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Cancer therapy frequently fails due to the emergence of resistance. Many tumors include phenotypically immature tumor cells, which have been implicated in therapy resistance. Neuroblastoma cells can adopt a lineage-committed adrenergic (ADRN) or an immature mesenchymal (MES) state. They differ in epigenetic landscape and transcription factors, and MES cells are more resistant to chemotherapy. Here we analyzed the response of MES cells to targeted drugs. Activating anaplastic lymphoma kinase (ALK) mutations are frequently found in neuroblastoma and ALK inhibitors (ALKi) are in clinical trials. ALKi treatment of ADRN neuroblastoma cells with a tumor-driving ALK mutation induced cell death. Conversely, MES cells did not express either mutant or wild-type ALK and were resistant to ALKi, and MES cells formed tumors that progressed under ALKi therapy. In assessing the role of MES cells in relapse development, TRAIL was identified to specifically induce apoptosis in MES cells and to suppress MES tumor growth. Addition of TRAIL to ALKi treatment of neuroblastoma xenografts delayed relapses in a subset of the animals, suggesting a role for MES cells in relapse formation. While ADRN cells resembled normal embryonal neuroblasts, MES cells resembled immature precursor cells, which also lacked ALK expression. Resistance to targeted drugs can therefore be an intrinsic property of immature cancer cells based on their resemblance to developmental precursors. Significance: In neuroblastoma, mesenchymal tumor cells lack expression of the tumor-driving ALK oncogene and are resistant to ALKi, but dual treatment with ALKi and mesenchymal cell–targeting TRAIL delays tumor relapse.

Background: Posterior fossa tumors (PFTs) are a morbid group of central nervous system tumors that most often present in childhood. While early diagnosis is critical to drive appropriate treatment, definitive diagnosis is currently only achievable through invasive tissue collection and histopathological analyses. Machine learning has been investigated as an alternative means of diagnosis. In this systematic review and meta-analysis, we evaluated the primary literature to identify all machine learning algorithms developed to classify and diagnose pediatric PFTs using imaging or molecular data. Methods: Of the 433 primary papers identified in PubMed, EMBASE, and Web of Science, 25 ultimately met the inclusion criteria. The included papers were extracted for algorithm architecture, study parameters, performance, strengths, and limitations. Results: The algorithms exhibited variable performance based on sample size, classifier(s) used, and individual tumor types being investigated. Ependymoma, medulloblastoma, and pilocytic astrocytoma were the most studied tumors with algorithm accuracies ranging from 37.5% to 94.5%. A minority of studies compared the developed algorithm to a trained neuroradiologist, with three imaging-based algorithms yielding superior performance. Common algorithm and study limitations included small sample sizes, uneven representation of individual tumor types, inconsistent performance reporting, and a lack of application in the clinical environment. Conclusions: Artificial intelligence has the potential to improve the speed and accuracy of diagnosis in this field if the right algorithm is applied to the right scenario. Work is needed to standardize outcome reporting and facilitate additional trials to allow for clinical uptake.

Neuroblastoma is a pediatric tumor of the adrenergic sympathetic lineage. Most high risk neuroblastoma go in complete clinical remission by chemotherapy, which is subsequently complemented by retinoic acid (RA) maintenance therapy. However, by unresolved mechanisms most tumors ultimately relapse as therapy-resistant disease. Neuroblastoma cell lines were recently found to include, besides lineage committed adrenergic (ADRN) tumor cells, also immature mesenchymal (MES) tumor cells. Here, we report that MES-type cells synthesize RA and require this metabolite for proliferation and motility. MES cells are even resistant to RA in vitro. MES cells appear to resemble Schwann Cell Precursors (SCP), which are motile precursors of the adrenergic lineage. MES and SCP cells express shared RA-synthesis and RA-target genes. Endogenous RA synthesis and RA resistance thus stem from normal programs of lineage precursors that are maintained in an immature tumor cell fraction. These cells are fully malignant in orthotopic patient-derived xenograft models and may mediate development of drug-resistant relapses.

Neuroblastomas are embryonal tumours of the sympathoadrenal lineage with a clinical course ranging from spontaneous regression to fatal progression. The Phox2B homeobox transcription factor functions in the differentiation of the sympatho-adrenal lineage. Targets of Phox2B are, for example, genes of the ( nor) adrenalin synthesis route, like Dopamine Beta Hydroxylase (DBH). Congenital Central Hypoventilation Syndrome was recently found to result from Phox2B mutations and two such patients in addition developed neuroblastoma. A germline mutation in Phox2B was identified in a family with hereditary neuroblastoma. Here, we report the first analysis of Phox2B in a series of 237 sporadic neuroblastomas and 22 cell lines. Six frameshift mutations were found in exons 2 and 3; including one in cell line SK-N-SH. Two patients showed de novo constitutional mutations. One of them was diagnosed with Haddad syndrome. All analysed cases expressed the mutated and wild-type Phox2B alleles. Ectopic expression of TrkA, the Nerve Growth Factor receptor, strongly downregulated Phox2B and DBH expression in cell line SH-SY5Y. However, TrkA and Phox2B showed a positive correlation in a panel of 66 neuroblastoma tumours. Although Phox2B mutations are infrequent ( 2.3%), they implicate a role for the Phox2B pathway in oncogenesis

The childhood tumour neuroblastoma originates from neural crest-derived progenitors of the sympathetic nervous system. By Serial Analysis of Gene Expression (SAGE), we previously identified the Drosophila Delta homologue Dlk1 as one of the genes most highly expressed in the neuroblastoma cell line SK-N-F1. The Delta-Notch pathway controls many differentiation steps in Drosophila and man. We analysed expression of 21 genes of this pathway in 21 neuroblastoma cell lines. Dlk1 expression was very high in 5 cell lines, while another subset expressed Notch3. The imprinting of Dlk1 was faithfully preserved in neuroblastomas. The single paternal allele can therefore produce over 0.5% of all cellular mRNAs. Dlk1 maps to 14q32, a region that exhibited LOH in 31/170 (18%) tumours. The random parental origin of the deleted alleles excluded Dlk1 as target of the LOH. In addition, Dlk1 was not amplified, rearranged or mutated in neuroblastoma cell lines and tumours. We therefore analysed whether high Dlk1 expression marks a specific differentiation stage of the sympatho-adrenal lineage. Many neuroblastomas arise in the adrenal medulla, which predominantly consists of chromaffin cells. Normal adrenal medulla exhibited equally high Dlk1 levels as the SK-N-F1 cell line. Chromaffin cells in young children are marked by noradrenalin production, which is mediated by dopamine-beta-hydroxylase (DBH). DBH expression in the neuroblastoma cell lines almost perfectly corresponded to Dlk1 expression. Neuroblastoma cell lines with high Dlk1 expression are therefore arrested in a relatively late stage of chromaffin lineage differentiation, while Notch3 expression might correspond to earlier precursor stages or to an alternative developmental fate. (C) 2003 Wiley-Liss, Inc

Deletions in the short arm of chromosome 1 (1p36) and MYCN amplification are common in neuroblastoma. Previously we showed evidence of at least two different neuroblastoma tumor-suppressor loci on 1p. One is associated with MYCN single-copy tumors and maps distal on 1p36.3. A second, more proximal locus maps to 1p36.1 and is deleted in about 90% of neuroblastomas with MYCN amplification. The cell line UHG-NP has the smallest 1p36 deletion of all neuroblastoma cell lines with MYCN amplifications. We assume that the more proximal locus maps within this deletion, close to its proximal border. Here we present the exact localization of the 1p deletion breakpoint of UHG-NP. A 600-kb PAC contig spanning the breakpoint was analyzed for genes and aberrations. Two more neuroblastoma-associated aberrations were mapped within 150 kb of the UHG-NP breakpoint. Within the contig, we identified nine genes expressed in neuroblastoma cells. One of these genes, AML2, maps 200 kb distal to the UHG-NP breakpoint but is expressed only rarely in neuroblastoma and showed no mutations.

Purpose: Neuroblastoma is a childhood tumor of the peripheral sympathetic nervous system with an often lethal outcome due to metastatic disease. Migration and epithelial–mesenchymal transitions have been implicated in metastasis but they are hardly investigated in neuroblastoma. Experimental Design: Cell migration of 16 neuroblastoma cell lines was quantified in Transwell migration assays. Gene expression profiling was used to derive a migration signature, which was applied to classify samples in a neuroblastoma tumor series. Differential expression of transcription factors was analyzed in the subsets. NOTCH3 was prioritized, and inducible transgene expression studies in cell lines were used to establish whether it functions as a master switch for motility. Results: We identified a 36-gene expression signature that predicts cell migration. This signature was used to analyse expression profiles of 88 neuroblastoma tumors and identified a group with distant metastases and a poor prognosis. This group also expressed a known mesenchymal gene signature established in glioblastoma. Neuroblastomas recognized by the motility and mesenchymal signatures strongly expressed genes of the NOTCH pathway. Inducible expression of a NOTCH intracellular (NOTCH3-IC) transgene conferred a highly motile phenotype to neuroblastoma cells. NOTCH3-IC strongly induced expression of motility- and mesenchymal marker genes. Many of these genes were significantly coexpressed with NOTCH3 in neuroblastoma, as well as colon, kidney, ovary, and breast tumor series. Conclusion: The NOTCH3 transcription factor is a master regulator of motility in neuroblastoma. A subset of neuroblastoma with high expression of NOTCH3 and its downstream-regulated genes has mesenchymal characteristics, increased incidence of metastases, and a poor prognosis. Clin Cancer Res; 19(13); 3485–94. ©2013 AACR.

Chromosomal band 1p36 probably harbours several neuroblastoma suppressor genes. A neuroblastoma patient has been described with a constitutional balanced translocation, t(1;17)(p36;q12-21). Cytogenetically, no loss of chromosomal material was visible. The 1p36 translocation breakpoint could therefore have inactivated one allele of a tumour suppressor gene, thus predisposing the patient to develop neuroblastoma. We localized this breakpoint by pulsed field gel electrophoresis, analysis of yeast artificial chromosomes, and fluorescence in situ hybridization. Here we report that the breakpoint is within a large cluster of small nuclear RNA U1 (RNU1) and some tRNA genes (TRE, TRN) on chromosomal band 1p36. The size of this cluster is over two megabases and it contains many other locally repeated sequences. Polyadenylated transcripts were identified for some of these sequences. In addition, the cluster is the target for integration of an adenovirus 5/SV40 hybrid virus. The translocation breakpoint maps distal of this viral integration site and proximal of marker PND.

Neuroblastoma is an embryonal tumour of the peripheral sympathetic nervous system (SNS). One of the master regulator genes for peripheral SNS differentiation, the homeobox transcription factor PHOX2B, is mutated in familiar and sporadic neuroblastomas. Here we report that inducible expression of PHOX2B in the neuroblastoma cell line SJNB-8 down-regulates MSX1, a homeobox gene important for embryonic neural crest development. Inducible expression of MSX1 in SJNB-8 caused inhibition of both cell proliferation and colony formation in soft agar. Affymetrix micro-array and Northern blot analysis demonstrated that MSX1 strongly up-regulated the Delta-Notch pathway genes DLK1, NOTCH3, and HEY1. In addition, the proneural gene NEUROD1 was down-regulated. Western blot analysis showed that MSX1 induction caused cleavage of the NOTCH3 protein to its activated form, further confirming activation of the Delta-Notch pathway. These experiments describe for the first time regulation of the Delta-Notch pathway by MSX1, and connect these genes to the PHOX2B oncogene, indicative of a role in neuroblastoma biology. Affymetrix micro-array analysis of a neuroblastic tumour series consisting of neuroblastomas and the more benign ganglioneuromas showed that MSX1, NOTCH3 and HEY1 are more highly expressed in ganglioneuromas. This suggests a block in differentiation of these tumours at distinct developmental stages or lineages.

Background Serial Analysis of Gene Expression (SAGE) is an efficient method to establish a complete mRNA expression profile of a tissue. Procedure We applied SAGE to identify expression of developmental control genes in neuroblastoma. Results. The human homologue of the Drosophila Delta gene Delta like-1 (DLK1) was shown to have an unusually high expression in a SAGE library of the SK-N-FI neuroblastoma cell line. Northern blot analysis confirmed high DLK1 expression in SK-N-FI and several other neuroblastoma cell lines. Signalling between Delta and its receptor Notch controls many differentiation steps in Drosophila and man, including neural crest cell fate decision. Conclusions Our data therefore suggest a role for the Delta-Notch pathway in neuroblast differentiation. Med. Pediatr. Oncol. 35:554–558, 2000. © 2000 Wiley-Liss, Inc.

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

Adult-type hematopoietic stem cells (HSCs) emerge in the aorta-gonad-mesonephros (AGM) region in the mid-gestation mouse embryo. Thereafter, HSCs migrate to the fetal liver (FL) and at birth, colonize the adult bone marrow. The molecular signaling cascades controlling HSCs in the AGM region is not yet known. Exogenous Hedgehog (Hh) added to AGM explants prior to HSC generation induces AGM HSCs and BMP pathway inhibition abolishes AGM HSC activity. In the FL, the BMP signaling pathway is not required for hematopoiesis. A role for the MAPK signaling pathway has been demonstrated in the adult hematopoiesis, but whether this pathway also controls AGM HSCs is not known. We hypothesize that Hh and BMP control the induction/expansion of AGM HSCs and cooperate with the MAPK pathway to control their maintenance and differentiation. To test whether HSCs are directly activated by BMP, we used transgenic BMP-response element (BRE)-gfp mice, in which GFP expression is an indicator of BMP pathway activation. When BRE-gfp E11 AGM cells were sorted for GFP expression and injected into adult irradiated mice, all long term repopulating HSCs were found in the BMP activated (GFP+) fraction. We next asked whether HSCs in the FL are activated by BMP. Surprisingly, we found high level, multilineage, self-renewing HSCs in both GFP+ and GFPfractions. This suggests that subsets of HSCs shift from an exclusively BMP-activated state, to a state of non-activation. This shift may be involved in the expansion of HSCs in the FL. Since HSCs expand in explant cultures of E11 AGMs, we examined whether after explant, AGM HSCs remain BMP-activated. Interestingly, after explant, both GFP+ and GFPfractions contained multilineage, self-renewing HSCs. In such explants when Hh or MAPK pathways are inhibited, only the non-BMP-activated HSC activity is abolished. The Hh inhibition effect on AGM HSCs could be rescued by exogeneous VEGF addition, but VEGF could not rescue the HSC defects caused by MAPK inhibition. These results suggest that VEGF acts downstream of Hh and further activates the MAPK pathway to control AGM HSCs. In conclusion, our data provide clear evidence of an interactive molecular cascade involving the BMP, Hh and MAPK signaling pathways in the control of AGM HSC development. P1087 TWO ADULT-TYPE HSC SUBSETS COEXISTENT IN MOUSE Mihaela Crisan, Chris Vink, Tomoko Yamada-Inagawa, Alex Neagu, Caterina Purini, Sofia Karkanpouna, Reinir van der Linden, and Elaine Dzierzak Cell Biology, Erasmus MC Stem Cell Institute, Rotterdam, Netherlands; Dept. of Molecular and Cell Biology, Centre of Biomedical Genetics, Leiden, Netherlands