Maria Łastowska

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.

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.

Comprehensive Genetic and Histopathologic Study Reveals Three Types of Neuroblastoma Tumors

PURPOSE To determine the relationship between multiple genetic features, tumor morphology, and prognosis in neuroblastoma. PATIENTS AND METHODS The genetic alterations and morphologic features that underpin three histopathologic risk classifications were analyzed in 108 neuroblastoma patients. Tumors were subdivided into four groups based on the three most frequent and prognostically significant genetic alterations (17q gain, 1p deletion, and MYCN amplification), and all other genetic, morphologic, and clinical data were analyzed with respect to these groups. RESULTS Our analyses identify three nonoverlapping tumor types with distinct genetic and morphologic features, defined here as types 1, 2, and 3. Type 1 tumors show none of the three significant genetic alterations and have good prognosis. Both type 2 (17q gain only or 17q gain and 1p del) and type 3 (17q gain, 1p del, and MYCN amplification) tumors progress. However, these tumor types are distinguished clinically by having significantly different median age at diagnosis and median progression-free survival (PFS). Multivariate analysis indicates that 17q gain is the only independent prognostic factor among all genetic, histopathologic, and clinical factors analyzed. Among histopathologic risk systems, the International Neuroblastoma Pathology Classification was the best predictor of PFS. CONCLUSION Our results indicate that specific combinations of genetic changes in neuroblastoma tumors contribute to distinct morphologic and clinical features. Furthermore, the identification of two genetically and morphologically distinct types of progressing tumors suggests that possibilities for different therapeutic regimens should be investigated.

Gain of chromosome arm 17q predicts unfavourable outcome in neuroblastoma patients

Gain of chromosome arm 17q has recently been reported in neuroblastoma tumours. We analysed 17q status in relation to other known prognostic features and clinical outcome in a series of 45 tumours. Chromosome 17 status was detected by cytogenetic analysis, fluorescence in situ hybridisation (FISH) anc comparative genomic hybridisation (CGH) and correlated with other clinical and genetic factors. Survival analysis was calculated by the Kaplan-Meier estimation. Twenty-eight out of 45 tumours showed 17q gain, and this was associated with established indicators of poor prognosis; stage 4 disease (P < 0.001), age above 1 year at diagnosis (P < 0.001), 1p deletion (P < 0.01), MYCN amplification (P = 0.03) and diploidy/tetraploidy (P = 0.04). 17q gain was associated with poor outcome: 3-year survival was 13.5% compared with 100% for tumours without 17q gain (P = 0.0001); and progression-free survival (PFS) was 8.1% after 3 years compared with 83% for 17q normal tumours (P = 0.0001). PFS in 28 MYCN non-amplified patients indicated that 17q status has discriminatory power within this group: PFS 0% for 17q gain (n = 14) versus 100% for normal 17q (n = 14) (P = 0.0001). This study indicates that 17q changes have prognostic significance in neuroblastoma and should be a target for molecular cytogenetic detection at diagnosis.

Breakpoint position on 17q identifies the most aggressive neuroblastoma tumors

Gain of chromosome arm 17q is a powerful prognostic factor in neuroblastoma, and the distribution of 17q breakpoints suggests that the dosage of one or more genes in 17q22–23 to 17qter is critical for tumor progression. To identify the smallest region of 17q gain, we used eight probes to map translocation breakpoints in 48 primary neuroblastoma tumors. We identified at least five different breakpoints, all localized within the proximal part of 17q (from D17Z1 to MPO). The shortest region of gain identified by these probes extends from MPO (17q23.1) to 17qter. Surprisingly, we found that breakpoints localized proximal to ERBB2 (17q12) were associated with significantly better patient survival than breakpoints localized distal to ERBB2. Breakpoints localized distal to ERBB2 identified patients with a particularly poor prognosis, higher mitotic karyorrhectic index, and stage 4 disease. This implies that breakpoint position on 17q is a discriminative factor within this prognostically poor group of patients. This result also suggests that the biological effect of 17q gain during neuroblastoma progression has a complex basis. We propose that this involves dosage alterations of genes localized on both sides of the 17q breakpoints, with a gene or genes mapping between 17cen and 17q12 acting to suppress progression, and a gene or genes mapping between 17q23.1 and 17qter acting to promote tumor progression.

Identification of a neuronal transcription factor network involved in medulloblastoma development

AbstractBackgroundMedulloblastomas, the most frequent malignant brain tumours affecting children, comprise at least 4 distinct clinicogenetic subgroups. Aberrant sonic hedgehog (SHH) signalling is observed in approximately 25% of tumours and defines one subgroup. Although alterations in SHH pathway genes (e.g. PTCH1, SUFU) are observed in many of these tumours, high throughput genomic analyses have identified few other recurring mutations. Here, we have mutagenised the Ptch+/- murine tumour model using the Sleeping Beauty transposon system to identify additional genes and pathways involved in SHH subgroup medulloblastoma development.ResultsMutagenesis significantly increased medulloblastoma frequency and identified 17 candidate cancer genes, including orthologs of genes somatically mutated (PTEN, CREBBP) or associated with poor outcome (PTEN, MYT1L) in the human disease. Strikingly, these candidate genes were enriched for transcription factors (p= 2x10-5), the majority of which (6/7; Crebbp, Myt1L, Nfia, Nfib, Tead1 and Tgif2) were linked within a single regulatory network enriched for genes associated with a differentiated neuronal phenotype. Furthermore, activity of this network varied significantly between the human subgroups, was associated with metastatic disease, and predicted poor survival specifically within the SHH subgroup of tumours. Igf2, previously implicated in medulloblastoma, was the most differentially expressed gene in murine tumours with network perturbation, and network activity in both mouse and human tumours was characterised by enrichment for multiple gene-sets indicating increased cell proliferation, IGF signalling, MYC target upregulation, and decreased neuronal differentiation.ConclusionsCollectively, our data support a model of medulloblastoma development in SB-mutagenised Ptch+/- mice which involves disruption of a novel transcription factor network leading to Igf2 upregulation, proliferation of GNPs, and tumour formation. Moreover, our results identify rational therapeutic targets for SHH subgroup tumours, alongside prognostic biomarkers for the identification of poor-risk SHH patients.

Regions syntenic to human 17q are gained in mouse and rat neuroblastoma

Gain of chromosome arm 17q is the most frequent chromosomal change in human neuroblastoma and is a powerful predictor of adverse outcome of disease. This suggests that the region of gain includes a gene or genes critical for tumor pathogenesis. Analyses of breakpoint positions have revealed that the shortest region of gain (SRG) extends from MPO (17q23.1) to 17qter. Because this encompasses >300 genes, it precludes the identification of candidate genes from human breakpoint data alone. However, mouse chromosome 11, which is syntenic to human chromosome 17, is gained in up to 30% of neuroblastoma tumors developed in a murine MYCN transgenic model of this disease. To confirm that this key genetic change indicates the involvement of a molecular pathway conserved between mouse and man and is not occurring coincidentally in the transgenic model, we used fluorescence in situ hybridization to analyze sporadic cases of both mouse and rat neuroblastoma. Our results confirmed the presence of chromosome 11 gain in all three of the mouse cell lines we analyzed, with the SRG extending from Stat5b (101.6 Mb) to tel. In addition, the rat neuroblastoma cell line harbors an extra copy of distal chromosome 10, extending from 92.8 to 109.3 Mb, which is also syntenic to human 17q. Comparison of the regions gained in all three species has excluded 4.2 Mb from the previously defined region of 17q gain in humans as a likely location of the candidate gene or genes, and strongly suggests that the molecular etiology of neuroblastoma is similar in all three species.

MYCN amplification and 17q in neuroblastoma: Evidence for structural association

MYCN oncogene amplification in neuroblastoma is statistically associated with gain of chromosome segment 17q21–qter. In neuroblastoma cell lines and primary tumors with MYCN amplification in the form of homogeneously staining regions (hsrs), juxtaposition of chromosome 17 material with MYCN sequences has occasionally been reported, raising the possibility of a physical affinity between MYCN and chromosome arm 17q. We used FISH to test for association between chromosome 17 segments and MYCN in eight neuroblastoma cell lines and two neuroblastoma primary tumors known to include hsrs. Evidence of an association was found in the chromosomes of both primary tumors; in one, a MYCN hsr was inserted into a structurally abnormal chromosome 17, in the other, an hsr in 16p was shown to be flanked by 17 material. In cell line NCG, hsrs in 4q and 16p were flanked by 17q material. These observations confirm the juxtaposition of 17q material with MYCN sequences in some neuroblastomas, and imply that there may be a physical or functional relationship between these two features in MYCN amplified neuroblastoma.