Biomedical subjects

John K Cowell

Publications and source records attributed to John K Cowell.

At least 37 records · Page 2Linked to original sources

PubMed2005

Molecular characterization of the t(3;9) associated with immortalization in the MCF10A cell line.

The t(3;9)(p14;p21) in the MCF10A human mammary gland epithelial cell line was the single cytogenetic event that accompanied the transition from primary culture to immortalized cell line, suggesting that it is related to the development of the immortalization phenotype. To study the molecular consequences of the breakpoints in this rearrangement, we used a combination of fluorescence in situ hybridization (FISH) and array comparative genomic hybridization (CGH). The 3p14 translocation breakpoint occurs within BAC RP11-795e22, which accommodates only the TAFA1 gene, a novel cysteine-rich secreted protein thought to be involved in cytokine signaling. TAFA1 is expressed in normal breast tissue, not in MCF10A, and shows differential expression in a range of breast cancer cell lines. The 9p translocation breakpoint results in a deletion of approximately 4 megabases on the derivative chromosome 9, which includes the CDKN2A (p16) gene. Array CGH and FISH analysis demonstrated that BAC 149i22, which contains the CDKN2A/B genes, is also deleted specifically on the apparently normal copy of chromosome 9, making MCF10A null for the p16/p15 genes. The exact extent of gains and losses of chromosome regions resulting from rearrangements involving chromosomes 1q, 5q, and 8q have also been characterized using the BAC arrays.

Cell Line, Tumor↗

PubMed2005

Truncating mutations in the ACVR2 gene attenuates activin signaling in prostate cancer cells.

Activins are classified as members of the TGFbeta superfamily of signaling molecules and both activin and TGFbeta ligands signal through structurally and functionally related serine/threonine kinase receptors. Defects in these signaling pathways have been associated with the initiation and progression of the cancer phenotype. Inactivating mutations in the TGFbeta type II receptor gene, TGFbetaR2, have been identified in a variety of tumors and cell lines, particularly those with microsatellite instability (MSI). More recently, mutations in the activin type II receptor gene, ACVR2, were identified in colon and pancreatic cell lines and tumors with MSI. Because prostate tumors appear to have a high incidence of MSI, we analyzed prostate cancer cell lines, with and without MSI, for ACVR2 and TGFbetaR2 mutations. Our analysis of 6 prostate cell lines revealed mutations in the ACVR2 gene in 22Rv-1, LAPC-4, DU145, and LNCaP cells and mutations in the TGFbetaR2 gene in 22Rv-1 and LAPC-4. PC3 and H660 cells were wild-type for ACVR2 and TFGbetaR2. All of the ACVR2 mutations were truncating mutations, and using an activin response assay, we demonstrate that truncating mutations of the ACVR2 gene result in a significant reduction in activin mediated cell signaling. Inactivation of ACVR2 is a common event in prostate cancer cells suggesting it may play an important role in the development of prostate cancer.

Activin Receptors↗

PubMed2004

LGI1, a putative tumor metastasis suppressor gene, controls in vitro invasiveness and expression of matrix metalloproteinases in glioma cells through the ERK1/2 pathway.

Gliomas take a number of different genetic routes in the progression to glioblastoma multiforme, a highly invasive variant that is mostly unresponsive to current therapies. Gliomas express elevated levels of matrix metalloproteinases (MMPs), which have been implicated in the control of proliferation and invasion as well as neovascularization. Progressive loss of LGI1 expression has been associated with the development of high grade gliomas. We have shown previously that the forced re-expression of LGI1 in different glioma cells inhibits proliferation, invasiveness, and anchorage-independent growth in cells null for its expression. Here, using Affymetrix gene chip analysis, we show that reexpression of LGI1 in T98G cells results in the down-regulation of several MMP genes, in particular MMP1 and MMP3. LGI1 expression also results in the inhibition of ERK1/2 phosphorylation but not p38 phosphorylation. Inhibition of the MAPK pathway using the pharmacological inhibitors PD98059, U0126, and SB203580 in T98G LGI1-null cells inhibits MMP1 and MMP3 production in an ERK1/2-dependent manner. Treatment of LGI1-expressing cells with phorbol myristate acetate prevents the inhibition of MMP1/3 and restores invasiveness and ERK1/2 phosphorylation, suggesting that LGI1 acts through the ERK/MAPK pathway. Furthermore, LGI1 expression promotes phosphorylation of AKT, which leads to phosphorylation of Raf1(Ser-259), an event shown previously to negatively regulate ERK1/2 signaling. These data suggest that LGI1 plays a major role in suppressing the production of MMP1/3 through the phosphatidylinositol 3-kinase/ERK pathway. Loss of LGI1 expression, therefore, may be an important event in the progression of gliomas that leads to a more invasive phenotype in these cells.

Cell Line, Tumor↗

PubMed2004

CLCA2 tumour suppressor gene in 1p31 is epigenetically regulated in breast cancer.

The calcium-activated chloride channel gene family is clustered in the 1p31 region, which is frequently deleted in sporadic breast cancer. Recent studies have indicated the association of the second member of this gene family (CLCA2) with the development of breast cancer and metastasis. We have now shown the absence of expression of CLCA2 in several breast cancer tumours and cell lines, which confirms the results from other reports. When overexpressed in CLCA2-negative cell lines, their tumorigenicity and metastasis capability were significantly reduced, suggesting a tumour suppressor role for CLCA2 in breast cancer. The mechanisms behind the silencing of CLCA2 in breast cancer, however, have not been elucidated to date. Although we were able to identify CLCA2 mutations in breast cancers, somatic mutations are not the major cause of CLCA2 gene silencing. On the other hand, treatment of breast cancer CLCA2-negative cell lines with demethylating agents was able to restore CLCA2 expression, suggesting an epigenetic inactivation of this gene. Bisulphite-sequencing of the promoter-associated CpG island of the CLCA2 gene in breast tumours demonstrated that the absence of expression in these tumours was caused by hypermethylation of the promoter CpG island. In contrast, in breast cancer cell lines, tumours, and control cell lines that express CLCA2, a much lower level, and often absence, of methylation of the promoter were demonstrated. These findings demonstrate that CLCA2 is frequently inactivated in breast cancer by promoter region hypermethylation, which makes it an excellent candidate for the 1p31 breast cancer tumour suppressor gene.

Base Sequence↗

PubMed2004

Manipulation of nonsense mediated decay identifies gene mutations in colon cancer Cells with microsatellite instability.

Cancer cells showing microsatellite instability (MSI) demonstrate a high frequency of acquired frameshift mutations that result in the generation of nonsense mutations. RNA transcripts carrying these nonsense mutations are usually targeted for degradation through the nonsense mediated decay (NMD) pathway. Blocking this pathway with drugs such as emitine, results in the 'stabilization' of these mutant transcripts, which can now be detected on cDNA arrays. Unfortunately, emetine also induces a stress response that results in upregulation of additional transcripts which contribute to the analysis of the array. As a result, identifying which genes truly carry nonsense mutations is made more difficult. To overcome this, we have combined the emetine treatment with actinomycin D, which effectively prevents the upregulation of stress response genes while still stabilizing mutant transcripts. When we applied this modified approach to the analysis of MSI-positive colon cancer cells, we identified mutations in the UVRAG and p300 genes.

Cell Line, Tumor↗

PubMed2004

A role for p300/CREB binding protein genes in promoting cancer progression in colon cancer cell lines with microsatellite instability.

Our manipulation of the nonsense-mediated decay pathway in microsatellite unstable colon cancer cell lines identified the p300 gene as a potential tumor suppressor in this subtype of cancer. Here, we have demonstrated that not only the p300 gene but also the highly homologous cAMP-response element-binding protein (CREB) binding protein (CBP) gene together are mutated in >85% of microsatellite instability (MSI)+ colon cancer cell lines. A limited survey of primary tumors with MSI+ shows that p300 is also frequently mutated in these cancers, demonstrating that these mutations are not consequences of in vitro growth. The mutations in both genes occur frequently in mononucleotide repeats that generate premature stop codons. Reintroduction of p300 into MSI colon cancer cells could only be supported in the presence of an inactivated CBP gene, suggesting the idea that one or the other function must be inactivated for cancer cell viability. p300 is known to acetylate p53 in response to DNA damage, and when MSI+ cells null for p300 activity are forced to reexpress exogenous p300 cells show slower growth and a flatter morphology. p53 acetylation is increased upon reexpression of p300, suggesting that MSI+ cells constitutively activate the DNA damage response pathway in the absence of DNA-damaging agents. In support of this hypothesis, c-ABL kinase, which is also activated in response to DNA damage, shows higher levels of basal kinase activity in MSI+ cells. These observations suggest that there is a selective growth/survival advantage to mutational inactivation of p300/CBP in cells with inactivated mismatch repair capabilities.

Acetylation↗

PubMed2004

Application of bacterial artificial chromosome array-based comparative genomic hybridization and spectral karyotyping to the analysis of glioblastoma multiforme.

Identification of genetic losses and gains is valuable in analysis of brain tumors. Locus-by-locus analyses have revealed correlations between prognosis and response to chemotherapy and loss or gain of specific genes and loci. These approaches are labor intensive and do not provide a global view of the genetic changes within the tumor cells. Bacterial artificial chromosome (BAC) arrays, which cover the genome with an average resolution of less than 1 MbP, allow defining the sum total of these genetic changes in a single comparative genomic hybridization (CGH) experiment. These changes are directly overlaid on the human genome sequence, thus providing the extent of the amplification or deletion, reflected by a megabase position, and gene content of the abnormal region. Although this array-based CGH approach (CGHa) seems to detect the extent of the genetic changes in tumors reliably, it has not been robustly tested. We compared genetic changes in four newly derived, early-passage glioma cell lines, using spectral karyotyping (SKY) and CGHa. Chromosome changes seen in cell lines under SKY analysis were also detected with CGHa. In addition, CGHa detected cryptic genetic gains and losses and resolved the nature of subtle marker chromosomes that could not be resolved with SKY, thus providing distinct advantages over previous technologies. There was remarkable general concordance between the CGHa results comparing the cell lines to the original tumor, except that the magnitude of the changes seen in the tumor sample was generally suppressed compared with the cell lines, a consequence of normal cells contaminating the tumor sample. CGHa revealed changes in cell lines that were not present in the original tumors and vice versa, even when analyzed at the earliest passage possible, which highlights the adaptation of the cells to in vitro culture. CGHa proved to be highly accurate and efficient for identifying genetic changes in tumor cells. This approach can accurately identify subtle, novel genetic abnormalities in tumors directly linked to the human genome sequence. CGHa far surpasses the resolution and information provided by conventional metaphase CGH, without relying on in vitro culture of tumors for metaphase spreads.

Brain Neoplasms↗

PubMed2004

Characterization of the 1p/19q chromosomal loss in oligodendrogliomas using comparative genomic hybridization arrays (CGHa).

Loss of genetic material from the short arm of chromosome 1 and the long arm of chromosome 19 in anaplastic oligodendrogliomas has been shown to predict responsiveness to chemotherapy. Currently, the most common approach used to detect this loss of 1p/19q material employs microsatellite/FISH analysis using markers along the length of these chromosome arms. This analysis is highly focused and carried out on a locus-by-locus basis and gives no indication of the extent of other genetic changes occurring in the tumor cells, which may be important in future studies to explore genetic heterogeneity in the response to treatment. We have investigated the use of comparative genomic hybridization arrays (CGHa) of bacterial artificial chromosomes (BACs) in the identification of tumor samples that carry loss of the 1p/19q chromosome arms. These BAC arrays carry approximately 6,000 BAC clones and provide an average inter-BAC resolution of 500 Kb. Using this approach we have clearly shown that 1p/19q loss in these cases, when compared with microsatellite-mediated detection of loss of heterozygosity, is due to physical hemizygous deletion of the whole chromosome arms in all cases. Furthermore, CGHa allows the simultaneous definition of the other genetic changes that are occurring in the tumors. From our survey of 14 tumors consisting of low-grade oligodendrogliomas (n = 6), anaplastic oligodendrogliomas (n = 5), or mixed oligoastrocytoma (n = 3). we were able to demonstrate the presence of additional genetic markers that were characteristic of the various grades of tumors as well as novel changes that had occurred. Thus, CGHa provides a robust, high throughput, genome-wide analysis of genetic changes of oligodendroglial tumors that can be used not only to predict chemo-responsiveness but also place these genetic changes in the context of other abnormalities in the same experiment without the need for extensive chromosome or LOH analysis.

Brain Neoplasms↗

PubMed2004

High throughput determination of gains and losses of genetic material using high resolution BAC arrays and comparative genomic hybridization.

Chromosome analysis has been a cornerstone both for the identification of genetic defects that predispose to a variety of genetic syndromes as well as for the analysis of cancer progression. The relatively low resolution of metaphase chromosomes, however, only allows characterization of major genetic events which are defined at the megabase level. The development of the human genome-wide bacterial artificial chromosome (BACs) libraries which were used as templates for the human genome project made it possible to design microarrays containing these BACs which can theoretically span the genome uninterrupted. Comparative genomic hybridization to these arrays using test and reference DNA samples reveals numerical chromosome abnormalities (deletions, gains and amplifications) which can be accurately defined with a resolution depending on the density of the arrays. Analysis of test DNA samples using these arrays reveals low level deletions and amplifications that cannot be detected by chromosome analysis and provides a global view of these genetic changes in a single overnight hybridization using a high throughput approach. The extent of the genetic changes can then be determined precisely and the gene content of the affected regions established. These BAC arrays have widespread application to the analysis of constitutional genetic abnormalities associated with human diseases as well as cancer patients and their tumors. The development of similar BAC arrays for the mouse genome means that it is now possible to extend the CGHa approach to the study of genetic disorders and cancer models in mice.

Animals↗

PubMed2003

Suppression of the cell proliferation and invasion phenotypes in glioma cells by the LGI1 gene.

The leucine-rich, glioma-inactivated (LGI1) gene, located in 10q24, was originally identified because it was interrupted and inactivated by a reciprocal chromosome translocation in the T98G glioma cell line. Loss of LGI1 expression in high-grade brain tumors is correlated with the frequent loss of chromosome 10 during progression of gliomas. To investigate whether this gene can suppress the malignant phenotype in glioma cells, we introduced the LGI1 gene into cells that do (U87) and do not (T98G and A172) express LGI1 endogenously. A172 and T98G cells showed a significant reduction in cell proliferation potential as a result of re-expression of LGI1, whereas U87 cells did not. Using BD matrigel matrix chamber assays we were also able to show that the migration ability of the reconstituted A172 and T98G cells was also reduced considerably. Finally, these reconstituted T98G and A172 cells showed a significant reduction in the ability to form colonies in soft agar compared with the parental cells. This analysis clearly demonstrates that re-expression of the LGI1 gene in glioma cells that were null for its activity can greatly reduce their malignant potential. These observations provide the opportunity to investigate the role of LGI1 in gliomagenesis and, since LGI1 is predicted to be a membrane-bound protein, potentially provides the opportunity to develop novel treatment strategies for malignant gliomas.

Agar↗

PubMed2003

ZNF198 protein, involved in rearrangement in myeloproliferative disease, forms complexes with the DNA repair-associated HHR6A/6B and RAD18 proteins.

A highly specific t(8;13)(p11;q12) translocation has been consistently identified in bone marrow cells from patients with an atypical myeloproliferative disease that is associated with peripheral blood eosinophila and T- or B-cell leukemias. In all patients analysed to date, the translocation event results in a chimeric gene in which the atypical zinc-finger domain of ZNF198 is fused to the N-terminal end of the catalytic domain of the FGFR1 receptor tyrosine kinase. To understand more about the consequences of this rearrangement we have investigated the normal function of the ZNF198 gene. Using yeast two-hybrid analysis we identified HHR6 as a protein binding partner and confirmed this using immunoprecipitation studies. The ZNF198/FGFR1 fusion protein also binds to HHR6. We demonstrate here that the human RAD18 is also present in the ZNF198/HHR6 protein complex, although it does not coimmunoprecipitate with the fusion kinase. Cells expressing the fusion kinase gene show a marked increased sensitivity to UVB irradiation, suggesting that it acts in a dominant-negative way to affect DNA repair. These observations support the idea that ZNF198, through its interaction with HHR6 and RAD18, may be involved in the DNA repair process.

Carrier Proteins↗

PubMed2003

The neural progenitor-restricted isoform of the MARK4 gene in 19q13.2 is upregulated in human gliomas and overexpressed in a subset of glioblastoma cell lines.

Alterations of 19q13 are frequently observed in glial neoplasms, suggesting that this region harbors at least one gene involved in gliomagenesis. Following our previous studies on structural 19q chromosome rearrangements in gliomas, we have undertaken a detailed FISH analysis of the breakpoints and identified a 19q13.2 intrachromosomal amplification of the MAP/microtubule affinity-regulating kinase 4 (MARK4) gene in three primary glioblastoma cell lines. Recent data suggest that this gene is involved in the Wnt-signaling pathway. We observed that the expression of the alternatively spliced MARK4L isoform is upregulated in both fresh and cultured gliomas and overexpressed in all of the above three glioblastoma cell lines. Interestingly, we also found that MARK4L expression is restricted to undifferentiated neural progenitor cells or proliferating glial precursor cells, whereas its expression is downregulated during glial differentiation. Perturbation of expression using antisense oligonucleotides against MARK4 in glioblastoma cell lines, consistently induced a decreased proliferation of tumor cells. Taken together, these data show that MARK4, which is normally expressed in neural progenitors, is re-expressed in gliomas and may become a key target of intrachromosomal amplification upon 19q rearrangements.

Cell Differentiation↗

PubMed2003

Application of spectral karyotyping to the analysis of the human chromosome complement of interspecies somatic cell hybrids.

Mouse-human somatic cell hybrids have been extensively used in the molecular genetic dissection of human disease-related chromosome rearrangements because of their ability to selectively and randomly eliminate human chromosomes. This technology allows the isolation of structural chromosome abnormalities, which then allows determination of the precise molecular address of chromosome breakpoints associated with deletions and translocations, down to the nucleotides involved. The main confounding problem with the analysis of somatic cell hybrids is determining the exact chromosome complement unequivocally and quickly. Spectral karyotyping can identify each of the individual human chromosomes in a normal metaphase spread, as well as structural chromosome rearrangements-although, because of potential cross-hybridization between the human probe and mouse DNA sequences during the hybridization reaction, it has not been determined whether the same analysis will selectively identify human chromosomes on a mouse background. We show (to our knowledge, for the first time) that, under modified conditions of chromosomal in situ suppression hybridization, the standard spectral karyotyping probe does not cross-react with mouse chromosomes and can be used to identify subtle structurally rearranged chromosomes in hybrid cells. This analysis allows for the rapid and unequivocal identification of the human chromosome complement in these hybrids, as well as structural chromosome rearrangements that occur between mouse and human chromosomes that might otherwise confound the analysis.

3T3 Cells↗

PubMed2003

The oncogenic fusion protein-tyrosine kinase ZNF198/fibroblast growth factor receptor-1 has signaling function comparable with interleukin-6 cytokine receptors.

The reciprocal t(8;13) chromosome translocation results in a fusion gene (FUS) in which the N-terminal half of the zinc finger protein ZNF198 is combined with the cytoplasmic domain of the fibroblast growth factor receptor-1 (FGFR1). Expression of FUS is suggested to provide growth-promoting activity to myeloid cells similar to the activity of hematopoietic cytokine receptors. This study determined the specificity of FUS to activate signal transduction pathways. Because no tumor cell line expressing FUS was available, the mode of FUS action was identified in cells transiently and stably transfected with an expression vector for FUS. FUS acted as a constitutively active protein-tyrosine kinase and mediated phosphorylation of STAT1, 3, and 5 but not STAT4 and 6. The same specificity but lower activity was determined for normal FGFR1. STAT activation by FUS, similar to that by interleukin-6-type cytokines, promoted STAT-specific induction of genes. The functionality of FUS, as well as the relative recruitment of STAT isoforms, was determined by the dimerizing function of the zinc finger domain. Replacement of the ZNF198 portion by the Bcr portion as present in the t(8;22) translocation shifted the signaling toward a more prominent STAT5 activation. This study documents that both gene partners forming the fusion oncogene define the activity and the signaling specificity of the protein-tyrosine kinase of FGFR1.

Animals↗

PubMed2003

Molecular characterization of a 7p15-21 homozygous deletion in a Wilms tumor.

Recent molecular studies have shown a relatively high rate of loss of heterozygosity (LOH) at band 7p15-21 in Wilms tumor. We previously reported that the minimal common region of LOH was located between markers D7S517 and D7S503 in bands 7p15-21. We also reported the identification of one Wilms tumor (GOS44) bearing a homozygous, interstitial deletion at a locus within this region. Homogeneous primary cell cultures have been derived from this tumor and have been used for all the subsequent analyses. Using PCR and a panel of STS markers mapping between D7S517 and D7S503, the physical boundaries of the homozygous deletion were determined to be between D7S638 and D7S644. The deleted region spans approximately 3 Mbp of genomic sequence and includes seven known genes (KIAA0744, KIAA0713, AHR, AGR2, NET6, HSPC028, and DGKB.) as well as five predicted genes with similarities to genes of known function (LOC-91802, -116364, -96009, -92511, and -92512). The proximal breakpoint was found to lie between exon 6 and exon 7 of KIAA0744, and the distal breakpoint lay between exon 17 and exon 18 of DGKB. It is unlikely that a functional fusion gene product was generated as a consequence of the fusion between these two genes, because they are oriented in opposite directions on the chromosome. This is the only reported homozygous deletion recorded so far in Wilms tumor, and it provides the means to identify the tumor-suppressor gene located in this deletion.

Chromosome Deletion↗

PubMed2003

Genomic organization and expression profile of the human and mouse WAVE gene family.

The WAVE gene family, which contains three members, has been shown to play a major role in the actin polymerization and cytoskeleton organization processes. We have identified the WAVE3 gene from Chromosome (Chr) 13q12, as being involved in one of the breakpoints of a t(1:13)(q21:q12) reciprocal translocation, in a patient with ganglioneuroblastoma (Sossey-Alaoui et al. 2002; Oncogene 21: 5967-5974). We have also reported the cloning of the mouse Wave3. During our analysis of the human gene map, we also noted that WAVE2 maps to Chr region lp35-36, which frequently undergoes loss of heterozygosity and deletion in advanced stage neuroblastoma. These data clearly indicate a possible involvement of the WAVE genes in the pathogenesis of neuroblastoma. In this study, we report the complete genomic organization and expression profile of the three human WAVE genes and their mouse orthologs. We show that the WAVE genes have distinctive expression patterns in both adult and fetal human and mouse tissues. We also show a high level of conservation between these genes, in both the nucleotide and protein sequences. We finally show that the genomic structure is highly conserved among these genes and that the mouse Wave genes map to chromosome regions that have synteny in the human genome. The gene content in these syntenic regions is also conserved, suggesting that the WAVE genes are derived from a common ancient ancestor by genome duplication. The genomic characterization and expression analysis of the WAVE genes provide the basis towards understanding the function of these genes. It also provides the first steps towards the development of mouse models for the role of the WAVE genes in actin and cytoskeleton organization in general, and in the development of neuroblastoma in particular.

Amino Acid Sequence↗

PubMed2003

High-resolution analysis of genetic events in cancer cells using bacterial artificial chromosome arrays and comparative genome hybridization.

Chromosome analysis of cancer cells has been one of the primary means of identifying key genetic events in the development of cancer. The relatively low resolution of metaphase chromosomes, however, only allows characterization of major genetic events that are defined at the megabase level. The development of the human genome-wide bacterial artificial chromosome (BAC) libraries that were used as templates for the human genome project made it possible to design microarrays containing these BACs that can theoretically span the genome uninterrupted. Competitive hybridization to these arrays using tumor and normal DNA samples reveals numerical chromosome abnormalities (deletions and amplifications) that can be accurately defined depending on the density of the arrays. At present, we are using arrays with 6,000 BACs, which provide an average resolution of less than 700 kb. Analysis of tumor DNA samples using these arrays reveals small deletions and amplifications that were not detectable by chromosome analysis and provides a global view of these genetic changes in a single hybridization experiment in 24 hours. The extent of the genetic changes can then be determined precisely and the gene content of the affected regions established. These arrays have widespread application to the analysis of cancer patients and their tumors and can detect constitutional abnormalities as well. The availability of these high-density arrays now provides the opportunity to classify tumors based on their genetic fingerprints, which will assist in staging, diagnosis, and even prediction of response to therapy. Importantly, subtle genetic changes that occur consistently in tumor cell types may eventually be used to stratify patients for clinical trials and to predict their response to custom therapies.

Chromosome Aberrations↗

PubMed2002

WAVE3, an actin-polymerization gene, is truncated and inactivated as a result of a constitutional t(1;13)(q21;q12) chromosome translocation in a patient with ganglioneuroblastoma.

Neuroblastoma (Nb) is a malignancy of the sympathetic nervous system which affects children in their first decade. It is the most common extra-cranial solid tumor in children with an incidence of approximately 1 in 8-10 000 live births annually and accounts for approximately 10% of all children's cancers. Ganglioneuroblastoma is a relatively benign form of Nb and consists of a mixture of fibrils, mature and maturing ganglion cells, as well as undifferentiated neuroblasts. During routine cytogenetic analysis of patients with different manifestations of neuroblastoma we have identified one patient with ganglioneuroblastoma that carries an apparently balanced t(1:13)(q21:q12) reciprocal translocation. Positional cloning of the translocation breakpoint on chromosome 13 resulted in the mapping of the breakpoint between coding exon 2 and exon 3 of WAVE3, a member of WASP gene family. Although the breakpoint region on chromosome 1 was localized to within 2 kb of genomic sequence, no gene was found to be interrupted on this chromosome. The WAVE3 transcript is mainly expressed in the nervous system and, like all the members of the WASP gene family, WAVE3 is a key element in actin polymerization and cytoskeleton organization. WAVE3, therefore, is important for cell differentiation and motility and its expression is lost in a number of low grade and stage 4S tumors. From analysis of its expression pattern and function, WAVE3 is a candidate tumor suppressor gene, at least in some forms of neuroblastoma.

Actins↗