Resting B cells as a transfer vehicle for Epstein-Barr virus infection of epithelial cells

Epstein-Barr virus (EBV), an orally transmitted herpesvirus, efficiently targets B lymphocytes through binding of the viral envelope glycoprotein gp350 to the complement receptor CD21. How the virus accesses epithelial cells is less well understood, because such cells are largely resistant to infection with cell-free virus in vitro. Here, we show that, after binding to primary B cells, most Epstein-Barr virions are not internalized but remain on the B cell surface and from there can transfer efficiently to CD21-negative epithelial cells, increasing epithelial infection by 10(3)- to 10(4)-fold compared with cell-free virus. Transfer infection is associated with the formation of B cell-epithelial conjugates with gp350/CD21 complexes focused at the intercellular synapse; transfer involves the gp85 and gp110 viral glycoproteins but is independent of gp42, the HLA class II ligand that is essential for B cell entry. Therefore, through efficient binding to the B cell surface, EBV has developed a means of simultaneously accessing both lymphoid and epithelial compartments; in particular, infection of pharyngeal epithelium by orally transmitted virus becomes independent of initial virus replication in the B cell system.

Lexically-based learning and early grammatical development

Pine & Lieven (1993) suggest that a lexically-based positional analysis can account for the structure of a considerable proportion of children's early multiword corpora. The present study tests this claim on a second, larger sample of eleven children aged between 1;0 and 3;0 from a different social background, and extends the analysis to later in development. Results indicate that the positional analysis can account for a mean of 60% of all the children's multiword utterances and that the great majority of all other utterances are defined as frozen by the analysis. Alternative explanations of the data based on hypothesizing underlying syntactic or semantic relations are investigated through analyses of pronoun case marking and of verbs with prototypical agent-patient roles. Neither supports the view that the children's utterances are being produced on the basis of general underlying rules and categories. The implications of widespread distributional learning in early language development are discussed.

Variation in utilization of computed tomography scanning for the investigation of minor head trauma in children: a Canadian experience

OBJECTIVES

To compare the utilization rates of CT scans in investigating minor head trauma in children in Canada, to identify the injuries determined by these scans, and to identify clinical findings that are highly associated with its diagnosis and the injury itself.

METHODS

A retrospective cohort study involving nine pediatric hospitals in Canada was conducted. A structured data collection method was used. Inclusion criteria included age 16 years or less, history of blunt head trauma, and a Glasgow Coma Scale score (GCS) greater than or equal to 13. Data collected included demographic information, type of injury, relevant clinical information, computed tomography (CT) scan data, and clinical outcome. Clinical findings associated with CT scan and positive CT scan were identified using logistic regression.

RESULTS

One thousand one hundred sixty-four children were included in the study. One hundred seventy-one (15%) had a CT scan, of which 60 (35%) were abnormal. There was a significant difference in the rate of ordering of CT scans among the participating hospitals, but no significant difference in the rate of abnormal CT scans. Mechanism of injury, GCS, and loss of consciousness were significantly related to the presence of an abnormal CT scan.

CONCLUSIONS

Although there is a significant difference in the utilization of CT scans to investigate minor head trauma in children across Canada, there is no significant difference in the frequency of head injuries in these patients. This suggests that it may be possible to determine clinical criteria that are predictive of a head injury in these patients.

Tetraspanin CD151 regulates transforming growth factor beta signaling: implication in tumor metastasis

Tetraspanin CD151 is associated with laminin-binding integrins and controls tumor cell migration and invasion. By analyzing responses of breast cancer cells to various growth factors, we showed that depletion of CD151 specifically attenuates transforming growth factor beta1 (TGFbeta1)-induced scattering and proliferation of breast cancer cells in three-dimensional Matrigel. CD151-dependent cell scattering requires its association with either alpha3beta1 or alpha6 integrins, but it is independent of the recruitment of CD151 to tetraspanin-enriched microdomains. We also found that CD151 regulates the compartmentalization of TGF-beta type I receptor (TbetaRI/ALK-5) and specifically controls the TGFbeta1-induced activation of p38. In contrast, signaling leading to activation of Smad2/3, c-Akt, and Erk1/2 proteins was comparable in CD151(+) and CD151(-) cells. Attenuation of TGFbeta1-induced responses correlated with reduced retention in the lung vascular bed, inhibition of pneumocyte-induced scattering of breast cancer cells in three-dimensional Matrigel, and decrease in experimental metastasis to the lungs. These results identify CD151 as a positive regulator of TGFbeta1-initiated signaling and highlight the important role played by this tetraspanin in TGFbeta1-induced breast cancer metastasis.

Sexual abuse and body-image distortion in the eating disorders

It has been suggested that there is a link between sexual abuse and bodily self-deprecation in women with eating disorders. In order to test that model, this study considers whether reported sexual abuse is associated with body-image distortion in anorexia and bulimia nervosa. There was no association with the reported presence of a history of abuse. However, the nature of any abuse was important. In particular, women who reported more recent abuse had a substantially greater level of bodysize overestimation. The clinical implications of this finding are discussed.

Epstein-Barr virus-induced B-cell transformation: quantitating events from virus binding to cell outgrowth

Epstein-Barr virus (EBV) infection and growth activation of human B cells is central to virus biology and disease pathogenesis, but is poorly understood in quantitative terms. Here, using virus at defined m.o.i., the different stages of this process at the single-cell level are followed in vitro. Virus binding to the B-cell surface, assayed by quantitative PCR, is highly efficient, particularly at the low m.o.i. values that most likely reflect physiologic events in vivo. However, only 10-15 % of bound virus genomes reach the cell nucleus, as visualized by sensitive fluorescence in situ hybridization (FISH) assay; viral genomes acquired per cell nucleus range from 1 to >10, depending on the m.o.i. Thereafter, despite differences in initial genome load, almost all nuclear genome-positive cells then go on to express the virus-encoded nuclear antigen EBNA2, upregulate the cell activation antigen CD23 and transit the cell cycle. EBNA2-positive cells in the first cycle post-infection then grow out to lymphoblastoid cell lines (LCLs) just as efficiently as do cells limiting-diluted from already established LCLs. This study therefore identifies EBV genome delivery to the nucleus as a key rate-limiting step in B-cell transformation, and highlights the remarkable efficiency with which a single virus genome, having reached the nucleus, then drives the transformation programme.

Limulus antilipopolysaccharide factor protects rabbits from meningococcal endotoxin shock

Limulus antilipopolysaccharide factor (LALF), an 11.8-kDa peptide isolated from amebocytes of Limulus polyphemus, neutralizes meningococcal lipooligosaccharide (LOS)-induced gelation of limulus amebocyte lysate. Rabbits challenged with an LD90 of LOS (10 micrograms/kg) premixed with LALF in vitro (n = 10) had significantly higher mean arterial pressure, arterial pH, serum bicarbonate concentrations, and survival (90% vs. 8%, P = .005) than did rabbits challenged with LOS alone. Relative to untreated controls, rabbits pretreated with LALF intravenously (iv) at 1.2 mg/kg (n = 21) also had significant improvements in physiologic measurements and higher survival (52% vs. 8%, P = .003). Even when LALF (1.2 mg/kg iv) was given 1/2 h after LOS challenge, animals showed significant improvements in physiologic measurements and survival (33% vs. 8% in untreated controls P = .028). LALF-treated animals also had significantly lower circulating endotoxin activity and tumor necrosis factor concentrations. Thus, LALF attenuates the toxic effects of meningococcal LOS in rabbits even when administered after LOS challenge and deserves further evaluation as a potential therapeutic agent for treating gram-negative septic shock.

Tetraspanin CD151 regulates glycosylation of (alpha)3(beta)1 integrin

The tetraspanin CD151 forms a stoichiometric complex with integrin alpha3beta1 and regulates its endocytosis. We observed that down-regulation of CD151 in various epithelial cell lines changed glycosylation of alpha3beta1. In contrast, glycosylation of other transmembrane proteins, including those associated with CD151 (e.g. alpha6beta1, CD82, CD63, and emmprin/CD147) was not affected. The detailed analysis has shown that depletion of CD151 resulted in the reduction of Fucalpha1-2Gal and bisecting GlcNAc-beta(1-->4) linkage on N-glycans of the alpha3 integrin subunit. The modulatory activity of CD151 toward alpha3beta1 was specific, because stable knockdown of three other tetraspanins (i.e. CD9, CD63, and CD81) did not affect glycosylation of the integrin. Analysis of alpha3 glycosylation in CD151-depleted breast cancer cells with reconstituted expression of various CD151 mutants has shown that a direct contact with integrin is required but not sufficient for the modulatory activity of the tetraspanin toward alpha3beta1. We also found that glycosylation of CD151 is also critical; Asn(159) --> Gln mutation in the large extracellular loop did not affect interactions of CD151 with other tetraspanins or alpha3beta1 but negated its modulatory function. Changes in the glycosylation pattern of alpha3beta1 observed in CD151-depleted cells correlated with a dramatic decrease in cell migration toward laminin-332. Migration toward fibronectin or static adhesion of cells to extracellular matrix ligands was not affected. Importantly, reconstituted expression of the wild-type CD151 but not glycosylation-deficient mutant restored the migratory potential of the cells. These results demonstrate that CD151 plays an important role in post-translation modification of alpha3beta1 integrin and strongly suggest that changes in integrin glycosylation are critical for the promigratory activity of this tetraspanin.

Effect of polymyxin B on experimental shock from meningococcal and Escherichia coli endotoxins

Meningococcemia is the most frequent cause of septic shock in healthy children. To determine whether polymyxin B (PMB) might improve mortality from meningococcal shock, its protective activity was evaluated in rabbits challenged with an LD90 of meningococcal lipooligosaccharide (LOS) and compared with an LD80 of Escherichia coli O111:B4 lipopolysaccharide (LPS). PMB (5 mg/kg) administered intravenously 30 min before meningococcal LOS challenge had no significant effect on heart rate, mean arterial pressure, serum bicarbonate, serum tumor necrosis factor (TNF) levels, or survival relative to controls. However, PMB premixed with LOS in vitro increased serum bicarbonate levels (P less than .05) and improved 24-h survival (P less than .05). In contrast, PMB given before E. coli LPS challenge increased serum bicarbonate levels, decreased TNF levels, and improved 24-h survival (all, P less than .05). In vitro studies confirmed that PMB at 10 micrograms/ml neutralized E. coli LPS but not meningococcal LOS activity. Thus, pretreatment with PMB apparently protects rabbits against shock induced by E. coli LPS but not by meningococcal LOS.

Regulation of HIV-1 infection in astrocytes: expression of Nef, TNF-alpha and IL-6 is enhanced in coculture of astrocytes with macrophages

'Restricted' human immunodeficiency virus type (HIV-1) infection of astrocytes is recognized in vivo in some pediatric and adult AIDS brains and in vitro in a small proportion of transfected primary fetal astrocytes. We investigated the extent of HIV-1JR-FL expression in fetal astrocytes and macrophages cultivated alone or together. Peak HIV-1 p24 antigen titres in supernatant fluids of macrophage cultures were increased with monocyte/macrophages from certain donors and were higher when macrophages were cocultivated with astrocytes. Structural HIV-1 gene (gp 41 and pol) products (protein and mRNA) were observed only in macrophages. Ten days after HIV-1JR-FL infection, astrocytes in a monoculture were stained negative or only weakly positive (1-2+) for Nef, whereas in a coculture up to 100% of astrocytes displayed Nef staining (up to 4+) in the cytoplasm. The streptavidine-biotine-peroxidase technique with certain monoclonal antibodies to Nef (Ovod et al, 1992) was specific for infected astrocytes. The intensity of Nef staining was higher in astrocytes cultivated with monocyte/macrophages from certain donors. In the coculture, tumor necrosis factor-alpha (TNF-alpha) was expressed in the astrocyte cytoplasm earlier after coinfection with HIV-1 and cytomegalovirus (CMV) compared to infection with HIV-1 alone. Interleukin-6 (IL-6) was secreted spontaneously and transiently in uninfected cocultures, but in a prolonged fashion following HIV-1 and HIV-1/CMV infections. The interactions between HIV-1- and CMV-infected macrophages and astrocytes lead to upregulation of TNF-alpha and IL-6 and enhancement of productive HIV-1 infection of macrophages and of 'restricted' HIV-1 infection of astrocytes with implications for the pathogenesis of AIDS dementia.

Epstein-Barr virus BNRF1 protein allows efficient transfer from the endosomal compartment to the nucleus of primary B lymphocytes

Epstein-Barr virus (EBV) is a tumor virus with marked B lymphotropism. After crossing the B-cell membrane, the virus enters cytoplasmic vesicles, where decapsidation takes place to allow transfer of the viral DNA to the cell nucleus. BNRF1 has been characterized as the EBV major tegument protein, but its precise function is unknown. We have constructed a viral mutant that lacks the BNRF1 gene and report here its in vitro phenotype. A recombinant virus devoid of BNRF1 (DeltaBNRF1) showed efficient DNA replication and production of mature viral particles. B cells infected with the DeltaBNRF1 mutant presented viral lytic antigens as efficiently as B cells infected with wild-type or BNRF1 trans-complemented DeltaBNRF1 viruses. Antigen presentation in B cells infected with either wild-type (EBV-wt) or DeltaBNRF1 virus was blocked by leupeptin addition, showing that both viruses reach the endosome/lysosome compartment. These data were confirmed by direct observation of the mutant virus in endosomes of infected B cells by electron microscopy. However, we observed a 20-fold reduction in the number of B cells expressing the nuclear protein EBNA2 after infection with a DeltaBNRF1 virus compared to wild-type infection. Likewise, DeltaBNRF1 viruses transformed primary B cells much less efficiently than EBV-wt or BNRF1 trans-complemented viruses. We conclude from these findings that BNRF1 plays an important role in viral transport from the endosomes to the nucleus.

Binding to syntenin-1 protein defines a new mode of ubiquitin-based interactions regulated by phosphorylation

Syntenin-1 is a PDZ domain-containing adaptor that controls trafficking of transmembrane proteins including those associated with tetraspanin-enriched microdomains. We describe the interaction of syntenin-1 with ubiquitin through a novel binding site spanning the C terminus of ubiquitin, centered on Arg(72), Leu(73), and Arg(74). A conserved LYPSL sequence in the N terminus, as well as the C-terminal region of syntenin-1, are essential for binding to ubiquitin. We present evidence for the regulation of this interaction through syntenin-1 dimerization. We have also established that syntenin-1 is phosphorylated downstream of Ulk1, a serine/threonine kinase that plays a critical role in autophagy and regulates endocytic trafficking. Importantly, Ulk1-dependent phosphorylation of Ser(6) in the LYPSL prevents the interaction of syntenin-1 with ubiquitin. These results define an unprecedented ubiquitin-dependent pathway involving syntenin-1 that is regulated by Ulk1.

Calcium binds dynamin I and inhibits its GTPase activity

Synaptic vesicle recycling is a neuronal specialization of endocytosis that requires the GTPase activity of dynamin I and is triggered by membrane depolarization and Ca2+ entry. To establish the relationship between dynamin I GTPase activity and Ca2+, we used purified dynamin I and analyzed its interaction with Ca2+ in vitro. We report that Ca2+ bound to dynamin I and this was abolished by deletion of dynamin's C-terminal tail. Phosphorylation of dynamin I by protein kinase C promoted formation of a dynamin I tetramer and increased Ca2+ binding to the protein. Moreover, Ca2+ inhibited dynamin I GTPase activity after stimulation by phosphorylation or by phospholipids but not after stimulation with a GST-SH3 fusion protein containing the SH3 domain of phosphoinositide 3-kinase. These results suggest that in resting nerve terminals, phosphorylation of dynamin I by protein kinase C converts it to a tetramer that functions as a Ca(2+)-sensing protein. By binding to Ca2+, dynamin I GTPase activity is specifically decreased, possibly to regulate synaptic vesicle recycling.

Defective infectious particles and rare packaged genomes produced by cells carrying terminal-repeat-negative epstein-barr virus

The Epstein-Barr virus (EBV) lytic program includes lytic viral DNA replication and the production of a viral particle into which the replicated viral DNA is packaged. The terminal repeats (TRs) located at the end of the linear viral DNA have been identified as the packaging signals. A TR-negative (TR(-)) mutant therefore provides an appropriate tool to analyze the relationships between EBV DNA packaging and virus production. Here, we show that supernatants from lytically induced 293 cells carrying TR mutant EBV genomes (293/TR(-)) contain large amounts of viral particles devoid of viral DNA which are nevertheless able to bind to EBV target cells. This shows that viral DNA packaging is not a prerequisite for virion formation and egress. Rather surprisingly, supernatants from lytically induced 293/TR(-) cells also contained rare infectious viruses carrying the viral mutant DNA. This observation indicates that the TRs are important but not absolutely essential for virus encapsidation.

Puncture wounds

Puncture wounds are common in children, and most are uncomplicated. For children who have a delayed presentation or signs of infection, consider the possibility of a retained foreign body. The diagnosis of P aeruginosa osteochondritis should be considered in any child who exhibits persistent signs and symptoms after puncture wounds; timely use of laboratory tests, radiologic imaging, and orthopedic referral is required.

Personal and clinical skin cancer prevention practices of US women physicians

OBJECTIVE

To document physician clinical and personal skin cancer prevention practices and associated characteristics.

DESIGN

A cross-sectional questionnaire survey of a representative sample of US women physicians.

SETTING

Mail survey.

SUBJECTS

Three thousand thirty-two nondermatologists and 95 dermatologists.

MAIN OUTCOME MEASURE

Personal and clinical practices.

RESULTS

Twenty-seven percent of nondermatologists counseled or screened their typical patients on skin cancer or sunscreen use at least once a year, while 49% did so less frequently, and 24% never counseled or screened at all. Of the 95 dermatologists, two thirds reported counseling or screening their typical patients at every visit. In bivariate analysis of nondermatologists, the distribution of counseling or screening was significantly (P<.05) associated with the following personal and professional characteristics: frequent sunscreen use, recent (within 2 years) skin examination, good health status, a primary care specialty, self-confidence in counseling or screening, extensive training in counseling or screening, high perceived relevance to the practice of the counseling or screening, nonurban practice site, and nonhospital-based or non-medical school-based practice. We found that 48% of all physicians always or nearly always used sunscreen, and 25% had received a clinical skin examination in the previous 2 years.

CONCLUSIONS

Although many primary care physicians report ever counseling or screening their typical patients about skin cancer and sunscreen use, increased professional education for primary care physicians could improve patient counseling about skin cancer prevention.

Ex vivo expansion and differentiation of unselected peripheral blood progenitor cells in serum-free media

The ability to expand and differentiate unselected PBPC was investigated. Cells were grown in serum-free media containing stem cell factor, GCSF and megakaryocyte growth and development factor (pegylated PEG-rHuMGDF) with or without supplemental serum. Optimal proliferation occurred when PBPC were cultured without prior Ficoll-Paque separation in serum-free media. Cell yields after 17 days of culture were proportional to the percentage of CD34+ cells in the starting population and were 1170+/-302-fold higher than the starting numbers of CD34+ cells. Granulocyte-macrophage colony-forming units increased over 12 days of culture, whereas the numbers of erythroid colony-forming cells peaked between 4 and 7 days. Elimination of PEG-rHuMGDF from cell cultures resulted in significantly lower yields of myeloid and erythroid colony-forming cells and total cell numbers. Cell differentiation into neutrophils was indicated by progressive increases in CD11b, CD15, and CD66b expression. Expanded neutrophils phagocytosed and killed bacteria as efficiently as neutrophils from normal donors. Large-scale expansion studies yielded similar proliferation and differentiation results as parallel small-scale cultures. Therefore, unselected PBPC can be efficiently expanded and differentiated into large numbers of functional mature neutrophils.

Monoclonal antibody to the gastrin receptor on parietal cells recognizes a 78-kDa protein

Four monoclonal antibodies reactive by immunofluorescence and by flow microfluorimetry with canine and porcine gastric parietal cell membranes were produced by fusion of mouse NS-1 myeloma cells with splenocytes from mice immunized with a population of canine gastric mucosal cells containing 60-70% parietal cells. One of these, an IgM antibody designated 2C1, reacted with the surface membranes of parietal cells by immunofluorescence, flow microfluorimetry, and immunogold electron microscopy; competed with 125I-labeled gastrin for binding to gastric cells; and inhibited by 56% maximal gastrin stimulation of [14C]aminopyrine uptake in parietal cells. The antibody immunoprecipitated 125I-labeled samples of a 78-kDa gastrin-binding protein purified from membrane extracts of porcine gastrin mucosa but did not recognize the same protein labeled covalently with 125I-labeled gastrin-(2-17)-hexadecapeptide. These observations suggest that the previously identified 78-kDa gastrin-binding protein is the gastrin receptor and that the antibody 2C1 is directed against the gastrin binding site of the gastrin receptor.

U.S. women physicians' residential radon testing practices

INTRODUCTION

These analyses were designed to elucidate U.S. physicians' perception of residential radon risk, as measured by the prevalence of residential radon testing using a representative sample of U.S. women physicians from the Women Physicians' Health Study database. In addition, characteristics of women physicians who were more likely to have conducted a residential radon test were identified.

METHODS

A random sample (n = 4,501 respondents) of U.S. women physicians aged 30 to 70 was obtained in the Women Physicians' Health Study. Analyses were conducted using SUDAAN.

RESULTS

The overall prevalence of residential radon testing among respondents was 18%, 2- to 6-fold higher than any estimate of residential radon testing in the general population. The strongest relationship with radon testing observed through logistic regression was with marital status; age, ethnicity, and region of residence were also related.

CONCLUSION

The study demonstrates that although U.S. women physicians are more likely to have conducted a personal residential radon test than the general population, 82% report not having done so. Increasing the awareness of physicians about the health risks associated with prolonged radon exposure will be essential if they are to play a role in addressing this important public health problem.

Effect of a human immunoglobulin preparation for intravenous use in a rabbit model of meningococcal endotoxin-induced shock

BACKGROUND AND METHODS

Endotoxin shock is mediated by various cytokines, including tumor necrosis factor. Treatment of patients with i.v. immunoglobulin has been shown to reduce the concentration of circulating cytokines. The purpose of this study was to determine the protective effects of immunoglobulin for i.v. use on meningococcal endotoxin-induced shock in a rabbit model. Experimental animals were challenged with i.v. meningococcal endotoxin (lipo-oligosaccharide) 10 micrograms/kg, and treated with either a 2-hr i.v. immunoglobulin infusion (400 mg/kg) or a similar saline infusion that was initiated 30 mins before endotoxin challenge. Control animals were challenged with saline alone.

RESULTS

Compared with untreated control animals, pulse rate increased (p less than .007) and mean arterial pressure and serum bicarbonate concentrations decreased (p less than .02) in both experimental groups, but did not differ between immunoglobulin-treated and saline-treated animals (p greater than .05) at any time after the endotoxin challenge. Geometric mean serum endotoxin concentrations were significantly (p less than .03) lower in the immunoglobulin-treated animals at 60, 120, 180, 240, 300, and 360 mins after the endotoxin challenge. The geometric mean serum tumor necrosis factor level at 1 hr after the endotoxin challenge in the immunoglobulin-treated experimental animals was lower than in saline-treated animals (5.53 vs. 8.47 tumor necrosis factor enzyme-linked immunosorbent assay U/mL), but not significantly so (p greater than .05). Mortality rate was similar in both experimental groups; eight (67%) of 12 saline-treated experimental rabbits and seven (70%) of ten immunoglobulin-treated rabbits died. All untreated control animals survived 24 hrs.

CONCLUSIONS

In this model of circulatory shock in rabbits, i.v. immunoglobulin: a) does not significantly alter the physiologic responses to endotoxin challenge; b) significantly reduces endotoxin concentrations; c) reduces tumor necrosis factor concentrations, but not significantly; and d) does not improve survival rate.

KIT Mutation and Loss of 14q May Be Sufficient for the Development of Clinically Symptomatic Very Low-Risk GIST

The aim of this study was to determine the minimal set of genetic alterations required for the development of a very low risk clinically symptomatic gastro-intestinal stromal tumour within the stomach wall. We studied the genome of a very low-risk gastric gastro-intestinal stromal tumour by whole-genome sequencing, comparative genomic hybridisation and methylation profiling. The studied tumour harboured two typical genomic lesions: loss of the long arm of chromosome 14 and an activating mutation in exon 11 of KIT. Besides these genetic lesions, only two point mutations that may affect tumour progression were identified: A frame-shift deletion in RNF146 and a missense mutation in a zinc finger of ZNF407. Whilst the frameshift deletion in RNF146 seemed to be restricted to this particular tumour, a similar yet germline mutation in ZNF407 was found in a panel of 52 gastro-intestinal stromal tumours from different anatomical sites and different categories. Germline polymorphisms in the mitotic checkpoint proteins Aurora kinase A and BUB1 kinase B may have furthered tumour growth. The epigenetic profile of the tumour matches that of other KIT-mutant tumours. We have identified mutations in three genes and loss of the long arm of chromosome 14 as the so far minimal set of genetic abnormalities sufficient for the development of a very low risk clinically symptomatic gastric stromal tumour.