Macrophage-Derived IL1ß and TNFα Regulate Arginine Metabolism in Neuroblastoma.

Neuroblastoma is the most common childhood solid tumor, yet the prognosis for high-risk disease remains poor. We demonstrate here that arginase 2 (ARG2) drives neuroblastoma cell proliferation via regulation of arginine metabolism. Targeting arginine metabolism, either by blocking cationic amino acid transporter 1 (CAT-1)-dependent arginine uptake in vitro or therapeutic depletion of arginine by pegylated recombinant arginase BCT-100, significantly delayed tumor development and prolonged murine survival. Tumor cells polarized infiltrating monocytes to an M1-macrophage phenotype, which released IL1ß and TNFα in a RAC-alpha serine/threonine-protein kinase (AKT)-dependent manner. IL1ß and TNFα established a feedback loop to upregulate ARG2 expression via p38 and extracellular regulated kinases 1/2 (ERK1/2) signaling in neuroblastoma and neural crest-derived cells. Proteomic analysis revealed that enrichment of IL1ß and TNFα in stage IV human tumor microenvironments was associated with a worse prognosis. These data thus describe an immune-metabolic regulatory loop between tumor cells and infiltrating myeloid cells regulating ARG2, which can be clinically exploited. SIGNIFICANCE: These findings illustrate that cross-talk between myeloid cells and tumor cells creates a metabolic regulatory loop that promotes neuroblastoma progression.

Metabolic profiling of the three neural derived embryonal pediatric tumors retinoblastoma, neuroblastoma and medulloblastoma, identifies distinct metabolic profiles.

The rare pediatric embryonal tumors retinoblastoma, medulloblastoma and neuroblastoma derive from neuroectodermal tissue and share similar histopathological features despite different anatomical locations and diverse clinical outcomes. As metabolism can reflect genetic and histological features, we investigated whether the metabolism of embryonal tumors reflects their similar histology, shared developmental and neural origins, or tumor location. We undertook metabolic profiling on 50 retinoblastoma, 39 medulloblastoma and 70 neuroblastoma using high resolution magic angle spinning magnetic resonance spectroscopy (1H-MRS). Mean metabolite concentrations identified several metabolites that were significantly different between the tumor groups including taurine, hypotaurine, glutamate, glutamine, GABA, phosphocholine, N-acetylaspartate, creatine, glycine and myoinositol, p < 0.0017. Unsupervised multivariate analysis found that each tumor group clustered separately, with a unique metabolic profile, influenced by their underlying clinical diversity. Taurine was notably high in all tumors consistent with prior evidence from embryonal tumors. Retinoblastoma and medulloblastoma were more metabolically similar, sharing features associated with the central nervous system (CNS). Neuroblastoma had features consistent with neural tissue, but also contained significantly higher myoinositol and altered glutamate-glutamine ratio, suggestive of differences in the underlying metabolism of embryonal tumors located outside of the CNS. Despite the histological similarities and shared neural metabolic features, we show that individual neuroectodermal derived embryonal tumors can be distinguished by tissue metabolic profile. Pathway analysis suggests the alanine-aspartate-glutamate and taurine-hypotaurine metabolic pathways may be the most pertinent pathways to investigate for novel therapeutic strategies. This work strengthens our understanding of the biology and metabolic pathways underlying neuroectodermal derived embryonal tumors of childhood.

Genome-wide DNA methylation analysis identifies MEGF10 as a novel epigenetically repressed candidate tumor suppressor gene in neuroblastoma.

Neuroblastoma is a childhood cancer in which many children still have poor outcomes, emphasising the need to better understand its pathogenesis. Despite recent genome-wide mutation analyses, many primary neuroblastomas do not contain recognizable driver mutations, implicating alternate molecular pathologies such as epigenetic alterations. To discover genes that become epigenetically deregulated during neuroblastoma tumorigenesis, we took the novel approach of comparing neuroblastomas to neural crest precursor cells, using genome-wide DNA methylation analysis. We identified 93 genes that were significantly differentially methylated of which 26 (28%) were hypermethylated and 67 (72%) were hypomethylated. Concentrating on hypermethylated genes to identify candidate tumor suppressor loci, we found the cell engulfment and adhesion factor gene MEGF10 to be epigenetically repressed by DNA hypermethylation or by H3K27/K9 methylation in neuroblastoma cell lines. MEGF10 showed significantly down-regulated expression in neuroblastoma tumor samples; furthermore patients with the lowest-expressing tumors had reduced relapse-free survival. Our functional studies showed that knock-down of MEGF10 expression in neuroblastoma cell lines promoted cell growth, consistent with MEGF10 acting as a clinically relevant, epigenetically deregulated neuroblastoma tumor suppressor gene. © 2016 The Authors. Molecular Carcinogenesis Published by Wiley Periodicals, Inc.

Metabolite profiling in retinoblastoma identifies novel clinicopathological subgroups.

BACKGROUND: Tumour classification, based on histopathology or molecular pathology, is of value to predict tumour behaviour and to select appropriate treatment. In retinoblastoma, pathology information is not available at diagnosis and only exists for enucleated tumours. Alternative methods of tumour classification, using noninvasive techniques such as magnetic resonance spectroscopy, are urgently required to guide treatment decisions at the time of diagnosis. METHODS: High-resolution magic-angle spinning magnetic resonance spectroscopy (HR-MAS MRS) was undertaken on enucleated retinoblastomas. Principal component analysis and cluster analysis of the HR-MAS MRS data was used to identify tumour subgroups. Individual metabolite concentrations were determined and were correlated with histopathological risk factors for each group. RESULTS: Multivariate analysis identified three metabolic subgroups of retinoblastoma, with the most discriminatory metabolites being taurine, hypotaurine, total-choline and creatine. Metabolite concentrations correlated with specific histopathological features: taurine was correlated with differentiation, total-choline and phosphocholine with retrolaminar optic nerve invasion, and total lipids with necrosis. CONCLUSIONS: We have demonstrated that a metabolite-based classification of retinoblastoma can be obtained using ex vivo magnetic resonance spectroscopy, and that the subgroups identified correlate with histopathological features. This result justifies future studies to validate the clinical relevance of these subgroups and highlights the potential of in vivo MRS as a noninvasive diagnostic tool for retinoblastoma patient stratification.

Neuroblastoma Arginase Activity Creates an Immunosuppressive Microenvironment That Impairs Autologous and Engineered Immunity.

Neuroblastoma is the most common extracranial solid tumor of childhood, and survival remains poor for patients with advanced disease. Novel immune therapies are currently in development, but clinical outcomes have not matched preclinical results. Here, we describe key mechanisms in which neuroblastoma inhibits the immune response. We show that murine and human neuroblastoma tumor cells suppress T-cell proliferation through increased arginase activity. Arginase II is the predominant isoform expressed and creates an arginine-deplete local and systemic microenvironment. Neuroblastoma arginase activity results in inhibition of myeloid cell activation and suppression of bone marrow CD34(+) progenitor proliferation. Finally, we demonstrate that the arginase activity of neuroblastoma impairs NY-ESO-1-specific T-cell receptor and GD2-specific chimeric antigen receptor-engineered T-cell proliferation and cytotoxicity. High arginase II expression correlates with poor survival for patients with neuroblastoma. The results support the hypothesis that neuroblastoma creates an arginase-dependent immunosuppressive microenvironment in both the tumor and blood that leads to impaired immunosurveillance and suboptimal efficacy of immunotherapeutic approaches.

Increased unsaturation of lipids in cytoplasmic lipid droplets in DAOY cancer cells in response to cisplatin treatment.

Increases in 1H nuclear magnetic resonance spectroscopy (NMR) visible lipids are a well-documented sign of treatment response in cancers. Lipids in cytoplasmic lipid droplets (LDs) are the main contributors to the NMR lipid signals. Two human primitive neuroectodermal tumour cell lines with different sensitivities to cisplatin treatment were studied. Increases in NMR visible saturated and unsaturated lipids in cisplatin treated DAOY cells were associated with the accumulation of LDs prior to DNA fragmentation due to apoptosis. An increase in unsaturated fatty acids (UFAs) was detected in isolated LDs from DAOY cells, in contrast to a slight decrease in UFAs in lipid extracts from whole cells. Oleic acid and linoleic acid were identified as the accumulating UFAs in LDs by heteronuclear single quantum coherence spectroscopy (HSQC). 1H NMR lipids in non-responding PFSK-1 cells were unchanged by exposure to 10 µM cisplatin. These findings support the potential of NMR detectable UFAs to serve as a non-invasive marker of tumour cell response to treatment.

The size of cytoplasmic lipid droplets varies between tumour cell lines of the nervous system: a 1H NMR spectroscopy study.

OBJECT: Cytoplasmic lipid droplets (LDs) are dynamic cellular organelles; their accumulation is associated with several cellular processes, such as cell proliferation, apoptosis and necrosis. (1)H Nuclear Magnetic Resonance (NMR) spectroscopy detects resonances from lipids present in cytoplasmic (LDs); an understanding of the relationship between LD characteristics and NMR lipid signals is important. MATERIALS AND METHODS: In this study, five nervous system cancer cell lines were investigated. Nile red staining was used to measure the diameter of LDs. High-resolution magic angle spinning NMR (HR-MAS) was performed on harvested cell pellets to quantify the patterns of lipid signals. RESULTS: LDs were present in all five cell lines with different morphology. An average LD diameter of approximately 0.2 µm was found in all cell types. Diameter of the largest LDs varied across the cell lines. The intensity of NMR lipid signals varied greatly between cell types, and a good correlation was found between total volume of LDs and the proton NMR lipid signal intensity at 0.9 and 1.3 ppm. CONCLUSION: The correlation implied that little NMR signal is detected from LDs of diameters less than approximately 0.34 µm, most likely due to restriction of rotational motion of the lipids.

The lipid composition of isolated cytoplasmic lipid droplets from a human cancer cell line, BE(2)M17.

(1)H nuclear magnetic resonance spectroscopy (NMR) resonances from lipids in tumours are associated with tumour grade and treatment response. The origin of these NMR signals is mainly considered to be cytoplasmic lipid droplets (LDs). Techniques exist for isolating LDs but little is known about their composition and its relationship to NMR signals. In this work, density-gradient ultracentrifugation was performed on homogenised human cancer cells to isolate LDs. (1)H NMR was performed on whole cells, isolated LDs and their extracts. Heteronuclear single quantum coherence spectroscopy (HSQC) and liquid chromatography mass spectroscopy (LC-MS) were performed on lipid extracts of LDs. Staining and microscopy were used to characterize isolated LDs. An excellent agreement in chemical shift and relative signal intensity was observed between lipid resonances in cells and isolated LD spectra supporting that NMR-visible lipids originate primarily from LDs. Isolated LDs showed high concentrations of unsaturated lipids, a oleic-to-linoleic acid ratio greater than two and a cholesteryl ester (ChE)-to-cholesterol (Ch) ratio close to unity. These ratios were several-fold greater than respective ratios in whole cells, demonstrating isolation is important to characterize LD composition. LDs contain a specific group of lipid species that are likely to contribute to the (1)H NMR spectrum of cells.

Lipid biomarkers of glioma cell growth arrest and cell death detected by 1 H magic angle spinning MRS.

Biomarkers of early response to treatment have the potential to improve cancer therapy by allowing treatment to be tailored to the individual. Alterations in lipids detected by in vivo MRS have been suggested as noninvasive biomarkers of cell stress and early indicators of cell death. An improved understanding of the relationship between MRS lipids and cell stress in vitro would aid in the translation of this technique into clinical use. Rat BT4C glioma cells were treated with 50 µ m cis-dichlorodiammineplatinum II (cisplatin), a commonly used chemotherapeutic agent, and harvested at several time points up to 72 h. High-resolution magic angle spinning (1) H MRS of cells was then performed on a 600-MHz NMR spectrometer. The metabolites were quantified using a time domain fitting method, TARQUIN. Increases were detected in saturated and polyunsaturated fatty acid resonances early during the exposure to cisplatin. The fatty acid CH(2) /CH(3) ratio was unaltered by treatment after allowing for contributions of macromolecules. Polyunsaturated fatty acids increased on treatment, with the group -CH=CH-CH(2) -CH=CH- accounting for all the unsaturated fatty acid signals. Transmission electron microscopy, in addition to Nile red and 4',6-diamino-2-phenylindole co-staining, revealed that the lipid increase was associated with cytoplasmic neutral lipid droplets. Small numbers of apoptotic and necrotic cells were detected by trypan blue, annexin V-fluorescein isothiocyanate-labelled flow cytometry and DNA laddering after up to 48 h of cisplatin exposure. Propidium iodide flow cytometry revealed that cells accumulated in the G1 stage of the cell growth cycle. In conclusion, an increase in the size of the lipid droplets is detected in morphologically viable cells during cisplatin exposure. (1) H MRS can detect lipid alterations during cell cycle arrest and progression of cell death, and has the potential to provide a noninvasive biomarker of treatment efficacy in vivo.

In vitro metabonomic study detects increases in UDP-GlcNAc and UDP-GalNAc, as early phase markers of cisplatin treatment response in brain tumor cells.

O-linked ß-N-acetylglucosamine glycosylation (O-GlcNAcylation) is important in a number of biological processes and diseases including transcription, cell stress, diabetes, and neurodegeneration and may be a marker of tumor metastasis. Uridine diphospho-N-acetylglucosamine (UDP-GlcNAc), the donor molecule in O-GlcNAcylation, can be detected by (1)H nuclear magnetic resonance spectroscopy ((1)H NMR), giving the potential to measure its level noninvasively, providing a novel biomarker of prognosis and treatment monitoring. In this in vitro metabonomic study, four brain cancer cell lines were exposed to cisplatin and studied for metabolic responses using (1)H NMR. The Alamar blue assay and DAPI staining were used to assess cell sensitivity to cisplatin treatment and to confirm cell death. It is shown that in the cisplatin responding cells, UDP-GlcNAc and uridine diphospho-N-acetylgalactosamine (UDP-GalNAc), in parallel with (1)H NMR detected lipids, increased with cisplatin exposure before or at the onset of the microscopic signs of evolving cell death. The changes in UDP-GlcNAc and UDP-GalNAc were not detected in the nonresponders. These glycosylated UDP compounds, the key substrates for glycosylation of proteins and lipids, are commonly implicated in cancer proliferation and malignant transformation. However, the present study mechanistically links UDP-GlcNAc and UDP-GalNAc to cancer cell death following chemotherapeutic treatment.

1H magnetic resonance spectroscopy metabolites as biomarkers for cell cycle arrest and cell death in rat glioma cells.

BACKGROUND: Improved non-invasive imaging biomarkers of treatment response contribute to optimising cancer management and metabolites detected by proton magnetic resonance spectroscopy ((1)H MRS) show promise in this area. Understanding (1)H MRS changes occurring in cells during cell stress and cell death in vitro should aid the selection of pertinent biomarkers for clinical use. METHODS: BT4C glioma cells in culture were exposed to either 50 µM cis-dichlorodiammineplatinum II (cisplatin) or starvation by culture in phosphate buffered saline. High resolution magic angle spinning (1)H MRS was performed on cells using a Varian 600 MHz nanoprobe and metabolites were quantified by a time domain fitting method. Cell viability was assessed by trypan blue, H&E, 4',6-diamino-2-phenylindole (DAPI), DNA laddering and annexin V-FITC labelled flow cytometry; propidium iodide flow cytometry was used to assess the cell cycle phase. RESULTS: With cisplatin exposure, cells initially accumulated in the G1 stage of the cell cycle with low numbers of apoptotic and necrotic cells and this was associated with decreases in phosphocholine, succinate, alanine, taurine, glycine and glutamate and increases in lactate and glycerophosphocholine (GPC). Starvation, leading to necrotic cell death within 6-18 h, caused decreases in succinate, alanine, glycine, and glutamate and increases in GPC. Principal component analysis revealed two patterns of metabolite changes, one common to both types of cell stress and another specific for necrosis secondary to cell starvation. CONCLUSIONS: (1)H MRS reveals alterations in multiple metabolites during cell cycle arrest and cell death which may provide early biomarker profiles of treatment efficacy in vivo.

A new familial cancer syndrome including predisposition to Wilms tumor and neuroblastoma.

Wilms tumor and neuroblastoma are childhood tumors of the kidney and undifferentiated neural crest cells, respectively. Both disorders are primarily sporadic, but familial Wilms tumor pedigrees and familial neuroblastoma pedigrees are each well recognized and account for approximately 1-3% of each tumor type. Families with Wilms tumor and neuroblastoma in the same, or related individuals, have not been reported. Here, we present nine families with two or more individuals with Wilms tumor and/or neuroblastoma. The affected individuals were otherwise well, without syndromic features. Although this co-occurrence might be due to chance in some families, the coexistence of two rare embryonal tumors in related individuals of multiple families suggests an underlying genetic susceptibility to both tumors. We undertook mutational analysis of the genes known to predispose to non-syndromic familial Wilms tumor (WT1) or neuroblastoma (PHOX2B, ALK) which excluded these as the underlying predisposition genes in the nine families. We also excluded epigenetic and copy-number abnormalities at 11p15 which are known to predispose to embryonal tumors including Wilms tumor and neuroblastoma. Overall, these data suggest that families with both Wilms tumor and neuroblastoma represent a previously unrecognized familial cancer syndrome in which the underlying predisposition gene(s) remain to be determined.

Common variations in BARD1 influence susceptibility to high-risk neuroblastoma.

We conducted a SNP-based genome-wide association study (GWAS) focused on the high-risk subset of neuroblastoma. As our previous unbiased GWAS showed strong association of common 6p22 SNP alleles with aggressive neuroblastoma, we restricted our analysis here to 397 high-risk cases compared to 2,043 controls. We detected new significant association of six SNPs at 2q35 within the BARD1 locus (P(allelic) = 2.35 x 10(-9)-2.25 x 10(-8)). We confirmed each SNP association in a second series of 189 high-risk cases and 1,178 controls (P(allelic) = 7.90 x 10(-7)-2.77 x 10(-4)). We also tested the two most significant SNPs (rs6435862, rs3768716) in two additional independent high-risk neuroblastoma case series, yielding combined allelic odds ratios of 1.68 each (P = 8.65 x 10(-18) and 2.74 x 10(-16), respectively). We also found significant association with known BARD1 nonsynonymous SNPs. These data show that common variation in BARD1 contributes to the etiology of the aggressive and most clinically relevant subset of human neuroblastoma.

High resolution magic angle spinning 1H NMR of childhood brain and nervous system tumours.

BACKGROUND: Brain and nervous system tumours are the most common solid cancers in children. Molecular characterisation of these tumours is important for providing novel biomarkers of disease and identifying molecular pathways which may provide putative targets for new therapies. 1H magic angle spinning NMR spectroscopy (1H HR-MAS) is a powerful tool for determining metabolite profiles from small pieces of intact tissue and could potentially provide important molecular information. METHODS: Forty tissue samples from 29 children with glial and primitive neuro-ectodermal tumours were analysed using HR-MAS (600 MHz Varian gHX nanoprobe). Tumour spectra were fitted to a library of individual metabolite spectra to provide metabolite values. These values were then used in a two tailed t-test and multi-variate analysis employing a principal component analysis and a linear discriminant analysis. Classification accuracy was estimated using a leave-one-out analysis and B632+ bootstrapping. RESULTS: Glial tumours had significantly (two tailed t-test p < 0.05) higher creatine and glutamine and lower taurine, phosphoethanolamine, phosphorylcholine and choline compared with primitive neuro-ectodermal tumours. Classification accuracy was 90%. Medulloblastomas (n = 9) had significantly (two tailed t-test p < 0.05) higher creatine, glutamine, phosphorylcholine, glycine and scyllo-inositol than neuroblastomas (n = 7), classification accuracy was 94%. Supratentorial primitive neuro-ectodermal tumours had metabolite profiles in keeping with other primitive neuro-ectodermal tumours whilst ependymomas (n = 2) had metabolite profiles intermediate between pilocytic astrocytomas (n = 10) and primitive neuro-ectodermal tumours. CONCLUSION: HR-MAS identified key differences in the metabolite profiles of childhood brain and nervous system improving the molecular characterisation of these tumours. Further investigation of the underlying molecular pathways is required to assess their potential as targets for new agents.

Stratification of pediatric ALL by in vitro cellular responses to DNA double-strand breaks provides insight into the molecular mechanisms underlying clinical response.

The molecular basis of different outcomes in pediatric acute lymphoblastic leukemia (ALL) remains poorly understood. We addressed the clinical significance and mechanisms behind in vitro cellular responses to ionizing radiation (IR)-induced DNA double-strand breaks in 74 pediatric patients with ALL. We found an apoptosis-resistant response in 36% of patients characterized by failure to cleave caspase-3, -7, -9, and PARP1 by 24 hours after IR and an apoptosis-sensitive response with the cleavage of the same substrates in the remaining 64% of leukemias. Resistance to IR in vitro was associated with poor early blast clearance at day 7 or 15 and persistent minimal residual disease (MRD) at day 28 of induction treatment. Global gene expression profiling revealed abnormal up-regulation of multiple prosurvival pathways in response to IR in apoptosis-resistant leukemias and differential posttranscriptional activation of the PI3-Akt pathway was observed in representative resistant cases. Importantly, pharmacologic inhibition of selected prosurvival pathways sensitized apoptosis-resistant ALL cells to IR in vitro. We suggest that abnormal prosurvival responses to DNA damage provide one of the mechanisms of primary resistance in ALL, and that they should be considered as therapeutic targets in children with aggressive disease.

Chromosome 6p22 locus associated with clinically aggressive neuroblastoma.

BACKGROUND: Neuroblastoma is a malignant condition of the developing sympathetic nervous system that most commonly affects young children and is often lethal. Its cause is not known. METHODS: We performed a genomewide association study by first genotyping blood DNA samples from 1032 patients with neuroblastoma and 2043 control subjects of European descent using the Illumina HumanHap550 BeadChip. Samples from three independent groups of patients with neuroblastoma (a total of 720 patients) and 2128 control subjects were then genotyped to replicate significant associations. RESULTS: We observed a significant association between neuroblastoma and the common minor alleles of three consecutive single-nucleotide polymorphisms (SNPs) at chromosome band 6p22 and containing the predicted genes FLJ22536 and FLJ44180 (P=1.71x10(-9) to 7.01x10(-10); allelic odds ratio, 1.39 to 1.40). Homozygosity for the at-risk G allele of the most significantly associated SNP, rs6939340, resulted in an increased likelihood of the development of neuroblastoma (odds ratio, 1.97; 95% confidence interval, 1.58 to 2.45). Subsequent genotyping of the three 6p22 SNPs in three independent case series confirmed our observation of an association (P=9.33x10(-15) at rs6939340 for joint analysis). Patients with neuroblastoma who were homozygous for the risk alleles at 6p22 were more likely to have metastatic (stage 4) disease (P=0.02), amplification of the MYCN oncogene in the tumor cells (P=0.006), and disease relapse (P=0.01). CONCLUSIONS: A common genetic variation at chromosome band 6p22 is associated with susceptibility to neuroblastoma.

1H MRS identifies specific metabolite profiles associated with MYCN-amplified and non-amplified tumour subtypes of neuroblastoma cell lines.

Neuroblastoma is the most common extracranial solid malignancy in children. The disease possesses a broad range of clinical phenotypes with widely varying prognoses. Numerous studies have sought to identify the associated genetic abnormalities in the tumour, resulting in the identification of useful prognostic markers. In particular, the presence of multiple copies of the MYCN oncogene (referred to as MYCN amplification) has been found to confer a poor prognosis. However, the molecular pathways involved are as yet poorly defined. Metabolite profiles generated by in vitro (1)H MRS provide a means of investigating the downstream metabolic consequences of genetic alterations and can identify potential targets for new agents. Thirteen neuroblastoma cell lines possessing multiple genetic alterations were investigated; seven were MYCN amplified and six MYCN non-amplified. In vitro magic angle spinning (1)H MRS was performed on cell suspensions, and the spectra analysed to obtain metabolite concentration ratios relative to total choline (tCho). A principal component analysis using these concentration ratios showed that MYCN-amplified and non-amplified cell lines form separate classes according to their metabolite profiles. Phosphocholine/tCho and taurine/tCho were found to be significantly raised (p < 0.05) and glycerophosphocholine/tCho significantly reduced (p < 0.05) in the MYCN-amplified compared with the MYCN non-amplified cell lines (two-tailed t test). (1)H MRS of the SH-EP1 cell line and an isogenic cell line transfected with the MYCN oncogene also showed that MYCN oncogene over-expression causes alterations in phosphocholine, glycerophosphocholine and taurine concentrations. Molecular pathways of choline and taurine metabolism are potential targets for new agents tailored to MYCN-amplified neuroblastoma.

Multilocus loss of heterozygosity allelotypes identify a genetic pathway associated with progression from low to high stage disease in neuroblastoma.

Neuroblastoma is a heterogeneous tumour with a variety of clinical phenotypes, ranging from a localised tumour with excellent outcome (stage 1) to a metastatic, usually fatal malignancy (stage 4). In order to investigate the genetic relationship between these tumour subtypes, a loss of heterozygosity (LOH) analysis was carried out. Composite LOH allelotypes incorporating data from 96 loci on 5 chromosomes (1p, 3p, 4p, 11q, 14q), were constructed for 62 neuroblastomas. Neuroblastomas with similar allelotypes were clustered into groups and allelotype patterns correlated with clinical features. Three distinct genetic subgroups of neuroblastoma were observed. The largest group (50% of tumours) was characterised by specific allelotype patterns indicative of a stepwise accumulation of genetic alterations (11q LOH-->1p, 4p, and/or 14q LOH-->3p LOH), associated with progression from low to high stage disease. These tumours are distinct from MYCN amplified neuroblastomas which have a more rapid and aggressive disease course, and also a proportion of low stage tumours, often ganglioneuromas or ganglioneuroblastomas, with restricted growth potential.

PHOX2B analysis in non-syndromic neuroblastoma cases shows novel mutations and genotype-phenotype associations.

Neuroblastoma (NB) is an embryonal tumor originating from neural crest cells and is one of the most common solid tumors of childhood. Recently, constitutional mutations in PHOX2B have been shown to confer an increased risk of NB. To date, mutations predisposing to neural crest tumors have been reported in 20 individuals from 16 families. These families included additional clinical features such as Hirschsprung (HSCR) disease or congenital central hypoventilation syndrome, either in the index case or relatives. The contribution of PHOX2B mutations to NB cases without additional features is unclear. To address this we sequenced PHOX2B in constitutional DNA from 86 individuals with non-syndromic NB (4 cases had a family history of NB). We identified two mutations, 600delC, a frameshift mutation in an individual with isolated, unifocal NB and G197D, a missense mutation that was present in a family with multiple individuals with NB but no evidence of autonomic dysfunction. These data demonstrate that PHOX2B mutations are a rare cause of non-syndromic NB. The mutations we identified are outside the domains typically mutated in PHOX2B syndromes. This provides further evidence that the underlying PHOX2B mutational mechanism influences tumor risk and suggests that the position of missense mutations may influence the resulting phenotype.

Neuroblastoma - a developmental perspective.

Genetic investigation of neuroblastoma has provided few clues to account for the variability in clinical phenotype which is such a characteristic feature of this tumour. Indeed, efforts to identify the primary genetic event(s) responsible for tumour development have been overwhelmed by the number and range of different genetic abnormalities observed, particularly in the more aggressive neuroblastoma subtypes. Since neuroblastoma is a consequence of aberrant development of the sympathetic nervous system (SNS), investigation of the genetic components known to be involved in the control of SNS developmental, may provide the key to understanding tumour behaviour. The neurotrophins and the glial family ligands both play very significant roles in different stages of SNS development and merit more detailed investigation as to how they might influence neuroblastoma tumorigenesis.