Christina Halsey

The role of hydroxyurea in sickle cell disease.

Although the molecular basis for the sickling disorders was identified more than 50 years ago (reviewed in Weatherall 2001), progress towards definitive therapy for sickle cell disease (SCD) has been frustratingly slow. Until the mid1990s, treatment was almost entirely supportive with no clinically useful drugs available to prevent or reverse the polymerization of HbS. However, a number of key observations about the role of HbF (Stevens et al, 1981; de Simone et al, 1982, Platt et al, 1984, 1991; Veith et al, 1985; Noguchi et al, 1993) led, in 1995, to the publication of a crucially important study in which a new therapeutic agent, hydroxyurea, was heralded as a major breakthrough in the management of SCD (Charache et al, 1995; Schechter & Rodgers, 1995). The initial clinical trials of hydroxyurea in SCD were stopped early as a result of outstanding results in the treatment arm and the drug was rapidly licensed in the USA for the treatment of patients with severe SCD. Since then, hydroxyurea has been used successfully in a variety of situations in SCD, including new studies in very young children (Wang et al, 2001). However, doubts remain both about its efficacy and safety in the long term. This review aims to outline current information about the mechanisms of action of hydroxyurea in SCD, its clinical efficacy in sickling disorders, the approaches to monitoring treatment and to update the evidence about its short-term and long-term toxicity.

Ras pathway mutations are prevalent in relapsed childhood acute lymphoblastic leukemia and confer sensitivity to MEK inhibition

For most children who relapse with acute lymphoblastic leukemia (ALL), the prognosis is poor, and there is a need for novel therapies to improve outcome. We screened samples from children with B-lineage ALL entered into the ALL-REZ BFM 2002 clinical trial (www.clinicaltrials.gov, #NCT00114348) for somatic mutations activating the Ras pathway (KRAS, NRAS, FLT3, and PTPN11) and showed mutation to be highly prevalent (76 from 206). Clinically, they were associated with high-risk features including early relapse, central nervous system (CNS) involvement, and specifically for NRAS/KRAS mutations, chemoresistance. KRAS mutations were associated with a reduced overall survival. Mutation screening of the matched diagnostic samples found many to be wild type (WT); however, by using more sensitive allelic-specific assays, low-level mutated subpopulations were found in many cases, suggesting that they survived up-front therapy and subsequently emerged at relapse. Preclinical evaluation of the mitogen-activated protein kinase kinase 1/2 inhibitor selumetinib (AZD6244, ARRY-142886) showed significant differential sensitivity in Ras pathway-mutated ALL compared with WT cells both in vitro and in an orthotopic xenograft model engrafted with primary ALL; in the latter, reduced RAS-mutated CNS leukemia. Given these data, clinical evaluation of selumetinib may be warranted for Ras pathway-mutated relapsed ALL.

Hemopoietic cell expression of the chemokine decoy receptor D6 is dynamic and regulated by GATA1

D6 scavenges inflammatory chemokines and is essential for the regulation of inflammatory and immune responses. Mechanisms explaining the cellular basis for D6 function have been based on D6 expression by lymphatic endothelial cells. In this study, we demonstrate that functional D6 is also expressed by murine and human hemopoietic cells and that this expression can be regulated by pro- and anti-inflammatory agents. D6 expression was highest in B cells and dendritic cells (DCs). In myeloid cells, LPS down-regulated expression, while TGF-beta up-regulated expression. Activation of T cells with anti-CD3 and soluble CD28 up-regulated mRNA expression 20-fold, while maturation of human macrophage and megakaryocyte precursors also up-regulated D6 expression. Competition assays demonstrated that chemokine uptake was D6 dependent in human leukocytes, whereas mouse D6-null cells failed to uptake and clear inflammatory chemokines. Furthermore, we present evidence indicating that D6 expression is GATA1 dependent, thus explaining D6 expression in myeloid progenitor cells, mast cells, megakaryocytes, and DCs. We propose a model for D6 function in which leukocytes, within inflamed sites, activate D6 expression and thus trigger resolution of inflammatory responses. Our data on D6 expression by circulating DCs and B cells also suggest alternative roles for D6, perhaps in the coordination of innate and adaptive immune responses. These data therefore alter our models of in vivo D6 function and suggest possible discrete, and novel, roles for D6 on lymphatic endothelial cells and leukocytes.

Consensus definitions of 14 severe acute toxic effects for childhood lymphoblastic leukaemia treatment: a Delphi consensus

Although there are high survival rates for children with acute lymphoblastic leukaemia, their outcome is often counterbalanced by the burden of toxic effects. This is because reported frequencies vary widely across studies, partly because of diverse definitions of toxic effects. Using the Delphi method, 15 international childhood acute lymphoblastic leukaemia study groups assessed acute lymphoblastic leukaemia protocols to address toxic effects that were to be considered by the Ponte di Legno working group. 14 acute toxic effects (hypersensitivity to asparaginase, hyperlipidaemia, osteonecrosis, asparaginase-associated pancreatitis, arterial hypertension, posterior reversible encephalopathy syndrome, seizures, depressed level of consciousness, methotrexate-related stroke-like syndrome, peripheral neuropathy, high-dose methotrexate-related nephrotoxicity, sinusoidal obstructive syndrome, thromboembolism, and Pneumocystis jirovecii pneumonia) that are serious but too rare to be addressed comprehensively within any single group, or are deemed to need consensus definitions for reliable incidence comparisons, were selected for assessment. Our results showed that none of the protocols addressed all 14 toxic effects, that no two protocols shared identical definitions of all toxic effects, and that no toxic effect definition was shared by all protocols. Using the Delphi method over three face-to-face plenary meetings, consensus definitions were obtained for all 14 toxic effects. In the overall assessment of outcome of acute lymphoblastic leukaemia treatment, these expert opinion-based definitions will allow reliable comparisons of frequencies and severities of acute toxic effects across treatment protocols, and facilitate international research on cause, guidelines for treatment adaptation, preventive strategies, and development of consensus algorithms for reporting on acute lymphoblastic leukaemia treatment.

Therapeutic challenges in childhood sickle cell disease. Part 1: current and future treatment options.

Sickle cell disease (SCD) is one of the commonest inherited diseases in the UK, affecting approximately 1 in 4000 live births every year. For the majority of patients, the mainstays of treatment are preventative and supportive. For those children with severe SCD, three major therapeutic options are currently available: blood transfusion, hydroxyurea and bone marrow transplantation. This review focuses on the relative roles of these therapeutic modalities in severe paediatric SCD and assesses the prospects for new treatment modalities, including non-myeloablative stem cell transplantation, short chain fatty acids, membrane active drugs and gene therapy.

The impact of therapy for childhood acute lymphoblastic leukaemia on intelligence quotients; results of the risk-stratified randomized central nervous system treatment trial MRC UKALL XI

BackgroundThe MRC UKALLXI trial tested the efficacy of different central nervous system (CNS) directed therapies in childhood acute lymphoblastic leukaemia (ALL). To evaluate morbidity 555/1826 randomised children underwent prospective psychological evaluations. Full Scale, verbal and performance IQs were measured at 5 months, 3 years and 5 years. Scores were compared in; (1) all patients (n = 555) versus related controls (n = 311), (2) low-risk children (presenting white cell count (WCC) < 50 × 109/l) randomised to intrathecal methotrexate (n = 197) versus intrathecal and high-dose intravenous methotrexate (HDM) (n = 202), and (3) high-risk children (WCC ≥ 50 × 109/l, age ≥ 2 years) randomised to HDM (n = 79) versus cranial irradiation (n = 77).ResultsThere were no significant differences in IQ scores between the treatment arms in either low- or high-risk groups. Despite similar scores at baseline, results at 3 and 5 years showed a significant reduction of between 3.6 and 7.3 points in all three IQ scores in all patient groups compared to controls (P < 0.002) with a higher proportion of children with IQs < 80 in the patient groups (13% vs. 5% at 3 years p = 0.003).ConclusionChildren with ALL are at risk of CNS morbidity, regardless of the mode of CNS-directed therapy. Further work needs to identify individuals at high-risk of adverse CNS outcomes.Trial registrationISRCTN: ISRCTN16757172

Interleukin-15 enhances cellular proliferation and upregulates CNS homing molecules in pre-B acute lymphoblastic leukemia

Genome-wide association studies have consistently implicated the interleukin-15 (IL-15) gene in acute lymphoblastic leukemia (ALL) biology, including associations with disease susceptibility, and increased risk of central nervous system (CNS) involvement. However, whether pre-B ALL blasts directly respond to IL-15 is unknown. Here, we show that most pre-B ALL primary samples and cell lines express IL-15 and components of its receptor and that primary pre-B ALL cells show increased growth in culture in response to IL-15. Investigation of mechanisms of action using IL-15-responsive SD-1 cells shows this growth advantage is maximal under low-serum conditions, mimicking those found in cerebrospinal fluid. IL-15 also upregulates PSGL-1 and CXCR3, molecules associated with CNS trafficking. Investigation of downstream signaling pathways indicates that IL-15 induces signal transducer and activator of transcription 5 (STAT5), extracellular signal-regulated kinase (ERK) 1/2, and to a lesser extent phosphatidylinositol 3-kinase (PI3K) and nuclear factor κB (NF-κB) phosphorylation. The IL-15-mediated growth advantage is abolished by mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (MEK/ERK), PI3K, and NF-κB inhibitors but preserved in the presence of STAT5 inhibition. Together, these observations provide a mechanistic link between increased levels of IL-15 expression and leukemogenesis, high-risk disease, and CNS relapse and suggest potential therapeutic targets.

The ability to cross the blood-cerebrospinal fluid barrier is a generic property of acute lymphoblastic leukemia blasts.

Prevention of central nervous system (CNS) relapse is critical for cure of childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Despite this, mechanisms of CNS infiltration are poorly understood, and the timing, frequency, and properties of BCP-ALL blasts entering the CNS compartment are unknown. We investigated the CNS-engrafting potential of BCP-ALL cells xenotransplanted into immunodeficient NOD.Cg- ITALIC! Prkdc (ITALIC! scid) ITALIC! Il2rg (ITALIC! tm1Wjl)/SzJ mice. CNS engraftment was seen in 23 of 29 diagnostic samples (79%): 2 of 2 from patients with overt CNS disease and 21 of 27 from patients thought to be CNS negative by diagnostic lumbar puncture. Histologic findings mimic human pathology and demonstrate that leukemic cells transit the blood-cerebrospinal fluid barrier situated close to the dural sinuses, the site of recently discovered CNS lymphatics. Retrieval of blasts from the CNS showed no evidence for chemokine receptor-mediated selective trafficking. The high frequency of infiltration and lack of selective trafficking led us to postulate that CNS tropism is a generic property of leukemic cells. To test this, we performed serial dilution experiments which showed CNS engraftment in 5 of 6 mice after transplant of as few as 10 leukemic cells. Clonal tracking techniques confirmed the polyclonal nature of CNS-infiltrating cells, with multiple clones engrafting in both the CNS and periphery. Overall, these findings suggest that subclinical seeding of the CNS is likely to be present in most BCP-ALL patients at original diagnosis, and efforts to prevent CNS relapse should concentrate on effective eradication of disease from this site rather than targeting entry mechanisms.

Research into cancer metabolomics: Towards a clinical metamorphosis

The acknowledgement that metabolic reprogramming is a central feature of cancer has generated high expectations for major advances in both diagnosis and treatment of malignancies through addressing metabolism. These have so far only been partially fulfilled, with only a few clinical applications. However, numerous diagnostic and therapeutic compounds are currently being evaluated in either clinical trials or pre-clinical models and new discoveries of alterations in metabolic genes indicate future prognostic or other applicable relevance. Altogether, these metabolic approaches now stand alongside other available measures providing hopes for the prospects of metabolomics in the clinic. Here we present a comprehensive overview of both ongoing and emerging clinical, pre-clinical and technical strategies for exploiting unique tumour metabolic traits, highlighting the current promises and anticipations of research in the field.

Necrotising external otitis caused by Aspergillus wentii: a case report

Necrotising external otitis (NEO) is a destructive, potentially fatal, infection usually seen in elderly diabetics or the immunocompromised. The commonest causative organism is Pseudomonas but immunocompromised patients are additionally susceptible to opportunistic infections. Here we describe the first reported case of NEO caused by a previously unknown human pathogen –Aspergillus wentii. A review of the literature reveals that fungal NEO is associated with a high rate of cranial nerve palsies suggesting that infections are not being treated rapidly enough to prevent morbidity. Fungal infection should be considered early in immunocompromised patients and microbiological diagnosis should be obtained wherever possible.