Different effects of TrkA expression in neuroblastoma cell lines with or without MYCN amplification

BACKGROUND

Expression of the neurotrophin receptor TrkA is associated with a favorable prognosis in neuroblastoma (NB) and promotes growth inhibition and neuronal differentiation. Aggressive, MYCN-amplified NB tumors express little or no TrkA mRNA, suggesting that MYCN overexpression may inhibit TrkA expression.

PROCEDURE

To study the interactions of TrkA expression and MYCN amplification in NB, we stably expressed the TrkA receptor in the MYCN single copy cell lines SH-SY5Y and NB69 as well as in the MYCN amplified cell lines CHP134 and IMR5.

RESULTS

All four transfected cell lines demonstrated high TrkA expression and similar activation of the TrkA receptor and of mitogen-activated protein kinases as well as induction of immediate-early genes in response to nerve growth factor (NGF). Introduction of TrkA restored NGF responsiveness of SH-SY5Y and NB69 cells, as demonstrated by morphologic differentiation, growth inhibition, and enhanced survival in serum-free medium. However, no morphologic, growth, or survival responses to NGF were detected in MYCN-amplified CHP134 and IMR5 TrkA transfectants.

CONCLUSIONS

Thus, transfection of TrkA into MYCN amplified NB cell lines only partly restored the TrkA/NGF signaling pathway, suggesting additional inhibitory effects of MYCN overexpression on TrkA signaling.

BIN1 inhibits colony formation and induces apoptosis in neuroblastoma cell lines with MYCN amplification

BACKGROUND

MYCN amplification and overexpression occurs in 25% of neuroblastomas and independently predicts for poor prognosis disease, an effect thought to be mediated by its role as a transcriptional activator of growth promoting genes. However, in many mammalian cells, deregulated expression of MYC family genes (including MYCN) induces apoptosis. We hypothesized that BIN1, a MYC interacting protein capable of inducing apoptosis, may be an important regulator of MYCN in neuroblastoma.

RESULTS

BIN1 expression was found to be reduced in MYCN-amplified cell lines. Further, forced expression of BIN1 markedly reduced colony formation in MYCN-amplified, but not single-copy, cell lines. This effect appeared to be caused by an increase in apoptosis, and was augmented by serum deprivation and concurrent cytotoxic drug therapy in cell culture

CONCLUSION

BIN1 inactivation may be necessary for MYCN overexpression to lead to cellular proliferation rather than programmed cell death in neuroblastomas with MYCN amplification.

Identification of a 1-megabase consensus region of deletion at 1p36.3 in primary neuroblastomas

BACKGROUND

Deletion of the distal short arm of chromosome 1 occurs frequently in neuroblastoma. In addition, neuroblastoma has been described in children with constitutional deletions within 1p36, supporting the existence of one or more neuroblastoma suppressor genes within this region.

PROCEDURE

We have pursued a 1p36 tumor suppressor gene identification strategy that has included deletion mapping of 566 primary neuroblastomas and 46 neuroblastoma-derived cell lines, and have determined the parental origin of the deleted 1p homologue in 44 cases to determine whether there is evidence for genomic imprinting within this region.

RESULTS AND CONCLUSIONS

We have identified a 1-Mb consensus region of deletion within 1p36.3 defined by primary tumor deletions, constructed a physical map of the region that is being sequenced to completion, and have identified and prioritized candidate genes within this region for further analyses.

Expression of neurotrophin receptor TrkA inhibits angiogenesis in neuroblastoma

BACKGROUND

Mechanisms regulating the expression of angiogenic factors in tumor cells are largely unknown. High expression of the neurotrophin receptor TrkA in neuroblastomas (NB) is associated with favorable prognosis, whereas TrkB is expressed on aggressive, MYCN-amplified NB.

PROCEDURE

To investigate the biological effects of TrkA and TrkB expression on angiogenesis in NB, we examined the expression of angiogenic factors in the human NB cell line SY5Y and its TrkA and TrkB transfectants.

RESULTS

In comparison to parental SY5Y cells, mRNA and protein levels of angiogenic factors were significantly reduced in SY5Y-TrkA cells, whereas SY5Y-TrkB cells did not demonstrate a significant change. Conditioned medium (CM) of parental SY5Y and SY5Y-TrkB cells induced endothelial cell proliferation, but this effect was completely absent in SY5Y-TrkA cells. TrkA expression also resulted in severely impaired tumorigenicity in a mouse xenograft model, and was associated with reduced angiogenic factor expression and less vascularization of tumors, as determined by immunohistochemistry and an in vivo Matrigel assay.

p75 mediated apoptosis in neuroblastoma cells is inhibited by expression of TrkA

BACKGROUND

Neurotrophins mediate their effects by binding to members of the Trk family of receptor tyrosine kinases and to the low-affinity nerve growth factor receptor p75. Nerve growth factor (NGF) has been demonstrated to support survival and differentiation of neuroblastoma (NB) cells by activation of the TrkA receptor. The p75 receptor belongs to the tumor necrosis factor (TNF) family of death receptors and has been suggested as a receptor that mediates apoptosis in neuronal and NB cells.

PROCEDURE

To investigate the effect of p75 expression in NB, we transfected the p75 cDNA into SH-SY5Y cells, an NB cell line lacking expression of both p75 and TrkA.

RESULTS

Cell clones expressing elevated levels of p75 showed a high degree of apoptosis even in 10% serum-supplemented medium. Apoptotic signaling by p75 was ligand-independent and only partly caspase-dependent. The level of apoptosis correlated directly with the expression level of the receptor, indicating that p75 may activate the cell death program directly. However, additional transfection of TrkA into SY5Y-p75 cells resulted in a significantly reduced rate of apoptosis even in the absence of NGF.

CONCLUSIONS

Thus, expression of the TrkA receptor itself inhibits p75 mediated apoptosis in NB cells.

Prognostic significance of EPHB6, EFNB2, and EFNB3 expressions in neuroblastoma

BACKGROUND

EPH family receptor tyrosine kinases and their ligand ephrins play pivotal roles in development. High-level expression of transcripts encoding EPHB6 receptors (EPHB6), its ligands ephrin-B2 and ephrin-B3 (EFNB2, EFNB3) is predictive of favorable disease outcome of neuroblastoma (NB). When combined with TrkA expression, the expression of EPHB6, EFNB2, or EFNB3 predicts more accurately the disease outcome than each of the four variables alone.

PROCEDURE

Cox regression and Kaplan-Meier analyses were used to assess the prognostic significance of EPHB6, EFNB2, EFNB3, and TrkA expressions in NB without MYCN amplification.

RESULTS

High-level expression of EFNB3 or TrkA predicted favorable NB outcome of NB without MYCN amplification (p < 0.03). As found in the general NB population, EPHB6, EFNB2, or EFNB3 expression in combination with TrkA expression was significantly predictive of the disease outcome of normal MYCN NB (p < 0.01).

CONCLUSIONS

EPHB6, EFNB2, and EFNB3 expressions may permit further refinement of the prognostic stratification of NB into favorable and unfavorable groups.

Schwann cell-conditioned medium inhibits angiogenesis in vitro and in vivo

BACKGROUND

Neuroblastomas are biologically heterogeneous tumors that consist of two main cell populations: neuroblastic/ganglionic cells and Schwann cells. The amount of Schwannian stroma strongly impacts prognosis. Low tumor vascularity, localized stage, and favorable outcome are associated with tumors that are Schwannian stroma-rich/stroma-dominant.

PROCEDURE

To investigate if Schwann cells play a role in inhibiting angiogenesis in neuroblastoma tumors, we examined the ability of human Schwann cell-conditioned medium to affect bFGF- and VEGF-induced endothelial cell proliferation and migration, and in vivo angiogenesis.

RESULTS

Schwann cell-conditioned medium significantly inhibited bFGF- and VEGF-induced endothelial cell proliferation and migration. This effect appears to be specific for endothelial cells as smooth muscle cell and fibroblast proliferation were not inhibited by this medium. Schwann cell-conditioned medium also inhibited in vivo angiogenesis in rat corneal assays.

CONCLUSIONS

Schwann cells produce a potent inhibitor(s) of angiogenesis that may be responsible for the low level of vascularity and more benign clinical behavior of Schwannian stroma-rich/stroma-dominant neuroblastoma tumors. Studies to identify the inhibitor(s) are ongoing.

Localization of a hereditary neuroblastoma predisposition gene to 16p12-p13

BACKGROUND

Hereditary predisposition to develop neuroblastoma segregates as an autosomal dominant Mendelian trait.

PROCEDURE

We have performed linkage analysis on 10 families with neuroblastoma to localize a hereditary neuroblastoma predisposition gene (HNB1).

RESULTS

A single genomic interval at chromosome bands 16p12-p13 was consistent with linkage (lod = 3.46), and identification of informative recombinants defined a 25.9-cM critical region between D16S748 and D16S3068. Loss of heterozygosity was identified in 5/12 familial (42%) and 55/259 nonfamilial (21%) neuroblastomas at multiple 16p polymorphic loci. A 12.8-cM smallest region of overlap of deletions was identified within the interval defined by linkage analysis (tel-D16S764-D16S412-cen).

CONCLUSIONS

Taken together, these data suggest that HNB1 is located at 16p12-p13 and that inactivation of this gene may contribute to the pathogenesis of nonfamilial neuroblastomas.

Deletion of 11q23 is a frequent event in the evolution of MYCN single-copy high-risk neuroblastomas

BACKGROUND

Deletions of the long arm of chromosome 11 are frequently identified in human neuroblastomas.

PROCEDURE

We screened 394 primary neuroblastomas and 52 tumor-derived cell lines with a panel of 11q and 11p polymorphic markers to determine the frequency of chromosome 11 allelic deletion, and to differentiate partial deletions of chromosome 11q (unb[11q] LOH) from whole chromosome loss.

RESULTS

Allelic deletion occurred most frequently at cytogenetic band 11q23 and was detected in 161 primary neuroblastomas (41%) and 18 cell lines (35%). Eighty-seven tumors (22%) had unb[11q] LOH with a heterogeneous distribution of deletion breakpoints. Unb[11q] LOH was highly correlated with age > 1 year at diagnosis (P = 0.008), stage 4 disease (P = 0.001), unfavorable Shimada histopathology (P < 0.001), and assignment to a high-risk therapeutic protocol (P < 0.001), and was inversely correlated with MYCN amplification (P = 0.018). Patients whose tumors showed unb[11q] LOH were less likely to survive (P < 0.001), but there was only a trend towards an independent prognostic influence in multivariate analyses.

CONCLUSIONS

Thus, structural rearrangements resulting in unb[11q] LOH commonly occur during the malignant evolution of high-risk neuroblastomas with single-copy MYCN.

Schwann cell-conditioned medium inhibits angiogenesis

Neuroblastomas are biologically heterogeneous tumors that consist of two main cell populations: neuroblastic/ganglionic cells and Schwann cells. The amount of Schwannian stroma strongly impacts prognosis, and favorable outcome is associated with tumors that are Schwannian stroma rich/stroma dominant. At the present time, there is controversy regarding the origin of Schwann cells in neuroblastoma tumors. However, recent studies have suggested that the Schwann cells in mature neuroblastoma tumors may be normal cells that produce soluble substances that enhance the survival and differentiation of neuroblastoma cell lines. Previously, we reported that in neuroblastoma, high vascular index correlated with clinically aggressive disease. In contrast, tumors with favorable histology and abundant Schwannian stroma had low tumor vascularity. As a first step toward investigating whether Schwann cells also play a role in inhibiting angiogenesis in neuroblastoma tumors, we examined the ability of conditioned medium collected from normal human Schwann cells to affect basic fibroblast growth factor- and vascular endothelial growth factor-induced endothelial cell proliferation and migration and in vivo angiogenesis. In vitro angiogenesis assays were also performed with conditioned medium collected from Schwann cells derived from a Schwannian stroma-dominant neuroblastoma tumor. Our results indicate that Schwann cells derived from either adult nerve or tumor tissue produce a potent inhibitor(s) of angiogenesis. Expression studies revealed tissue inhibitor of metalloproteinase (TIMP)-2 in conditioned medium collected from both normal and tumor-derived Schwann cells. In addition, TIMP-2 was detected in the cytoplasm of Schwann cells and ganglion cells in stroma-rich/stroma-dominant neuroblastoma tumors by immunohistochemistry studies. We postulate that the low level of vascularity and more benign clinical behavior of Schwannian stroma-rich/stroma-dominant neuroblastoma tumors result from the Schwann cell production of TIMP-2 and/or other inhibitors of angiogenesis.

Implications of EPHB6, EFNB2, and EFNB3 expressions in human neuroblastoma

Neuroblastoma (NB) is a common pediatric tumor that exhibits a wide range of biological and clinical heterogeneity. EPH (erythropoietin-producing hepatoma amplified sequence) family receptor tyrosine kinases and ligand ephrins play pivotal roles in neural and cardiovascular development. High-level expression of transcripts encoding EPHB6 receptors (EPHB6) and its ligands ephrin-B2 and ephrin-B3 (EFNB2, EFNB3) is associated with low-stage NB (stages 1, 2, and 4S) and high TrkA expression. In this study, we showed that EFNB2 and TrkA expressions were associated with both tumor stage and age, whereas EPHB6 and EFNB3 expressions were solely associated with tumor stage, suggesting that these genes were expressed in distinct subsets of NB. Kaplan-Meier and Cox regression analyses revealed that high-level expression of EPHB6, EFNB2, and EFNB3 predicted favorable NB outcome (P<0.005), and their expression combined with TrkA expression predicted the disease outcome more accurately than each variable alone (P<0.00005). Interestingly, if any one of the four genes (EPHB6, EFNB2, EFNB3, or TrkA) was expressed at high levels in NB, the patient survival was excellent (>90%). To address whether a good disease outcome of NB was a consequence of high-level expression of a "favorable NB gene," we examined the effect of EPHB6 on NB cell lines. Transfection of EPHB6 cDNA into IMR5 and SY5Y expressing little endogenous EPHB6 resulted in inhibition of their clonogenicity in culture. Furthermore, transfection of EPHB6 suppressed the tumorigenicity of SY5Y in a mouse xenograft model, demonstrating that high-level expressions of favorable NB genes, such as EPHB6, can in fact suppress malignant phenotype of unfavorable NB.

Resistance to TRAIL-induced apoptosis in primitive neuroectodermal brain tumor cells correlates with a loss of caspase-8 expression

TNF-related apoptosis-inducing ligand (TRAIL) is a potent inducer of apoptosis in adult malignant glioma and various other human solid tumor models but not in normal tissues. To characterize the TRAIL death pathway in childhood primitive neuroectodermal brain tumor (PNET), 8 human PNET cell lines were tested for TRAIL-induced apoptosis. TRAIL-sensitivity of the PNET cell lines was correlated with mRNA expression levels of TRAIL, its agonistic (TRAIL-R1, TRAIL-R2) and antagonistic (TRAIL-R3, TRAIL-R4) receptors, cellular FLICE-like inhibitory protein (cFLIP), caspase-3 and caspase-8. Three of 8 PNET cell lines tested were susceptible to TRAIL-induced apoptosis. Sensitivity to TRAIL-induced apoptosis did not correlate with mRNA expression of TRAIL receptors or cFLIP. However, all TRAIL-sensitive PNET cell lines expressed caspase-8 mRNA and protein, while none of the five TRAIL-resistant PNET cell lines expressed caspase-8 protein. Treatment with the methyltransferase inhibitor 5-aza-2'-deoxycytidine restored mRNA expression of caspase-8 and TRAIL-sensitivity in formerly TRAIL-resistant PNET cells, suggesting that gene methylation inhibits caspase-8 transcription in these cells. We conclude, that loss of caspase-8 mRNA is an important mechanism of TRAIL-resistance in PNET cells. Treatment with recombinant soluble TRAIL, possibly in combination with methyltransferase inhibitors, represents a promising therapeutic approach for PNET that deserves further investigation.

Physical mapping of the CA6, ENO1, and SLC2A5 (GLUT5) genes and reassignment of SLC2A5 to 1p36.2

Several human malignancies frequently exhibit deletions or rearrangements of the distal short arm of chromosome 1 (1p36), and a number of genetic diseases also map to this region. The carbonic anhydrase (CA6) and alpha-enolase (ENO1) genes, previously mapped to 1p36, were physically linked in yeast- and P1-artificial chromosome (YAC and PAC) contigs. PACs from the contig were mapped to 1p36.2 by fluorescence in situ hybridization. The ESTs D1S2068, D1S274E, D1S3275, and stSG4370 were also placed in the same contig. The physical map was integrated with the genetic map of chromosome 1 by assignment of genetic markers D1S160, D1S1615, and D1S503 to the contig. Sequencing of the EST clone representing D1S274E indicated that it was derived from the same transcript as D1S2068E and corresponded to the SLC2A5 (GLUT5) gene, previously assigned to 1p31. Reassignment of SLC2A5 to 1p36.2 was confirmed by somatic cell and radiation hybrid mapping panels and was consistent with previous EST mapping data. Sequencing of the EST clone for D1S274E revealed the presence of intronic sequences, suggesting that the clone was derived from an unprocessed message. The presence of unprocessed and/or alternatively spliced EST clones has potential ramifications for EST-based genomic projects. This information should facilitate the mapping of tumor suppressor and genetic disease loci that have been localized to this region.

Gene amplification in PNETs/medulloblastomas: mapping of a novel amplified gene within the MYCN amplicon

OBJECTIVES

The pathological entity of primitive neuroectodermal tumour/medulloblastoma (PNET/MB) comprises a very heterogeneous group of neoplasms on a clinical as well as on a molecular level. We evaluated the importance of DNA amplification in medulloblastomas and other primitive neuroectodermal tumours (PNETs) of the CNS.

METHOD

Restriction landmark genomic scanning (RLGS), a method that allows the detection of low level amplification, was used. RLGS provides direct access to DNA sequences circumventing positional cloning efforts. Furthermore, we analysed several samples by CGH.

DESIGN

Twenty primary medulloblastomas, five supratentorial PNETs, and five medulloblastoma cell lines were studied.

RESULTS

Although our analysis confirms that gene amplification is generally a rare event in childhood PNET/MB, we found a total of 17 DNA fragments that were amplified in seven different tumours. Cloning and sequencing of several of these fragments confirmed the previous finding of MYC amplification in the cell line D341 Med and identified novel DNA sequences amplified in PNET/MB. We describe for the first time amplification of the novel gene, NAG, in a subset of PNET/MB. Despite genomic amplification, NAG was not overexpressed in the tumours studied. We have determined that NAG maps less than 50 kb 5' of DDX1 and approximately 400 kb telomeric of MYCN on chromosome 2p24.

CONCLUSION

We found a similar but slightly higher frequency of amplification than previously reported. We present several DNA fragments that may belong to the CpG islands of novel genes amplified in a small subset of PNET/MB. As an example we describe for the first time the amplification of NAG in the MYCN amplicon in PNET/MB.

Prognostic and biological role of neurotrophin-receptor TrkA and TrkB in neuroblastoma

Expression of different neurotrophin receptors of the tyrosine kinase (Trk) family plays an important role in the biology and clinical behavior of neuroblastomas (NB). Observations from several independent studies suggest that high expression of TrkA is present in NB with favorable biological features and highly correlated with patient survival, whereas TrkB is mainly expressed on unfavorable, aggressive NB with MYCN-amplification. To determine expression of Trk receptors and ligands in primary NB, we developed a reliable semiquantitative duplex RT-PCR protocol, that requires only 1 microgram RNA per tumor sample. Activation of TrkA by its ligand nerve growth factor (NGF) initiates a cascade of signaling events and promotes neuronal differentiation in vitro. Activation of TrkB by its ligand brain derived neurotrophic factor (BDNF) has been associated with proliferation and survival of NB cells. To study Trk signal transduction pathways and their biological effects in NB, we stably expressed TrkA and TrkB cDNA in the human NB cell line SH-SY5Y. Introduction of TrkA and TrkB restored responsiveness of SH-SY5Y cells to the ligands NGF and BDNF, respectively, and resulted in morphological differentiation. Expression of TrkA resulted in growth inhibition of the transfectants compared to parental cells, whereas TrkB transfectants demonstrated an increased proliferation rate. Further insight into the differences of TrkA and TrkB signaling may suggest new options for the treatment of NB. As expression of TrkA is a strong prognostic factor especially in MYCN non-amplified NB, a prospective study of Trk receptor expression using RT-PCR should be performed for German neuroblastoma patients.

High-level expression of angiogenic factors is associated with advanced tumor stage in human neuroblastomas

Angiogenesis is essential for tumor growth and metastasis and depends on the production of angiogenic factors by tumor cells. Neuroblastoma (NB) is a common pediatric tumor of neural crest origin, which is biologically and clinically heterogeneous. Increased tumor vascular index correlates with poor outcome of NB. To determine which angiogenic factors contribute to NB angiogenesis and thereby support tumor progression, we examined the expression of eight angiogenic factors [vascular endothelial growth factor (VEGF), VEGF-B, VEGF-C, basic fibroblast growth factor, angiopoietin (Ang)-1, Ang-2, transforming growth factor alpha, and platelet-derived growth factor (PDGF)] by semiquantitative RT-PCR in 37 NB primary tumors and in 22 NB cell lines. We also analyzed the relationship between angiogenic factor expression and clinicopathological factors as well as patient survival. All eight angiogenic factors examined were expressed at various levels in NB cell lines and tumors, suggesting their involvement in NB angiogenesis. The expression levels of most angiogenic factors were correlated with each other, suggesting their synergy in regulating the angiogenic process. Significantly higher expression levels of VEGF, VEGF-B, VEGF-C, basic fibroblast growth factor, Ang-2, transforming growth factor alpha, and PDGF-A (P < 0.0001-0.026) were found in advanced-stage tumors (stages 3 and 4) compared with low-stage tumors (stages 1, 2, and 4S). Expression of PDGF-A was significantly associated with patient survival (P = 0.04). The redundancy in angiogenic factor expression suggests that inhibition of VEGF bioactivity alone might not be a sufficient approach for antiangiogenic therapy of human NB.

Natural history and biology of stage A neuroblastoma: a Pediatric Oncology Group Study

PURPOSE

To prospectively analyze the outcome of patients with Stage A neuroblastoma (NB) treated with surgery alone, especially with regard to the prognostic significance of age, tumor site, MYCN copy number, tumor cell ploidy, and histology.

PATIENTS AND METHODS

The clinical course of 329 patients with Stage A disease registered on the POG NB Biology Study #9047 between February, 1990 and October, 1997 were evaluated. Age, tumor site, MYCN copy number, tumor cell ploidy, and histology were analyzed for their impact on event-free survival (EFS) and survival (S).

RESULTS

The 5-year estimated EFS and S rates for the 329 patients were 91% (+/-3%) and 96% (+/-2%), respectively. The EFS rate was similar for infants younger than 12 months and children age 12 months or older, but age older than 12 months was predictive of lower S rates (P = 0.044). Patients with adrenal, abdominal non-adrenal, thoracic, and cervical tumors had similar S rates. The majority of patients had tumors with favorable biologic features, and only 3% had MYCN amplification. For infants with diploid tumors, the EFS rate was 82% (+/-16%), but effective therapy yielded an S rate of 100%. Rate of S was 80% (+/-26%) and 64% (+/-27%) for patients with unfavorable tumor histology and MYCN-amplified tumors, respectively.

CONCLUSION

The outcome for patients with Stage A NB treated with surgery alone is excellent. Although EFS and S rates were significantly worse for patients with MYCN-amplified tumors, a subset achieved long-term remission after surgery alone. For patients with Stage A and MYCN amplification, additional factors are needed to distinguish the patients who will achieve long-term remission with surgery alone from those who will develop recurrent disease.

Loss of heterozygosity at 1p36 independently predicts for disease progression but not decreased overall survival probability in neuroblastoma patients: a Children's Cancer Group study

PURPOSE

To determine the independent prognostic significance of 1p36 loss of heterozygosity (LOH) in a representative group of neuroblastoma patients.

PATIENTS AND METHODS

Diagnostic tumor specimens from 238 patients registered onto the most recent Children's Cancer Group phase III clinical trials were assayed for LOH with 13 microsatellite polymorphic markers spanning chromosome band 1p36. Allelic status at 1p36 was correlated with other prognostic variables and disease outcome.

RESULTS

LOH at 1p36 was detected in 83 (35%) of 238 neuroblastomas. There was a correlation of 1p36 LOH with age at diagnosis greater than 1 year (P = .026), metastatic disease (P<.001), elevated serum ferritin level (P<.001), unfavorable histopathology (P<.001), and MYCN oncogene amplification (P<.001). LOH at 1p36 was associated with decreased event-free survival (EFS) and overall survival (OS) probabilities (P<.0001). For the 180 cases with single-copy MYCN, 1p36 LOH status was highly correlated with decreased EFS (P = .0002) but not OS (P = .1212). Entering 1p36 LOH into a multivariate regression model suggested a trend toward an independent association with decreased EFS (P = .0558) but not with decreased OS (P = .3687). Furthermore, allelic status at 1p36 was the only prognostic variable that was significantly associated with decreased EFS in low-risk neuroblastoma patients (P = .0148).

CONCLUSION

LOH at 1p36 is independently associated with decreased EFS, but not OS, in neuroblastoma patients. Determination of 1p36 allelic status may be useful for predicting which neuroblastoma patients with otherwise favorable clinical and biologic features are more likely to have disease progression.

Molecular dissection of TrkA signal transduction pathways mediating differentiation in human neuroblastoma cells

Activation of the neurotrophin receptor TrkA by its ligand nerve growth factor (NGF) initiates a cascade of signaling events leading to neuronal differentiation in vitro and might play an important role in the differentiation of favorable neuroblastomas (NB) in vivo. To study TrkA signal transduction pathways and their effects on differentiation in NB, we stably expressed wild-type TrkA and five different TrkA mutants in the NGF unresponsive human NB cell line SH-SY5Y. Resulting clones were characterized by TrkA mRNA and protein expression, and by autophosphorylation of the receptor. Introduction of wild-type TrkA restored NGF responsiveness of SH-SY5Y cells, as demonstrated by morphological differentiation, activation of mitogen-activated protein kinases (MAPK) and induction of immediate-early genes. Expression of TrkA in the absence of NGF resulted in growth inhibition of transfectants compared to parental cells, whereas NGF-treatment increased their proliferation rate. Analysis of downstream signal transduction pathways indicated that NGF-induced differentiation was dependent on TrkA kinase activity. Our data suggest that several redundant pathways are present further downstream, but activation of the RAS/MAPK signaling pathway seems to be of major importance for NGF mediated differentiation of NB cells. Our results also show that the signaling effector SH2-B is a substrate of NGF-mediated Trk signaling in NB, whereas it is not activated by NGF in rat pheochromocytoma PC12 cells. This might explain the differences we observed in TrkA signaling between neuroblastoma and PC12 cells. Further insight into TrkA signaling may suggest new options for the treatment of NB.

Relative quantitative RT-PCR protocol for TrkB expression in neuroblastoma using GAPD as an internal control

An RT-PCR protocol for the relative quantitative measurement of TrkB transcripts using glyceraldehyde-3-phosphate-dehydrogenase (GAPD) transcripts as an internal control is described. Both TrkB and GAPD sequences were co-amplified in the exponential phase of amplification using 5'-biotinylated primers. The PCR products were subjected to PAGE, electro-transferred to nylon membrane and detected by a chemiluminescent procedure using alkaline phosphatase conjugated with avidin. Signals detected on X-ray film were analyzed by densitometry. The ratio between TrkB and GAPD expression levels was determined to normalize the expression levels of TrkB transcripts. Initially, strong signals of GAPD transcripts led to overexposure of X-ray film compared to those of TrkB, which causes difficulties in the accurate determination of the TrkB/GAPD ratio. To circumvent this problem, uniformly biotinylated GAPD primers were replaced with a mixture of biotinylated and non-biotinylated GAPD primers of the same sequence and concentration. GAPD signals detected on X-ray film were proportionally decreased as the amount of biotin-labeled primers was reduced in the total GAPD primers. This modification enabled both GAPD and TrkB signals to be analyzed within the linear range of X-ray film detection without affecting the amplification efficiency of TrkB sequence. Use of composite primers may have a wide range of applicability in quantitative analysis of nucleic acids.

Biologic factors determine prognosis in infants with stage IV neuroblastoma: A prospective Children's Cancer Group study

PURPOSE

A prospective Children's Cancer Group study, CCG-3881, has been completed to determine if a more accurate prediction of prognosis by biologic features can identify subgroups of infants with stage IV neuroblastoma (NBL) who require differing intensities of treatment.

PATIENTS AND METHODS

One hundred thirty-four infants were registered from June 1989 to August 1995, with a median follow-up of 47.1 months (range, 0 to 88 months). The biologic factors examined were tumor MYCN copy number, Shimada histopathologic classification, serum ferritin, and bone marrow immunocytology (sensitivity, one tumor cell per 10(5) bone marrow cells). Patients treated on CCG-3881 (n = 116) received four-drug chemotherapy for 9 months (cisplatin, cyclophosphamide, doxorubicin, and etoposide), with surgery and local radiation to residual disease. After January 1991, all subsequent infants with tumor MYCN amplification (n = 18) were transferred after one cycle of therapy to the high-risk CCG-3891 protocol (open January 1991 to April 1996) for more intensive treatment.

RESULTS

The 3-year event-free survival (EFS) and overall survival (mean +/- SD) for the 134 infants were 63% +/- 5% and 71% +/- 5%, respectively. Patients whose tumors were without MYCN amplification had a 93% +/- 4% 3-year EFS, whereas those with amplified MYCN had a 10% +/- 7% 3-year EFS (P <. 0001). Each of the other biologic features studied had prognostic significance in univariate analysis but not after stratifying by MYCN copy number.

CONCLUSION

Infants less than 1 year of age at diagnosis with stage IV NBL have a much improved outcome compared with children >/= 1 year of age. Nonamplified MYCN tumors identify a group of infants with a 93% +/- 4% EFS, whereas amplified MYCN copy number clearly identifies patients who are unlikely to survive despite intensive chemotherapy.

Favorable biology and outcome of stage IV-S neuroblastoma with supportive care or minimal therapy: a Children's Cancer Group study

PURPOSE

Stage IV-S neuroblastoma is a metastatic disease associated with spontaneous regression and good survival, but 10% to 20% of infants die from early complications. The purpose of this study was to evaluate outcome and prognostic factors in infants with stage IV-S neuroblastoma treated prospectively with supportive care only or, in symptomatic patients, with low-dose cytotoxic therapy.

PATIENTS AND METHODS

Eighty eligible infants were studied for response and survival with supportive care or, for symptomatic patients, cyclophosphamide 5 mg/kg/d for 5 days with or without hepatic radiation of 4.5 Gy over 3 days. Staging was reviewed centrally, and MYCN gene copy number, Shimada histopathologic classification, serum ferritin levels, and bone marrow immunocytology were determined.

RESULTS

Stage IV-S and International Neuroblastoma Staging System stage 4S were 98% concordant. MYCN was not amplified in any of the tumors tested (n = 58), and Shimada histopathologic classification was favorable in 96% (n = 68/71). The 5-year event-free survival (EFS) rate for all infants was 86% and the survival rate was 92%. Supportive care was the only treatment provided for 44 (55%) of 80 infants, and their 5-year survival rate was 100%, compared with 81% survival for those requiring cytotoxic therapy for symptoms (P =.005). Five of six deaths were in infants younger than 2 months of age at diagnosis and were due to complications of extensive abdominal involvement with respiratory compromise or disseminated intravascular coagulation. Although age </= 3 months at diagnosis was significant for EFS (P =. 043), it was less significant for survival (P =.077). The only other significant factor predictive for improved survival was favorable Shimada histopathologic classification. Sites of metastatic involvement (liver, skin, or bone marrow) and surgical resection of the primary tumor were not significant for survival.

CONCLUSION

This study confirms the favorable biologic features and excellent survival of infants with stage IV-S neuroblastoma with minimal therapy. Infants younger than 2 months old at diagnosis with rapidly progressive abdominal disease may benefit from earlier and more intensive treatment.

Antitumor activity of CEP-751 (KT-6587) on human neuroblastoma and medulloblastoma xenografts

Neuroblastoma (NBL) and medulloblastoma (MBL) are tumors of the neuroectoderm that occur in children. NBL and MBL express Trk family tyrosine kinase receptors, which regulate growth, differentiation, and cell death. CEP-751 (KT-6587), an indolocarbazole derivative, is an inhibitor of Trk family tyrosine kinases at nanomolar concentrations. This study was designed to determine the effect of CEP-751 on the growth of NBL and MBL cell lines as xenografts. In vivo studies were conducted on four NBL cell lines (IMR-5, CHP-134, NBL-S, and SY5Y) and three MBL cell lines (D283, D341, and DAOY) using two treatment schedules: (a) treatment was started after the tumors were measurable (therapeutic study); or (b) 4-6 days after inoculation, before tumors were palpable (prevention study). CEP-751 was given at 21 mg/kg/dose administered twice a day, 7 days a week; the carrier vehicle was used as a control. In therapeutic studies, a significant difference in tumor size was seen between treated and control animals with IMR-5 on day 8 (P = 0.01), NBL-S on day 17 (P = 0.016), and CHP-134 on day 15 (P = 0.034). CEP-751 also had a significant growth-inhibitory effect on the MBL line D283 (on day 39, P = 0.031). Inhibition of tumor growth of D341 did not reach statistical significance, and no inhibition was apparent with DAOY. In prevention studies, CEP-751 showed a modest growth-inhibitory effect on IMR5 (P = 0.062) and CHP-134 (P = 0.049). Furthermore, inhibition of growth was greater in the SY5Y cell line transfected with TrkB compared with the untransfected parent cell line expressing no detectable TrkB. Terminal deoxynucleotidyl transferase-mediated nick end labeling studies showed CEP-751 induced apoptosis in the treated CHP-134 tumors, whereas no evidence of apoptosis was seen in the control tumors. Finally, there was no apparent toxicity identified in any of the treated mice. These results suggest that CEP-751 may be a useful therapeutic agent for NBL or MBL.

Treatment of high-risk neuroblastoma with intensive chemotherapy, radiotherapy, autologous bone marrow transplantation, and 13-cis-retinoic acid. Children's Cancer Group

BACKGROUND

Children with high-risk neuroblastoma have a poor outcome. In this study, we assessed whether myeloablative therapy in conjunction with transplantation of autologous bone marrow improved event-free survival as compared with chemotherapy alone, and whether subsequent treatment with 13-cis-retinoic acid (isotretinoin) further improves event-free survival.

METHODS

All patients were treated with the same initial regimen of chemotherapy, and those without disease progression were then randomly assigned to receive continued treatment with myeloablative chemotherapy, total-body irradiation, and transplantation of autologous bone marrow purged of neuroblastoma cells or to receive three cycles of intensive chemotherapy alone. All patients who completed cytotoxic therapy without disease progression were then randomly assigned to receive no further therapy or treatment with 13-cis-retinoic acid for six months.

RESULTS

The mean (+/-SE) event-free survival rate three years after the first randomization was significantly better among the 189 patients who were assigned to undergo transplantation than among the 190 patients assigned to receive continuation chemotherapy (34+/-4 percent vs. 22+/-4 percent, P=0.034). The event-free survival rate three years after the second randomization was significantly better among the 130 patients who were assigned to receive 13-cis-retinoic acid than among the 128 patients assigned to receive no further therapy (46+/-6 percent vs. 29+/-5 percent, P=0.027).

CONCLUSIONS

Treatment with myeloablative therapy and autologous bone marrow transplantation improved event-free survival among children with high-risk neuroblastoma. In addition, treatment with 13-cis-retinoic acid was beneficial for patients without progressive disease when it was administered after chemotherapy or transplantation.