Amplification and expression of the N-myc gene in neuroblastoma

Calreticulin Expression Controls Cellular Redox, Stemness, and Radiosensitivity to Function as a Novel Adjuvant for Radiotherapy in Neuroblastoma

Radiotherapy (RT) is currently only used in children with high-risk neuroblastoma (NB) due to concerns of long-term side effects as well as lack of effective adjuvant. Calreticulin (CALR) has served distinct physiological roles in cancer malignancies; nonetheless, impact of radiation on chaperones and molecular roles they play remains largely unknown. In present study, we systemically analyzed correlation between CALR and NB cells of different malignancies to investigate potential role of CALR in mediating radioresistance of NB. Our data revealed that more malignant NB cells are correlated to lower CALR expression, greater radioresistance, and elevated stemness as indicated by colony- and neurospheroid-forming abilities and vice versa. Of note, manipulating CALR expression in NB cells of varying endogenous CALR expression manifested changes in not only stemness but also radioresistant properties of those NB cells. Further, CALR overexpression resulted in greatly enhanced ROS and led to increased secretion of proinflammatory cytokines. Importantly, growth of NB tumors was significantly hampered by CALR overexpression and was synergistically ablated when RT was also administered. Collectively, our current study unraveled a new notion of utilizing CALR expression in malignant NB to diminish cancer stemness and mitigate radioresistance to achieve favorable therapeutic outcome for NB.

Genetics of congenital solid tumors

When we discuss the genetics of tumors, we cannot fail to remember that in the second decade of the twentieth century, more precisely in 1914, Theodore Boveri defined for the first time the chromosomal bases of cancer. In the last 30 years, progresses in genetics have only confirmed Boveri's remarkable predictions made more than 80 years ago. Before the cloning of the retinoblastoma 1 (RB1) gene, the existence of a genetic component in most, if not all, solid childhood tumors were well known. The existence of familial tumor aggregations has been found much more frequently than researchers expected to find at random. Sometimes, the demonstration of this family predisposition was very difficult, because the survival of children diagnosed as having a certain tumor, up to an age at which reproduction and procreation is possible, was very rare. In recent years, advances in the diagnosis and treatment of these diseases have made it possible for these children to survive until the age when they were able to start their own families, including the ability to procreate. Four distinct groups of so-called cancer genes have been identified: oncogenes, which promote tumor cell proliferation; tumor suppressor genes, which inhibit this growth/proliferation; anti-mutational genes, with a role in deoxyribonucleic acid (DNA) stability; and micro-ribonucleic acid (miRNA) genes, with a role in the posttranscriptional process.

MYCN is amplified during S phase, and c‑myb is involved in controlling MYCN expression and amplification in MYCN‑amplified neuroblastoma cell lines

Neuroblastoma derived from primitive sympathetic neural precursors is a common type of solid tumor in infants. MYCN proto-oncogene bHLH transcription factor (MYCN) amplification and 1p36 deletion are important factors associated with the poor prognosis of neuroblastoma. Expression levels of MYCN and c-MYB proto-oncogene transcription factor (c-myb) decline during the differentiation of neuroblastoma cells; E2F transcription factor 1 (E2F1) activates the MYCN promoter. However, the underlying mechanism of MYCN overexpression and amplification requires further investigation. In the present study, potential c-Myb target genes, and the effect of c-myb RNA interference (RNAi) on MYCN expression and amplification were investigated in MYCN-amplified neuroblastoma cell lines. The mRNA expression levels and MYCN gene copy number in five neuroblastoma cell lines were determined by quantitative polymerase chain reaction. In addition, variations in potential target gene expression and MYCN gene copy number between pre- and post-c-myb RNAi treatment groups in MYCN-amplified Kelly, IMR32, SIMA and MHH-NB-11 cell lines, normalized to those of non-MYCN-amplified SH-SY5Y, were examined. To determine the associations between gene expression levels and chromosomal aberrations, MYCN amplification and 1p36 alterations in interphases/metaphases were analyzed using fluorescence in situ hybridization. Statistical analyses revealed correlations between 1p36 alterations and the expression of c-myb, MYB proto-oncogene like 2 (B-myb) and cyclin dependent kinase inhibitor 1A (p21). Additionally, the results of the present study also demonstrated that c-myb may be associated with E2F1 and L3MBTL1 histone methyl-lysine binding protein (L3MBTL1) expression, and that E2F1 may contribute to MYCN, B-myb, p21 and chromatin licensing and DNA replication factor 1 (hCdt1) expression, but to the repression of geminin (GMNN). On c-myb RNAi treatment, L3MBTL1 expression was silenced, while GMNN was upregulated, indicating G₂/M arrest. In addition, MYCN gene copy number increased following treatment with c-myb RNAi. Notably, the present study also reported a 43.545% sequence identity between upstream of MYCN and Drosophila melanogaster amplification control element 3, suggesting that expression and/or amplification mechanisms of developmentally-regulated genes may be evolutionarily conserved. In conclusion, c-myb may be associated with regulating MYCN expression and amplification. c-myb, B-myb and p21 may also serve a role against chromosome 1p aberrations. Together, it was concluded that MYCN gene is amplified during S phase, potentially via a replication-based mechanism.

N-MYC Oncogene Amplification: A Consequence of Genomic Instability in Human Neuroblastoma

Increase of the dosage of cellular oncogenes by DNA amplification is a frequent genetic alteration of cancer cells and arises as the consequence of genomic instability. The presence of amplified cellular oncogenes is usually signaled by conspicuous chromosomal abnormalities "double minutes," or "homogeneously staining chromosomal regions." Some human cancers carry a specific amplified oncogene at high incidence. In neuroblastomas, which are tumors of the peripheral nervous system that arise from primitive neuroectodermal cells derived from neural crest, the amplification of the gene N-MYC has been associated with aggressively growing cancers and is an indicator for poor prognosis. N-MYC amplification is of predictive value for iden tifying neuroblastoma patients who either require specific therapeutic regimens or who do not benefit from chemotherapy. The Neuroscientist 1:277-285, 1995

Favorable histology, MYCN-amplified 4S neonatal neuroblastoma

We report a neonate with 4S neuroblastoma and MYCN amplification, but favorable Shimada histology, successfully treated with chemotherapy and 13-cis-retinoic acid without stem cell transplantation. MYCN amplification in neuroblastoma is usually associated with unfavorable Shimada histology; the presence of these features in infants with 4S disease confers a poor prognosis. A small number of infants with 4S neuroblastoma and MYCN amplification have favorable Shimada histology. In this subgroup of infants, histopathology may be equally important in predicting outcome.

Expression profiling and characterization of 4200 genes cloned from primary neuroblastomas: identification of 305 genes differentially expressed between favorable and unfavorable subsets

Neuroblastoma (NBL), one of the most common childhood solid tumors, has a distinct nature in different prognostic subgroups: NBL in patients under 1 year of age usually regresses spontaneously, whereas that in patients over 1 year of age often grows aggressively and eventually kills the patient. To understand the molecular mechanism of biology and tumorigenesis of NBL, we decided to perform a comprehensive approach to unveil the gene expression profiles among the NBL subsets. We constructed the subset-specific oligo-capping cDNA libraries from the primary NBL tissues with favorable (F: stage 1, high expression of TrkA and a single copy of MYCN) and unfavorable (UF: stage 3 or 4, decreased expression of TrkA and MYCN amplification) characteristics and randomly cloned 4654 cDNAs. Among 4243 cDNAs sequenced successfully, 1799 (42.4%) were the genes with unknown function. Excluding the housekeeping genes, an expression profile of each subset was extremely different. To determine the genes expressed differentially between F and UF subsets, we performed semiquantitative reverse transcriptase (RT)-PCR for each of the 1842 independent genes using RNA obtained from 16 F and 16 UF NBLs as template. This revealed that 278 genes were highly expressed in the F subset as compared to the UF one, while, surprisingly, only 27 genes were expressed at higher levels in the UF rather than the F subset. These differentially expressed genes included 194 genes with unknown function. Many of the genes expressed at high levels in the F subset were related to catecholamine biosynthesis, small GTPases, synapse formation, synaptic vesicle transport, and transcription factors regulating differentiation of the neural crest-derived cells. On the other hand, the genes expressed at high levels in the UF subset included transcription factors and/or receptors that might regulate neuronal growth and differentiation. The chromosomal mapping of those genes showed some clusters. Thus, our mass-identification and characterization of the differentially expressed genes between the subsets may become a powerful tool for finding the important genes of NBL as well as developing new diagnostic and therapeutic strategies against aggressive NBL.

Amplification of oncogenes revisited: from expression profiling to clinical application

Regulatory or structural alterations of cellular oncogenes have been implicated in the causation of cancers. Amplification represents one of the major molecular pathways by which gene expression is constitutively enhanced above the level of physiologically normal variation. Consequently, the significance of oncogene amplification in tumorigenesis originally had emerged from expression profiling of tumor cells by oncogene arrays. Amplified oncogenes have been found associated with more aggressive tumor variants and in selected settings are clinical markers to determine patient prognosis.

Human neuroblastomas with unfavorable biologies express high levels of brain-derived neurotrophic factor mRNA and a variety of its variants

The expression of human brain-derived neurotrophic factor (BDNF) was investigated in 16 primary human neuroblastomas with favorable biologies, 15 with unfavorable biologies, and in human neuroblastoma cell lines. We demonstrated higher expressions of human BDNF mRNA in neuroblastomas with unfavorable biologies and with N-myc amplification than in those with favorable biologies. For the first time we revealed the composition of splice variants of human BDNF mRNA and analyzed their expression in neuroblastomas by reverse transcription polymerase chain reaction (RT-PCR). Interestingly, human BDNF mRNA consisted of at least six isoforms, four isoforms resembling those of rat BDNF mRNA, a human-specific isoform and a new isoform. The expression of four isoforms were more prominent in tumors with unfavorable biologies than in those with favorable biologies (P<0.05). As previously we had reported, over 80% of the primary tumors expressed either the full-length form of BDNF receptor, TRKB, or a truncated form of TRKB lacking the tyrosine kinase domain. The full-length TRKB was predominantly detected in tumors with unfavorable biologies, and the truncated one in those with favorable biologies. These results suggest that an autocrine and/or paracrine mechanism involving BDNF may stimulate signal transduction via TRKB receptors rich in neuroblastomas with unfavorable biologies, resulting in an aberrant survival of tumor cells.

MYCN expression is not prognostic of adverse outcome in advanced-stage neuroblastoma with nonamplified MYCN

PURPOSE

The clinical significance of MYCN expression in children with neuroblastoma (NB) remains controversial. To determine the prognostic significance of MYCN expression in the absence of MYCN amplification, we analyzed MYCN mRNA and protein expression in tumors from 69 patients.

PATIENTS AND METHODS

Sixty-nine NB tumor samples with nonamplified MYCN from patients with stage C or D disease were obtained from the Pediatric Oncology Group Neuroblastoma Tumor Bank. MYCN mRNA was analyzed using a real-time reverse transcriptase polymerase chain reaction assay, and MYCN protein was examined by Western blot analyses.

RESULTS

The estimated 5-year event-free survival (EFS) and survival (S) rates plus SE for the cohort were 57% +/- 17% and 60% +/- 16%, respectively. Infants younger than 1 year had significantly higher rates of EFS and S than children >/= 1 year of age (P =.003 and P <.001, respectively); patients with stage C disease had better outcome than those with stage D NB (P <.001); and patients with hyperdiploid tumors had better outcome than those with diploid NB (P <.001). Surprisingly, outcome was slightly better for patients with high versus low levels of MYCN mRNA expression (4-year S, 70% +/- 13% v 50% +/- 16%; P =.290), and for patients with tumors that expressed MYCN protein (4-year S, 73% +/- 19% v 53% +/- 15%, respectively; P =.171).

CONCLUSION

High levels of MYCN expression are not prognostic of adverse outcome in patients with advanced-stage NB with nonamplified MYCN. A trend associating high levels of MYCN expression with improved outcome was observed.

A novel intron element operates posttranscriptionally To regulate human N-myc expression

Precisely regulated expression of oncogenes and tumor suppressor genes is essential for normal development, and deregulated expression can lead to cancer. The human N-myc gene normally is expressed in only a subset of fetal epithelial tissues, and its expression is extinguished in all adult tissues except transiently in pre-B lymphocytes. The N-myc gene is overexpressed due to genomic amplification in the childhood tumor neuroblastoma. In previous work to investigate mechanisms of regulation of human N-myc gene expression, we observed that N-myc promoter-chloramphemicol acelyltransferase reporter constructs containing sequences 5' to exon 1 were active in all cell types examined, regardless of whether endogenous N-myc RNA was detected. In contrast, inclusion of the first exon and a portion of the first intron allowed expression only in those cell types with detectable endogenous N-myc transcripts. We investigated further the mechanisms by which this tissue-specific control of N-myc expression is achieved. Using nuclear run-on analyses, we determined that the N-myc gene is actively transcribed in all cell types examined, indicating a posttranscriptional mode of regulation. Using a series of N-myc intron 1 deletion constructs, we localized a 116-bp element (tissue-specific element [TSE]) within the first intron that directs tissue-specific N-myc expression. The TSE can function independently to regulate expression of a heterologous promoter-reporter minigene in a cell-specific pattern that mirrors the expression pattern of the endogenous N-myc gene. Surprisingly, the TSE can function in both sense and antisense orientations to regulate gene expression. Our data indicate that the human N-myc TSE functions through a posttranscriptional mechanism to regulate N-myc expression.

Amplification of oncogenes in human cancer cells

Gene amplification refers to a genomic change that results in an increased dosage of the gene(s) affected. Amplification represents one of the major molecular pathways through which the oncogenic potential of proto-oncogenes is activated during tumorigenesis. The architecture of amplified genomic structures is simple in some tumor types, involving in the vast majority of cases only one gene, such as MYCN in neuroblastomas. On the other hand, it can be complex and discontinuous, involving several syntenic co-amplified genes, such as in the 11q13 amplification in breast cancer, although in many of these cases there may be a single target gene. The presence of different nonsyntenic amplified genes raises the possibility that cells of certain tumors are susceptible to independent amplification events. In general, the amplified genes do not undergo additional damage by mutations. The data indicate that it is the enhanced level of a wild-type protein that contributes to tumorigenesis.

Comparison of the diagnostic and prognostic value of biological markers in neuroblastoma. Proposal for a common methodology of analysis. SENSE group

BACKGROUND

The prognosis of pediatric neuroblastoma depends both on clinical presentation and on certain cellular and molecular characteristics. Screening programs have been initiated in infants of less than one year of age, based on the hypothesis that neuroblastoma progresses from early to late clinical stages through a classical multistep process linked to an accumulation of molecular abnormalities. However, recent analyses suggest that most cases discovered by screening are low stage tumors considered as dysembryogenetic residues devoid from major abnormalities and that high-grade tumors with molecular abnormalities are unrelated diseases.

AIM OF THE REVIEW

To confirm one or the other hypothesis, and eventually identify biological factors possibly responsible for the initiation and progression of the disease, it is of utmost importance that all investigators agree on biological criteria for analysis when neuroblastoma tissue is available in screened and unscreened populations. This paper reviews the biological tools available for prognosis in neuroblastoma, the priority for analysis of biological markers according to both methodological reliability and feasibility, and the conditions of tissue storage for further analysis of these biological markers.

CONCLUSION

The standardized biological evaluation of neuroblastoma will allow to collect sufficient data for multivariate analysis; such analysis is now fundamental if one wants to clearly define the respective impacts of biological abnormalities on neuroblastoma progression.

Molecular basis for heterogeneity in human neuroblastomas

Neuroblastomas demonstrate both clinical and biological heterogeneity. We have proposed that neuroblastomas may be classified in three genetically distinct subtypes, based on cytogenetic and molecular analysis. The first comprises those with hyperdiploid or triploid modal karyotypes (or compatible DNA content by flow cytometry), 1p LOH and MYCN amplification are absent, and TRKA expression is high. These patients are likely to be infants with low stages of disease (stages 1, 2, or 4S by the International Neuroblastoma Staging System), and they have a very favourable outcome (> 90% cure). The second group consists of tumours that generally have a near diploid or tetraploid modal chromosome number or DNA content but lack MYCN amplification. They usually have 1p allelic loss, 14q allelic loss or other structural changes, and TRKA expression is usually low. These patients are generally older with advanced stages of disease (stages 3 or 4), and they have a slowly progressive course, with a cure rate of 25-50%. The third group is characterised by tumours with MYCN amplification. These tumours are generally near diploid or tetraploid, with 1p allelic loss, and low or absent TRKA expression. The patients are usually between 1 and 5 years of age with advanced stages of disease, and they have a very poor prognosis (< 5%). It remains to be determined if tumours in one group ever evolve into a less unfavourable group, but current evidence suggests that they are distinct genetically. The identification of the oncogenes, suppressor genes and growth factor receptor pathways involved in neuroblastomas has provided great insight into the mechanisms of malignant transformation and progression, and ultimately they may provide the targets for future therapy.

Poor outcome in patients with advanced stage neuroblastoma and coincident opsomyoclonus syndrome

BACKGROUND

Most patients with neuroblastoma who present with opsomyoclonus have a good prognosis. Neuroblastomas from such patients have been reported to contain a single copy of the N-myc gene. The authors describe three cases of patients with advanced neuroblastoma with opsomyoclonus, which had poor outcomes despite multimodal therapy.

METHODS

Amplification and expression of the N-myc gene were examined in these three primary tumors using Southern and Northern blot analyses. Then, flow cytometric analysis of the cellular DNA contents of these tumors was performed.

RESULTS

N-myc amplification was observed in two tumors and N-myc RNA overexpression was observed in all three. Analysis of the cellular DNA contents of the tissue specimens revealed hyperdiploidy in all three tumors; one had a triploid index and the other two had hypotetraploid indexes.

CONCLUSIONS

These findings suggest that a poor outcome for patients with opsomyoclonus may be associated with N-myc gene activation (amplification and/or overexpression) and that a hyperdiploid tumor is not always associated with a good prognosis.

Cytogenetic abnormalities in two cases of neuroblastoma

Neuroblastomas are common solid tumors in children. We report chromosome analysis of two neuroblastomas, each studied at diagnosis and at recurrence. The first case was a clinical stage D tumor which showed 45,X-Y, add(1)(p34),der(15)t(Y;15)(q11;p13), and double minutes on cytogenetic analysis at diagnosis. At recurrence, the same structural abnormalities were present along with a homogeneously staining region (hsr) at 8q22, 19p12, or 3p23 in each of three related clones. The hsr were shown to represent amplification of the N-myc gene by in situ hybridization. Cytogenetic analysis of the second tumor, stage D-S, showed 48-54,XX,der(1)add (1)(q41), +2, +7, +7, inv(9), +17, + mar. The lack of demonstrative involvement of 1p or visible evidence of gene amplification has also characterized the limited number of D-S specimens previously described, suggesting that stage D-S neuroblastoma indeed differs from stage D disease at the genetic level.

N-myc gene copy number in neuroblastoma cell lines and resistance to experimental treatment

The N-myc oncogene is amplified in approximately 30% of neuroblastomas. It is well established that cases of neuroblastoma with amplified N-myc have markedly poorer prognosis than those in which N-myc copy number is not elevated. The mechanism for this association is not known but may be related to cellular resistance to radiation or cytotoxic drugs. Seven human neuroblastoma cell lines were used to investigate the relationship between N-myc copy number or expression and sensitivity to ionising radiation and to cisplatin. N-myc copy number was assessed by Southern blotting and hybridisation using the p-Nb1 probe. The signal produced by DNA from the cell lines was compared with that of single copy N-myc from normal human placental DNA. A range of N-myc copy numbers from 1 to 800 was found. Expression levels of N-myc mRNA were compared by "dot blotting" and subsequent hybridisation to the p-Nb1 probe. Radiosensitivity was assessed by surviving fraction at 2 Gy (SF2) following 60Co gamma irradiation. Values ranged from 0.13 to 0.52. Sensitivity to cisplatin was indicated by comparison of isoeffective concentrations (concentration required to produce 1 log cell kill). These ranged from 7.5 to 13 microM. Cisplatin studies showed a correlation between N-myc copy number (though not expression) and resistance to this drug. If this relationship is causal it may explain why treatment fails in those patients with an elevated N-myc copy number. However, no correlation was found between N-myc copy number or expression and sensitivity to radiation. It is possible that N-myc amplification confers resistance to some but not all treatments used in the therapy of neuroblastoma. Further investigations along these lines may lead to the identification of agents which are most appropriate for the treatment of neuroblastoma with amplified N-myc gene.

Paratesticular neuroblastoma with N-myc activation

The authors describe a case of disseminated neuroblastoma discovered as a paratesticular tumor in a 7-month-old boy. The ectopic adrenal tissues adjacent to the paratesticular tumor and multiple lesions in the adrenal gland and skin suggested the possibility of multifocal primary tumors. Although infantile neuroblastoma diagnosed at less than 1 year of age generally responds well to treatment irrespective of distant metastases, metastases developed, and the boy died of disease within 7 months. All multiple lesions had amplification and overexpression of the N-myc protooncogene, which might explain the aggressive phenotype of this rare case.

Chromosome 12 alterations and c-Ki-ras mutations in colorectal tumors

c-Ki-ras mutations and gains of chromosome 12, where this gene is mapped, were both studied in a series of 47 colorectal cancers. Mutations at codon 12 and 13 were detected in 17 (36%) and gains of chromosome 12 in 7 (15%) cases. In this sample, gains of chromosome 12 occur in tumors either with or without c-Ki-ras mutations, suggesting that gains of chromosome 12 are independent from the mutation of c-Ki-ras.

Association between high levels of expression of the TRK gene and favorable outcome in human neuroblastoma

BACKGROUND AND METHODS

The nerve growth factor receptor is expressed in some neuroblastomas, in which its primary component is encoded by the TRK protooncogene. To determine the relation of the expression of TRK messenger RNA in neuroblastomas to other clinical and laboratory variables, we studied frozen tumor samples from 77 patients. In addition, we tested two primary neuroblastomas that expressed TRK for responsiveness to nerve growth factor.

RESULTS

TRK expression strongly correlated with favorable tumor stage (I, II, and IVS vs. III and IV), younger age (< 1 year vs. > or = 1 year), normal N-myc copy number, and low level of N-myc expression. N-myc amplification (indicated by a high copy number) correlated with advanced tumor stage, older age, an adrenal site of the primary tumor, low level of expression of TRK, and high level of expression of N-myc. Analysis of five-year cumulative-survival rates demonstrated an association of a very favorable outcome with a high level of TRK expression (86 percent vs. 14 percent) and with normal N-myc copy number (84 percent vs. 0 percent). Univariate analysis showed that these two variables were the most powerful predictors of outcome (chi-square = 51.30, P < 0.001; and chi-square = 93.61, P < 0.001, respectively). TRK expression still had significant prognostic value when the analysis was restricted to tumors without N-myc amplification. In primary cultures of neuroblastoma cells expressing TRK, exposure to nerve growth factor induced early gene expression and neurite outgrowth, but deprivation of nerve growth factor led to neuronal cell death.

CONCLUSIONS

A high level of expression of the TRK proto-oncogene in a neuroblastoma is strongly predictive of a favorable outcome. A tumor with a functional nerve growth factor receptor may be dependent on the neurotrophin nerve growth factor for survival and may regress in its absence, allowing a new approach to the treatment of certain patients with neuroblastoma.

N-myc oncogene and urinary catecholamines in children with neuroblastoma

This paper reports the analysis of N-myc amplification, urinary vanillylmandelic acid (VMA), and norepinephrine (NE) excretion and survival in 22 children with neuroblastoma and 7 with ganglio-neuroblastoma. Five patients had N-myc amplification (from 30 to more than 200 copies), all of whom had advanced-stage disease. The urinary excretion of VMA was normal in all of them, only one showed increased NE excretion. All patients with stage C-D disease and one copy of N-myc had increased VMA urinary excretion and increased (9/14) or normal (5/14) NE urinary excretion. All patients with stage A or B disease had one copy of N-myc. Half of them showed increased VMA urinary levels, while only 3/10 showed increased NE urinary values. Comparison of cumulative survival curves in relation to N-myc amplification and to VMA and NE urinary excretion showed a clear parallelism. Amplification of N-myc corresponded to normal VMA and NE urinary excretion, and was associated with the worst prognosis (P < 0.01), while increased VMA and/or NE excretion was found in patients with only one copy of N-myc.

Neuroblastoma. Effect of genetic factors on prognosis and treatment

BACKGROUND AND METHODS. Genetic analysis of tumor tissue has provided considerable insight into mechanisms of malignant transformation and progression. Neuroblastomas have been studied by cytogenetics, flow cytometry, and molecular genetic techniques, and these studies have identified several specific abnormalities that allow subclassification of these tumors into genetic/clinical subtypes. RESULTS AND DISCUSSION. Four genetic abnormalities have been identified that are characteristic of certain neuroblastomas. These include: (1) loss of heterozygosity (LOH) for the short arm of chromosome 1, including band 1p36; (2) amplification of the N-myc protooncogene; (3) hyperdiploidy, or near triploidy; and (4) defects in expression or function of the nerve growth factor receptor (NGFR). Abnormalities of the NGFR are found in virtually all neuroblastoma cell lines, and some primary tumors. The latter have not been studied extensively. Hyperdiploidy is associated with lower stages of disease and with a favorable outcome in infants. LOH for chromomors. The latter have not been studied extensively. Hyperdiploidy is associated with lower stages of disease and with a favorable outcome in infants. LOH for chromosome 1, band p36, and N-myc amplification are more common in patients older than 1 year of age with advanced stages of disease. The latter two genetic abnormalities may be related, and LOH for 1p36 may precede the development of amplification. When these abnormalities are combined with assessment of DNA content, three distinct genetic subsets of neuroblastomas can be identified. The first is characterized by a hyperdiploid or near-triploid modal karyotype, with few if any cytogenetic rearrangements. These patients generally are younger than 1 year of age with localized disease and a good prognosis. The second has a near-diploid karyotype, with no consistent abnormality identified currently. These patients generally are older with more advanced stages of disease that progress slowly and are often fatal. The third group has a near-diploid or tetraploid karyotype, with deletions or LOH for 1p36, amplification of N-myc, or both. These patients generally are older with advanced stages of disease that rapidly are progressive. Thus, genetic analysis of neuroblastoma cells provides information that has prognostic significance and can direct a more appropriate choice of treatment.

Overexpression of multiple oncogenes related to histological grade of astrocytic glioma

The expression of the c-erbB-1, c-myc, Ha/N-ras and c-fos oncogenes was investigated in 62 astrocytomas of low, intermediate and high grades by immunogold silver histochemistry. Elevated expression of c-erbB-1 was observed in 95%, 48% and 86% of low, intermediate and high grade tumours respectively, c-myc in 5%, 33% and 76% respectively, Ha/N-ras in 0, 43% and 71% respectively and c-fos in 55%, 48% and 52% respectively. Controls included normal brain and tumour sections immunoreacted with pre-immune serum or with antisera absorbed with synthetic peptides. Analysis of co-overexpression revealed that low grade tumours co-overexpressed a maximum of two of these genes, intermediate grade tumours a maximum of three of these genes, while co-overexpression of all four genes was observed in some high grade tumours. Co-overexpression of c-erbB-1 and c-fos was frequently observed in low grade astrocytomas and may be predictive of non-progression. On the other hand, there was a statistically significant increase in the number of tumours overexpressing Ha/N-ras or c-myc with increasing grade of tumour, suggesting that overexpression of these two oncogenes may be indicative of progression.

Detection of MYCN amplification in three neuroblastoma cell lines by non-radioactive chromosomal in situ hybridization

A non-radioactive chromosomal in situ hybridization technique utilizing a biotin-streptavidin-polyalkaline-phosphatase complex was successfully applied to three neuroblastoma cell lines for detection of MYCN amplification. These cell lines, designated PER-106, PER-107, and PER-108, were derived from consecutive bone marrow samples taken from a patient with stage IV neuroblastoma. The cell line derived at diagnosis (PER-106) exhibited MYCN amplification in the form of variable numbers of double-minute chromosomes, small fragments, and rings of varying sizes. This observed variability of MYCN amplification may explain the reported heterogeneity of both MYCN mRNA and protein expression among individual cells of some neuroblastomas. The cell lines derived from subsequent samples (PER-107 and PER-108) contained amplified MYCN as two consistent homogeneously staining regions in every cell. These were located on the short arms of chromosomes 6 and 14. Thus, amplified MYCN was identified in each cell line and demonstrated the concurrent evolution of amplification with cytogenetic abnormalities.

Selection of appropriate cellular and molecular biologic diagnostic tests in the evaluation of cancer

In this article, the use of cellular and molecular markers to diagnose and stage tumors is discussed. Their role in the evaluation of tumor prognosis and tumor susceptibility also is covered. The immunologic, cytogenetic, and molecular phenotype is discussed. Traditional markers are compared with newer methodologic approaches including evaluation of oncogenes, tumor suppressor genes, and genes that predict tumor susceptibility. These discussions are presented in relation to specific tumors. Finally, statements one might use to decide which tests to perform are presented.

Molecular biology in the diagnosis and prognosis of solid and lymphoid tumors

The application of molecular biology to the study of human malignancies has led to tremendous gains in our understanding of their pathogenesis. Although their practical applications are still somewhat limited at this point, the use of molecular diagnostic tools is likely to grow at a very rapid rate as newer and more accurate prognostic markers are identified. The availability of reliable prognostic markers should allow earlier intervention in patients with aggressive disease but exhibiting only limited extent of disease at the time of initial diagnosis. Early intervention in such cases could realistically increase the probability of cure, since highly aggressive tumor cells are more likely to be eliminated by early institution of cytotoxic chemotherapy (4). The p53 tumor suppressor gene clearly represents the most promising potential prognostic marker at present, because of both the multiple phenotypic alterations caused by different p53 mutations and the high frequency of p53 mutations which have been observed in a variety of human cancers. Other prognostic markers related to oncogenes and tumor suppressor genes are almost certain to follow. Validation of new prognostic markers requires a knowledge of both histopathologic diagnostic criteria as well as the consequences for the patient of each diagnosis. There is bound to be some "shake-out" in the field of molecular diagnostics just as there was with other recently introduced techniques such as immunohistochemistry and flow cytometry which were found to provide additional useful information for some tumors and not for others. Since the clinical-pathologic studies needed for verification of putative prognostic markers require relatively long periods of follow up, progress in this area will almost certainly lag behind the ability of molecular biologists to identify new and potentially useful prognostic markers. Our collective ability to reap tangible gains in the clinical arena from our heavy investments in molecular biology and biotechnology depends to a large extent on open channels of communication between clinical and basic scientists. As our ever-increasing insights into oncogenic processes spawn new diagnostic and prognostic markers, our priorities should remain focused on those areas which are inadequately addressed by current methods, and we should avoid the technological trap of devising redundant solutions which increase the expense, but not the efficiency of patient care.

Cloning and physical mapping of DNA sequences encompassing a region in N-myc amplicons of a human neuroblastoma cell line

Cloning and physical mapping of DNA sequences encompassing N-myc amplicons of a human neuroblastoma cell line were done. A number of lambda phage clones within this region were isolated using the probes prepared by the phenol emulsion reassociation technique. Based on the restriction mapping, they were integrated into 8 contigs with sizes of 25-60 kb which, in total, encompassed a 330 kb region. Several amplicons, 100, 420, 480 and 520 kb in size as a Notl fragment, were identified using hexagonal field gel electrophoresis, and the contigs were assigned in these Notl fragments. The region encompassed by the contigs was equivalent to some 60-80% of the amplicons identified as a Notl fragment. In order to compare the amplified regions flanking the N-myc gene among the cell lines, the phage clones to cover the whole contigs were used for hybridization as a probe. The results showed that the portions of the whole contigs ranging 18-45% were also amplified in the cell lines examined. These results allowed us to identified the 'rearranged sites' which were rather evenly distributed, one at every 40 kb, through the contigs. These observations lead to the idea that an amplified DNA domain is constructed after the multiple rearrangements and then increases in number, finally resulting in the formation of subsets of amplicons with sequence homogeneity.

Biology of tumors of the peripheral nervous system

Tumors of the peripheral nervous system include neuroblastomas, pheochromocytomas, and neuroepitheliomas. Neuroblastomas and pheochromocytomas are adrenergic in origin and share certain genetic features, whereas neuroepitheliomas are thought to be cholinergic and are characterized by distinct genetic features. Neuroblastomas are characterized by deletion of the short arm of chromosome 1 (1p), amplification of the MYCN proto-oncogene, and hyperdiploidy in subsets of tumors. All three of these genetic features have prognostic value in subsets of patients. Allelic loss of 14q also occurs with increased frequency, but the prognostic importance of this abnormality is not known yet. Pheochromocytomas have not been studied as extensively, but allelic loss for 1p appears to be a frequent change, and no clear examples of oncogene activation have been identified to date. Neuroepitheliomas are characterized by translocation between chromosomes 11 and 22. Although they have a characteristic pattern of proto-oncogene expression, it is not clear that any of these oncogenes are activated specifically, and no sites of allelic loss have been identified to date. Thus, cytogenetic and molecular analysis of neuroblastomas, pheochromocytomas, and neuroepitheliomas are useful in distinguishing them from each other and from other tumors in selected cases. Furthermore, certain genetic markers are useful in predicting clinical behavior, especially for neuroblastoma.

Neuroblastoma stage IV-S: a heterogeneous disease

Eighteen patients were diagnosed and treated for Stage IV-S neuroblastoma at The Hospital for Sick Children, Toronto between January 1971 and December 1988. All patients were 6 months of age or younger at diagnosis. Nine patients (50%) have remained disease free with a mean follow-up of 9.3 years. Of the seven patients under 6 weeks of age at presentation, four presented in the early neonatal period and died, three due to mechanical complications related to progressive disease, and one due to late recurrence. The remaining three patients under 6 weeks of age, two of whom had skin involvement at diagnosis, are alive and disease free. Six of the 11 patients over 6 weeks of age at presentation survived, combined modality therapy (CMT) being more effective than single modality treatment. N-myc was studied from tumor tissue at diagnosis in four patients and was amplified in three (25x, 25x, 100x), all of whom had late disease progression and died. The patient with a single gene copy has no evidence of disease 24 months following diagnosis. Our study confirms the heterogeneity described in this clinically defined group of patients. Because of it, management of Stage IV-S neuroblastoma cannot be uniform and until further development of a subclassification, or a reclassification based on molecular biologic markers is developed, pediatric oncologists will regularly be confronted with a decision whether or not to treat a newly presenting patient that fits into the clinical classification IV-S.

Enhanced expression of the cellular oncogene MYCN and progression of human neuroblastoma

A central issue in cancer research is how tumors evolve and acquire a more aggressive phenotype. It is a widely discussed hypothesis that tumor cell populations progress by evolutionary change as a result of the generation of a variant cell through genomic instability followed by selection of particular variant clones having a growth advantage within the particular tissue environment. Genetic instability appears to be characteristic of neoplastic cells, but no consistent increase in instability seems to accompany progression of the malignant phenotype of the tumor. It is reasonable to assume that quantitative or qualitative changes of cellular oncogenes contribute to the emergence of more malignant phenotypes. Although any one of the molecular changes of cellular oncogenes identified over the past years is a good candidate as an element in progression, amplification appears particularly frequently as a correlate to advanced tumor stage. The fact that amplification does not show up in all progressing tumors of a particular type, for instance in only 50% of advanced-stage neuroblastomas, is often construed as speaking against a role in progression. One should be aware, however, that it is the enhanced expression of a gene consequent to amplification and not amplification per se that affects the cellular phenotype. There are alternative molecular pathways by which expression of a particular gene may become deregulated. During the past decade much information has accrued about genetic alterations in tumor cells. The activation of the oncogenic potential of cellular genes can take different routes among which mutational alteration, translocation and amplification predominate. In particular, amplification has found its way to practical use due to its association with more aggressively growing types of human cancer. MYCN amplification in neuroblastoma is a paradigm for the prognostic significance of oncogene alteration, and at the same time has represented the clinical debut of oncogene research. The full significance of oncogene amplification as a predictor for poor prognosis became clear with the more recent identification of amplified ERBB2 in aggressively growing breast cancers. The state of the art is that amplified cellular oncogenes define cancer patients who have a poor prognosis and require a specific therapeutic regimen.

Amplification of the MYCN oncogene and deletion of putative tumour suppressor gene in human neuroblastomas

Human neuroblastoma cells often carry non-random chromosomal abnormalities signalling genetic alterations. Quite frequent are 'double minutes' (DMs) and homogeneously staining regions (HSRs), both cytogenetic manifestations of amplified DNA, and chromosome 1p-deletions indicating loss of genetic information. With the identification of amplified MYCN and the demonstration of a consensus deletion spanning the chromosome 1p36.1-2 region it appears now likely that both amplification of a cellular oncogene and loss of a tumour-suppressor gene play an important role in neuroblastoma. Amplification of MYCN is an indicator for poor prognosis, even when classical morphological criteria would suggest a better outcome. Consequently, patients with amplification are subjected to more intensive therapeutic regimens. Amplification of MYCN is a paradigm for the clinical use of an oncogene alteration.

Neuroblastoma--clinical applications of molecular parameters

At least two genetic events have been identified which are characteristic of certain neuroblastomas. These are loss of a critical region on the short arm of chromosome 1, and amplification of the MYCN proto-oncogene. Our studies suggest that the two genetic events may be related, and that loss of heterozygosity (LOH) for chromosome 1p may precede the development of amplification. RAS gene mutations appear to be rare, and no other oncogene has been shown to be consistently activated by amplification or other mechanism. LOH for chromosome 14q has been identified recently, but its frequency and significance is not clear. Based on flow cytometric analysis of DNA content, tumour cytogenetics and molecular studies, three distinct genetic subsets of neuroblastomas are emerging. The first is characterized by a hyperdiploid or near-triploid modal karyotype, with few if any cytogenetic rearrangements. These patients are generally less than one year of age with localized disease and a good prognosis. The second group is characterized by a near-diploid or near-tetraploid karyotype, with no consistent rearrangement identified to date. They are generally older patients with more advanced stages of disease that progress slowly and are ultimately fatal. The third group is characterized by a near-diploid or tetraploid karyotype, with deletions or LOH for chromosome 1p, amplification of MYCN, or both. These patients are generally older with advanced stages of disease which is rapidly progressive. Thus, genetic analysis of neuroblastoma cells by karyotype, flow cytometry and determination of MYCN copy number provides information that has prognostic significance and can more appropriately direct the choice of treatment. A better understanding of these genetic abnormalities and the biochemical pathways that they effect may provide insights into malignant transformation and progression, as well as provide targets for future therapeutic approaches.

N-myc oncogene and stage IV-S neuroblastoma. Preliminary observations on ten cases

We studied the clinical significance of genomic amplification of N-myc in Stage IV-S neuroblastoma, with reference to spontaneous regression. Among 103 neuroblastomas in which N-myc was measured, ten were Stage IV-S (eight children were younger than and two were older than 1 year of age). The number of copies of N-myc was 1 to 3 in five patients, four to ten in one patient, and more than ten in four patients, and the survivors of each group were four, one, and one (recurrent), respectively. Of 41 patients younger than 1 year of age, N-myc amplification of more than three copies was found only in Stage IV-S neuroblastoma. Cure with a tendency to regress spontaneously was seen in five of eight patients younger than 1 year of age. However, two patients older than 1 year of age classified as Stage IV-S (one with N-myc amplification) died of progressive disease. In two patients (1 and 3 months of age) with a huge hepatic involvement and in whom the tumor had an amplified N-myc of more than ten copies, tumor regression occurred but there was a relapse to a progressive state later. The overexpression of N-myc mRNA occurred in nine of ten stage IV-S tumors and did not correlate with the prognosis. The vanillylmandelic acid (VMA) to homovanillic acid (HVA) ratio was low in tumors with an increased number of copies of N-myc. Serum lactate dehydrogenase (LDH) levels were increased in Stage IV-S patients with N-myc amplification but not in those with regressing tumors and without N-myc amplification. These data suggest that N-myc amplification may affect the final outcome in the patient classified as Stage IV-S, but tumor regression can occur early after birth and appears to be independent of N-myc amplification.

Amplification of cellular oncogenes: a predictor of clinical outcome in human cancer

Increased dosage of cellular oncogenes resulting from amplification of DNA is a frequent genetic abnormality of tumor cells and the study of oncogene amplification has been paradigmatic for the usefulness of molecular genetic research in clinical oncology. Certain types of human tumors carry an amplified cellular oncogene at frequencies of up to 50-60%. Human neuroblastoma has been prototypic for the importance of oncogene amplification in tumorigenesis, and evidence is emerging that amplification may be an early event involved in a more malignant form of this cancer. It is unclear at which stage amplification plays a role in other cancers. Amplification of cellular oncogenes is a good predictor of clinical outcome in some human malignancies.

Clinical value of N-myc oncogene amplification in 52 patients with neuroblastoma included in recent therapeutic protocols

Southern blot analysis of neuroblastoma (NB) cell DNA from 52 patients (58 samples) allowed the detection of an N-myc amplification on three of the 13 BM samples and three of 13 tumor samples at diagnosis, on two of 17 tumor samples taken after induction therapy, on three of seven BM samples and two of the five local tumor samples taken after relapse. N-myc was amplified in two of the 15 patients with stage I to III NB and in 10 of the 36 patients with stage IV neuroblastoma over 1 year of age. Conclusions from the analysis are as follows: first tumor samples obtained on previously treated patients are histologically modified and detection of N-myc amplification is not accurate; consequently N-myc amplification must be defined at diagnosis. Surgical biopsies of the primary tumors can, however, be delayed and malignant cells obtained by ultrasound-guided punctures or analyzed on bone marrow samples if they represent more than 50% of the total population. Second, any attempt to define the prognostic value must be performed on a group of patients treated with a new aggressive protocol of chemotherapy; it will require a multiparametric analysis including, in particular, results of an extensive clinical staging at diagnosis and histological criteria.

Abdominal, retroperitoneal and sacrococcygeal tumours of the newborn and the very young infant. Report from the Kiel Paediatric Tumour Registry

We examined 226 abdominal, retroperitoneal and sacrococcygeal tumours in newborns and infants aged 6 months or less. Most frequent were neuroblastomas (n = 83) followed by germ cell tumours (n = 76), 37 of which were immature and 32 were mature teratomas. Fully malignant germ cell tumours and malignant germ cell tumour components were much rarer in this age group (9.2%) than in older children (58.1%). The majority of germ cell tumours were localized in the sacrococcygeal region (72.4%). Next in frequency were tumours of the kidney (n = 54), including 28 congenital mesoblastic nephromas. In contrast to children over 6 months of age, kidney tumours were frequently low grade malignant with a favourable prognosis. Among liver tumours there were 19 infantile haemangioendotheliomas and 9 hepatoblastomas. By contrast, at ages 7-24 months hepatoblastomas (n = 28) were much more frequent than haemangioendotheliomas (n = 2). Tumours in the newborn and very young infant differ from those in older children in many respects: (1) the relative frequency; (2) localization; (3) distribution of histological types; (4) degree of differentiation, often associated with a tendency toward maturation but occasionally also with increasing malignancy; and (5) prognosis, which is comparatively favourable.

Cytogenetic findings and prognosis in neuroblastoma with emphasis on marker chromosome 1

The relationship between cytogenetic findings and prognosis in 51 pediatric patients with neuroblastoma is described. Patients were classified into the following four groups based on karyotypic findings: (1) near diploidy, 42 to 47 chromosomes (n = 11); (2) hyperdiploidy, 50 to 56 chromosomes (n = 4); (3) near triploidy, 60 to 77 chromosomes (n = 33); and (4) hypotetraploidy, 80 to 83 chromosomes (n = 3). Patients with near diploid or hypotetraploid karyotypes also had several structural abnormalities including marker chromosome 1, with or without double minutes (DM) or homogeneously staining regions (HSR). Most of these patients were 1 year of age or older and had advanced tumors. The patients who were in the hyperdiploid or near triploid category had few structural abnormalities; all of them, except one, were younger than 1 year of age, had localized tumors, and are long-term, disease-free survivors. Kaplan-Meier analysis of survival rates disclosed a significant difference favoring the latter group (P less than 0.001). N-myc gene amplification was found in five patients of the former group but in no patients of the latter group. The presence or absence of DM or HSR in the former group had no statistically demonstrable effect on survival. However, the presence of marker chromosome 1 appears to indicate a poor prognosis. Five patients with Stage IV-S disease had near triploid abnormalities similar to findings in patients with localized tumors. We propose that localized and Stage IV-S neuroblastomas can be classified as one disease category, and that patients with near diploid or hypotetraploid karyotypes are clinically distinct from those having hyperdiploid or near triploid karyotypes. We consider that chromosomal pattern is a more influential prognostic factor than age, disease stage, or N-myc gene amplification.

Similar chromosomal patterns and lack of N-myc gene amplification in localized and IV-S stage neuroblastomas in infants

Chromosome analysis was performed on 33 neuroblastomas in infants. Near triploid chromosome abnormalities (range, 60 to 77) were found in 29 patients with localized and IV-S stage neuroblastoma, and hyperdiploidy (range, 50 to 56) in 3 patients with localized neuroblastoma. No marker chromosome 1, homogeneously staining region (HSR), or double minutes (DMS) was observed in these patients, all of which have been previously reported in advanced neuroblastomas. N-myc gene amplification was not detected in any of these patients. All the patients were completely free of disease 4-45 months after diagnosis. Only one patient with stage IV neuroblastoma had a marker chromosome 1 (mode 46) and N-myc gene amplification and relapsed. Five patients with IV-S neuroblastoma lacking N-myc gene amplification had near triploid chromosomal abnormalities similar to those seen in localized neuroblastoma in infants. We consider that, cytogenetically, localized and IV-S neuroblastoma may be within the same disease category and different from advanced neuroblastoma.

Complete pathologic maturation and regression of stage IVS neuroblastoma without treatment

Spontaneous maturation of Stage IVS neuroblastoma has been postulated as a mechanism for its favorable prognosis, but this has rarely been documented pathologically. We report on a patient with congenital Stage IVS neuroblastoma who had extensive subcutaneous and bone-marrow involvement. Serial photographs, biopsies, and vanillomandelic acid determinations documented the tumor's initial progression which was followed by spontaneous maturation and involution of the patient's disease over a 6-year period. No cytotoxic therapy was administered. Favorable biologic prognostic factors were documented, including tumor DNA and protein analyses for N-myc amplification or overexpression and analysis for serum neuron-specific enolase and ferritin. Implications for management and therapy of Stage IVS neuroblastoma are discussed with reference to this case and the recent literature.

Incidence of ras gene mutations in neuroblastoma

Using a rapid dot-blot screening procedure based on DNA amplification and hybridization to synthetic oligonucleotide probes, we investigated 18 neuroblastomas in various clinical stages for the presence of ras mutations. In none of the samples was a mutation in the relevant codons 12, 13 or 61 of Ha-ras, Ki-ras or N-ras found. These data virtually exclude the participation of mutated ras genes in the genesis of neuroblastoma.