eight out of 13 (62%) patients with RA responded. The median duration of response was 15·5 months (2–42+ months) at the time of analysis.

Low IPSS score and bone marrow hypocellularity in MDS patients predict hematological responses to antithymocyte globulin

Immunosuppressive therapy has been shown to induce sustained hematological responses in a subset of patients with myelodysplastic syndromes (MDS). In particular, antithymocyte globulin (ATG), a polyclonal immunoglobulin induces hematological responses in up to 60% of MDS patients. We report herein on the results of a retrospective multicenter study on the use of ATG in the treatment of 96 patients with MDS. Patients were evaluated for duration of response to ATG, as well as survival after administration of ATG. The median age of the cohort was 54.7 years (range: 19–75 years), with a median follow-up of 33.8 months (range: 0.8–133 months). A total of 40 patients (42%) achieved a hematological response, of which 30 patients (75%) had a durable hematological response lasting a median duration of 31.5 months (range: 6–92 months). On multivariate analysis, both low International Prognostic Scoring System (IPSS) and bone marrow (BM) hypocellularity were independent predictive factors for improved response to ATG (IPSS Int-2/high: odds ratio (OR) 0.08, P=0.018 and BM normo/hypercellularity: OR 0.49, P=0.012). In addition, IPSS was the sole predictor of overall survival, with Int-2/high risk patients having a significantly poorer survival outcome (OR 0.08, P<0.01). In conclusion, this study identifies BM hypocellularity and a low IPSS as important factors predicting response to ATG.

Prospective study of rabbit antithymocyte globulin and cyclosporine for aplastic anemia from the EBMT Severe Aplastic Anaemia Working Party

Rabbit antithymocyte globulin (rATG; thymoglobulin, Genzyme) in combination with cyclosporine, as first-line immunosuppressive therapy, was evaluated prospectively in a multicenter, European, phase 2 pilot study, in 35 patients with aplastic anemia. Results were compared with 105 age- and disease severity-matched patients from the European Blood and Marrow Transplant registry, treated with horse ATG (hATG; lymphoglobulin) and cyclosporine. The primary end point was response at 6 months. At 3 months, no patients had achieved a complete response to rATG. Partial response occurred in 11 (34%). At 6 months, complete response rate was 3% and partial response rate 37%. There were 10 deaths after rATG (28.5%) and 1 after subsequent HSCT. Infections were the main cause of death in 9 of 10 patients. The best response rate was 60% for rATG and 67% for hATG. For rATG, overall survival at 2 years was 68%, compared with 86% for hATG (P = .009). Transplant-free survival was 52% for rATG and 76% for hATG (P = .002). On multivariate analysis, rATG (hazard ratio = 3.9, P = .003) and age more than 37 years (hazard ratio = 4.7, P = .0008) were independent adverse risk factors for survival. This study was registered at www.clinicaltrials.gov as NCT00471848.