Tissue factor pathway inhibitor is a potential modifier of bleeding risk in factor XI deficiency

BACKGROUND

Factor (F) XI deficiency is associated with increased bleeding risk in some individuals. Neither FXI levels nor clinical clotting assays predict the bleeding risk. Compared with controls, FXI-deficient bleeders have reduced clot formation, decreased fibrin network density, and increased susceptibility to fibrinolysis. Tissue factor pathway inhibitor (TFPI) was recently implicated as a modifying factor in individuals with bleeding of unknown cause.

OBJECTIVES

To determine the potential of TFPI in modifying the bleeding risk in FXI-deficient individuals.

METHODS

The effects of TFPI on thrombin generation and clot formation, structure, and fibrinolysis in FXI-deficient plasma were measured in vitro in the absence or presence of inhibitory anti-TFPI antibody or exogenous recombinant TFPIα. Total plasma TFPI concentration was measured in 2 independent cohorts of controls and FXI-deficient individuals classified as bleeders or nonbleeders (cohort 1: 10 controls and 16 FXI-deficient individuals; cohort 2: 48 controls and 57 FXI-deficient individuals) and correlated with ex vivo plasma clot formation and fibrinolysis parameters associated with bleeding risk.

RESULTS

In an in vitro FXI deficiency model, inhibition of TFPI enhanced thrombin generation and clot formation, increased the network density, and decreased fibrinolysis, whereas an increase in TFPI had the opposite effects. Compared with controls, plasma from FXI-deficient bleeders had higher TFPI concentration. Total plasma TFPI concentrations correlated with parameters from ex vivo clotting and fibrinolysis assays that differentiate FXI-deficient bleeders and nonbleeders.

CONCLUSION

Coagulation and fibrinolysis parameters that differentiate FXI-deficient nonbleeders and bleeders were altered by plasma TFPIα. Total plasma TFPI was increased in FXI-deficient bleeders. TFPI may modify the bleeding risk in FXI-deficient individuals.

The Use and Effectiveness of an Online Diagnostic Support System for Blood Film Interpretation: Comparative Observational Study

Background

The recognition and interpretation of abnormal blood cell morphology is often the first step in diagnosing underlying serious systemic illness or leukemia. Supporting the staff who interpret blood film morphology is therefore essential for a safe laboratory service. This paper describes an open-access, web-based decision support tool, developed by the authors to support morphological diagnosis, arising from earlier studies identifying mechanisms of error in blood film reporting. The effectiveness of this intervention was assessed using the unique resource offered by the online digital morphology Continuing Professional Development scheme (DM scheme) offered by the UK National External Quality Assessment Service for Haematology, with more than 3000 registered users. This allowed the effectiveness of decision support to be tested within a defined user group, each of whom viewed and interpreted the morphology of identical digital blood films.

Objective

The primary objective of the study was to test the effectiveness of the decision support system in supporting users to identify and interpret abnormal morphological features. The secondary objective was to determine the pattern and frequency of use of the system for different case types, and to determine how users perceived the support in terms of their confidence in decision-making.

Methods

This was a comparative study of identical blood films evaluated either with or without decision support. Selected earlier cases from the DM scheme were rereleased as new cases but with decision support made available; this allowed a comparison of data sets for identical cases with or without decision support. To address the primary objectives, the study used quantitative evaluation and statistical comparisons of the identification and interpretation of morphological features between the two different case releases. To address the secondary objective, the use of decision support was assessed using web analytical tools, while a questionnaire was used to assess user perceptions of the system.

Results

Cases evaluated with the aid of decision support had significantly improved accuracy of identification for relevant morphological features (mean improvement 9.8%) and the interpretation of those features (mean improvement 11%). The improvement was particularly significant for cases with higher complexity or for rarer diagnoses. Analysis of website usage demonstrated a high frequency of access for web pages relevant to each case (mean 9298 for each case, range 2661-24,276). Users reported that the decision support website increased their confidence for feature identification (4.8/5) and interpretation (4.3/5), both within the context of training (4.6/5) and also in their wider laboratory practice (4.4/5).

Conclusions

The findings of this study demonstrate that directed online decision support for blood morphology evaluation improves accuracy and confidence in the context of educational evaluation of digital films, with effectiveness potentially extending to wider laboratory use.

A diagnostic evaluation of single screen testing for malaria in the returning traveler: A large retrospective cohort study

BACKGROUND

Screening for malaria in the returning traveler has often required repeat testing; however, audit data suggest that patients have not been reattending. We sought to ascertain if this was safe by examining the diagnostic efficacy of a single screen consisting of a rapid diagnostic test (RDT) and a thin film.

METHODS

We conducted a retrospective cohort study of patients with suspected malaria who attended in the past 5 years from two large teaching hospitals. We assessed the diagnostic accuracy of a single screen, reporting measures of sensitivity and specificity. To establish a reference standard, we cross-linked data with the national malaria registry held at Public Health England and regional centers.

RESULTS

The cohort consisted of 1365 patients, of whom 33 opted out of the research and one did not have a complete initial screen. Of those 1331 screens there were 74 cases of Plasmodium falciparum (prevalence of 5.6%) and 104 of any malaria species (prevalence of 7.8%). Sensitivity for the detection of P. falciparum was 100.00% (95% confidence interval [CI] = 95.1 to 100), with a specificity of 99.4% (95% CI = 98.9 to 99.8). For the detection of any species of malaria the sensitivity was slightly lower due to the presence of one false negative; sensitivity was 99.0% (95% CI = 94.8 to 100) and specificity was 99.5% (95% CI = 98.9 to 99.8).

CONCLUSIONS

A single thin film and RDT is likely to be sufficient as a first screen for falciparum malaria in the returning traveler with important caveats. For those sent home from emergency departments, appropriate safety netting must be provided. Further prospective study is required to investigate this approach.

Switchable foldamer ion channels with antibacterial activity

Synthetic ion channels may have applications in treating channelopathies and as new classes of antibiotics, particularly if ion flow through the channels can be controlled. Here we describe triazole-capped octameric α-aminoisobutyric acid (Aib) foldamers that "switch on" ion channel activity in phospholipid bilayers upon copper(ii) chloride addition; activity is "switched off" upon copper(ii) extraction. X-ray crystallography showed that CuCl₂ complexation gave chloro-bridged foldamer dimers, with hydrogen bonds between dimers producing channels within the crystal structure. These interactions suggest a pathway for foldamer self-assembly into membrane ion channels. The copper(ii)-foldamer complexes showed antibacterial activity against B. megaterium strain DSM319 that was similar to the peptaibol antibiotic alamethicin, but with 90% lower hemolytic activity.

Quantitative Assay of Mutated Nucleophosmin in Acute Myeloid Leukemia

Background

In our previous work, we provided strong evidence that nucleophosmin (NPM) gene mutation has an important role in leukemogenesis of primary acute myeloid leukemia (AML). Furthermore, we speculated a new targeted therapy in patients with primary AML and bearing mutated NPM (mNPM). Based on these results together with findings of other researchers, it was essential to develop a method for accurate detection of mNPM.

Methods

Our method based on utilizing the most recent flow cytometeric techniques and instruments in measuring mNPM. Attributed to their availability and technical feasibility, we used human leukemia cell lines to validate our method.

Results

The main findings were differential expression of wild-type NPM (wtNPM) within the same sample. Furthermore flow cytometry (FCM) was a simple straightforward tool for quantitative assay of mNPM.

Conclusions

In this work we developed an innovative technique that could enable quantitative assay of mNPM, and ease its use as a biomarker in cytogenetic and molecular prognostication of primary AML. In addition the study suggested that FCM could differentiate mNPM expression within cells of the same patient thus could be used for monitoring of minimal residual disease.

Synthesis and biological activity of a CXCR4-targeting bis(cyclam) lipid

A bis(cyclam)-capped cholesterol lipid designed to bind C-X-C chemokine receptor type 4 (CXCR4) was synthesised in good overall yield from 4-methoxyphenol through a seven step synthetic route, which also provided a bis(cyclam) intermediate bearing an octaethyleneglycol-primary amine that can be easily derivatised. This bis(cyclam)-capped cholesterol lipid was water soluble and self-assembled into micellar and non-micellar aggregates in water at concentrations above 8 μM. The bioactivity of the bis(cyclam)-capped cholesterol lipid was assessed using primary chronic lymphocytic leukaemia (CLL) cells, first with a competition binding assay then with a chemotaxis assay along a C-X-C motif chemokine ligand 12 (CXCL12) concentration gradient. At 20 μM, the bis(cyclam)-capped cholesterol lipid was as effective as the commercial drug AMD3100 for preventing the migration of CLL cells, despite a lower affinity for CXCR4 than AMD3100.

Abnormal plasma clot formation and fibrinolysis reveal bleeding tendency in patients with partial factor XI deficiency

Individuals with factor XI (FXI) deficiency have a variable bleeding risk that cannot be predicted from plasma FXI antigen or activity. This limitation can result in under- or overtreatment of patients and risk of bleeding or thrombosis. Previously, plasma clot fibrinolysis assays showed sensitivity to bleeding tendency in a small cohort of patients with severe FXI deficiency. Here, we determined the ability of plasma clot formation, structure, and fibrinolysis assays to predict bleeding tendency in a larger, independent cohort of patients with severe and partial FXI deficiency. Patients were characterized as nonbleeders or bleeders based on bleeding after tonsillectomy and/or dental extraction before diagnosis of FXI deficiency. Blood was collected in the absence or presence of the contact pathway inhibitor corn trypsin inhibitor (CTI). Clotting was triggered in platelet-poor plasma with tissue factor, CaCl2, and phospholipids in the absence and presence of thrombomodulin or tissue plasminogen activator. Clot formation and fibrinolysis were assessed by turbidity and confocal microscopy. CTI-treated plasmas from bleeders showed significantly reduced clot formation and decreased resistance to fibrinolysis compared with plasmas from controls or nonbleeders. Differences were enhanced in the presence of CTI. A model that combines activated partial thromboplastin time with the rate of clot formation and area under the curve in fibrinolysis assays identifies most FXI-deficient bleeders. These results show assays with CTI-treated platelet-poor plasma reveal clotting and clot stability deficiencies that are highly associated with bleeding tendency. Turbidity-based fibrinolysis assays may have clinical utility for predicting bleeding risk in patients with severe or partial FXI deficiency.

ASP2215 in the treatment of relapsed/refractory acute myeloid leukemia with FLT3 mutation: background and design of the ADMIRAL trial

Acute myeloid leukemia (AML) is a heterogeneous disease with cure rates of only 30-40% in patients <60 years old. Cytogenetic and molecular markers have improved our understanding of the different prognostic entities in AML. FLT3 mutations are present in 30-40% of AML cases, conferring a poor prognosis with reduced survival. AXL activates FLT3, impacting adversely on outcome. Both FLT3 and AXL constitute promising molecular targets. ASP2215 (gilteritinib) is a novel, dual FLT3/AXL inhibitor with promising early phase trial data (NCT02014558). A Phase III randomized multicenter clinical trial, comparing ASP2215 to salvage chemotherapy in relapsed/refractory AML with FLT3-mutations is now open to recruitment (NCT02421939). Trial design and objectives are discussed here.

Role of Nucleophosmin Gene Mutation in Leukemogenesis of Acute Myeloid Leukemia

Background

Acute myeloid leukemia (AML) is a hematopoietic stem cell disorder that carries very poor prognosis. Understanding molecular basis of AML leukemogenesis could lead to the emergence of effective targeted therapies for AML. AML bearing nucleophosmin (NPM) gene mutation has distinct features. This study was conducted to investigate the role of mutated (m) NPM in pathogenesis of de novo AML through studying its contribution in proliferation of AML cell line cells.

Methods

Two types of human leukemia cell lines were used. One of them was a model for AMLs with mNPM and the other for AMLs with wild type (wt) NPM. Assessment of the proliferative role of mNPM in AML was carried out using cell culture and viability studies. The obtained results were reaffirmed by immunocytochemical and immunoblotting techniques.

Results

Analysis of results was done with the appropriate computer software. It showed higher proliferative potential of cells with mNPM compared to those bearing wtNPM only. Furthermore, the immunocytochemical studies demonstrated subcellular localization of NPM isoforms during various phases of mitosis. Mitosis was associated with cytoplasmic translocation of wtNPM in certain phases, while localization of mNPM remained unchanged throughout the cell cycle. Results of immunoblotting showed little or no change in protein expression of either NPM moieties during mitosis.

Conclusions

The current study demonstrated important contribution of NPM gene mutation in enhancing proliferation of AML cell lines. These results confirmed the role of mNPM in AML leukemogenesis, and highlighted the importance of targeting mNPM in new evolving AML therapies.

Web-Based Virtual Microscopy of Digitized Blood Slides for Malaria Diagnosis: An Effective Tool for Skills Assessment in Different Countries and Environments

Background

Morphological examination of blood films remains the reference standard for malaria diagnosis. Supporting the skills required to make an accurate morphological diagnosis is therefore essential. However, providing support across different countries and environments is a substantial challenge.

Objective

This paper reports a scheme supplying digital slides of malaria-infected blood within an Internet-based virtual microscope environment to users with different access to training and computing facilities. The feasibility of the approach was established, allowing users to test, record, and compare their own performance with that of other users.

Methods

From Giemsa stained thick and thin blood films, 56 large high-resolution digital slides were prepared, using high-quality image capture and 63x oil-immersion objective lens. The individual images were combined using the photomerge function of Adobe Photoshop and then adjusted to ensure resolution and reproduction of essential diagnostic features. Web delivery employed the Digital Slidebox platform allowing digital microscope viewing facilities and image annotation with data gathering from participants.

Results

Engagement was high with images viewed by 38 participants in five countries in a range of environments and a mean completion rate of 42/56 cases. The rate of parasite detection was 78% and accuracy of species identification was 53%, which was comparable with results of similar studies using glass slides. Data collection allowed users to compare performance with other users over time or for each individual case.

Conclusions

Overall, these results demonstrate that users worldwide can effectively engage with the system in a range of environments, with the potential to enhance personal performance through education, external quality assessment, and personal professional development, especially in regions where educational resources are difficult to access.

Do We Know Why We Make Errors in Morphological Diagnosis? An Analysis of Approach and Decision-Making in Haematological Morphology

BACKGROUND

The laboratory interpretation of blood film morphology is frequently a rapid, accurate, and cost-effective final-stage of blood count analysis. However, the interpretation of findings often rests with a single individual, and errors can carry significant impact. Cell identification and classification skills are well supported by existing resources, but the contribution and importance of other skills are less well understood.

METHODS

The UK external quality assurance group in haematology (UK NEQAS(H)) runs a Continued Professional Development scheme where large digital-images of abnormal blood smears are presented using a web-based virtual microscope. Each case is answered by more than 800 individuals. Morphological feature selection and prioritisation, as well as diagnosis and proposed action, are recorded. We analysed the responses of participants, aiming to identify successful strategies as well as sources of error.

FINDINGS

The approach to assessment by participants depended on the affected cell type, case complexity or skills of the morphologist. For cases with few morphological abnormalities, we found that accurate cell identification and classification were the principle requirements for success. For more complex films however, feature recognition and prioritisation had primary importance. Additionally however, we found that participants employed a range of heuristic techniques to support their assessment, leading to associated bias and error.

INTERPRETATION

A wide range of skills together allow successful morphological assessment and the complexity of this process is not always understood or recognised. Heuristic techniques are widely employed to support or reinforce primary observations and to simplify complex findings. These approaches are effective and are integral to assessment; however they may also be a source of bias or error. Improving outcomes and supporting diagnosis require the development of decision-support mechanisms that identify and support the benefits of heuristic strategies while identifying or avoiding associated biases.

FUNDING

The CPD scheme is funded by participant subscription.

Lymphocytes from chronic lymphocytic leukaemia undergo ABL1-linked amoeboid motility and homotypic interaction as an early adaptive change to ex vivo culture

BACKGROUND

Those stimuli that together promote the survival, differentiation and proliferation of the abnormal B-lymphocytes of chronic lymphocytic leukaemia (CLL) are encountered within tissues, where together they form the growth-supporting microenvironment. Different tissue-culture systems promote the survival of the neoplastic lymphocytes from CLL, partly replicating the in vivo tissue environment of the disorder. In the present study, we focussed on the initial adaptive changes to the tissue culture environment focussing particularly on migratory behaviour and cellular interactions.

METHODS

A high-density CLL culture system was employed to test CLL cell-responses using a range of microscopic techniques and flow cytometric analyses, supported by mathematical measures of cell shape-change and by biochemical techniques. The study focussed on the evaluation of changes to the F-actin cytoskeleton and cell behaviour and on ABL1 signalling processes.

RESULTS

We showed that the earliest functional response by the neoplastic lymphocytes was a rapid shape-change caused through rearrangement of the F-actin cytoskeleton that resulted in amoeboid motility and promoted frequent homotypic interaction between cells. This initial response was functionally distinct from the elongated motility that was induced by chemokine stimulation, and which also characterised heterotypic interactions between CLL lymphocytes and accessory cells at later culture periods. ABL1 is highly expressed in CLL lymphocytes and supports their survival, it is also recognised however to have a major role in the control of the F-actin cytoskeleton. We found that the cytoplasmic fraction of ABL1 became co-localised with F-actin structures of the CLL lymphocytes and that the ABL1 substrate CRKL became phosphorylated during initial shape-change. The ABL-inhibitor imatinib mesylate prevented amoeboid movement and markedly reduced homotypic interactions, causing cells to acquire a globular shape to rearrange F-actin to a microvillus form that closely resembled that of CLL cells isolated directly from circulation.

CONCLUSION

We suggest that ABL1-induced amoeboid motility and homotypic interaction represent a distinctive early response to the tissue environment by CLL lymphocytes. This response is separate from that induced by chemokine or during heterotypic cell-contact, and may play a role in the initial entry and interactions of CLL lymphocytes in tissues.

British Society of Haematology, Slide Session presented at the Annual Scientific Meeting, Brighton 2009

Seven cases were discussed by an expert panel at the 2009 Annual Scientific Meeting of the British Society of Haematology. These cases are presented in a similar format to that adopted for the meeting. There was an initial discussion of the presenting morphology, generation of differential diagnoses and then, following display of further presenting and diagnostic information, each case was concluded with provision of a final diagnosis.

Ribosome-associated nucleophosmin 1: increased expression and shuttling activity distinguishes prognostic subtypes in chronic lymphocytic leukaemia

Two distinct groups of chronic lymphocytic leukaemia (CLL) are distinguished by the presence or absence of somatic hypermutation of the immunoglobulin heavy-chain gene. CLL without somatic hypermutation has an adverse outcome, but the precise biological differences that underlie this more aggressive clinical-course are unclear. Using a proteomic approach, we found that the two prognostic forms of CLL were consistently distinguished according to their protein expression pattern. The most important difference observed related to the different expression of nucleophosmin 1 between the two forms of CLL. This different expression was not related to apoptosis, proliferation or gene mutation. However, co-immunoprecipitation experiments identified an association between nucleophosmin 1 and ribosomal proteins. Using immunocytofluorescence, nucleophosmin 1 expression was identified in the nucleoli and nucleoplasm of all cells, but in a proportion of cells, nucleophosmin had been transferred from the nucleoplasm to the cytoplasm. Both the fluorescent intensity, and the frequency of cytoplasmic nucleophosmin 1 expression, was higher in CLL without somatic hypermutation. We propose therefore, that nucleophosmin 1, in association with ribosomal proteins, undergoes nucleo-cytoplasmic shuttling in CLL. This process is most prominent in un-mutated CLL and may signify altered protein biosynthesis.

British Society for Haematology, slide session, annual scientific meeting, Glasgow, 2008

A morphology session is held each year at the Annual Scientific Meeting of the British Society of Haematology. Prior to the meeting this year, eight morphology cases were made available to BSH members as glass slides and also digitally as 'virtual slides'. A panel of invited commentators who had no prior knowledge of the diagnosis discussed the eight cases. An initial limited history and blood count are given with representative images from the case material; this is followed by the discussants' comments and suggested diagnosis. The actual clinical diagnosis is then given with other relevant information.

Hydroxycarbamide associated platelet count oscillations in a patient with polycythaemia vera. A case report and review of the literature

We describe an unusual case of oscillating platelet counts in a patient with polycythaemia vera. Following commencement of cytoreductive hydroxycarbamide therapy, episodes of thrombocytopenia were followed regularly by thrombocytosis. Platelet counts fluctuated periodically between approximately 200 and 800 x 109/l, with a 28 day cycle duration. Frequent adjustment of the hydroxycarbamide dose was not successful in preventing the oscillations in platelet count. In contrast, maintenance of a constant dose led to a gradual damping of the cycles and thus termination of the large oscillations. The case further implicates hydroxycarbamide as a potential cause of cyclic variations in platelet counts, and demonstrates that cessation of this drug is not always necessary in order to treat this phenomenon.

Review of the UK NEQAS (H) digital morphology pilot scheme for continuing professional development accessed via the internet

UK NEQAS (H) developed and instigated a pilot scheme for digital morphology, which was accessed by participants over the internet in order to assess the viability of using high quality images as an educational tool for continuing professional development. The pilot scheme was trialled over a 2-year period with eight releases totalling 16 morphology cases. Digital images allowed participating individuals to examine and comment on exactly the same cells and compare their findings with those of other participants, consensus data from traditional glass slide surveys and expert opinion. Feedback from participants on their experience was then relayed back to the development team by UK NEQAS (H) in order to drive the educational format and to ensure that any new scheme would meet the requirements of the users.

The use of isobaric tag peptide labeling (iTRAQ) and mass spectrometry to examine rare, primitive hematopoietic cells from patients with chronic myeloid leukemia

Chronic Myeloid Leukemia (CML) is a hematopoietic stem cell disease, associated with a t(9, 22) chromosomal translocation leading to formation of the BCR/ABL chimeric protein, which has an intrinsic tyrosine kinase activity. Recently, the BCR/ABL tyrosine kinase inhibitor imatinib mesylate (imatinib) has been successfully used clinically, although, disease relapse can still occur. The precise detail of the mechanism by which CML cells respond to imatinib is still unclear. We therefore systematically examined the effects of imatinib on the primitive CML cell proteome, having first established that the drug inhibits proliferation and induces increased apoptosis and differentiation. To define imatinib-induced effects on the CML proteome, we employed isobaric tag peptide labeling (iTRAQ) coupled to two-dimensional liquid chromatography/tandem mass spectrometry. Given the limited clinical material available, the isobaric tag approach identified a large population of proteins and provided relative quantification on four samples at once. Novel consequences of the action of imatinib were identified using this mass spectrometric approach. DEAD-box protein 3, heat shock protein 105 kDa, and peroxiredoxin-3 were identified as potential protein markers for response to imatinib.

The rho-kinase inhibitors Y-27632 and fasudil act synergistically with imatinib to inhibit the expansion of ex vivo CD34(+) CML progenitor cells

Evidence from cell line-based studies indicates that rho-kinase may play a role in the leukaemic transformation of human cells mediated by the BCR/ABL tyrosine kinase, manifest clinically as chronic myeloid leukaemia (CML). We therefore employed two separate inhibitors, Y-27632 and fasudil, to inhibit the activity of rho-kinase against ex vivo CD34(+) cells collected from patients with CML. We compared the effects of rho-kinase inhibition in those cells with the effects of direct inhibition of BCR/ABL using the specific inhibitor imatinib. We found that inhibition of rho-kinase inhibited the effective proliferation, and reduced survival of CML progenitor cells. When combined with imatinib, rho-kinase inhibition added to the anti-proliferative and pro-apoptotic effects of the BCR/ABL inhibitor. Our studies may indicate therapeutic benefit in some cases for the combination of rho-kinase inhibitors with imatinib.

Digital imaging of haematological morphology

Microscopic images of haematological cells are now routinely photographed using digital cameras. Advances in technology mean that the quality of such digital images can now approach that viewed through a microscope. At the same time there is an emerging appreciation that such images can be used in many roles: digital images are now being used to construct digital 'virtual slides', or are being employed together with cell recognition systems for morphological screening. Additionally, an Internet-based viewing systems allow access to on-line annotation, as well as real-time data gathering and feedback. The process of viewing digital images differs from the viewing of glass slides through a microscope; however, such images can provide diagnostic equivalence, and have an emerging role in areas such as education, quality control and continuing professional development. This review explores some of the present strengths, weaknesses and future applications of digital imaging in haematology.

The use of digital 'virtual slides' in the quality assessment of haematological morphology: results of a pilot exercise involving UK NEQAS(H) participants

We report the results of a pilot study assessing the use of digital 'virtual slides' in haematological quality assessment. Conducted together with the UK National External Quality Assessment Scheme for General Haematology, the study involved 166 separate participants, using the format of a typical assessment exercise. The results revealed substantial concordance of observations made using digital slides with those reported in previous glass slide surveys that used identical cases. Participant feedback strongly supported the use of electronic slides in teaching and assessment roles. Our results suggest roles for this new electronic resource in external quality assessment (EQA), education and continuing professional development.

Molecular pathogenesis of chronic myeloid leukaemia

The abnormal haemopoietic precursor cells of chronic myeloid leukaemia (CML) carry the cytogenetic abnormality [t(9;22)(q34;q11)] – a reciprocal translocation that results in the expression of a chimaeric protein derived from the fused BCR and ABL genes. This Bcr–Abl protein tyrosine kinase mediates an array of effects on signal transduction pathways affecting cell survival, proliferation, adhesion and genetic stability. The end-result of these abnormal signalling processes is a bi- or triphasic clinical disease. Initially, CML is characterised by the presence of an excess of myeloid progenitor cells and their mature progeny. This chronic phase of CML is followed, either directly or with an intervening ‘accelerated phase’, by a stage where primitive blast cells predominate (acute transformation). This review discusses the role of Bcr–Abl-mediated signalling events in cellular transformation, genetic instability and disease progression in CML, and describes current developments in CML treatment using a Bcr–Abl inhibitor.

Proteomic Analysis of Chronic Lymphocytic Leukemia Subtypes with Mutated or Unmutated Ig VH Genes

Chronic lymphocytic leukemia (CLL) is a common hematopoietic malignant disease with variable outcome. CLL has been divided into distinct groups based on whether somatic hypermutation has occurred in the variable region of the immunoglobulin heavy-chain locus or alternatively if the cells express higher levels of the CD38 protein. We have analyzed the proteome of 12 cases of CLL (six mutated (M-CLL) and six unmutated (UM-CLL) immunoglobulin heavy-chain loci; seven CD38-negative and five CD38-positive) using two-dimensional electrophoresis and mass spectrometry. Statistical evaluation using principal component analysis indicated significant differences in patterns of protein expression between the cases with and without somatic mutation. Specific proteins indicated by principal component analysis as varying between the prognostic groups were characterized using mass spectrometry. The levels of F-actin-capping protein beta subunit, 14-3-3 beta protein, and laminin-binding protein precursor were significantly increased in M-CLL relative to UM-CLL. In addition, primary sequence data from tandem mass spectrometry showed that nucleophosmin was present as several protein spots in M-CLL but was not detected in UM-CLL samples, suggesting that several post-translationally modified forms of nucleophosmin vary between these two sample groups. No specific differences were found between CD38-positive and -negative patient samples using the same approach. The results presented show that proteomic analysis can complement other approaches in identifying proteins that may have potential value in the biological and diagnostic distinction between important clinical subtypes of CLL.

The normal cellular prion protein is strongly expressed by myeloid dendritic cells

Abnormal isoforms of the prion protein (PrP(Sc)) that cause prion diseases are propagated and spread within the body by "carrier" cell(s). Cells of the immune system have been strongly implicated in this process. In particular, PrP(Sc) is known to accumulate on follicular dendritic cells (FDCs) in individuals affected by variant Creutzfeld-Jakob disease. However, FDCs do not migrate widely and the natural history of prion disorders suggests other cells may be required for the transport of PrP(Sc) from the site of ingestion to lymphoid organs and the central nervous system. Substantial evidence suggests that the spread of PrP(Sc) requires bone marrow-derived cells that express normal cellular prion protein (PrP(C)). This study examined the expression of PrP(C) on bone marrow-derived cells that interact with lymphoid follicles. High levels of PrP(C) are present on myeloid dendritic cells (DCs) that surround the splenic white pulp. These myeloid DCs are ontologically and functionally distinct from the FDCs. Consistent with these observations, expression of PrP(C) was strongly induced during the generation of mature myeloid DCs in vitro. In these cells PrP(C) colocalized with major histocompatibility complex class II molecules at the level of light microscopy. Furthermore, given the close anatomic and functional connection of myeloid DCs with lymphoid follicles, these results raise the possibility that myeloid DCs may play a role in the propagation of PrP(Sc) in humans.

Endothelial interactions of hairy cells: the importance of alpha 4 beta 1 in the unusual tissue distribution of the disorder

The tissue-homing of all lymphocytes involves their interactions with endothelial cells (ECs) and with various tissue accessory cells. However, in hairy cell leukemia (HCL), these processes are particularly prominent and result in diagnostic appearances in the spleen, liver, and bone marrow. The present study explores the mechanisms that underlie these tissue reactions. Using a human umbilical vein EC (HUVEC) model, various possible receptor-ligand interactions between hairy cells (HCs) and ECs were examined and a central importance for alpha 4 beta 1/vascular cell adhesion molecule-1 (VCAM-1) was established. This receptor-ligand pair was shown to be important both for strong adhesion and for HC motility/transmigration. A similar importance for alpha 4 beta 1/VCAM-1 was established for the interaction between HCs and relevant tissue accessory cells. The in vitro relevance of these findings was confirmed by the demonstration of VCAM-1 in HCL spleen and by the fact that, in frozen sections, HCs adhered (via VCAM-1) to the red pulp, but not to other areas of normal spleen. These results indicate that alpha 4 beta 1/VCAM-1 is central to the interaction between HCs and endothelium/accessory cells. Such interactions, together with the intrinsic cell activation characteristic of HCL and the HC's consequent ability to interact with matrix, are responsible for many of the characteristic features of the disease.

Granulocyte-macrophage colony-stimulating factor receptor: stage-specific expression and function on late B cells

Granulocyte-macrophage colony-stimulating factor (GM-CSF) receptors (GMR) are expressed on myeloid cells throughout their maturational sequence. During myelopoiesis, GM-CSF induces the proliferation of precursors and has multiple effects on more mature cells; such effects include induction of maturation and priming for subsequent stimulation. GMR is expressed on a range of other cell types including acute leukemic blasts of myeloid and lymphoid lineage, but has been little studied on more mature lymphoid cells. Using sensitive triple-layer immunophenotypic techniques, we show here that both the alpha and beta c chains of the GMR are expressed on hairy cells (HCs) and myelomatous plasma cells (PCs), but not on chronic lymphocytic leukemia (CLL) or prolymphocytic leukemia (PLL) lymphocytes. The receptor was demonstrable on normal PCs in tonsil, but not on either activated or resting tonsillar B cells or on circulating normal B lymphocytes. The expression of the receptor is therefore stage specific, rather than a feature of activation. Perhaps, surprisingly, in view of its effects on myeloid cells, GM-CSF did not stimulate the proliferation or differentiation of HCs and did not protect them from apoptosis. However, the cytokine had a profound effect on the interaction of the HC with its environment. Thus, the cytokine caused a major cytoskeletal reorganization resulting in the inhibition of motility and loss of adhesion to cellular and matrix ligands. These studies indicate the importance of GM-CSF outside myelopoiesis and demonstrate a previously unrecognized stage specific role for the cytokine in B-cell biology. Taken together with our previous report that M-CSF enhances B-cell motility, the present findings indicate that myeloid growth factors act in concert to facilitate the controlled migration of certain B cells into and within tissues.

Integrin function in chronic lymphocytic leukemia

Integrins are central to many aspects of the tissue localization of normal and malignant lymphocytes. We examined how integrin function, rather than simple expression, might determine disease behavior in chronic lymphocyte leukemia (CLL). Using fluorescence-activated cell sorting (FACS) and immunoprecipitation, we first established the precise integrin heterodimer expression of a representative group of CLL patients (beta1 consistently present, with variable alpha 3, alpha 4, and alpha 5; alpha 4 beta 7 often expressed; alpha L beta 2 high; alpha V beta 3 absent). Regarding function, we initially examined the ability of CLL cells to interact with endothelium, because such interaction is the initial event determining the entry of CLL lymphocytes into tissues. The abnormal lymphocytes were shown to bind at low levels to unstimulated endothelium via beta 2/intercellular adhesion molecule (ICAM). However, when the endothelium was stimulated, markedly enhanced interaction with endothelium was observed in approximately half the cases; in these patients, the neoplastic population expressed alpha 4 beta 1, which conferred the ability to adhere strongly to stimulated endothelium via the alpha 4 beta 1 ligand, vascular cellular adhesion molecule-1 (VCAM-1). In relation to the migration of CLL cells within tissues, the abnormal lymphocytes showed differential binding to various adhesive proteins; they did not attach to basement membrane components, but displayed variable adhesion to fibronectin (FN). Finally, we examined the role of cell activation in these processes, and showed that activated CLL lymphocyte populations showed an increased capacity to adhere to both endothelium and matrix. Moreover, ex vivo CLL cells showed no capacity to migrate through endothelium/stroma, but were able to do so after cytokine stimulation. These studies show how the constitutive integrin expression/function, the intrinsic activation state of the cell, and the capacity of cytokines to modify integrin-mediated function all combine to determine the different patterns of clinical disease observed in CLL.

Integrin receptors and hairy cell leukaemia

The ability of a cell to recognize and specifically localise within an appropriate tissue environment is essential to the proliferation and survival of that cell. The integrin family of cell-surface adhesion-receptors are essential to such tissue localisation, allowing a migrating cell to specifically recognise, localise within-, and respond to- the cellular or extracellular matrix ligands that characterise a given tissue. We have investigated how the expression and activity of integrin receptors underlies the consistent and unusual tissue distribution of the malignant B lymphocytes of hairy cell leukaemia (HCL). In this report we review our published work in this area. Our findings are then discussed within the context of current knowledge of integrin receptors and their ligands, and in relation to the clinical features of HCL.

Expression of the human mucosal lymphocyte antigen, HML-1, by T cells activated with mitogen or specific antigen in vitro

Expression of the human mucosal lymphocyte antigen, HML-1 (CD103), recently identified as a novel alpha E beta 7 integrin, was studied on peripheral blood lymphocytes activated with mitogen or specific antigen. HML-1 was up-regulated on PHA activated T-lymphoblasts cultured in 100IU/ml interleukin-2 (IL-2), reaching a peak of > 50% positive cells at day 7, and expression was maintained at this level throughout the 28-day culture period. Following a transient decrease in the percentage of L-selectin cells, expression of this molecule was maintained on most PHA T-lymphoblasts. Cells activated by purified protein derivative of M. tuberculosis (PPD) or in mixed lymphocyte culture also up-regulated and maintained HML-1 expression for 14 days. In contrast, in all cases the percentage of CD25+ cells rose initially but subsequently declined over the same time periods. When freshly isolated cells from tonsil, spleen, mesenteric lymph node and lung were analysed, only lung contained significant numbers (39 +/- 6%) of HML-1+ cells. In both freshly isolated and activated cell populations the great majority of HML-1+ cells co-expressed CD8 although some HML-1+ CD8- cells were also present. Production of TGF-beta 1 peaked early during T-lymphoblast and MLR cultures and was not related to induction of HML-1 expression. Immunoprecipitation studies showed that the HML-1 molecule expressed on 10-day PHA T-lymphoblasts was indistinguishable from that found on intestinal intraepithelial lymphocytes and that no alpha 4 beta 7 integrin was expressed by these cells. Although HML-1 expression is essentially restricted to mucosal leucocytes in vivo, these experiments show that it is readily induced and maintained along with co-expression of L-selectin following CD8+ T-lymphocyte activation in vitro.

Hairy cell interactions with extracellular matrix: expression of specific integrin receptors and their role in the cell's response to specific adhesive proteins

Integrin/extracellular-matrix interactions are central to the migration, localization, and subsequent function of lymphocytes within tissues. In hairy cell leukemia (HCL) the malignant cells display a highly characteristic tissue distribution in which interactions with extracellular matrix (ECM) are often prominent. Therefore, we used HCL as a model in which to investigate the poorly understood integrin/ECM interactions that underlie the migratory behavior of malignant B lymphocytes. Using a combined approach involving immunocytochemistry, flow cytometry, and immunoprecipitation analysis, hairy cells (HCs) were shown to have a consistent and distinctive phenotype (mainly alpha 4 beta 1, alpha 5 beta 1, alpha v beta 1, and alpha v beta 3). Furthermore, functional studies utilising adhesion assays, time-lapse video-microscopy and image analysis showed that the HCs displayed very specific adhesive behaviour in response to relevant adhesive protein ligands. HCs were able to adhere to different extents on all the adhesive proteins examined, but, on laminin and collagen, binding was weak with little cytoplasmic spreading. In contrast, the cells showed strong adhesion both to fibronectin (FN) and to vitronectin (VN). On FN, the cells spread extensively with nonpolarized cytoplasmic projections, whereas on VN cytoplasmic projections were markedly polarized. This polarized morphology was shown to reflect cell motility. Investigation of the role of individual integrin receptors in the cell movement response suggested that alpha v beta 3 is the major integrin responsible for this motile behavior. These results are discussed in relation to the limited previous data on leukemic and activated B-cell integrins, and we suggest that the HC integrins play a significant role in the characteristic behavior of HCs within tissues.

The function of c-fms in hairy-cell leukemia: macrophage colony-stimulating factor stimulates hairy-cell movement

Hairy cells (HCs) and some activated B cells express high levels of macrophage colony-stimulating factor (M-CSF) (CSF-1) receptor, but the functional effects of the cytokine on B cells have not been previously identified. Using video microscopy, image analysis, and migration assays, M-CSF was shown to induce chemokinetic and chemotactic movement of HCs. This movement response involved transition to a highly mobile, rounded cell form and was accompanied by distinctive changes in F-actin polymerization and distribution. Furthermore, the M-CSF-induced motility was substantially modified by the adhesive protein used as a substratum and involved qualitative changes in the function of the alpha v beta 3 integrin of HCs. It is suggested that the findings are relevant to the pathophysiology of hairy-cell leukemia (HCL) in particular, and to the biology of B-cell migration in general.

The bone marrow fibrosis of hairy-cell leukemia is caused by the synthesis and assembly of a fibronectin matrix by the hairy cells

Hairy-cell leukemia (HCL) is a proliferation of clonal B-lymphocytes with features of activation. The disease has a number of distinctive characteristics, prominent among which is the fine reticulin fibrosis invariably present in the bone marrow. However, fibroblast infiltration has never been noted in the marrow and the origin of the fibrosis has not been established. The present studies show that the hairy cells (HCs) of HCL produce an insoluble matrix of fibronectin (FN) in vitro. FN synthesis was shown by the appearance of cellular FN on the surface of cells cultured in serum-free medium and by immunoprecipitation of the metabolically labeled protein from HC aggregates. Moreover, the HCs were shown to assemble FN into disulphide-bonded multimers. This assembly was blocked by a 70-kD amino-terminal fragment of the molecule that blocks FN multimer formation by fibroblasts. HCs expressed abundant VLA-5, an FN receptor not present on normal circulating B lymphocytes, but important in matrix formation. Furthermore, HCs were shown to adhere to an FN fragment containing the VLA-5 binding site. It is therefore suggested that the VLA-5 of HCs is implicated in their assembly of FN matrix. The in vivo relevance of the findings was established by the demonstration of FN in association with infiltrating HCs in bone marrow sections from patients with HCL. It is concluded that the HCs synthesise and assemble an FN matrix and that this is at least partly responsible for the bone marrow fibrosis so characteristic of the disease.