Loss of heterozygosity for chromosome 14q in neuroblastoma

Chromosome 1p status in neuroblastoma correlates with higher expression levels of miRNAs targeting neuronal differentiation pathway

Neuroblastoma (NB) is characterized by acquired segmental and numerical chromosome aberrations. Although deletions of distal 1p and 11q are frequent alterations, no candidate tumor suppressor gene residing in these chromosomal sites could be identified so far. In the present study, we detected the genomic imbalances of six neuroblastoma cell lines using the multiplex ligation-dependent probe amplification (MLPA) technique and the microRNA (miRNA) expression profiles of the cell lines by a microarray study. According to MLPA results, we aimed to assess the miRNA expression profiles of the cell lines harboring 11q and 1p deletions. The cell lines with 1p deletions revealed statistically significant higher levels of expression for 29 miRNAs in contrast to the cell lines without 1p deletion in microarray study. We also performed GO enrichment analysis for predicted targets of the differentially expressed miRNAs. According to GO enrichment analysis, miRNAs that showed the high change in expression was associated with neuronal differentiation. We showed that hsa-miR-494, hsa-miR-495, and hsa-miR-543 target most of mRNAs in neuronal differentiation pathway. Although limited to the cell lines, our results highly suggest that NBs with different segmental chromosome abnormalities may have different dysregulated miRNA expression signatures that target the genes involved in neuronal differentiation.

Nanomedicines and cell-based therapies for embryonal tumors of the nervous system

Embryonal tumors of the nervous system are neoplasms predominantly affecting the pediatric population. Among the most common and aggressive ones are neuroblastoma (NB) and medulloblastoma (MB). NB is a sympathetic nervous system tumor, which is the most frequent extracranial solid pediatric cancer, usually detected in children under two. MB originates in the cerebellum and is one of the most lethal brain tumors in early childhood. Their tumorigenesis presents some similarities and both tumors often have treatment resistances and poor prognosis. High-risk (HR) patients require high dose chemotherapy cocktails associated with acute and long-term toxicities. Nanomedicine and cell therapy arise as potential solutions to improve the prognosis and quality of life of children suffering from these tumors. Indeed, nanomedicines have been demonstrated to efficiently reduce drug toxicity and improve drug efficacy. Moreover, these systems have been extensively studied in cancer research over the last few decades and an increasing number of anticancer nanocarriers for adult cancer treatment has reached the clinic. Among cell-based strategies, the clinically most advanced approach is chimeric-antigen receptor (CAR) T therapy for both pathologies, which is currently under investigation in phase I/II clinical trials. However, pediatric drug research is especially hampered due not only to ethical issues but also to the lack of efficient pre-clinical models and the inadequate design of clinical trials. This review provides an update on progress in the treatment of the main embryonal tumors of the nervous system using nanotechnology and cell-based therapies and discusses key issues behind the gap between preclinical studies and clinical trials in this specific area. Some directions to improve their translation into clinical practice and foster their development are also provided.

miR-99b-5p, miR-380-3p, and miR-485-3p are novel chemosensitizing miRNAs in high-risk neuroblastoma

Neuroblastoma is a deadly childhood cancer arising in the developing sympathetic nervous system. High-risk patients are currently treated with intensive chemotherapy, which is curative in only 50% of children and leaves some surviving patients with life-long side effects. microRNAs (miRNAs) are critical regulators of neural crest development and are deregulated during neuroblastoma tumorigenesis, making miRNA-based drugs an attractive therapeutic avenue. A functional screen of >1,200 miRNA mimics was conducted in neuroblastoma cell lines to discover miRNAs that sensitized cells to low doses (30% inhibitory concentration [IC30]) of doxorubicin and vincristine chemotherapy used in the treatment of the disease. Three miRNAs, miR-99b-5p, miR-380-3p, and miR-485-3p, had potent chemosensitizing activity with doxorubicin in multiple models of high-risk neuroblastoma. These miRNAs underwent genomic loss in a subset of neuroblastoma patients, and low expression predicted poor survival outcome. In vitro functional assays revealed each of these miRNAs enhanced the anti-proliferative and pro-apoptotic effects of doxorubicin. We used RNA sequencing (RNA-seq) to show that miR-99b-5p represses neuroblastoma dependency genes LIN28B and PHOX2B both in vitro and in patient-derived xenograft (PDX) tumors. Luciferase reporter assays demonstrate that PHOX2B is a direct target of miR-99b-5p. We anticipate that restoring the function of the tumor-suppressive miRNAs discovered here may be a valuable therapeutic strategy for the treatment of neuroblastoma patients.

Gene utility recapitulates chromosomal aberrancies in advanced stage neuroblastoma

Neuroblastoma (NB) is the most common extracranial solid tumor in children. Although only a few recurrent somatic mutations have been identified, chromosomal abnormalities, including the loss of heterozygosity (LOH) at the chromosome 1p and gains of chromosome 17q, are often seen in the high-risk cases. The biological basis and evolutionary forces that drive such genetic abnormalities remain enigmatic. Here, we conceptualize the Gene Utility Model (GUM) that seeks to identify genes driving biological signaling via their collective gene utilities and apply it to understand the impact of those differentially utilized genes on constraining the evolution of NB karyotypes. By employing a computational process-guided flow algorithm to model gene utility in protein–protein networks that built based on transcriptomic data, we conducted several pairwise comparative analyses to uncover genes with differential utilities in stage 4 NBs with distinct classification. We then constructed a utility karyotype by mapping these differentially utilized genes to their respective chromosomal loci. Intriguingly, hotspots of the utility karyotype, to certain extent, can consistently recapitulate the major chromosomal abnormalities of NBs and also provides clues to yet identified predisposition sites. Hence, our study not only provides a new look, from a gene utility perspective, into the known chromosomal abnormalities detected by integrative genomic sequencing efforts, but also offers new insights into the etiology of NB and provides a framework to facilitate the identification of novel therapeutic targets for this devastating childhood cancer.

Multiple Endocrine Tumors Associated with Germline MAX Mutations: Multiple Endocrine Neoplasia Type 5?

CONTEXT

Pathogenic germline MAX variants are associated with pheochromocytoma and paraganglioma (PPGL), pituitary neuroendocrine tumors and, possibly, other endocrine and nonendocrine tumors.

OBJECTIVE

To report 2 families with germline MAX variants, pheochromocytomas (PCs) and multiple other tumors.

METHODS

Clinical, genetic, immunohistochemical, and functional studies at University hospitals in Australia on 2 families with germline MAX variants undergoing usual clinical care. The main outcome measures were phenotyping; germline and tumor sequencing; immunohistochemistry of PC and other tumors; functional studies of MAX variants.

RESULTS

Family A has multiple individuals with PC (including bilateral and metastatic disease) and 2 children (to date, without PC) with neuroendocrine tumors (paravertebral ganglioneuroma and abdominal neuroblastoma, respectively). One individual has acromegaly; immunohistochemistry of PC tissue showed positive growth hormone-releasing hormone staining. Another individual with previously resected PCs has pituitary enlargement and elevated insulin-like growth factor (IGF-1). A germline MAX variant (c.200C>A, p.Ala67Asp) was identified in all individuals with PC and both children, with loss of heterozygosity in PC tissue. Immunohistochemistry showed loss of MAX staining in PCs and other neural crest tumors. In vitro studies confirmed the variant as loss of function. In Family B, the proband has bilateral and metastatic PC, prolactin-producing pituitary tumor, multigland parathyroid adenomas, chondrosarcoma, and multifocal pulmonary adenocarcinomas. A truncating germline MAX variant (c.22G>T, p.Glu8*) was identified.

CONCLUSION

Germline MAX mutations are associated with PCs, ganglioneuromas, neuroblastomas, pituitary neuroendocrine tumors, and, possibly, parathyroid adenomas, as well as nonendocrine tumors of chondrosarcoma and lung adenocarcinoma, suggesting MAX is a novel multiple endocrine neoplasia gene.

Typical numerical alterations in genome identified by array CGH analysis in neuroblastoma tumors

<abstract><sec> <title>Introduction</title> <p>The clinical variability in the course of neuroblastoma (NB) is closely linked to diverse genetic changes acquired by tumor cells. Rapid NB progression is associated with oncogene MYCN amplification (MNA) and segmental chromosomal aberrations (SCA). Alternatively, numerical chromosomal alterations (NCA) have positive impact on treatment. So far, no studies have been undertaken to identify NCA that may group NB patients. Therefore, the aim of the study was to identify NCA typical for NB.</p> </sec><sec> <title>Materials and methods</title> <p>Copy number alterations in NB tumor genome (fresh samples N = 94; formalin-fixed paraffin-embedded specimens N = 66) were analyzed with a pangenomic array CGH technique.</p> </sec><sec> <title>Results</title> <p>The profile with NCA was observed in 72 (45%) cases, NCA+SCA in 37 (23%), normal in 35 (22%) and MNA in 16 (10%). Samples with NCA were characterized by whole chromosome gains: 17, 7, 6 (78%, 65%, 51%, respectively) and copy loss of chromosome 14 (57%). Similarly to NCA, patients with a combined NCA and SCA profile were also characterized by gain of whole chromosome 17 and 7 (35% both) and loss of chromosome 14 (38%), but with lower frequency. In the combined NCA and SCA profiles, typical NB changes such as deletion 1p36 (27%) and gain 17q (41%) were observed, as well as deletion 11q (24%). The same alterations were detected in MNA samples (44%, 44%, 19%, respectively). A difference was found in spanning 11q deletion between MNA and NCA+SCA subgroup, which may suggest new prognostic markers in NB. In MNA subgroup specific NCA was not indicated.</p> </sec><sec> <title>Conclusions</title> <p>The hypothesis that NCA in NB tumors are more frequent in younger children with good prognosis was confirmed. To gain new insights into the pathogenesis of NB and to establish molecular targets for diagnosis and therapy, candidate genes in the altered chromosomal regions must be investigated.</p> </sec></abstract>

Genetic predisposition and chromosome instability in neuroblastoma

Neuroblastoma (NB) is a pediatric tumor of embryonic origin. About 1-2% of all NBs are familial cases, and genetic predisposition is suspected for the remaining cases. During the last decade, genome-wide association studies (GWAS) and high-throughput sequencing approaches have been used to identify associations among common and rare genetic variants and NB risk. Substantial data has been produced by large patient cohorts that implicate various genes in NB tumorigenesis, such as CASC15, BARD1, CHEK2, LMO1, LIN28B, AXIN2, BRCA1, TP53, SMARCA4, and CDK1NB. NB, as well as other pediatric cancers, has few recurrent mutations but several copy number variations (CNVs). Almost all NBs show both numerical and structural CNVs. The proportion between numerical and structural CNVs differs between localized and metastatic tumors, with a greater prevalence of structural CNVs in metastatic NB. This genomic chaos frequently identified in NBs suggests that chromosome instability (CIN) could be one of the major actors in NB oncogenesis. Interestingly, many NB-predisposing variants occur in genes involved in the control of genome stability, mitosis, and normal chromosome separation. Here, we discuss the relationship between genetic predisposition and CIN in NB.

Identification of RNA-Binding Proteins as Targetable Putative Oncogenes in Neuroblastoma

Neuroblastoma is a common childhood cancer with almost a third of those affected still dying, thus new therapeutic strategies need to be explored. Current experimental therapies focus mostly on inhibiting oncogenic transcription factor signalling. Although LIN28B, DICER and other RNA-binding proteins (RBPs) have reported roles in neuroblastoma development and patient outcome, the role of RBPs in neuroblastoma is relatively unstudied. In order to elucidate novel RBPs involved in MYCN-amplified and other high-risk neuroblastoma subtypes, we performed differential mRNA expression analysis of RBPs in a large primary tumour cohort (n = 498). Additionally, we found via Kaplan–Meier scanning analysis that 685 of the 1483 tested RBPs have prognostic value in neuroblastoma. For the top putative oncogenic candidates, we analysed their expression in neuroblastoma cell lines, as well as summarised their characteristics and existence of chemical inhibitors. Moreover, to help explain their association with neuroblastoma subtypes, we reviewed candidate RBPs’ potential as biomarkers, and their mechanistic roles in neuronal and cancer contexts. We found several highly significant RBPs including RPL22L1, RNASEH2A, PTRH2, MRPL11 and AFF2, which remain uncharacterised in neuroblastoma. Although not all RBPs appear suitable for drug design, or carry prognostic significance, we show that several RBPs have strong rationale for inhibition and mechanistic studies, representing an alternative, but nonetheless promising therapeutic strategy in neuroblastoma treatment.

A Novel Phenotype of Germline Pathogenic Variants in MAX: Concurrence of Pheochromocytoma and Ganglioneuroma in a Chinese Family and Literature Review

Background:MYC associated factor X (MAX) is a tumor suppressor gene and has been identified as one of the pathogenic genes of hereditary pheochromocytoma (PCC). To date, there have been no reports of ganglioneuroma (GN) with MAX variants. Case Presentation: The proband was a 45-years-old Chinese female with paroxysmal hypertension and palpitations who had undergone adrenalectomy for PCC 14 years ago. Her plasma free normetanephrine and 24-h urinary norepinephrine excretion were significantly increased, and abdominal computed tomography (CT) revealed an irregular mass in the left adrenal region, suggesting a recurrence of PCC. The mass was surgically removed and pathologically diagnosed as PCC with lymph node metastasis. The proband's son suffered from paroxysmal hypertension and palpitations. His plasma free metanephrine levels were normal. CT revealed a mass in the right adrenal. The tumor was surgically removed, and the pathological diagnosis was GN. Genetic testing of peripheral blood DNA revealed that the proband and her son had germline pathogenic MAX variant c.C97T, p.Arg33Ter, while proband's parents did not have MAX variants. Tumor DNA sequencing showed the same MAX variant (c.C97T, p.Arg33Ter) in PCC of the proband and GN of her son, both with retention of heterozygosity. Immunohistochemistry demonstrated loss of MAX protein expression in most tumor cells in PCC of the proband and some Schwannian cells in GN of the proband's son. Conclusion: We report a family with a new clinical phenotype of germline pathogenic variants in MAX who developed both PCC and GN. Germline pathogenic variants in MAX may contribute to the development of GN. Our findings suggest that it is not just paternally inherited MAX variants that can cause tumors.

Targeting anaplastic lymphoma kinase in neuroblastoma

Over the last decade, anaplastic lymphoma kinase (ALK), a receptor tyrosine kinase (RTK), has been identified as a fusion partner in a diverse variety of translocation events resulting in oncogenic signaling in many different cancer types. In tumors where the full‐length ALK RTK itself is mutated, such as neuroblastoma, the picture regarding the role of ALK as an oncogenic driver is less clear. Neuroblastoma is a complex and heterogeneous tumor that arises from the neural crest derived peripheral nervous system. Although high‐risk neuroblastoma is rare, it often relapses and becomes refractory to treatment. Thus, neuroblastoma accounts for 10–15% of all childhood cancer deaths. Since most cases are in children under the age of 2, understanding the role and regulation of ALK during neural crest development is an important goal in addressing neuroblastoma tumorigenesis. An impressive array of tyrosine kinase inhibitors (TKIs) that act to inhibit ALK have been FDA approved for use in ALK‐driven cancers. ALK TKIs bind differently within the ATP‐binding pocket of the ALK kinase domain and have been associated with different resistance mutations within ALK itself that arise in response to therapeutic use, particularly in ALK‐fusion positive non‐small cell lung cancer (NSCLC). This patient population has highlighted the importance of considering the relevant ALK TKI to be used for a given ALK mutant variant. In this review, we discuss ALK in neuroblastoma, as well as the use of ALK TKIs and other strategies to inhibit tumor growth. Current efforts combining novel approaches and increasing our understanding of the oncogenic role of ALK in neuroblastoma are aimed at improving the efficacy of ALK TKIs as precision medicine options in the clinic.

Neuroblastoma in children: Update on clinicopathologic and genetic prognostic factors

Neuroblastoma is the most common extracranial solid tumor in childhood accounting for 8-10% of all childhood malignancies. The tumor is characterized by a spectrum of histopathologic features and a heterogeneous clinical phenotype. Modern multimodality therapy results in variable clinical response ranging from cure in localized tumors to limited response in aggressive metastatic disease. Accurate clinical staging and risk assessment based on clinical, surgical, biologic and pathologic criteria are of pivotal importance in assigning prognosis and planning effective treatment approaches. Numerous studies have analyzed the presence of several clinicopathologic and biologic factors in association with the patient's prognosis and outcome. Although patient's age, tumor stage, histopathologic classification, and MYCN amplification are the most commonly validated prognostic markers, several new gene mutations have been identified in sporadic and familial neuroblastoma cases that show association with an adverse outcome. Novel molecular studies have also added data on chromosomal segmental aberrations in MYCN nonamplified tumors. In this review, we provide an updated summary of the clinical, serologic and genetic prognostic indicators in neuroblastoma including classic factors that have consistently played a role in risk stratification of patients as well as newly discovered biomarkers that may show a potential significance in patients' management.

Next generation sequencing of microRNAs from isogenic neuroblastoma cell lines isolated before and after treatment

Neuroblastoma is a pediatric cancer of the developing sympathetic nervous system. High risk neuroblastoma patients typically undergo an initial remission in response to treatment, followed by recurrence of aggressive tumors that have become refractory to further treatment. Recent works have underlined the involvement of microRNAs (miRNAs) in neuroblastoma development and evolution of drug resistance. In this study we have used deep sequencing technology to identify miRNAs differentially expressed in neuroblastoma cell lines isolated from 6 patients at diagnosis and at relapse after intensive treatments. This approach revealed a panel of 42 differentially expressed miRNAs, 8 of which were upregulated and 34 were downregulated. Most strikingly, the 14q32 miRNA clusters encode 22 of the downregulated miRNAs. Reduced expression of 14q32 miRNAs in tumors associated with poor prognosis factors was confirmed in a cohort consisting of 226 primary neuroblastomas. In order to gain insight into the nature of the genes that may be affected by the differentially expressed miRNAs we utilized Ingenuity Pathway Analysis (IPA). This analysis revealed several biological functions and canonical pathways associated with cancer progression and drug resistance. The results of this study contribute to the identification of miRNAs involved in the complex processes of surviving therapeutic treatment and developing drug resistance in neuroblastoma.

Genome instability model of metastatic neuroblastoma tumorigenesis by a dictionary learning algorithm

Background

Metastatic neuroblastoma (NB) occurs in pediatric patients as stage 4S or stage 4 and it is characterized by heterogeneous clinical behavior associated with diverse genotypes. Tumors of stage 4 contain several structural copy number aberrations (CNAs) rarely found in stage 4S. To date, the NB tumorigenesis is not still elucidated, although it is evident that genomic instability plays a critical role in the genesis of the tumor. Here we propose a mathematical approach to decipher genomic data and we provide a new model of NB metastatic tumorigenesis.

Method

We elucidate NB tumorigenesis using Enhanced Fused Lasso Latent Feature Model (E-FLLat) modeling the array comparative chromosome hybridization (aCGH) data of 190 metastatic NBs (63 stage 4S and 127 stage 4). This model for aCGH segmentation, based on the minimization of functional dictionary learning (DL), combines several penalties tailored to the specificities of aCGH data. In DL, the original signal is approximated by a linear weighted combination of atoms: the elements of the learned dictionary.

Results

The hierarchical structures for stage 4S shows at the first level of the oncogenetic tree several whole chromosome gains except to the unbalanced gains of 17q, 2p and 2q. Conversely, the high CNA complexity found in stage 4 tumors, requires two different trees. Both stage 4 oncogenetic trees are marked diverged, up to five sublevels and the 17q gain is the most common event at the first level (2/3 nodes). Moreover the 11q deletion, one of the major unfavorable marker of disease progression, occurs before 3p loss indicating that critical chromosome aberrations appear at early stages of tumorigenesis. Finally, we also observed a significant (p = 0.025) association between patient age and chromosome loss in stage 4 cases.

Conclusion

These results led us to propose a genome instability progressive model in which NB cells initiate with a DNA synthesis uncoupled from cell division, that leads to stage 4S tumors, primarily characterized by numerical aberrations, or stage 4 tumors with high levels of genome instability resulting in complex chromosome rearrangements associated with high tumor aggressiveness and rapid disease progression.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-015-0132-y) contains supplementary material, which is available to authorized users.

SIX1 overexpression in diffuse-type and grade III gastric tumors: Features that are associated with poor prognosis

Background:

Gastric cancer is the second most common cancer worldwide. In Iran, the incidence of gastric cancer is well above the world average, and is the first common cancer in Iranian men and the third one in women. Located at chromosome 14q23, SIX1 is a homolog of the Drosophila ‘sine oculis’ (so) gene and is highly conserved in numerous species. In addition to the role of SIX1 in the development, its expression is frequently dysregulated in multiple cancers. This study aimed to evaluate the clinicopathological features of the expression of SIX1 gene in gastric adenocarcinoma.

Materials and Methods:

Thirty pairs of gastric tissue samples from patients with gastric adenocarcinoma were evaluated for SIX1 gene expression using quantitative real-time polymerase chain reaction. A paired t-test or one-way ANOVA with post hoc multiple comparisons were used to analyze the differences between groups. Statistical significance was defined as P ≤ 0.05.

Results:

SIX1 expression was decreased in tumoral samples. However, its expression increased significantly in diffuse-type gastric cancer. Furthermore, there was a trend toward statistical significance in increasing SIX1 gene expression with higher grades. Of note, the difference was significant between grades I and III.

Conclusions:

The results suggest that SIX1 gene expression might be used in the future as a potential biomarker to predict the outcome of the disease as diffuse-type and grade III of gastric tumors are associated with poor prognosis.

Prognostic significance of low DICER expression regulated by miR-130a in cervical cancer

Dicer is crucial for the maturation of microRNAs (miRNAs) and its dysregulation may contribute to tumor initiation and progression. The study explored the clinical implications of Dicer and its post-transcriptional regulation by microRNAs in cervical cancer. qRT-PCR and immunohistochemistry investigated Dicer mRNA and protein levels in cervical cancer tissues. The relationship between Dicer expression and survival was analyzed. MiRNA target prediction identified miRNAs that might target Dicer. Luciferase reporter and gain- or loss-of-function assays were performed. The results showed that 36.7% of cervical cancer cases showed low expression of Dicer mRNA and 63.3% cases showed high expression. At the protein level, 51% cases showed negative expression and 49% cases showed positive expression. Dicer mRNA and protein expressions were significantly associated with distant metastasis and recurrence in cervical cancer (P=0.002 and P=0.012, respectively). Multivariate Cox analysis indicated that low Dicer expression (P=0.016) and tumor stage (P=0.047) were independent predictors. Among the miRNAs predicted to target Dicer, 10 were detected by RT-PCR; their expressions were significantly higher in cervical cancers with lower Dicer expression than in those with higher Dicer expression and were negatively correlated with Dicer expression level (P<0.05). In vitro experiments demonstrated that miR-130a directly targeted Dicer mRNA to enhance migration and invasion in SiHa cells. Finally, survival analysis indicated that higher expression of miR-130a was significantly associated with poor disease-free survival. Taken together, Dicer expression regulated by miR-130a is an important potential prognostic factor in cervical cancer.

Recurrent pre-existing and acquired DNA copy number alterations, including focal TERT gains, in neuroblastoma central nervous system metastases

Stage 4 neuroblastomas have a high rate of local and metastatic relapse and associated disease mortality. The central nervous system (CNS) is currently one of the most common isolated relapse sites, yet the genomic alterations that contribute to these metastases are unknown. This study sought to identify recurrent DNA copy number alterations (CNAs) and target genes relating to neuroblastoma CNS metastases by studying 19 pre-CNS primary tumors and 27 CNS metastases, including 12 matched pairs. SNP microarray analyses revealed that MYCN amplified (MYCNA) tumors had recurrent CNAs different from non-MYCNA cohorts. Several CNAs known to be prevalent among primary neuroblastomas occurred more frequently in CNS metastases, including 4p-, 7q+, 12q+, and 19q- in non-MYCNA metastases, and 9p- and 14q- irrespective of MYCNA status. In addition, novel CNS metastases-related CNAs included 18q22.1 gains in non-MYCNA pre-CNS primaries and 5p15.33 gains and 15q26.1→tel losses in non-MYCNA CNS metastases. Based on minimal common regions, gene expression, and biological properties, TERT (5p), NR2F2 (15q), ALDH1A3 (15q), CDKN2A (9p), and possibly CDH7 and CDH19 (18q) were candidate genes associated with the CNS metastatic process. Notably, the 5p15 minimal common region contained only TERT, and non-MYCNA CNS metastases with focal 5p15 gains had increased TERT expression, similar to MYCNA tumors. These findings suggest that a specific genomic lesion (18q22.1 gain) predisposes to CNS metastases and that distinct lesions are recurrently acquired during metastatic progression. Among the acquired lesions, increased TERT copy number and expression appears likely to function in lieu of MYCNA to promote CNS metastasis.

Comprehensive cytogenomic profile of the in vitro neuronal model SH-SY5Y

The widely studied SH-SY5Y human neuroblastoma cell line provides a classic example of how a cancer cell line can be instrumental for discoveries of broad biological and clinical significance. An important feature of the SH-SY5Y cells is their ability to differentiate into a functionally mature neuronal phenotype. This property has conferred them the potential to be used as an in vitro model for studies of neurodegenerative and neurodevelopmental disorders. Here, we present a comprehensive assessment of the SH-SY5Y cytogenomic profile. Our results advocate for molecular cytogenetic data to inform the use of cancer cell lines in research.

Expression of miR-487b and miR-410 encoded by 14q32.31 locus is a prognostic marker in neuroblastoma

BACKGROUND

Combination of age at diagnosis, stage and MYCN amplification stratifies neuroblastoma into low-risk and high-risk. We aimed to establish whether a microRNA (miRNA) signature could be associated with prognosis in both groups.

METHODS

Microarray expression profiling of human miRNAs and quantitative reverse-transcriptase PCR of selected miRNAs were performed on a preliminary cohort of 13 patients. Results were validated on an independent cohort of 214 patients. The relationship between miRNA expression and the overall or disease-free survival was analysed on the total cohort of 227 patients using the log-rank test and the multivariable Cox proportional hazard model.

RESULTS

A total of 15 of 17 miRNAs that discriminated high-risk from low-risk neuroblastoma belonged to the imprinted human 14q32.31 miRNA cluster and two, miR-487b and miR-410, were significantly downregulated in the high-risk group. Multivariable analyses showed miR-487b expression as associated with overall survival and disease-free survival in the whole cohort, independently of clinical covariates. Moreover, miR-487b and miR-410 expression was significantly associated with disease-free survival of the non-MYCN-amplified favourable neuroblastoma: localised (stage 1, 2 and 3) and stage 4 of infant <18 months.

CONCLUSION

Expression of miR-487b and miR-410 shows predictive value beyond the classical high-/low-risk stratification and is a biomarker of relapse in favourable neuroblastoma.

Advances in the understanding of constitutional and somatic genomic alterations in neuroblastoma

Advances in the field of genomics have led to multiple recent discoveries in the understanding of genetic predisposition and molecular pathogenesis of the childhood cancer neuroblastoma. Neuroblastoma is the most common extracranial solid tumor of childhood and is responsible for 10% of childhood cancer related mortality. The genetic etiology of rare families with hereditary neuroblastoma is now largely understood, with the majority having activating mutations in the anaplastic lymphoma kinase (ALK) gene. Genome-wide association studies have identified multiple common, low penetrance genetic polymorphisms that are associated with a predisposition to sporadic neuroblastoma, and these associations are disease phenotype specific. While many of the discoveries related to variations in the host genome that predispose to neuroblastoma are recent, there is a long and robust history of investigation of tumor cell genomics, leading to the identification of multiple biomarkers of tumor aggressiveness. Current patient risk stratification algorithms utilize key genomic features for therapy assignment. Microarray-based tumor DNA and RNA profiling techniques and next generation sequencing efforts may further refine these risk groups and identify new tractable therapeutic targets. Moving forward, integrative genomics efforts will be needed to discover how the interaction of germline genetic variations influence oncogenesis in neuroblastoma-both initiation and progression. In this review, we summarize the recent advances in the understanding of germline predisposition and molecular pathogenesis of neuroblastoma.

The connections between neural crest development and neuroblastoma

Neuroblastoma (NB), the most common extracranial solid tumor in childhood, is an extremely heterogeneous disease both biologically and clinically. Although significant progress has been made in identifying molecular and genetic markers for NB, this disease remains an enigmatic challenge. Since NB is thought to be an embryonal tumor that is derived from precursor cells of the peripheral (sympathetic) nervous system, understanding the development of normal sympathetic nervous system may highlight abnormal events that contribute to NB initiation. Therefore, this review focuses on the development of the peripheral trunk neural crest, the current understanding of how developmental factors may contribute to NB and on recent advances in the identification of important genetic lesions and signaling pathways involved in NB tumorigenesis and metastasis. Finally, we discuss how future advances in identification of molecular alterations in NB may lead to more effective, less toxic therapies, and improve the prognosis for NB patients.

microRNA signature and expression of Dicer and Drosha can predict prognosis and delineate risk groups in neuroblastoma

Neuroblastoma is a common childhood tumor and accounts for 15% of pediatric cancer deaths. To investigate the microRNA (miRNA) profile and role of Dicer and Drosha in neuroblastoma, we assessed the expression of 162 human miRNAs, Dicer and Drosha in 66 neuroblastoma tumors by using real-time PCR methods. We found global downregulation of miRNA expression in advanced neuroblastoma and identified 27 miRNAs that can clearly distinguish low- from high-risk patients. Furthermore, expression levels of Dicer or Drosha were low in high-risk neuroblastoma tumors, which accounted for global downregulation of miRNAs in advanced disease and correlated with poor outcome. Notably, for patients with non-MYCN-amplified tumors, low expression of Dicer can serve as a significant and independent predictor of poor outcome (hazard ratio, 9.6; P = 0.045; n = 52). Using plausible neural networks to select a combination of 15 biomarkers that consist of 12 miRNAs' signature, expression levels of Dicer and Drosha, and age at diagnosis, we were able to segregate all patients into four distinct patterns that were highly predictive of clinical outcome. In vitro studies also showed that knockdown of either Dicer or Drosha promoted the growth of neuroblastoma cell lines. Our results reveal that a combination of 15 biomarkers can delineate risk groups of neuroblastoma and serve as a powerful predictor of clinical outcome. Moreover, our findings of growth promotion by silencing Dicer/Drosha implied their potential use as therapeutic targets for neuroblastoma.

Genetics and genomics of neuroblastoma

Neuroblastoma is a pediatric cancer of the developing sympathetic nervous system that most often affects young children. It remains an important pediatric problem because it accounts for approximately 15% of childhood cancer mortality. The disease is clinically heterogeneous, with the likelihood of cure varying greatly according to age at diagnosis, extent of disease, and tumor biology. This extreme clinical heterogeneity reflects the complexity of genetic and genomic events associated with development and progression of disease. Inherited genetic variants and mutations that initiate tumorigenesis have been identified in neuroblastoma and multiple somatically acquired genomic alterations have been described that are relevant to disease progression. This chapter focuses on recent genome-wide studies that have utilized high-density single nucleotide polymorphism (SNP) genotyping arrays to discover genetic factors predisposing to tumor initiation such as rare mutations at locus 2p23 (in ALK gene) for familial neuroblastoma, common SNPs at 6p22 (FLJ22536 and FLJ44180) and 2q35 (BARD1), and a copy number polymorphism at 1q21.1 (NBPF23) for sporadic neuroblastoma. It also deals with well known and recently reported somatic changes in the tumor genome such as mutations, gain of alleles and activation of oncogenes, loss of alleles, or changes in tumor-cell ploidy leading to the diverse clinical behavior of neuroblastomas. Finally, this chapter reviews gene expression profiles of neuroblastoma associated with pathways of the signaling of neurotrophins and apoptotic factors that could have a role in neuroblastoma development and progression. Looking forward, a major challenge will be to understand how inherited genetic variation and acquired somatic alterations in the tumor genome interact to exact phenotypic differences in neuroblastoma, and cancer in general.

Regulation of Beclin 1 in autophagy

Class III phosphatidylinositol 3-kinase (PI3KC3) plays a pleiotropic role in autophagy and protein sorting pathways. The human core complex of PI3KC3 consists of three major components including PI3KC3/hVps34, p150 and Beclin 1. How the specificity of PI3KC3 complex is derived towards autophagy is not clear. Utilizing a sequential affinity purification coupled with mass spectrometry approach, we have successfully purified a human Beclin 1 complex and cloned a novel protein we called Barkor (Beclin 1-associated autophagy-related key regulator). The function of Barkor in autophagy has been manifested in several assays, including stress-induced LC3 lipidation, autophagosome formation and Salmonella typhimurium amplification. Mechanistically, Barkor competes with UV radiation resistance associated gene product (UVRAG) for interaction with Beclin 1, and orients Beclin 1 to autophagosomes. Barkor shares considerable sequence homology with Atg14 in yeast, representing an evolutionary conserved autophagy specific regulatory step in early autophagosome formation.

Comparison of primary neuroblastoma tumors and derivative early-passage cell lines using genome-wide single nucleotide polymorphism array analysis

Stromal contamination is one of the major confounding factors in the analysis of solid tumor samples by single nucleotide polymorphism (SNP) arrays. As we propose to use genome-wide SNP microarray analysis as a diagnostic platform for neuroblastoma, the sensitivity, specificity, and accuracy of these studies must be optimized. To investigate the effects of stromal contamination, we derived early-passage cell lines from nine primary tumors and compared their genomic signature with that of the primary tumors using 100K SNP arrays. The average concordance between tumor and cell line for raw loss of heterozygosity (LOH) calls was 96% (range, 91-99%) and for raw copy number alterations, 71% (range, 43-87%). In general, there were a larger number of LOH events identified in the cell lines compared with the matched tumor samples (mean increase, 3.2% +/- 1.9%). We have developed an algorithm that shows that the presence of stroma contributes to under-reporting of LOH and copy number loss. Notable findings in this sample set were uniparental disomy of chromosome arms 11p, 1q, 14q, and 15q and a novel area of amplification on chromosome band 11p15. Our analysis shows that LOH was identified significantly more often in derived cell lines compared with the original tumor samples. Although these may in part be due to clonal selection during adaptation to tissue culture, our study indicates that stromal contamination may be a major contributing factor in underestimation of LOH and copy number loss events.

Comparison of different techniques for the detection of genetic risk-identifying chromosomal gains and losses in neuroblastoma

Neuroblastoma (NB) is a pediatric neoplasia that shows complex combinations of acquired genetic aberrations. The specific genes and the molecular mechanisms responsible for development and progression of NB remain poorly understood. Our main objective is to compare the results obtained with different techniques for the detection of genomic data in 20 patients with NB using the information obtained to select the appropriate technique in routine analysis for the therapeutic stratification. The genetic methods used in this study are multiprobe fluorescence in situ hybridization (FISH) assay, metaphasic comparative genomic hybridization (mCGH), array comparative genomic hybridization (aCGH), and the multiplex ligation-dependent probe amplification (MLPA). Genomic copy number abnormalities were used to group the cases in four categories: MYCN amplification cases; 11q deletion tumors; cases with partial chromosome gains or losses and samples with entire chromosome alterations. The data obtained from the multigenomic techniques showed a high degree of concordance and our findings support the hypothesis that NB consists of biologically distinct subgroups that differ by genetic characteristics of prognostic relevance. FISH will be essential for the mandatory study of MYCN status. The use of MLPA as routine technique is an advantage procedure for detecting the implication of the common genetic alterations in NB.

Neuroblastomas have distinct genomic DNA profiles that predict clinical phenotype and regional gene expression

Neuroblastoma is a heterogeneous neoplasm that has served as a paradigm for the clinical utility of somatically acquired genomic aberrations. DNA copy number alterations (CNA) are currently used to predict prognosis, including MYCN amplification and deletions at chromosome bands 1p36 and 11q23. We predicted that genome-wide assessment of DNA aberrations in neuroblastoma tumors would provide a more precise estimation of clinical phenotype, and could be used to predict outcome. We measured CNAs in a representative set of 82 diagnostic tumors on a customized high-resolution BAC array-based CGH platform supplemented with additional clones across 1p36, 2p24, 3p21-22, 11q14-24, and 16p12-13, and integrated these data with RNA expression data. We used an unbiased statistical method to define a set of minimal common regions (MCRs) of aberration. Unsupervised hierarchical clustering identified four distinct genomic subclasses. First, a subset of tumors with a clinically benign phenotype showed predominantly whole chromosome gains and losses. Second, tumors with MYCN amplification had a unique genomic signature of 1p deletion and 17q gain, but few other rearrangements. Third, tumors with an aggressive clinical phenotype without MYCN amplification, showed multiple structural rearrangements. Most notable were deletions of 3p, 4p, and 11q and gain of 1q, 2p, 12q, and 17q. Lastly, there was a subset of tumors with an aggressive clinical phenotype and no detectable DNA CNAs. The genomic subsets were highly correlated with patient outcome, and individual MCRs remained prognostic in a multivariable model. DNA signature patterns embed important prognostic information in diagnostic neuroblastoma samples, and can identify candidate cancer-related genes.

Epigenetic silencing of prostaglandin E receptor 2 (PTGER2) is associated with progression of neuroblastomas

We previously identified a cluster of prostanoid receptor genes, prostaglandin D2 receptor (PTGDR) and prostaglandin E receptor 2 (PTGER2), as possible targets for DNA methylation in advanced types of neuroblastoma (NB) using bacterial artificial chromosome array-based methylated CpG island amplification method. Among them, in this study, we found that PTGER2 was frequently silenced in NB cell lines, especially in those with MYCN amplification, through epigenetic mechanisms. In NB cell lines, DNA methylation pattern within a part of CpG island was inversely correlated with PTGER2 expression, and histone H3 and H4 deacetylation and histone H3 lysine 9 methylation within the putative promoter region were more directly correlated with silencing of this gene. Methylation of PTGER2 was observed more frequently in advanced-type of primary NBs compared with early-stage tumors. Growth of NB cells lacking endogenous PTGER2 expression was inhibited by restoration of the gene product by transient and stable transfection. A PTGER2-selective agonist, butaprost, increased intracellular cyclic adenosine monophosphate (cAMP) level, inhibited cell growth and induced apoptosis of NB cells stably expressing exogenous PTGER2. 8-Bromo-cAMP also inhibited growth of NB cells lacking PTGER2 expression, but not cells expressing this gene. Taken together, it is suggested that NB cells may lose responsiveness to PTGER2-mediated growth inhibition/apoptosis through epigenetic silencing of PTGER2 and/or disruption of downstream cAMP-dependent pathway during the neuroblastomagenesis.

TheREToncogene is a critical component of transcriptional programs associated with retinoic acid–induced differentiation in neuroblastoma

Differentiation is a key feature in pathologic classification and prognosis of neuroblastic tumors, although the underlying molecular mechanisms are not well defined. To identify key differentiation-related molecules and pathways, we evaluated gene expression during retinoic acid (RA)-induced differentiation of seven neuroblastic tumor cell lines. Transcriptional response to RA was highly variable among cell lines despite the fact that six of seven showed similar morphologic changes. RA consistently altered expression of a small set of genes, some of which are known to play a role in neurogenesis and differentiation. Expression of genes that were regulated by RA was associated with important clinical subgroups of neuroblastic tumors and were differentially expressed by stroma-rich and stroma-poor subtypes. RET, a receptor tyrosine kinase involved with differentiation, was consistently up-regulated throughout the time course of RA treatment in the majority of neuroblastic tumor cell lines. Interference with RET activation abrogated RA-induced transcriptional programs and differentiation, suggesting a key role of RET in this process. The core set of RA-regulated genes includes critical molecular components of pathways necessary for neuroblastic tumor differentiation and have potential as therapeutic targets and molecular markers of response to differentiating agents.

Implications of MYCN amplification in patients with stage 4 neuroblastoma who undergo intensive chemotherapy

BACKGROUND/PURPOSE

This study aims to clarify the implications of MYCN amplification in patients with high-risk neuroblastomas treated with 2 different regimens of induction chemotherapy established by the Japan Study Group for Advanced Neuroblastoma.

METHODS

Between 1985 and 2003 in Japan, 392 patients with stage 4 neuroblastomas who were older than 12 months were treated with 2 regimens of induction chemotherapy (the combination of cyclophosphamide [CTX], cisplatin [CDDP], pirarubicin, and vincristine or etoposide). Regimen 91A3 or 98A3 (A3) (CTX 2400 mg/m2, CDDP 125 mg/m2) was a higher dose combination of CTX and CDDP than regimen 85A1 or 91A1 (A1) (CTX 1200 mg/m2, CDDP 90 mg/m2). The 392 cases were classified into 3 groups (A, 1 copy; B, 2-9 copies; C, more than 10 copies) based on the MYCN amplification status by a Southern blot analysis.

RESULTS

The 5-year overall survival rate (5-YS) was 41.1% for all 392 cases. Regarding the MYCN amplification status, the 5-YS was 46.6% for A group (n = 227), 22.7% for B group (n = 26), and 36.0% for C group (n = 139). A fluorescence in situ hybridization analysis showed the presence of the cells with more than 10 copies in cases with 2 to 9 copies based on the Southern blot findings. Of the 227 patients in a group, the 5-YS was 46.7% for the 70 cases treated by A3 and 47.0% for 154 cases treated by A1 (nonsignificant). The 5-YS of the 210 patients with stem cell transplantation (SCT) (51.%) was significantly better than that of the 127 patients without SCT (41.1%) (P < .05).

CONCLUSIONS

Regarding the MYCN amplification status, the tumor aggressiveness might thus be different between 2 and 9 copies and a single copy of MYCN. In neuroblastomas with 2 and 9 copies of MYCN based on a Southern blot analysis, the MYCN amplification status should be analyzed using the fluorescence in situ hybridization method. Induction chemotherapy followed by SCT according to the Japan Study Group for Advanced Neuroblastoma protocol improved the outcome of neuroblastomas with MYCN amplification; however, obtaining a further improvement in the long-term survival of stage 4 neuroblastomas may therefore require the development of an even more effective treatment modality.

High-resolution analysis of allelic imbalance in neuroblastoma cell lines by single nucleotide polymorphism arrays

Genomic copy number changes are detectable in many malignancies, including neuroblastoma, using techniques such as comparative genomic hybridization (CGH), microsatellite analysis, conventional karyotyping, and fluorescence in situ hybridization (FISH). We report the use of 10K single nucleotide polymorphism (SNP) microarrays to detect copy number changes and allelic imbalance in six neuroblastoma cell lines (IMR32, SHEP, NBL-S, SJNB-1, LS, and SKNBE2c). SNP data were generated using the GeneChip DNA Analysis and GeneChip chromosome copy number software (Affymetrix). SNP arrays confirmed the presence of all previously reported cytogenetic abnormalities in the cell lines, including chromosome 1p deletion, MYCN amplification, gain of 17q and 11q, and 14q deletions. In addition, the SNP arrays revealed several chromosome gains and losses not detected by CGH or karyotyping; these included gain of 8q21.1 approximately 24.3 and gain of chromosome 12 in IMR-32 cells; loss at 4p15.3 approximately 16.1 and loss at 16p12.3 approximately 13.2, 11q loss with loss of heterozygosity (LOH) at 11q14.3 approximately 23.3 in SJNB-1 cells; and loss at 8p21.2 approximately 23.3 and 9p21.3 approximately 22.1 with corresponding LOH in SHEP cells. The SNP arrays refined the mapping of the 2p amplicons in LS, BE2c, and IMR-32 cell lines, the 12q amplicon in LS cells, and also identified an 11q13 amplicon in LS cells. There was good concordance among SNP arrays, CGH, and karyotyping. SNP array analysis is a powerful tool for the detection of allelic imbalance in neuroblastoma and also allows identification of LOH without changes in copy number (uniparental disomy).

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.

DNA methylation and allelic losses on chromosome arm 14q in oligodendroglial tumours

Cytogenetic and molecular genetic studies have shown frequent losses on the long arm of chromosome 14 in different types of human gliomas. Using differential methylation hybridization as a genome-wide screening approach to determine DNA methylation patterns in gliomas, we recently identified two DNA fragments in 14q23.1 (CGI-clone musical sharp396) and 14q32.12 (CGI-clone musical sharp519) that were differentially methylated between astrocytic gliomas and mixed oligoastrocytomas. To validate this observation, we examined these 14q32.12 locus for methylation in an extended series of 43 astrocytic and oligodendroglial gliomas. All tumours were additionally investigated for loss of heterozygosity (LOH). Microsatellite analysis showed LOH in seven of 28 (25%) oligodendroglial tumours and three of 15 (20%) astrocytic tumours. Seven tumours demonstrated LOH at all informative 14q loci whereas three tumours carried partial deletions defining a commonly deleted region at 14q22.3-q32.1 between the microsatellite markers D14S282 and D14S995. Methylation-specific PCR analysis of the 14q32.12 locus revealed hypermethylation in 12 of 43 gliomas (28%). Hypermethylation was restricted to tumours with oligodendroglial differentiation (12 of 28 tumours, 43%). However, none of the hypermethylated tumours demonstrated LOH on 14q and vice versa. In total, 19 of 28 oligodendroglial tumours (68%) showed either hypermethylation at the 14q32.12 locus or LOH at 14q22.3-q32.2. Taken together, our data lend further support for the location of one or more yet to be identified glioma-associated tumour suppressor gene(s) on 14q. In addition, the restriction of 14q32.12 methylation to oligodendroglial tumours suggests a role for epigenetic DNA modifications in these particular gliomas.

Gene amplification is a mechanism of Six1 overexpression in breast cancer

The Six1 homeoprotein plays a critical role in expanding progenitor populations during normal development via its stimulation of proliferation and inhibition of apoptosis. Overexpression of Six1 is observed in several tumor types, suggesting that when expressed out of context, Six1 may contribute to tumorigenesis by reinstating properties normally conveyed on developing cells. Indeed, Six1 contributes to tumor cell proliferation both in breast cancer and in rhabdomyosarcomas, in which it is also implicated in metastasis. Whereas Six1 overexpression has been reported in several tumor types, the mechanism responsible for its overexpression has not previously been examined. Here we show that a change in gene dosage may contribute to Six1 mRNA overexpression. Significant Six1 gene amplification and overrepresentation occurs in numerous breast cancer cell lines as compared with normal mammary epithelial cells, and the changes in gene dosage correlate with increased Six1 mRNA levels. Of 214 human infiltrating ductal breast carcinomas examined for Six1 gene dosage, 4.7% show Six1 amplification/overrepresentation, and tumors that exhibit an increase in Six1 gene dosage overexpress Six1 mRNA. These data implicate Six1 gene amplification/overrepresentation as a mechanism of Six1 mRNA overexpression in human breast cancer.

The biologic basis for neuroblastoma heterogeneity and risk stratification

PURPOSE OF REVIEW

Neuroblastoma serves as the paradigm for the clinical utility of tumor-specific biologic data for prognostication. This review will describe the genetic and biologic basis for the diverse clinical phenotypes observed in neuroblastoma patients. It will also discuss the current approach to risk classification and how this may change in the future.

RECENT FINDINGS

The biologic basis of neuroblastoma has come into clearer focus. PHOX2B is the first bona fide neuroblastoma predisposition gene identified, but is mutated in only a small subset of cases. Somatically acquired alterations at chromosome arms 3p and 11q are highly correlated with acquisition of metastases in the absence of MYCN amplification and may be useful as prognostic markers. The Children's Oncology Group risk classification system has been validated, with current emphasis on further refinement such as reevaluation of the age cutoff used to stratify therapy, and incorporation of additional molecular genetic markers is being studied prospectively. High-throughput genome scale analyses of neuroblastomas are further clarifying the genetic basis of this heterogeneous disease.

SUMMARY

Neuroblastoma remains a significant challenge as high-risk patients are treated with intensive multimodal therapies but cure rates remain suboptimal. There is remarkable heterogeneity observed in tumor phenotype, ranging from spontaneous regression to relentless progression. There are literally dozens of clinical and biologic markers that have been proposed as being predictive of disease outcome, but large clinical correlative studies are sharpening the focus of which markers can be used by the clinician to optimize therapy for an individual patient.

Pediatric neuroblastomas: genetic and epigenetic 'danse macabre'

Neuroblastomas are the most frequently occurring solid tumors in children under 5 years. Spontaneous regression is more common in neuroblastomas than in any other tumor type, especially in young patients under 12 months. Unfortunately, the full clinical spectrum of neuroblastomas also includes very aggressive tumors, unresponsive to multi-modality treatment and accounting for most of the pediatric cancer mortalities under 5 years of age. It is generally emphasized that more than one biological entity of neuroblastoma exists. Structural genetic defects such as amplification of MYCN, gain of chromosome 17q and LOH of 1p and several other chromosomal regions have proven to be valuable as prognostic factors and will be discussed in relation to their clinical relevance. Recent research is starting to uncover important molecular pathways involved in the pathogenesis of neuroblastomas. The aim of this review is to discuss several important aspects of the biology of the neuroblast, such as the role of overexpressed oncogenes like MYCN and cyclin D1, the mechanisms leading to decreased apoptosis, like overexpression of BCL-2, survivin, NM23, epigenetic silencing of caspase 8 and the role of tumor suppressor genes, like p53, p73 and RASSF1A. In addition, the role of specific proteins overexpressed in neuroblastomas, such as the neurotrophin receptors TrkA, B and C in relation to spontaneous regression and anti-angiogenesis will be discussed. Finally, we will try to relate these pathways to the embryonal origin of neuroblastomas and discuss possible new avenues in the therapeutic approach of future neuroblastoma patients.

Advances in the diagnosis and treatment of neuroblastoma

Neuroblastoma, a childhood neoplasm arising from neural crest cells, is characterized by a diversity of clinical behavior ranging from spontaneous remission to rapid tumor progression and death. To a large extent, outcome can be predicted by the stage of disease and the age at diagnosis. However, the molecular events responsible for the variability in response to treatment and the rate of tumor growth remain largely unknown. Over the past decade, transformation-linked genetic changes have been identified in neuroblastoma tumors that have contributed to the understanding of tumor predisposition, metastasis, treatment responsiveness, and prognosis. The Children's Oncology Group recently developed a Neuroblastoma Risk Stratification System that is currently in use for treatment stratification purposes, based on clinical and biologic factors that are strongly predictive of outcome. This review discusses the current risk-based treatment approaches for children with neuroblastoma and recent advances in biologic therapy.

Neuroblastoma: biological insights into a clinical enigma

Neuroblastoma is a tumour derived from primitive cells of the sympathetic nervous system and is the most common solid tumour in childhood. Interestingly, most infants experience complete regression of their disease with minimal therapy, even with metastatic disease. However, older patients frequently have metastatic disease that grows relentlessly, despite even the most intensive multimodality therapy. Recent advances in understanding the biology and genetics of neuroblastomas have allowed classification into low-, intermediate- and high-risk groups. This allows the most appropriate intensity of therapy to be selected - from observation alone to aggressive, multimodality therapy. Future therapies will focus increasingly on the genes and biological pathways that contribute to malignant transformation or progression.