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G Laureys

Publications and source records attributed to G Laureys.

At least 19 recordsLinked to original sources
PubMed2006

Genome wide measurement of DNA copy number changes in neuroblastoma: dissecting amplicons and mapping losses, gains and breakpoints.

In the past few years high throughput methods for assessment of DNA copy number alterations have witnessed rapid progress. Both 'in house' developed BAC, cDNA, oligonucleotide and commercial arrays are now available and widely applied in the study of the human genome, particularly in the context of disease. Cancer cells are known to exhibit DNA losses, gains and amplifications affecting tumor suppressor genes and proto-oncogenes. Moreover, these patterns of genomic imbalances may be associated with particular tumor types or subtypes and may have prognostic value. Here we summarize recent array CGH findings in neuroblastoma, a pediatric tumor of the sympathetic nervous system. A total of 176 primary tumors and 53 cell lines have been analyzed on different platforms. Through these studies the genomic content and boundaries of deletions, gains and amplifications were characterized with unprecedented accuracy. Furthermore, in conjunction with cytogenetic findings, array CGH allows the mapping of breakpoints of unbalanced translocations at a very high resolution.

Cell Line, Tumor↗
PubMed2004

Molecular analysis of the putative tumour-suppressor gene EXTL1 in neuroblastoma patients and cell lines.

Although neuroblastoma is the most common extracranial solid tumour of childhood, little is known about its aetiology. Together with MYCN amplification and chromosome 17q gain, chromosome 1p deletion is one of the most frequently occurring genetic abnormalities in neuroblastoma. Based upon mapping of deletion breakpoints, putative tumour suppressor gene loci have been assigned to the distal part of the short arm of chromosome 1. Recently, the EXTL1 gene was suggested as a candidate neuroblastoma-suppressor gene and to evaluate this hypothesis, we performed 1p deletion analysis and mutation screening of the EXTL1-coding region on DNA from 22 primary neuroblastomas and 21 neuroblastoma cell lines. Deletions of the chromosome region 1p36.1, including the EXTL1 gene, were detected in several neuroblastoma cell lines and primary tumours. EXTL1 mutation screening resulted in the detection of one unclassified variant (Ser28Cys) but could not provide additional evidence of EXTL1 being involved in the aetiology of neuroblastoma.

Cell Line, Tumor↗
PubMed2003

[The neuroblastoma, "enfant terrible" among pediatric tumors].

Neuroblastoma belongs to the group of small blue round cell tumors and originates in precursor cells of the sympathetic neural tissue. This tumor occurs at the pediatric age and has fascinated and intrigued both clinicians and researchers because of its variable and often unpredictable clinical behaviour. Indeed, the clinical outcome of neuroblastoma patients not only depends on the clinical extension of the disease, but also on other factors including age at diagnosis, presence or absence in the tumor cells of molecular and biological characteristics with prognostic value (e.g. amplification of the oncogene MYCN, frequently associated with chromosome 1p-deletion is predictive for poor survival chance). In 1983 an abdominal stage 3 neuroblastoma was diagnosed in a 9-months old boy. He died of the disease 3 years later. Karyotyping studies in this patient revealed a constitutional chromosome translocation t(1;17) with a breakpoint involving the terminal part of the chromosome 1p arm. We hypothesized that this patient was predisposed to the development of neuroblastoma because he carried in all his somatic cells a chromosomal abnormality involving the region frequently deleted in neuroblastoma tumor cells. We assumed that the chromosomal translocation breakpoints might indicate the regions harbouring genes involved in neuroblastoma development. A somatic cell fusion experiment was performed between the patient's fibroblasts (the only remaining source of patient material) and a fast growing Chinese hamster ovary cell line to assure the possibilities to perform further research. These somatic cell hybrids indeed contained the human translocation chromosomes. Further characterization of the translocation breakpoints by FISH (fluorescent in situ hybridisation) resulted in the identification of NPPA (formerly PND, the gene for pronatriodilatine) and A12M2 (an adenovirus integration site) as flanking markers for the 1p breakpoint. The 17q breakpoint was located between the NF1 (neurofibromatosis 1) gene and the SCYA7 (harboring the gene encoding the monocyte chemotactic protein-3). Starting from these markers chromosome walking experiments furthered the characterization of the chromosomal breakpoint regions and enabled to identify breakpoint overlapping cosmids. Sequence analysis of these markers is ongoing and will reveal if the breakpoint regions indeed harbour a gene involved in neuroblastoma development.

Abdominal Neoplasms↗
PubMed2001

Comparative genomic hybridization (CGH) analysis of stage 4 neuroblastoma reveals high frequency of 11q deletion in tumors lacking MYCN amplification.

We have studied the occurrence and association of 11q deletions with other chromosomal imbalances in Stage 4 neuroblastomas. To this purpose we have performed comparative genomic hybridization (CGH) analysis on 50 Stage 4 neuroblastomas and these data were analyzed together with those from 33 previously published cases. We observed a high incidence of 11q deletion in Stage 4 neuroblastoma without MYCN amplification (59%) whereas 11q loss was only observed in 15% of neuroblastomas with MYCN-amplification (p = 0.0002) or 11% of cases with 1p deletion detected by CGH (p = 0.0001). In addition, 11q loss showed significant positive correlation with 3p loss (p = 0.0002). Event-free survival was poor and not significantly different for patients with or without 11q deletion. Our study provides further evidence that Stage 4 neuroblastomas with 11q deletions represent a distinct genetic subgroup that typically shows no MYCN-amplification nor 1p deletion. Moreover, it shows that neuroblastomas with 11q deletion also often present 3p deletion. This genetic subgroup shows a similar poor prognosis as MYCN amplified 4 neuroblastomas.

Adolescent↗
PubMed2001

Multicentre analysis of patterns of DNA gains and losses in 204 neuroblastoma tumors: how many genetic subgroups are there?

PROCEDURE: Analysis of comparative genomic hybridization (CGH) data of 120 tumors from four different studies, and data of 84 previously unpublishied tumors, allowed delineation of at least six different genetic subsets of neuroblastomas. RESULTS AND CONCLUSIONS: A small number of tumors show no detectable imballances. A second group of tumors presents with gains and losses of whole chromosomes and is found predominantly in prognostically favorable stage 1 and 2 tumors. The remaining groups are characterized by the presence of partial chromosome imbalances, and are found mostly in stage 3, 4, and 4S tumors. The third group shows 17q gain without 11q loss, 1p loss, or MYCN amplification (MNA). The fourth group has 1p deletion or MNA, and finally, a fifth group shows 11q loss without 1p deletion or MNA, and is found mainly in stage 4 tumors. The latter group is significantly associated with losses of 3p, 4p, and 14q.

Chromosome Aberrations↗
PubMed2001

Combined M-FISH and CGH analysis allows comprehensive description of genetic alterations in neuroblastoma cell lines.

Cancer cell lines are essential gene discovery tools and have often served as models in genetic and functional studies of particular tumor types. One of the future challenges is comparison and interpretation of gene expression data with the available knowledge on the genomic abnormalities in these cell lines. In this context, accurate description of these genomic abnormalities is required. Here, we show that a combination of M-FISH with banding analysis, standard FISH, and CGH allowed a detailed description of the genetic alterations in 16 neuroblastoma cell lines. In total, 14 cryptic chromosome rearrangements were detected, including a balanced t(2;4)(p24.3;q34.3) translocation in cell line NBL-S, with the 2p24 breakpoint located at about 40 kb from MYCN. The chromosomal origin of 22 marker chromosomes and 41 cytogenetically undefined translocated segments was determined. Chromosome arm 2 short arm translocations were observed in six cell lines (38%) with and five (31%) without MYCN amplification, leading to partial chromosome arm 2p gain in all but one cell line and loss of material in the various partner chromosomes, including 1p and 11q. These 2p gains were often masked in the GGH profiles due to MYCN amplification. The commonly overrepresented region was chromosome segment 2pter-2p22, which contains the MYCN gene, and five out of eleven 2p breakpoints clustered to the interface of chromosome bands 2p16 and 2p21. In neuroblastoma cell line SJNB-12, with double minutes (dmins) but no MYCN amplification, the dmins were shown to be derived from 16q22-q23 sequences. The ATBF1 gene, an AT-binding transcription factor involved in normal neurogenesis and located at 16q22.2, was shown to be present in the amplicon. This is the first report describing the possible implication of ATBF1 in neuroblastoma cells. We conclude that a combined approach of M-FISH, cytogenetics, and CGH allowed a more complete and accurate description of the genetic alterations occurring in the investigated cell lines.

Chromosome Painting↗
PubMed2000

Chromosome 2 short arm translocations revealed by M-FISH analysis of neuroblastoma cell lines.

PROCEDURE: M-FISH analysis was performed on 18 neuroblastoma cell lines, which were previously studied with cytogenetic, standard FISH and CGH data. RESULTS: One of the most striking findings of this study was the detection of chromosome 2 short arm rearrangements in 61% of the investigated cell lines. These rearrangements resulted from translocations with various partner chromosomes. All translocations, except one were unbalanced, leading to the consistent gain of chromosome segment 2pter-p22. A cryptic balanced translocation t(2;4) was observed with a breakpoint located in the vicinity of MYCN in cell line NBL-S. CONCLUSIONS: Combination of M-FISH results together with cytogenetic, standard FISH and CGH data yielded the most comprehensive description of chromosome 2 short arm rearrangements, leading to a consistent gain of chromosome 2 short arm material.

Child↗
PubMed2000

Long-term results of three randomized trials (58831, 58832, 58881) in childhood acute lymphoblastic leukemia: a CLCG-EORTC report. Children Leukemia Cooperative Group.

We present here the long-term results of three randomized clinical trials conducted on children with newly diagnosed acute lymphoblastic leukemia (ALL) between 1983 and 1998 by the Children Leukemia Cooperative Group (CLCG) from EORTC. In study 58831/32, the overall event-free survival (EFS) rates (+/- s.e.) at 6 and 10 years were 66% +/- 1.8% and 65% +/- 1.8%, respectively, and the risk of isolated central nervous system (CNS) relapse was 6% +/- 1% and 7% +/- 1%, respectively. In patients with a standard risk of relapse the omission of cyclophosphamide had no adverse effect on disease-free survival rates at 10 years (trial 58831). In medium- and high-risk patients the omission of radiotherapy did not increase the risk of CNS or systemic relapse (trial 58832). In study 58881 (1989-1998) the overall EFS rate at 8 years was 68.4% +/- 1.2% and the risk of isolated CNS relapse was 4.2%+/-0.5%. In this trial which adressed three randomized questions, the following results were obtained: the combination of cytarabine at high doses with methotrexate at high doses during interval therapy did not improve prognosis. The addition of 6-mercaptopurine iv during maintenance increased the risk of late relapse. E. coli asparaginase was more toxic and has a higher efficacy than Erwinia asparaginase. Leukocyte counts >100 x 10(9)/l, specific genetic abnormalities, a poor initial response to steroids or a high level of minimal residual disease at early time points were consistently associated with an adverse prognosis in the 58881 trial.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1999

Discrepant flow cytometric expression and function of P-glycoprotein in neuroblastic tumors.

BACKGROUND: Patients suffering from neuroblastic tumors are currently being classified into prognostic subsets based on different clinical and biologic features. In this study, a triple-color flow cytometric assay and a functional test were applied to neuroblastoma cell lines and patients with a neuroblastic tumor, and the value of P-glycoprotein expression and function as potential prognostic characteristics, was determined. METHODS: Twenty-two single-cell suspensions prepared from tumors, and neuroblasts from four bone marrow samples were analyzed by triple-color flow cytometry. Neuroblasts were identified by NB84-positivity and absence of CD45. P-glycoprotein expression was evaluated using 4E3 and MRK16 antibodies. Eighteen samples were tested with a functional assay, based on accumulation and retention of rhodamine-123 with and without the inhibitor verapamil. Six neuroblastoma cell lines were also evaluated. RESULTS: P-glycoprotein expression was seen in 18 of 26 patient samples and in three of six cell lines. The highest expression levels were found in low stage neuroblastoma and well-differentiated tumors; whereas the highest activities were found in stage 4 neuroblastoma and the lowest in ganglioneuroblastoma and ganglioneuroma patients. In 10 of 17 samples, concordant results were found between the flow cytometric immunological test and immunocytochemistry. CONCLUSIONS: The described flow cytometric technique is a new, alternative approach to detect P-glycoprotein expression and function in neural crest tumors. Based on the expression level and the activity value, patients can be segregated into different phenotypic groups. In particular, those patients with high P-glycoprotein activity might benefit from treatment regimens containing reversal agents.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Gain of chromosome arm 17q and adverse outcome in patients with neuroblastoma.

BACKGROUND: Gain of genetic material from chromosome arm 17q (gain of segment 17q21-qter) is the most frequent cytogenetic abnormality of neuroblastoma cells. This gain has been associated with advanced disease, patients who are > or =1 year old, deletion of chromosome arm 1p, and amplification of the N-myc oncogene, all of which predict an adverse outcome. We investigated these associations and evaluated the prognostic importance of the status of chromosome 17. METHODS: We compiled molecular cytogenetic analyses of chromosome 17 in primary neuroblastomas in 313 patients at six European centers. Clinical and survival information were collected, along with data on 1p, N-myc, and ploidy. RESULTS: Unbalanced gain of segment 17q21-qter was found in 53.7 percent of the tumors, whereas the chromosome was normal in 46.3 percent. The gain of 17q was characteristic of advanced tumors and of tumors in children > or =1 year of age and was strongly associated with the deletion of 1p and amplification of N-myc. No tumor showed amplification of N-myc in the absence of either deletion of 1p or gain of 17q. Gain of 17q was a significant predictive factor for adverse outcome in univariate analysis. Among the patients with this abnormality, overall survival at five years was 30.6 percent (95 percent confidence interval, 21 to 40 percent), as compared with 86.0 percent (95 percent confidence interval, 78 to 91 percent) among those with normal 17q status. in multivariate analysis, gain of 17q was the most powerful prognostic factor, followed by the presence of stage 4 disease and deletion of 1p (hazard ratios, 3.4, 2.3, and 1.9, respectively). CONCLUSIONS: Gain of chromosome segment 17q21-qter is an important prognostic factor in children with neuroblastoma.

Analysis of Variance↗
PubMed1999

Technetium-99m sestamibi imaging in paediatric neuroblastoma and ganglioneuroma and its relation to P-glycoprotein.

Imaging with technetium-99m sestamibi offers a non-invasive approach to detect the presence of functional P-glycoprotein (Pgp), one of the major causes of multidrug resistance, in human malignancies. A clinical role for Pgp has been suggested in the subpopulation of primary neuroblastoma without amplification of the proto-oncogene MYCN. We wanted to evaluate the usefulness of 99mTc-sestamibi scintigraphy in the screening of neural crest tumours for the presence of Pgp. In ten children suffering from MYCN-negative neuroblastoma, ganglioneuroblastoma or ganglioneuroma, 99mTc-sestamibi imaging was performed at initial diagnosis. All patients underwent planar imaging 20-30 min and 3.5-4 h after intravenous injection of 740 MBq/1.73 m2 99mTc-sestamibi. Tumour to normal tissue ratios, as well as washout rates, were determined and compared with in vitro flow cytometric analysis of Pgp expression and function. Pgp expression was analysed flow cytometrically with the monoclonal antibodies 4E3 and MRK16, and Pgp function was evaluated by means of rhodamine 123 uptake and efflux either in the absence or in the presence of the Pgp inhibitor verapamil. In nine of ten patients, we found that the intratumoral 99mTc-sestamibi activity was comparable to the background activity, which might be suggestive of Pgp presence. This was confirmed flow cytometrically in all but one patient. 99mTc-sestamibi enhancement was seen in the primary tumour and the bone marrow metastases of one of the ten patients, and this result was concordant with a negative Pgp status. The findings presented suggest that 99mTc-sestamibi imaging results might correlate with the presence of functional Pgp in neural crest tumours without MYCN amplification.

3-Iodobenzylguanidine↗
PubMed1999

P-glycoprotein is an independent prognostic factor predicting relapse in childhood acute lymphoblastic leukaemia: results of a 6-year prospective study.

P-glycoprotein (P-gp), a cellular drug-efflux pump, is thought to be one of the major causes of multidrug resistance (MDR) in malignancies. Since therapeutic strategies are being developed to circumvent drug resistance by inhibiting P-gp function, large prospective studies evaluating the clinical relevance of P-gp in childhood acute lymphoblastic leukaemia (ALL) are warranted. P-gp expression was evaluated over a period of 6 years in 102 consecutive patients with de novo childhood ALL and in 35 children with relapse of ALL. Bone marrow and blood smears were studied immunocytochemically with two monoclonal antibodies at initial diagnosis and at relapse. P-gp expression was found in 14 (14%) patients at initial diagnosis. After induction treatment, complete remission was achieved in 100/102 patients (98%), of whom 19 relapsed. Cumulative event-free survival was significantly higher in the P-gp-negative group compared with the P-gp-positive population (Logrank P = 0.02). Multivariate analysis showed the results to be independent of age, WBC count and karyotype, and concomitantly underlined the importance of MDR1 phenotype detection in childhood ALL. P-gp expression was more frequently found at relapse (34%) than at primary diagnosis (P = 0.01). In the relapsed patient group, P-gp-positive patients had a 2-fold greater risk for adverse clinical outcome than the P-gp-negative relapsed patients. P-gp expression was not induced by exposure to previous chemotherapy since the majority of P-gp-negative patients remained negative at relapse. P-glycoprotein expression in newly diagnosed childhood ALL is an independent adverse prognostic parameter with a predictive value for relapse.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Genetic heterogeneity of neuroblastoma studied by comparative genomic hybridization.

Comparative genomic hybridization (CGH) analysis was performed on 36 neuroblastomas of both low and high stage of disease. This study significantly increases the number of neuroblastoma tumors studied by CGH. Analysis of larger series of tumors is particularly important in view of the different clinical subgroups that are recognized for this tumor. The present data and a comparison with all published CGH data on neuroblastoma provide further insights into the genetic heterogeneity of neuroblastoma. Stage 1, 2, and 4S tumors showed predominantly whole chromosome gains and losses. A similar pattern of whole chromosome imbalances, although less frequent, was observed in stage 3 and 4 tumors, in addition to partial chromosome gains and losses. An increase in chromosome 17 or 17q copy number was observed in 81% of tumors. The most frequent losses, either through partial or whole chromosome underrepresentation, were observed for 1p (25%), 3p (25%), 4p (14%), 9p (19%), 11q (28%), and 14q (31%). The presence of 3p, 11q or 14q deletions defines a genetic subset of neuroblastomas and contributes to the further genetic characterization of stage 3 and 4 tumors without MYCN amplification (MNA) and 1p deletion. The present study also provides additional evidence for a possible role of genes at 11q13 in neuroblastoma. In a few cases, 1p deletion or MNA detected by FISH or Southern blotting was not found by CGH, indicating that the use of a second, independent technique for evaluation of these genetic parameters is recommended.

Adolescent↗
PubMed1998

Activity of iodine-123 metaiodobenzylguanidine in childhood neuroblastoma: lack of relation to tumour differentiation in vivo.

Neuroblastoma (NB) tumour cells have a remarkable tendency to differentiate spontaneously or under the influence of certain drugs. It is not clear whether metaiodobenzylguanidine (MIBG) uptake correlates with differentiation of NB cells. In 28 tumours of 26 patients, iodine-123 MIBG uptake in primary NBs was studied in relation to tumour differentiation, tumour size, cell density and degree of necrosis in subsequently resected specimens. Genetic features such as the presence of chromosomal aberrations (1p-deletion and MYCN amplification) and/or P-glycoprotein (mdr-1 gene product) were also evaluated in relation to MIBG uptake. A highly variable and unpredictable intensity of MIBG uptake was observed in primary as well as secondary resected tumours. This intensity did not relate to any of the above-mentioned factors except that there was a trend towards more intense uptake with increasing size of the tumour. We conclude from our observations that, in contrast to commonly held opinion, well-differentiated tumours do not a priori show a lower MIBG uptake in vivo, even when there are a low number of viable cells and a high degree of necrosis. The degree of differentiation or tumour viability and necrosis following longstanding chemotherapeutic treatment cannot be predicted by the MIBG scan findings. The observed MIBG uptake may be importantly influenced by factors other than those associated with cellular differentiation.

3-Iodobenzylguanidine↗
PubMed1997

Comparative genomic hybridization analysis of human neuroblastomas: detection of distal 1p deletions and further molecular genetic characterization of neuroblastoma cell lines.

Deletions of the short arm of chromosome 1 and MYCN amplification are the most frequently encountered genetic changes in disseminated neuroblastomas and neuroblastoma cell lines. Different strategies have been followed for detection of these and other genomic changes in neuroblastoma including karyotyping, FISH, and LOH, each with its own limitations. Here we report upon the evaluation of comparative genomic hybridization (CGH) in the analysis of neuroblastoma cell lines, with the emphasis on the assessment of the reliability of CGH for the detection of distal 1p deletions. We have analyzed seven neuroblastoma cell lines for which the 1p status was previously studied in detail using FISH and LOH. Our results show that CGH allows reliable detection of distal 1p deletions, including a small interstitial deletion in cell line SK-N-AS. Furthermore, CGH also allows the detection of chromosomal imbalance which would otherwise remain undetected, and provides useful information for further molecular characterization of chromosomal imbalances.

Child, Preschool↗
PubMed1997

Sensitive and reliable detection of genomic imbalances in human neuroblastomas using comparative genomic hybridisation analysis.

Deletions of the short arm of chromosome 1, extra copies of chromosome 17q and MYCN amplification are the most frequently encountered genetic changes in neuroblastomas. Standard techniques for detection of one or more of these genetic changes are karyotyping, FISH analysis and LOH analysis by Southern blot or PCR. Each of these techniques has its own particular limitations. More recently, comparative genomic hybridisation (CGH) was introduced for detection of genomic imbalances including deletions, duplications and gene amplification. We evaluated the sensitivity and reliability of CGH for detection of the most frequently encountered genetic changes in neuroblastoma. For this purpose a panel of well-characterised neuroblastoma cell lines as well as a series of 11 primary neuroblastomas was analysed. Our results show that CGH is a valuable tool for the genetic characterisation of neuroblastomas, both for the detection of frequently occurring genomic imbalances and for the identification of previously unnoticed genetic changes.

Child, Preschool↗
PubMed1997

Analysis of 1;17 translocation breakpoints in neuroblastoma: implications for mapping of neuroblastoma genes.

Deletions and translocations resulting in loss of distal 1p-material are known to occur frequently in advanced neuroblastomas. Fluorescence in situ hybridisation (FISH) showed that 17q was most frequently involved in chromosome 1p translocations. A review of the literature shows that 10 of 27 cell lines carry 1;17 translocations. Similar translocations were also observed in primary tumours. Together with the occurrence of a constitutional 1;17 translocation in a neuroblastoma patient, these observations suggest a particular role for these chromosome re-arrangements in the development of neuroblastoma. Apart from the loss of distal 1p-material, these translocations invariably lead to extra copies of 17q. This also suggested a possible role for genes on 17q in neuroblastoma tumorigenesis. Further support for this hypothesis comes from the observation that in those cell lines without 1;17 translocations, other chromosome 17q translocations were present. These too lead to extra chromosome 17q material. Molecular analysis of 1;17 translocation breakpoints revealed breakpoint heterogeneity both on 1p and 17q, which suggests the involvement of more than 2 single genes on 1p and 17q. The localisation of the different 1p-breakpoints occurring in 1;17 translocations in neuroblastoma are discussed with respect to the recently identified candidate tumor suppressor regions and genes on 1p. In this study, we focused on the molecular analysis of the 17q breakpoints in 1;17 translocations. Detailed physical mapping of the constitutional 17q breakpoint allowed for the construction of a YAC contig covering the breakpoint. Furthermore, a refined position was determined for a number of 17q breakpoints of 1;17 translocations found in neuroblastoma cell lines. The most distal 17q breakpoint was identified in cell line UHG-NP and mapped telomeric to cosmid cCI17-1049 (17q21). This suggests that genes involved in a dosage-dependent manner in the development of neuroblastoma map in the distal segment 17q22-qter. Future studies aim at the molecular cloning of 1;17 translocation breakpoints and at deciphering the mechanisms leading to 1;17 translocations and possibly to the identification of neuroblastoma genes at or in the vicinity of these breakpoints.

Chromosome Mapping↗