Molecular biology and genetics of human neuroblastoma

The Role of Biopsy in the Workup of Patients with Neuroblastoma: Comparison of the Incidence of Surgical Complications and the Diagnostic Reliability of Diverse Techniques

Neuroblastoma (NB) is the most common extracranial solid tumor in childhood, accounting for approximately 15% of all cancer-related deaths in the pediatric population. The overall survival of children with high-risk disease is around 40-50% despite the aggressive treatment protocols. In accordance with the most recent guidelines, a complete classification of the primary tumor, including its histopathological and molecular analysis, is necessary. In this regard, the biopsy of the primary tumor is an important diagnostic procedure adopted not only to confirm the diagnosis but also for staging and risk stratification of the disease. In this study, the authors describe their unicentric experience with four different approaches adopted for sampling NB tumors: (i) the open incisional biopsy; (ii) the minimally invasive thoracoscopic/laparoscopic incisional biopsy; (iii) the ultrasound-guided core needle biopsy; (iv) the laparoscopic-assisted core needle biopsy. The benefits of each technique are analyzed along with their contraindications.

Droplet digital PCR as an alternative to FISH for MYCN amplification detection in human neuroblastoma FFPE samples

Background

MYCN amplification directly correlates with the clinical course of neuroblastoma and poor patient survival, and serves as the most critical negative prognostic marker. Although fluorescence in situ hybridization (FISH) remains the gold standard for clinical diagnosis of MYCN status in neuroblastoma, its limitations warrant the identification of rapid, reliable, less technically challenging, and inexpensive alternate approaches.

Methods

In the present study, we examined the concordance of droplet digital PCR (ddPCR, in combination with immunohistochemistry, IHC) with FISH for MYCN detection in a panel of formalin-fixed paraffin-embedded (FFPE) human neuroblastoma samples.

Results

In 112 neuroblastoma cases, ddPCR analysis demonstrated a 96–100% concordance with FISH. Consistently, IHC grading revealed 92–100% concordance with FISH. Comparing ddPCR with IHC, we observed a concordance of 95–98%.

Conclusions

The results demonstrate that MYCN amplification status in NB cases can be assessed with ddPCR, and suggest that ddPCR could be a technically less challenging method of detecting MYCN status in FFPE specimens. More importantly, these findings illustrate the concordance between FISH and ddPCR in the detection of MYCN status. Together, the results suggest that rapid, less technically demanding, and inexpensive ddPCR in conjunction with IHC could serve as an alternate approach to detect MYCN status in NB cases, with near-identical sensitivity to that of FISH.

MiRNA Influences in Neuroblast Modulation: An Introspective Analysis

Neuroblastoma (NB) is the most common occurring solid paediatric cancer in children under the age of five years. Whether of familial or sporadic origin, chromosome abnormalities contribute to the development of NB and cause dysregulation of microRNAs (miRNAs). MiRNAs are small non-coding, single stranded RNAs that target messenger RNAs at the post-transcriptional levels by repressing translation within all facets of human physiology. Such gene 'silencing' activities by miRNAs allows the development of regulatory feedback loops affecting multiple functions within the cell, including the possible differentiation of neural stem cell (NSC) lineage selection. Neurogenesis includes stages of self-renewal and fate specification of NSCs, migration and maturation of young neurones, and functional integration of new neurones into the neural circuitry, all of which are regulated by miRNAs. The role of miRNAs and their interaction in cellular processes are recognised aspects of cancer genetics, and miRNAs are currently employed as biomarkers for prognosis and tumour characterisation in multiple cancer models. Consequently, thorough understanding of the mechanisms of how these miRNAs interplay at the transcriptomic level will definitely lead to the development of novel, bespoke and efficient therapeutic measures, with this review focusing on the influences of miRNAs on neuroblast modulations leading to neuroblastoma.

MicroRNA-141 and its associated gene FUS modulate proliferation, migration and cisplatin chemosensitivity in neuroblastoma cell lines

In the present study, a novel signaling pathway of microRNA-141 (miR-141)/fused in sarcoma (FUS) was investigated in neuroblastoma (NB). Gene expression of miR-141 was evaluated in 6 NB cell lines. IMR-32 and SH-SY5Y cells were transduced with the miR-141 mimic lentivirus. The effects of miR-141 upregulation on cell proliferation, cell division, migration, chemosensitivity and in vivo explants were evaluated by MTT, cell cycle, wound-healing, cisplatin sensitivity and in vivo tumor growth assays, respectively. The correlation between miR-141 and the FUS gene was evaluated by luciferase assay and qRT-PCR. FUS was also downregulated in IMR-32 and SH-SY5Y cells to evaluate its impact on NB regulation. miR-141 was downregulated in both MYCN- and non-MYCN-amplified NB cell lines. In the IMR-32 and SH-SY5Y cells, lentivirus-induced miR-141 upregulation inhibited cancer proliferation, cell cycle progression, migration and increased cisplatin chemosensitivity in vitro. In addition, miR-141 upregulation reduced the in vivo growth of IMR-32 tumor explants. FUS was found to be inversely regulated by miR-141 in NB. Small interfering RNA (siRNA)-induced FUS downregulation had similar tumor-suppressive effects as miR-141 upregulation on NB cell proliferation, cell cycle progression, migration and cisplatin chemosensitivity. Our data indicate that miR-141 and the FUS gene, which are inversely correlated, play significant functional roles in regulating human NB.

Assessment of fine needle aspiration cytology samples for molecular genetic analysis in neuroblastoma

PURPOSE

To assess the utility of fine needle aspiration cytology (FNAC) samples for molecular genetic analysis of neuroblastoma.

METHODS

The case files from the pediatric solid tumor clinic were reviewed to identify 20 neuroblastoma patients whose pre-treatment FNAC slides were preserved in the cytology laboratory. The FNAC slides were destained, air dried and hybridisation with fluorescence in situ hybridisation (FISH) probes was performed as per protocol. All slides were screened and analyzed carefully under the fluorescent microscope. Over four-fold increase of the N-myc signal numbers was defined as N-myc amplification. Focal occurrence of cells (at least 50) showing N-myc amplification surrounded by non-amplified tumor cells was defined as focal N-myc amplification. Presence of three or more signals for the long arm of chromosome 17 was defined as 17q gain.

RESULTS

FISH analysis gave informative results for all the FNAC smears in our study. FISH analysis of FNAC smears showed N-myc amplification in 5 (25 %) out of 20 patients and 15 (75 %) showed normal N-myc copy number. Three out of these five patients had homogenous amplification and two patients had focal N-myc amplification, indicating tumor heterogeneity. On investigation of chromosome 17q status, 5 (25 %) out of 20 patients demonstrated gain of 17q and 15 (75 %) patients showed normal 17q status. Four out of the five patients with 17q gain also showed N-myc amplification.

CONCLUSIONS

The current study indicates that FNAC is a rapid and atraumatic diagnostic method for neuroblastoma which provides sufficient material for molecular genetic analyses by means of FISH.

The role of genetic and epigenetic alterations in neuroblastoma disease pathogenesis

Neuroblastoma is a highly heterogeneous tumor accounting for 15 % of all pediatric cancer deaths. Clinical behavior ranges from the spontaneous regression of localized, asymptomatic tumors, as well as metastasized tumors in infants, to rapid progression and resistance to therapy. Genomic amplification of the MYCN oncogene has been used to predict outcome in neuroblastoma for over 30 years, however, recent methodological advances including miRNA and mRNA profiling, comparative genomic hybridization (array-CGH), and whole-genome sequencing have enabled the detailed analysis of the neuroblastoma genome, leading to the identification of new prognostic markers and better patient stratification. In this review, we will describe the main genetic factors responsible for these diverse clinical phenotypes in neuroblastoma, the chronology of their discovery, and the impact on patient prognosis.

A chemical screen identifies the chemotherapeutic drug topotecan as a specific inhibitor of the B-MYB/MYCN axis in neuroblastoma

The transcription factor MycN is the prototypical neuroblastoma oncogene and a potential therapeutic target. However, its strong expression caused by gene amplification in about 30% of neuroblastoma patients is a considerable obstacle to the development of therapeutic approaches aiming at eliminating its tumourigenic activity. We have previously reported that B-Myb is essentially required for transcription of the MYCN amplicon and have also shown that B-MYB and MYCN are engaged in a feed forward loop promoting the survival/proliferation of neuroblastoma cells. We postulated that pharmacological strategies breaking the B-MYB/MYCN axis should result in clinically desirable effects. Thus, we implemented a high throughput chemical screen, using a curated library of ~1500 compounds from the National Cancer Institute, whose endpoint was the identification of small molecules that inhibited B-Myb. At the end of the screening, we found that the compounds pinafide, ellipticine and camptothecin inhibited B-Myb transcriptional activity in luciferase assays. One of the compounds, the topoisomerase-1 inhibitor camptothecin, is of considerable clinical interest since its derivatives topotecan and irinotecan are currently used as first and second line treatment agents for various types of cancer, including neuroblastoma. We found that neuroblastoma cells with amplification of MYCN are more sensitive than MYCN negative cells to camptothecin and topotecan killing. Campothecin and topotecan caused selective down-regulation of B-Myb and MycN expression in neuroblastoma cells. Notably, forced overexpression of B-Myb could antagonize the killing effect of topotecan and camptothecin, demonstrating that the transcription factor is a key target of the drugs. These results suggest that camptothecin and its analogues should be more effective in patients whose tumours feature amplification of MYCN and/or overexpression of B-MYB.

Molecular analysis of gene amplification in tumors

Detection of gene amplification in human cancer cells has both clinical and biological importance. Amplified genes can be classified in one of two categoriesas oncogenes or as genes conferring drug resistance. Both types of gene amplification may alter clinical management of the patient. The basic protocol describes preparation and quantitation of DNA from tumor tissue and the use of conventional Southern blot hybridization analysis to detect and quantify gene amplification. The first alternate protocol provides an approach to quickly screen tumor samples for gene amplification using slot blot hybridization analysis. The second alternate protocol describes the use of the polymerase chain reaction (PCR) for analyzing tumors that may be difficult to analyze because of degradation or limited amounts of DNA. A explains the proper methods for obtaining, processing, storing, and shipping tumor tissue for DNA analysis.

Genome wide measurement of DNA copy number changes in neuroblastoma: dissecting amplicons and mapping losses, gains and breakpoints

In the past few years high throughput methods for assessment of DNA copy number alterations have witnessed rapid progress. Both 'in house' developed BAC, cDNA, oligonucleotide and commercial arrays are now available and widely applied in the study of the human genome, particularly in the context of disease. Cancer cells are known to exhibit DNA losses, gains and amplifications affecting tumor suppressor genes and proto-oncogenes. Moreover, these patterns of genomic imbalances may be associated with particular tumor types or subtypes and may have prognostic value. Here we summarize recent array CGH findings in neuroblastoma, a pediatric tumor of the sympathetic nervous system. A total of 176 primary tumors and 53 cell lines have been analyzed on different platforms. Through these studies the genomic content and boundaries of deletions, gains and amplifications were characterized with unprecedented accuracy. Furthermore, in conjunction with cytogenetic findings, array CGH allows the mapping of breakpoints of unbalanced translocations at a very high resolution.

Loss of chromosome 1 in myxopapillary ependymoma suggests a region out of chromosome 22 as critical for tumour biology: a FISH analysis of four cases on touch imprint smears

OBJECTIVE

Ependymomas are glial tumours. They constitute approximately 5-10% of intracranial tumours and are tumours which can recur. Predictive factors of outcome in ependymomas are not well established. Karyotypic studies are relatively scarce and loss of chromosome 22 has been described to correlate with recurrence. We are unaware of any reports involving chromosome 1 aberrations in the malignant progression of ependymomas.

METHODS

Cytogenetic analysis of four myxopapillary ependymomas was performed using double target fluorescent in situ hybridization (FISH), focusing on chromosomes 1 and 22.

RESULTS

One patient's tumour had recurred. FISH was performed on 500 nuclei/tumours. All four cases showed a loss of chromosome 22q while only one showed an additional loss of chromosome 1p, and this was the one that recurred.

CONCLUSIONS

We support the presence of a tumour suppressor gene on 1p associated with relapse in myxopapillary ependymomas and suggest that status of chromosome 1p by FISH may indicate a high-risk group of patients harbouring this tumour. More studies of this type are needed towards this direction as our results refer to a minimal number of individuals analysed.

Persistent inhibition of FLIP(L) expression by lentiviral small hairpin RNA delivery restores death-receptor-induced apoptosis in neuroblastoma cells

Neuroblastoma represents the most common and deadly solid tumour of childhood, which disparate biological and clinical behaviour can be explained by differential regulation of apoptosis. To understand mechanisms underlying death resistance in neuroblastoma cells, we developed small hairpin of RNA produced by lentiviral vectors as tools to selectively interfere with FLIP(L), a major negative regulator of death receptor-induced apoptosis. Such tools revealed highly efficient in interfering with FLIP(L) expression and function as they almost completely repressed endogenous and/or exogenously overexpressed FLIP(L) protein and fully reversed FLIP(L)-mediated TRAIL resistance. Moreover, interference with endogenous FLIP(L) and FLIP(S) significantly restored FasL sensitivity in SH-EP neuroblastoma cell line. These results reveal the ability of lentivirus-mediated shRNAs to specifically and persistently interfere with FLIP expression and support involvement of FLIP in the regulation of death receptor-mediated apoptosis in neuroblastoma cells. Combining such tools with other therapeutic modalities may improve treatment of resistant tumours such as neuroblastoma.

Use of Chromogenic In Situ Hybridization to Identify MYCN Gene Copy Number in Neuroblastoma Using Routine Tissue Sections

Amplification of MYCN in neuroblastoma is associated with a poor prognosis. However, methods for estimating the number of MYCN genes based on pooled cells do not address copy number heterogeneity at the cell level and can underestimate or even miss amplification. MYCN copy number can be directly assessed by fluorescence in situ hybridization, but evaluation of tissue histology is next to impossible. We have used a chromogenic method for in situ hybridization (CISH) that enables determination of MYCN copy number using routine light microscopy on routinely processed paraffin sections. Of 41 cases studied, CISH identified 100% of the 18 cases that were determined to be amplified by other techniques and was more sensitive than Southern blotting or quantitative DNA polymerase chain reaction. Because the technique evaluates individual tumor cells, heterogeneity of MYCN copy number was apparent from cell to cell. When defined as 50% or greater variation in copy number between cells in amplified tumors, almost 30% of cases were scored as heterogeneous. Heterogeneity reflects different tumor clones and its role has likely been under-recognized and underestimated in neuroblastoma biology. CISH will provide a valuable tool to assess this phenomenon in conjunction with other morphologic parameters in neuroblastoma specimens, to further our understanding of the biology of this childhood tumor.

Sublethal irradiation promotes invasiveness of neuroblastoma cells

Neuroblastoma is the most frequent extracranial solid tumour of childhood. Despite multiple clinical efforts, clinical outcome has remained poor. Neuroblastoma is considered to be radiosensitive, but some clinical studies including the German trial NB90 failed to show a clinical benefit of radiation therapy. The mechanisms underlying this apparent discrepancy are still unclear. We have therefore investigated the effects of radiation on neuroblastoma cell behaviour in vitro. We show that sublethal doses of irradiation up-regulated the expression of the hepatocyte growth factor (HGF) and its receptor c-Met in some neuroblastoma cell lines. The increase in HGF/c-Met expression was correlated with enhanced invasiveness and activation of proteases degrading the extracellular matrix. Thus, irradiation at sublethal doses may promote the metastatic dissemination of neuroblastoma cells through activating the HGF/c-Met pathway and triggering matrix degradation.

Correlation of MYCN amplification with MCM7 protein expression in neuroblastomas: A chromogenic in situ hybridization study in paraffin sections

Amplification of the MYCN oncogene in neuroblastomas is generally associated with a more aggressive clinical course. Recently, 1 of the minichromosome maintenance proteins, MCM7, was found to be a direct target of the MYCN transcription factor in neuroblastoma. To confirm this correlation, chromogenic in situ hybridization (CISH) to detect MYCN amplification and immunohistochemical staining for MCM7 protein expression were performed on paraffin tissue sections of 26 neuroblastomas cases and of 4 recurrences of these tumors. Seven of the primary tumors showed MYCN amplification, and all were stage 3 or 4 tumors. Only 4 of these showed MCM7 overexpression. However, 11 primary tumors overexpressed MCM7. The 4 patients with MCM7 expression associated with MYCN amplification all died from the tumor. In contrast, the 7 patients with MCM7 overexpression but no MYCN amplification were all younger than 1 year of age and have shown good survival. This suggests that MCM7 overexpression by itself is not related to a poorer prognosis as is MYCN amplification. In addition, the 4 pairs of primary and recurrent tumors all showed changes in MCM7 expression from negative to positive, whereas none of them had MYCN amplification. This study showed that MCM7 overexpression is not necessarily correlated with MYCN amplification or an aggressive clinical course. Interpretation of the results of CISH was quite easy and straightforward because the preparations were viewed with an ordinary light microscope with good preservation of the tissue morphology.

In vivoechographic evidence of tumoral vascularization and microenvironment interactions in metastatic orthotopic human neuroblastoma xenografts

Human neuroblastoma (NB) is the second most frequent solid tumor of childhood and represents a highly heterogeneous disease at clinical and biologic levels. Little progress has been made to improve the poor prognosis of patients with high-stage NB. Tumor progression and metastatic dissemination still represent major obstacles to the successful treatment of advanced stage disease. In order to develop and evaluate new, targeted, therapeutic strategies, fully defined and biologically relevant in vivo models of NB are strongly needed. We have developed an orthotopic model of metastatic human NB in the nude mouse, using 2 well-characterized NB cell lines. Tumor growth, vascular properties and metastatic patterns were investigated using a sensitive and newly developed in vivo echographic technology in addition to immunohistochemistry and PCR analyses. Results show that implantation of low numbers of NB cells directly into the adrenal gland of nude mice resulted in rapid and homogeneous tumor growth without tumor morbidity. Nude mice were shown to rapidly develop highly vascularized adrenal tumors that selectively metastasized to the liver and bone marrow. In addition, the newly formed mouse vessels in orthotopic but not in heterotopic tumors, were found to express the highly angiogenic alphavbeta3 integrin marker, indicating the development of a truly malignant neovasculature in orthotopic conditions only. This observation confirms the impact of the regional microenvironment on tumor biology and suggests the existence of cross-talk with the tumor cells. In conclusion, such model faithfully reproduces the growth, vascular and metastatic patterns as observed in patients. It therefore represents a powerful and biologically relevant tool to improve our understanding of the biology of NB and to develop and assess new antiangiogenic and metastasis-targeted therapies.

Molecular analysis of the putative tumour-suppressor gene EXTL1 in neuroblastoma patients and cell lines

Although neuroblastoma is the most common extracranial solid tumour of childhood, little is known about its aetiology. Together with MYCN amplification and chromosome 17q gain, chromosome 1p deletion is one of the most frequently occurring genetic abnormalities in neuroblastoma. Based upon mapping of deletion breakpoints, putative tumour suppressor gene loci have been assigned to the distal part of the short arm of chromosome 1. Recently, the EXTL1 gene was suggested as a candidate neuroblastoma-suppressor gene and to evaluate this hypothesis, we performed 1p deletion analysis and mutation screening of the EXTL1-coding region on DNA from 22 primary neuroblastomas and 21 neuroblastoma cell lines. Deletions of the chromosome region 1p36.1, including the EXTL1 gene, were detected in several neuroblastoma cell lines and primary tumours. EXTL1 mutation screening resulted in the detection of one unclassified variant (Ser28Cys) but could not provide additional evidence of EXTL1 being involved in the aetiology of neuroblastoma.

Automatic quantification of gene amplification in clinical samples by IQ-FISH

BACKGROUND

The reliable detection and quantification of gene amplifications is crucial to clinical practice. Although there are different detection techniques, the fluorescence in situ hybridization (FISH) method has become highly accepted over past years because it is a reliable, robust, and quick method. Unfortunately, automatic quantification of gene amplification based on fluorescence intensities has not been possible thus far. Because current spot counting methods are reliable only when analyzing low amplification rates, we attempted to establish another method, i.e., to quantify the intensity of different FISH signals using an automatic fluorescence microscopical device on interphase nuclei: interphase quantitative FISH (IQ-FISH).

METHODS

We quantified the fluorescence intensities of the differently labeled FISH probes (MYCN and D2Z) hybridized to three different neuroblastoma cell lines, six peripheral blood (PB) samples, 10 spiked PB samples, and nine neuroblastoma samples using the Metafer4 system (MetaSystems, Altlussheim, Germany). To obtain the MYCN copy number per cell, the ratio between the fluorescence intensities of the MYCN gene and reference sequence (D2Z) was calculated. For automatic analysis of the HER-2/neu status in tumor cells, labeled FISH probes specific for HER-2/neu and a chromosome 17-specific probe were hybridized to peripheral blood and tumor specimens and analyzed using the automatic device.

RESULTS

When measuring the fluorescence intensity per cell for both probe pairs (MYCN/D2Z and HER-2/17p), amplified and non-amplified cells, showed distinct peaks with only little overlap. Whereas normal cells showed a fluorescence ratio peak for MYCN/D2Z between 200 and 800, cells with MYCN amplification clearly exceeded this ratio value (1000 to 25,000). When mixing a varying number of MYCN amplified cells (range 9-91%) to normal PB, the spiked tumor cells could be identified. Even one neuroblastoma tumor cell in 1000 mononucleated cells could reliably be detected using our device. In neuroblastoma patient samples, non-amplified cells were distinguished from amplified cells. Automatically and manually counted signals gave matching results in amplified and non-amplified samples. HER-2/neu-amplified cells were automatically detected in the breast cancer samples analyzed.

CONCLUSION

The automatic measurement of fluorescence signal intensities not only allows a reliable discrimination between non-amplified and amplified cells but also exact quantification of amplified sequences. This is the prerequisite for the following applications: detection of amplified cells in the bone marrow and second-look specimens; comparison between primary and relapse or pre- and post-chemotherapeutic specimens; detection of tumors with focal gene amplification; and quantification of elimination of amplified gene sequences.

Abnormal constitutional karyotypes in patients with neuroblastoma: a report of four new cases and review of 47 others in the literature

Anomalies of constitutional karyotype, which have led to the discovery of oncogenes and tumor-suppressor genes in embryonal tumors such as retinoblastoma and Wilms tumor, have, until recently, rarely been reported until recently in neuroblastoma. We present four new cases of neuroblastoma associated with (a) a mosaicism for monosomy 22; (b) an 11q interstitial deletion; (c) a pericentric inversion of chromosome 9 at band 9p21; and (d) a Robertsonian translocation t(13;14). These anomalies and 47 others in the literature are worthy of interest, because some are recurrent, involving the same chromosome regions (1p36, 2p23, 3q, 11q23, and 15q), and some anomalies are situated on chromosome regions known to contain genes involved in neuroblastoma development (1p, 2p, 9p, 11q, 16q, and 17q). Chromosome regions 3q and 15q, observed several times, may also contain genes significant for neuroblastoma onset or development. Furthermore, the lack of neuroblastoma in patients with Down syndrome and Klinefelter or triple-X syndromes, together with a probable excess of neuroblastoma in patients with Turner syndrome, suggests that genes of importance for neuroblastoma may map to chromosomes X and 21. A search for genes implicated in neuroblastoma biology should use these data.

High level of stabilized angiostatin mediated by adenovirus delivery does not impair the growth of human neuroblastoma xenografts

Human neuroblastoma (NB) is a highly heterogeneous childhood cancer secreting a high level of vascular endothelial growth factor (VEGF). Its vascularization has been clearly correlated with metastatic progression and poor outcome. Thus, molecules that target the vascular endothelium are regarded as new therapeutics of clinical interest. Angiostatin, an internal fragment of plasminogen containing the first four kringle structures, has been described as a powerful angiogenic inhibitor. We used a recombinant adenovirus encoding the human angiostatin kringle 1-3 directly fused to human serum albumin HSA (AdK3-HSA). Coupling to HSA has been previously shown to increase the in vivo half-life of this angiostatic factor, and to lead to tumor growth inhibition in the MDA-MB-231 carcinoma model. For the assessment of antiangiogenic gene therapy in the human NB IGR-N835 tumor model, 5 x 10(9) PFU of AdK3-HSA were intravenously injected in tumor-bearing athymic mice presenting either of the following experimental settings: early stage, established, and minimal residual tumors. No delay in tumor growth was observed in animals treated with AdK3-HSA as compared to those treated with the empty virus AdCO1. In early-stage tumors, kinetics of tumor occurrence and tumor growth were similar in AdK3-HSA- and AdCO1-treated animals. K3-HSA was found to be expressed at high levels (the mean value for the three experiments being 19.4+/-15.9 microg/ml) in the circulation of all animals up to 21-35 days after virus injection. In addition, IGR-N835 tumors were found to be highly vascularized and to release high amounts of angiogenic factors, in particular VEGF (665+/-370 pg/mg total protein). Thus, in spite of high circulating levels, K3-HSA may be unable to displace the NB proangiogenic switch. In this regard, a more promising target to inhibit NB angiogenesis seems to be the VEGF/VEGFR system.

Arginine deiminase and other antiangiogenic agents inhibit unfavorable neuroblastoma growth: potentiation by irradiation

In spite of aggressive therapy, children suffering from neuroblastoma have a poor prognosis. Therapeutic failure is most often observed in neuroblastomas with unfavorable features, including amplification/over-expression of the N-myc oncogene, rapid growth, effective angiogenesis and/or the tendency to metastasize. Here, we have used cultured human neuroblastoma cells with such features and we have examined whether antiangiogenic agents alone or in combination with tumor irradiation inhibit their angiogenesis and growth in vivo. We report that antiangiogenic agents (arginine deiminase, SU5416 and DC101) inhibit in vivo growth of neuroblastomas with unfavorable properties and that these effects are potentiated by simultaneous irradiation. Combination of either agent with irradiation leads to a reduction in the absolute number of tumor vessels and of perfused tumor vessels. Combination of arginine deiminase or DC101 with irradiation does not increase tumor hypoxia. Our data demonstrate for the first time that arginine deiminase suppresses the growth of unfavorable experimental neuroblastomas and that this effect is potentiated by irradiation. We suggest that antiangiogenesis alone or in combination with established therapeutic regimen may improve the outcome of unfavorable neuroblastomas in a clinical setting.

Neuroblastoma: biological insights into a clinical enigma

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

Genomic medicine and neuroblastoma

Neuroblastic tumors are a broad biological and clinical spectrum of neoplastic disease that has long captured the attention of clinicians and scientists alike. It is the most common solid extracranial tumor in children and accounts for 8-10% of all childhood tumors. Tumors are derived from neural crest cells and neural differentiation is common. Neuroblastoma is unique in that it presents with at least three distinct patterns of disease. Locoregional disease (Stage 1, 2, 3) does not metastasize to bone or bone marrow. Stage 4 is a systemic disease with widespread metastasis that responds to chemotherapy but many develop resistance. Stage 4s presents in infancy, is widespread and can spontaneously regress with no intervention, leaving a focus of fibrosis or calcification. Prognosis correlates with age, stage and tumor biological profile. The goal of this review is to provide an overview of the disease and highlight diagnostic, prognostic and therapeutic advances in neuroblastoma. Recommendations and resources for the evaluation and treatment of this disease are outlined.

Evaluation of genetic heterogeneity in neuroblastoma

BACKGROUND AND METHODS

The prognosis in neuroblastoma, which is the most common solid tumor in children, tends to vary greatly, and many studies have demonstrated both clinical and biological factors to be closely correlated with the outcome. In order to select the optimal treatment according to the degree of malignancy of neuroblastoma, it is essential to accurately and rapidly identify any genetic heterogeneity associated with the prognosis. We assessed the status of some genetic abnormalities (MYCN amplification, deletion of the short arm of chromosome 1, DNA ploidy, and a gain of the chromosome 17q region) associated with the prognosis using several molecular biological methods.

RESULTS AND CONCLUSIONS

The combination of several molecular biological techniques is thus considered to be useful for elucidating the degree of malignancy of neuroblastoma. In particular, diagnostic analyses based on a combination of the fluorescence in situ hybridization (FISH) method and the quantitative polymerase chain reaction (PCR) method may be considered to be the most effective methods for quickly and accurately evaluating any aberrations in the gene dosages associated with the patients' outcomes.

Genomic structure and mutational analysis of the human KIF1B gene which is homozygously deleted in neuroblastoma at chromosome 1p36.2

In order to clone candidate tumor suppressor genes whose loss contributes to the pathogenesis of neuroblastoma (NB), we performed polymerase chain reaction (PCR) screening using a high-density sequence tagged site-content map within a commonly deleted region (chromosome band 1p36) in 24 NB cell lines. We found a approximately 480 kb homozygously deleted region at chromosome band 1p36.2 in one of the 24 NB cell lines, NB-1, and cloned the human homologue (KIF1B-beta) of the mouseKif1B-beta gene in this region. The KIF1B-beta gene had at least 47 exons, all of which had a classic exon-intron boundary structure. Mouse Kif1B is a microtubule-based putative anterograde motor protein for the transport of mitochondria in neural cells. We performed mutational analysis of the KIF1B-beta gene in 23 cell lines using 46 sets of primers and also an allelic imbalance (AI) analysis of KIF1B-beta in 50 fresh NB samples. A missense mutation at codon 1554, GTG (Gly) to ATG (Met), silent mutations at codon 409 (ACG to ACA) and codon 1721 (ACC to ACT), and polymorphisms at codon 170, GAT (Asp) to GAA (Glu), and at codon 1087, TAT (Tyr), to TGT (Cys), were all identified, although their functional significances remain to be determined. The AI for KIF1B-beta was slightly higher (38%) than those for the other two markers (D1S244, D1S1350) (35 and 32%) within the commonly deleted region (1p36). Reverse transcriptase-PCR analysis of the KIF1B-beta gene revealed obvious expression in all NB cell lines except NB-1, although decreased expression of the KIF1B-beta gene was found in a subset of early- and advanced-stage NBs. These results suggest that the KIF1B-beta gene may not be a candidate for tumor suppressor gene of NB.

Cytogenetics of neuroblastoma: a study using fine needle aspiration cultures

Neuroblastoma is associated with chromosomal aberrations of 1p and 1q in a majority of cases. Some nonrandom secondary changes were observed in this study. The role of these changes in the development and progression of neuroblastoma is examined. Chromosomal analysis was performed on 33 children with neuroblastoma using fine needle aspiration cultures. Metaphases were observed in 57.5% of cases. 86.6% showed the involvement of chromosome 1. Double minutes and unidentifiable markers was also observed. The most frequent secondary changes included add(4)(q35), add(11)(p13), add(14)(q32), add(16)(q12). add(17)(p13), add(19)(q12) and add(21)(q22). Minority of cases showed deletions and translocations. Ploidy pattern ranged from diploid to hypotetraploid. The present study substantiates aberration of chromosome 1 in the form of deletions, additions, duplications and iso-chromosome with some notable secondary abnormalities.

Comparative genomic hybridization (CGH) analysis of stage 4 neuroblastoma reveals high frequency of 11q deletion in tumors lacking MYCN amplification

We have studied the occurrence and association of 11q deletions with other chromosomal imbalances in Stage 4 neuroblastomas. To this purpose we have performed comparative genomic hybridization (CGH) analysis on 50 Stage 4 neuroblastomas and these data were analyzed together with those from 33 previously published cases. We observed a high incidence of 11q deletion in Stage 4 neuroblastoma without MYCN amplification (59%) whereas 11q loss was only observed in 15% of neuroblastomas with MYCN-amplification (p = 0.0002) or 11% of cases with 1p deletion detected by CGH (p = 0.0001). In addition, 11q loss showed significant positive correlation with 3p loss (p = 0.0002). Event-free survival was poor and not significantly different for patients with or without 11q deletion. Our study provides further evidence that Stage 4 neuroblastomas with 11q deletions represent a distinct genetic subgroup that typically shows no MYCN-amplification nor 1p deletion. Moreover, it shows that neuroblastomas with 11q deletion also often present 3p deletion. This genetic subgroup shows a similar poor prognosis as MYCN amplified 4 neuroblastomas.

DNA fragmentation factor 45 (DFF45) gene at 1p36.2 is homozygously deleted and encodes variant transcripts in neuroblastoma cell line

Recently, loss of heterozygosity (LOH) studies suggest that more than two tumor suppressor genes lie on the short arm of chromosome 1 (1p) in neuroblastoma (NB). To identify candidate tumor suppressor genes in NB, we searched for homozygous deletions in 20 NB cell lines using a high-density STS map spanning chromosome 1p36, a common LOH region in NB. We found that the 45-kDa subunit of the DNA fragmentation factor (DFF45) gene was homozygously deleted in an NB cell line, NB-1. DFF45 is the chaperon of DFF40, and both molecules are necessary for caspase 3 to induce apoptosis. DFF35, a splicing variant of DFF45, is an inhibitor of DFF40. We examined 20 NB cell lines for expression and mutation of DFF45 gene by reverse transcription (RT)-polymerase chain reaction (PCR) and RT-PCR-single-strand conformation polymorphism. Some novel variant transcripts of the DFF45 gene were found in NB cell lines, but not in normal adrenal gland and peripheral blood. These variants may not serve as chaperons of DFF40, but as inhibitors like DFF35, thus disrupting the balance between DFF45 and DFF40. No mutations of the DFF45 gene were found in any NB cell line, suggesting that the DFF45 is not a tumor suppressor gene for NB. However, homozygous deletion of the DFF45 gene in the NB-1 cell line may imply the presence of unknown tumor suppressor genes in this region.

Detection of MYCN gene amplification in neuroblastoma by fluorescence in situ hybridization: a pediatric oncology group study

To assess the utility of fluorescence in situ hybridization (FISH) for analysis of MYCN gene amplification in neuroblastoma, we compared this assay with Southern blot analysis using tumor specimens collected from 232 patients with presenting characteristics typical of this disease. The FISH technique identified MYCN amplification in 47 cases, compared with 39 by Southern blotting, thus increasing the total number of positive cases by 21%. The major cause of discordancy was a low fraction of tumor cells (< or =30% replacement) in clinical specimens, which prevented an accurate estimate of MYCN copy number by Southern blotting. With FISH, by contrast, it was possible to analyze multiple interphase nuclei of tumor cells, regardless of the proportion of normal peripheral blood, bone marrow, or stromal cells in clinical samples. Thus, FISH could be performed accurately with very small numbers of tumor cells from touch preparations of needle biopsies. Moreover, this procedure allowed us to discern the heterogeneous pattern of MYCN amplification that is characteristic of neuroblastoma. We conclude that FISH improves the detection of MYCN gene amplification in childhood neuroblastomas in a clinical setting, thus facilitating therapeutic decisions based on the presence or absence of this prognostically important biologic marker.

[Retroperitoneal neuroblastoma in the adult: case report and review of the literature]

Retroperitoneal neuroblastoma is a rare embryonic tumor of the sympathetic nervous system that is specific to the child. In this study, the case is reported of an infant who underwent median laparotomy at the age of 14 months for a tumor which occupied the left half of the abdomen. The lesion was large, hard, and not very mobile. It was considered to be unresectable, and the histological findings after biopsy showed it to be a neuroblastoma. Radiotherapy was then initiated, which successfully reduced the tumor size. A second investigation at the age of three years detected an unresectable tumor of 5 cm. A further biopsy was performed, and the histological findings showed the lesion to be a partially developed ganglioneuroblastoma. The patient has been followed up regularly by ultrasonography which has shown no increase in tumor size. She is now 20 years old, and is asymptomatic. The last computed tomography scan visualized a 62-mm retroperitoneal mass with no metastases. Surgery was decided against in favor of regular monitoring. This case is particular due to the prolonged survival of the patient, regression of histological stage, and reduction in size of the tumor after radiotherapy. It is remarkable that the diagnosis of neuroblastoma was made when the patient was 14 months old, and that she is still alive at 20 years old.

Multicentre analysis of patterns of DNA gains and losses in 204 neuroblastoma tumors: how many genetic subgroups are there?

PROCEDURE

Analysis of comparative genomic hybridization (CGH) data of 120 tumors from four different studies, and data of 84 previously unpublishied tumors, allowed delineation of at least six different genetic subsets of neuroblastomas.

RESULTS AND CONCLUSIONS

A small number of tumors show no detectable imballances. A second group of tumors presents with gains and losses of whole chromosomes and is found predominantly in prognostically favorable stage 1 and 2 tumors. The remaining groups are characterized by the presence of partial chromosome imbalances, and are found mostly in stage 3, 4, and 4S tumors. The third group shows 17q gain without 11q loss, 1p loss, or MYCN amplification (MNA). The fourth group has 1p deletion or MNA, and finally, a fifth group shows 11q loss without 1p deletion or MNA, and is found mainly in stage 4 tumors. The latter group is significantly associated with losses of 3p, 4p, and 14q.

Loss of heterozygosity for chromosome 14q in neuroblastoma

BACKGROUND

Neuroblastoma is a genetically heterogeneous disease, with subsets of tumors demonstrating rearrangements of several genomic regions. Preliminary studies from several groups have identified loss of heterozygosity (LOH) for the long arm of chromosome 14 (14q) in 20-25% of primary neuroblastomas.

PROCEDURE

To determine precisely the frequency and extent of 14q deletions, we performed LOH analysis for a large series of primary neuroblastomas using a panel of 11 highly polymorphic markers.

RESULTS

LOH was detected in 83 of 372 tumors (22%). Although the majority of tumors with allelic loss demonstrated allelic loss for all informative markers, 13 cases showed LOH for only a portion of 14q. A single consensus region of deletion, which was shared by all tumors with 14q LOH, was defined within 14q23-q32 between D14S588 and the 14q telomere. Allelic loss for 14q was strongly correlated with the presence of 11q LOH (P < 0.001 ) and inversely correlated with MYCN amplification (P= 0.04).

CONCLUSIONS

LOH for 14q was evident in all clinical risk groups, indicating that this abnormality may be a universal feature of neuroblastoma tumor development. These findings suggest that a tumor suppressor gene involved in the initiation or progression of neuroblastoma is located within distal 14q.

Fluorescence in situ hybridization techniques for the rapid detection of genetic prognostic factors in neuroblastoma. United Kingdom Children's Cancer Study Group

Neuroblastoma is the commonest extracranial solid tumour in children. There are a number of molecular genetic features known which are of prognostic importance and which are used to direct therapy. Identification and targeting of high-risk individuals with intensive therapeutic regimens may allow an improvement in survival rates. The most powerful biological parameters associated with prognosis in this malignancy are chromosomal changes, especially MYCN amplification, deletion of chromosome 1p and aneuploidy. Rapid characterization of these aberrations at the time of diagnosis is paramount if stratification according to risk group is to be achieved. This paper describes the rapid detection of del(1p), MYCN amplification and trisomy using interphase fluorescence in situ hybridization on imprints from fresh tumour biopsies. The results are related to those obtained by standard molecular methods and karyotyping.

c-MYC and nodular malignant melanoma. A case report

BACKGROUND

The incidence of skin cancer has been rising since the 1950s. About 75% of skin cancer-associated deaths are caused by malignant melanoma. Nodular malignant melanoma accounts for 20% of melanocytic malignant tumors and is associated with a relatively poor prognosis. Extensive research has been undertaken, but a molecular marker that can predict a more aggressive course of melanoma still has not been found.

METHODS

The authors applied cytogenetic and molecular genetic techniques to a case of nodular malignant melanoma. They used comparative genomic hybridization (CGH) to identify chromosomal regions affected by genomic changes and interphase fluorescence in situ hybridization (FISH) on touch preparations of the tissue to elucidate the CGH findings further. To investigate the functionality of the affected c-MYC gene, the authors detected its transcript via reverse transcription and polymerase chain reaction.

RESULTS

CGH revealed a copy number gain in the 6p and 8q24-8qter region. FISH with c-MYC and centromere eight specific probes revealed that the tumor, in contrast to unaffected skin, was characterized by a gain in copy numbers of the c-MYC gene. The c-MYC gene transcript was detected at higher levels in the tumor than in the tissue taken from the safety margin.

CONCLUSIONS

The WAF1 gene located on chromosome 6p, which in this case had a copy number gain, might be involved in melanoma pathogenesis. The authors suggest that the c-MYC gene plays an important role in melanoma development and progression. The c-MYC gene seems to be affected by gaining functional copies, leading to a change in the normally regulated gene-dose effect.

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.

MYCN gene amplification. Identification of cell populations containing double minutes and homogeneously staining regions in neuroblastoma tumors

Neuroblastoma is the second most common solid tumor occurring in children. Amplification of the MYCN oncogene is associated with poor prognosis. To identify neuroblastoma tumors with MYCN amplification, we studied the number of copies of MYCN in interphase cells by fluorescence in situ hybridization in 20 neuroblastoma patients. MYCN amplification appeared in 7 tumor specimens. Interphase and metaphase studies showed a tumor cell population with both forms of amplification, double minutes and homogeneously staining regions, in two patients. These patients showed a smaller tumor cell subpopulation with the presence of more than one homogeneously staining region, suggesting that gene amplification was undergoing karyotype evolution.

Current aspects of biology, risk assessment, and treatment of neuroblastoma

Neuroblastoma is one of the most intensely studied solid malignancies that affect the pediatric age groups; its clinical presentation, treatment strategies and ultimate prognosis vary greatly. The biologic and genetic character of each tumor has an important impact on disease behavior, and clinical staging now incorporates these factors to generate an overall therapy plan. The clinical presentation of neuroblastoma is related to primary tumor location, production of metabolically active substances, and the presence of metastatic disease. There are also prognostically important associated syndromes including opsoclonus-myoclonus, Horner's syndrome, neurofibromatosis, and a variety of other neurocristopathies. The histologic features of the tumor are of prognostic significance and are utilized in treatment stratification. The International Neuroblastoma Staging System (INSS) has unified classic clinical staging. Features at diagnosis and those determined by initial operation are combined with biologic prognostic factors to achieve risk group assignment for virtually all patients. There are groups of children in which limited therapy is curative and intermediate-risk situations where standard multimodality treatment provides favorable outcomes. Unfortunately, there are many patients with high-risk disease that require intensive strategies, but success is still limited. It is in these most resistant patients that innovative approaches are being undertaken and novel strategies are being investigated.

Frequent deregulation of p16 and the p16/G1 cell cycle-regulatory pathway in neuroblastoma

Alterations of the p16 gene in neuroblastoma are very rare. Pronounced expression of p16 at both the transcript and protein levels, however, was observed in 7 of 19 (39%) neuroblastoma cell lines and 2 of 6 (33%) primary neuroblastoma samples. As p16 expression is tightly controlled in a feedback loop with Rb, we investigated the possibility that changes in p16 expression were reflective of alterations of the downstream components in the G1 regulatory pathway. Two cell lines and one primary sample highly expressing p16 were shown to harbor CDK4 amplification. The cyclin D2 gene was infrequently expressed in neuroblastoma cell lines and did not correlate with p16 expression. Slight variations in the expression of CDK6, cyclins D1, D3 and E; and E2F1 and E2F2 among the cell lines were observed, without apparent correlation with p16 status. No mutations to the p16-binding site of CDK4 and CDK6 nor any mutations to the coding region of p16 itself were identified in neuroblastoma cell lines. Despite frequent N-myc amplification in these cell lines, no relationship with this gene was observed either. All cell lines contained Rb protein with varying degrees of phosphorylation, which bears no correlation with p16 expression. Overall, alterations of the G1 pathway in neuroblastoma included relatively frequent p16 expression and infrequent CDK4 amplification and cyclin D2 expression. Despite a reported feedback relationship between p16 expression and Rb/G1 deregulation, p16 expression in neuroblastoma cell lines is independent of Rb gene and phosphorylation status and, in contrast to other cell lines where expression of p16 leads to G1/S arrest, neuroblastoma cell lines proliferate in the presence of elevated levels of p16.

Mononucleotide repeat instability is infrequent in neuroblastoma

Neuroblastoma is a pediatric malignancy of the sympathetic nervous system and is frequently characterized by genetic aberrations (including aneuploidy, chromosomal deletions, translocations, and gene amplification) that suggest inherent genomic instability. Mutations in mismatch repair (MMR) genes have been associated with genomic instability in several human cancers, such as those of the hereditary nonpolyposis colorectal cancer (HNPCC) syndrome. In these cases, replication errors at microsatellite repeats lead to microsatellite instability (MSI) and mutagenesis. In neuroblastoma, we and others have detected MSI infrequently when analyzed at di- or tetranucleotide repeat polymorphic markers. More recently, however, mutations in the MMR gene GTBP/hMSH6 have been associated with a limited phenotype of instability at mononucleotide repeats only (e.g., polyadenine tracts). Furthermore, mononucleotide repeats appear to be common downstream targets of MSI-related mutagenesis and are present in the transforming growth factor-beta receptor-II gene (TGF beta RII), the BAX proapoptosis gene, and the insulin-like growth factor II receptor gene (IGFIIR) frequently in tumors arising in HNPCC kindreds. Therefore, we analyzed 46 matched normal and tumor DNAs representing all clinical stages of neuroblastoma with the use of five polymorphic mononucleotide repeat markers to assess for MSI at mononucleotide repeats. Only one tumor (2%) demonstrated mononucleotide repeat instability, and the instability was at a single locus. We conclude that MSI, including mononucleotide repeat instability, is infrequent in human neuroblastoma, and therefore defects in DNA mismatch repair are not responsible for the genomic instability seen in this neoplasm.

Molecular cytogenetic delineation of 17q translocation breakpoints in neuroblastoma cell lines

It has recently been recognized that unbalanced translocations resulting in the gain of material from 17q are the most common chromosomal changes in neuroblastoma. These rearrangements are associated with established indicators of bad prognosis and poor patient survival. We have used 13 fluorescence in situ hybridization (FISH) probes to map 12 translocation breakpoints on 17q in 10 neuroblastoma cell lines, identifying at least seven different breakpoints, all localized within the proximal half of 17q (268-369 cR, 53-68 cM). These results suggest that the dosage of a gene, or genes, in 17q22-qter is responsible for the clinical effects of 17q gain, rather than the disruption of a specific gene. This region contains two genes, nm23-H1 and NGFR, already implicated in neuroblastoma biology.

Cytogenetics and the surgeon: an invaluable tool in diagnosis, prognosis and counselling of patients with solid tumours

BACKGROUND

Cytogenetic studies have become an important part of tumour characterization. In a minority of tumours cytogenetic and/or molecular studies may be of help for diagnosis, selection of treatment protocols and predicting outcome.

METHODS

This article reviews the literature on solid tumour translocations and established family cancer syndromes. In addition, the potential importance of genetics in management of patients with breast, ovarian and pancreatic carcinoma is reviewed.

RESULTS AND CONCLUSION

Cytogenetic analysis of tumours may help confirm the diagnosis when conventional histology demonstrates no evidence of differentiation along a particular tissue pathway. For patients with well defined cancer syndromes, cytogenetic and molecular analysis offers the prospect of screening to reduce the risk of malignant disease. For many malignancies the underlying genetic anomalies are gradually being elucidated. Further studies designed to demonstrate the significance of these findings can only be undertaken if tumour material is collected and stored in optimal conditions for cytogenetic and/or molecular biological studies.

Human neuroblastoma demonstrating clonal evolution in vivo

Neuroblastoma demonstrates various clinical behaviors, ranging from spontaneous regression to rapid progression regardless of the therapy used. To study the possibility that progression occurs in neuroblastoma through the accumulation of genetic aberrations, we analyzed the clonal constitution of the primary tumor and metastatic tumor samples from a stage-4 patient. Using cytofluorometry and FISH analyses, intratumor clonal heterogeneity was revealed. In the initial primary tumor sample, the nuclear DNA content indicated the coexistence of diploid and aneuploid clones, and the copy number of chromosome 1 varied from two to six. The chromosome 1 aneusomy population was composed of MYCN-amplified and 1p-deleted clones, whereas, in the chromosome 1 disomy population, coexistence of MYCN-amplified and non-amplified clones as well as 1p-deleted and 1p-intact clones was revealed. In the primary tumor after chemotherapy, the DNA-diploid component had become predominant, although the coexistence of MYCN-amplified and non-amplified clones could still be demonstrated in poorly- and well-differentiated tumor regions, respectively. This contrasted with the findings in the metastatic tumors, in which either diploid or aneuploid clone with MYCN amplification and 1p deletion dominated completely in each metastatic site. The findings suggest that the aneuploid clones had evolved from a diploid clone with MYCN amplification and a 1p deletion which, in turn, may have evolved from a diploid clone with neither MYCN nor 1p abnormality. This illustrates how various stages of multiple-step tumorigenesis may provide clues to a better understanding of the clinical heterogeneity of neuroblastoma.

Detection of double minute chromosomes in a child with acute lymphoblastic leukemia

A child with acute lymphoblastic leukemia (ALL) whose predominant leukemic clone demonstrated double minute chromosomes (dmin) is presented. The patient had no history of mutagen or carcinogen exposure and responded well to combination chemotherapy. Although dmin have been described in acute myelogenous leukemia and various solid tumors in adults, their presence in childhood neoplasms is less frequent and limited primarily to neurogenic tumors. This is the first documentation of dmin in childhood ALL, suggesting that there may be an unrecognized subgroup of ALL patients with gene amplification.