Expression of the amplified domain in human neuroblastoma cells

Butyrylcholinesterase as a Blood Biomarker in Neuroblastoma

Blood-based biomarkers are important in the detection of the disease and in the assessment of responses to therapy. In this study, butyrylcholinesterase was evaluated as a potential biomarker in newly diagnosed neuroblastoma (NB) patients at diagnosis and longitudinally during treatment. Plasma butyrylcholinesterase activities in age-matched and sex-matched children were used as controls. Pretreatment butyrylcholinesterase levels in NB subjects are on an average 2 times lower than butyrylcholinesterase levels in healthy subjects. Significantly, butyrylcholinesterase activities are ∼40% lower in MYCN-amplified as compared with nonamplified disease. As the course of chemotherapy progresses, butyrylcholinesterase activities recover and normalize to control values. The evident response to treatment indicates that plasma butyrylcholinesterase is a good biomarker of tumor response to therapy. Depressed butyrylcholinesterase levels in NB subjects are not caused by hepatic deficits suggesting a specific role for butyrylcholinesterase in NB. Further examination of the mechanism of altered butyrylcholinesterase production require an animal model that best approximates human condition. Studies in mice show that murine NB allografts significantly reduce butyrylcholinesterase activity in plasma. This finding correlates with changes observed in NB patients. In contrast, human NB xenografts produce the opposite effect, that is, butyrylcholinesterase plasma levels rise as the xenograft size increases. In the absence of any liver damage, dissimilarities between butyrylcholinesterase production in murine and human NB models suggest species-specific signaling pathways. This disparity also suggests that human NB xenograft mouse models do not approximate the human disease.

Polymerase chain reaction compared with dot blotting for the determination of N-myc gene amplification in neuroblastoma

The magnitude of N-myc amplification (NMA) influences the treatment strategy of localized neuroblastomas. Reliable assays are therefore needed for all types of tumor samples. The aim of this comparative study of 119 tumor samples was to determine whether a polymerase chain reaction (PCR)-based assay could replace the current dot blot assay as a routine and reliable means of determining NMA. The 2 assays exhibited comparable sensitivity and were completely concordant for samples containing at least 20% neuroblastoma cells. In their present state, both assays remain semi-quantitative since an absolute quantification of the N-myc copy number in clinical samples is limited by uncertainty about the amplification level of reference cell lines and by the estimation of the proportion of malignant cells. However, PCR offers several advantages over dot blotting, such as feasibility on minute samples, simplicity, standardization, rapidity and cost effectiveness.

Prognostic significance of the proliferative activity in neuroblastoma

The prognostic significance of the immunohistochemically assessed growth fraction in neuroblastomas was determined in relation to tumor grade and tumor stage. A total of 101 cases of neuroblastoma were examined with the monoclonal antibodies PC10 against proliferating cell nuclear antigen (PCNA) and Ki-S5 against the Ki-67 protein. Patients were followed for a mean time of 4.8 years. Expression of both PC10 and Ki-S5 was found to be significantly linked to tumor grade and tumor stage. Prognostically favorable stage IVs was associated with low PCNA and Ki-S5 levels. For ganglioneuroblastoma, significant differences were found between the diffuse and the composite type. In univariate analysis of stage III and IV tumors, Ki-S5 and PCNA scores were significantly correlated with disease-free survival (P < 0.0015), allowing definition of a subset of cases with favorable outcome. As to Shimada's group with poor prognosis, significant differences in the clinical course were found for low and high Ki-S5 scores (P = 0.036) but not for PCNA. In multivariate analysis, only patient age, Shimada's grade, and Ki-S5 scores achieved prognostic significance. We conclude that proliferation marker Ki-S5 may provide substantial prognostic information and might become a useful adjunct for predicting the clinical courses of neuroblastoma.

Structural organization of MYCN amplicons of neuroblastoma tumors, xenografts, and cell lines characterized by the sequences encompassing the MYCN amplicons in a human neuroblastoma cell line

We characterized differences in the structural organization of the MYCN amplicons of a number of neuroblastomas by analyzing 8 contigs spanning 330 kb cloned from the MYCN amplicon of a neuroblastoma cell line. Some regions were amplified in almost all specimens, the conserved regions (CRs), and others were differentially amplified in some subsets, the non-conserved regions (NCRs). CRs constituted only 20% of the 330 kb region, with the remainder being NCRs. The regions that inevitably co-segregate with the MYCN gene make up the core, whereas flanking regions are retained at random. If a histogram of the frequency with which the amplified NCR sequences from one specimen match those of the cell line MC-NB-I shows a random distribution, the NCRs would co-segregate with MYCN as a result of random events. However, both the tumors and cell lines/xenografts showed a distribution with two distinct peaks; one from a group containing a small number of sequences with a fairly high degree of homology to the NCRs of MC-NB-I, and the other from a group containing a large number of sequences with little homology. These results indicate that the flanking segments are preferentially co-segregated with MYCN by a non-random mechanism.

Development of a two color immunofluorescence stain and immunolocalization method for N-myc and c-myc oncoproteins with a newly generated mouse IgM anti N-myc antibody

A new mouse monoclonal antibody specific for N-myc oncoprotein was generated and used in combination with an anti-c-myc antibody to develop two color immunofluorescence staining and ultrastructural immunolocalization of N-myc and c-myc in well established (SK-N-SH; CHP 126) and in newly established neuroblastoma (NB) cell lines. Analysis and quantitation of c-myc and N-myc in dually stained cells was done by flow cytometry. Immunolocalization was done by staining with immunogold secondary antibodies and transmission electron microscopy. The results obtained from analysis of 13 newly established NB cell lines revealed, great heterogeneity in the expression of N-myc oncoprotein with 10/13 cell lines over expressing the protein. C-myc oncoprotein was also expressed in all cell lines, however, the level of expression was 4-10-fold lower than the N-myc oncoprotein. Localization studies of c-myc and N-myc oncoproteins on the level of light microscopy and electron microscopy revealed exclusive nuclear localization of c-myc whereas N-myc was localized to the nucleus and to the cytoplasm.

Diagnostic utility of oncogenes and their products in human cancer

The first clear cut association of an oncogene with a specific cancer is the c-abl translocation in chronic myelogenous leukemia and acute lymphocytic leukemia; it has been observed in 90% of CML cases examined. This is the major contributing factor to its being the target of the first oncogene-based FDA-approved diagnostic test. Although the role of the abl translocation in the tumorigenic process is not yet understood, it is clear that somehow it must be causally related to the disease, and thus is an ideal target for a diagnostic test. The association of this oncogene with a specific cancer is the model on which all others may be based in the future. Second generation tests could easily include PCR on mRNA, and/or in situ hybridization, both of which could be performed using blood samples. Both methods would provide a faster means of testing a large number of cells, however, the methodologies must be improved through automation and computer-aided image analysis, respectively, in order to become useful routine tests. Both neu and epidermal growth factor receptor (EGFR) appear to have a close correlation between overexpression of the gene product and outcome of disease in breast cancer; valuable information for prognosis of the disease. And again, although the actual mechanism of action of these molecules and how this relates to the tumorigenic process is not yet known, it is believed from the very nature of the molecules that they must in some way contribute to the progression of the disease. In both cases, the protein products are overexpressed in tissue, and in the case of Neu, it appears as through at least some of the patients have a Neu-related protein in their serum. These molecules present relatively easy targets for the development of diagnostic/prognostic assays, as antibodies are easily made and can be incorporated into a variety of assay formats. Current assays available, an ELISA for Neu and a radio-ligand binding assay for EGFR, are highly sensitive, reproducible and relatively easy to perform. Only the ELISA is commercially available, however, and hence allows for easy comparison between laboratories. An abvious step towards the routine measurement of EGFR then is the development of a comparable commercially available test. An improvement for both types of assay would be the incorporation of an internal control to gauge the cellular component of the tissue samples that are tested. The outcome of the applications of myc and ras to cancer diagnostics is not so easily predictable, with a couple of exceptions.(ABSTRACT TRUNCATED AT 400 WORDS)

Changes in the number of mitochondrial genomes during human development

Using a cDNA probe for the mitochondrially encoded third subunit of cytochrome c oxidase (COIII) we found a progressive increase in the number of mitochondrial DNA molecules in specific human tissues during normal fetal development. The data indicate that the tissue, rather than the final number of mitochondrial genomes, apparently plays a dominant role in determining the gestational stage at which the adult complement of this DNA is established.

Increased N-myc mRNA expression associated with dibutyryl cyclic AMP induced neuroblastoma differentiation

The N-myc cellular oncogene is frequently amplified and expressed at a high level in neuroectodermal tumor cells such as neuroblastoma and retinoblastoma. We examined N-myc expression in NCB-20 hybrid (N18TG2 neuroblastoma x embryonic Chinese Hamster brain) cells. After five days of culture, cells treated with 1 mM db cAMP show extensive neurite outgrowth and secrete acetylcholinesterase into the media at a level three times higher than untreated control. In situ hybridizations, dot blots, and Northern analyses reveal four- to eight-fold higher levels of N-myc mRNA in the treated, differentiated cells than in the untreated, undifferentiated controls. Our results show that the highly differentiated state is not incompatible with a high level of N-myc mRNA.

N-myc amplification and neuron-specific enolase production of a neuroblastoma cell line and germ cell tumor cell lines

N-myc gene amplification of the gynecological malignant tumor cell lines and a neuroblastoma cell line was studied by the Southern hybridization method along with the production of neuron-specific enolase (NSE) by these cell lines. N-myc amplification and NSE production were observed side by side in three cell lines: neuroblastoma cell line HSNB, endodermal sinus tumor cell line HAEST, and malignant teratoma cell line HUOT. However, N-myc amplification and NSE production disappeared gradually following successive passages of the HAEST and HUOT lines. With respect to the HUOT line, these parameters disappeared along with the cells of nervous origin. N-myc amplification and NSE production were not observed in nine other cell lines.

Proto-oncogene analyses in brain tumors

The present study determined which oncogenes (N-myc, c-myc, v-sis, or v-fos) were amplified and which messenger ribonucleic acids (mRNA's) accumulated in 10 primary human brain tumors of neuroectodermal origin. The tumors included four glioblastomas multiforme, one mixed glioma (astrocytoma grade I and ependymoma), one astrocytoma grade II, one cystic cerebellar astrocytoma, one ependymoma, one ganglioglioma, and one medulloblastoma. The relative amounts of polyadenylated (poly(A)+) RNA's homologous to these genes and their copy number were determined using the RNA and deoxyribonucleic acid blot hybridization techniques. The N-myc and v-sis probes hybridized strongly to the poly(A)+ RNA from the same recurrent glioblastoma with gene amplifications (N-myc 80 copies; v-sis three to four copies). The c-myc probe hybridized strongly to the recurrent medulloblastoma without gene amplification. The amplification or abundant accumulation of mRNA's homologous to their oncogenes may be involved in tumorigenesis or the aggressiveness of these malignant brain tumors of neuroectodermal origin and may be good molecular indicators of an extremely malignant state in these tumors.

Gene expression in implanted rat hepatocytes following retroviral-mediated gene transfer

An hepatocyte transplantation-gene transfer protocol has been developed whereby liver cells containing an expressing NeoR gene can be successfully implanted in vivo. Adult primary cultures of rat hepatocytes, after infection with the retroviral vector N2, were grown on a floating solid support (coated with purified collagen IV) in a serum-free hormonally defined medium designed for hepatocytes that also contained G418. Under these conditions, normal adult hepatocytes expressing the NeoR gene could be grown to high density. The solid supports holding the gene-engineered hepatocytes were then implanted into adult rats into subcutaneous and intraperitoneal sites. After one to two weeks, the supports were removed and shown to still contain the gene-engineered hepatocytes expressing the NeoR gene. These results suggest that cells from solid organs, such as the liver, are potential targets for gene transfer and expression studies in vivo.

Rapid cloning of multiple amplified nucleotide sequences from human neuroblastoma cell lines by phenol emulsion competitive DNA reassociation

A protocol for the rapid cloning of many DNA fragments from an amplified genomic region is described. The procedure is based on a modification of the phenol-emulsion reassociation technique (PERT) previously used to clone DNA fragments missing from a chromosomal deletion [Kunkel et al., Proc. Natl. Acad. Sci. USA 82 (1985) 4778-4782]. The procedure was used to construct recombinant libraries in the plasmid pBR322 which were highly enriched for amplified sequences from two neuroblastoma cell lines, CHP-126 and IMR-32. Many new amplified DNA fragments were isolated from these libraries, indicating that the PERT methodology should be of general use in isolating amplified DNA from other cell lines and tumors.

Differential expression of myc family genes during murine development

The myc family of cellular oncogenes contains three known members. The N-myc and c-myc genes have 5'-noncoding exons, strikingly homologous coding regions, and display similar oncogenic potential in an in vitro transformation assay. The L-myc gene is less well characterized, but shows homology to N-myc and c-myc (ref. 6; also see below). c-myc is expressed in most dividing cells, and deregulated expression of this gene has been implicated in the development of many classes of tumours. In contrast, expression of N-myc has been found only in a restricted set of tumours, most of which show neural characteristics; these include human neuroblastoma, retinoblastoma and small cell lung carcinoma (SCLC). L-myc expression has so far been found only in SCLC. Activated N-myc and L-myc expression has been implicated in oncogenesis; for example, although N-myc expression has been found in all neuroblastomas tested, activated (greatly increased) N-myc expression, resulting from gene amplification, is correlated with progression of the tumour. We now report that high-level expression of N- and L-myc is very restricted with respect to tissue and stage in the developing mouse, while that of c-myc is more generalized. Furthermore, we demonstrate that N-myc is not simply a neuroectoderm-specific gene; both N- and L-myc seem to be involved in the early stages of multiple differentiation pathways. Our findings suggest that differential myc gene expression has a role in mammalian development and that the normal expression patterns of these genes generally predict the types of tumours in which they are expressed or activated.

Human N-myc is closely related in organization and nucleotide sequence to c-myc

N-myc, a cellular gene related to the c-myc proto-oncogene, was originally identified on the basis of its very frequent amplification and overexpression in a restricted set of tumours, most notably human neuroblastomas. That N-myc may have a causal role in the genesis of these tumours is suggested by the observation that in the rat embryo fibroblast co-transformation assay it has a transforming potential similar to that of c-myc. The apparent structural and functional homology of N-myc and c-myc suggests that they may be members of the same protooncogene family. However, despite these apparent similarities, expression of the two genes appears to be dramatically different with respect to tumour specificity, as well as tissue and developmental stage specificity. To further elucidate the common and unique aspects of N-myc and c-myc gene structure and function in normal and transformed cells, we have determined the organization of human N-myc and the nucleotide sequence of its messenger product, and we report here that N-myc and c-myc have a similar intron/exon structure and that their protein products share regions of significant homology.

Association of multiple copies of the N-myc oncogene with rapid progression of neuroblastomas

Eighty-nine patients with untreated primary neuroblastomas were studied to determine the relation between the number of copies of the N-myc oncogene and survival without disease progression. Genomic amplification (3 to 300 copies) of N-myc was detected in 2 of 16 tumors in Stage II, 13 of 20 in Stage III, and 19 of 40 in Stage IV; in contrast, 8 Stage I and 5 Stage IV-S tumors all had 1 copy of the gene (P less than 0.01). Analysis of progression-free survival in all patients revealed that amplification of N-myc was associated with the worst prognosis (P less than 0.0001); the estimated progression-free survival at 18 months was 70 per cent, 30 per cent, and 5 per cent for patients whose tumors had 1, 3 to 10, or more than 10 N-myc copies, respectively. Of 16 Stage II tumors, 2 with amplification metastasized, whereas only 1 of 14 without amplification did so (P = 0.03). Stage IV tumors with amplification progressed most rapidly: nine months after diagnosis the estimated progression-free survival was 61 per cent, 47 per cent, and 0 per cent in patients whose tumors had 1, 3 to 10, or more than 10 copies, respectively (P less than 0.0001). These results suggest that genomic amplification of N-myc may have a key role in determining the aggressiveness of neuroblastomas.

Amplified DNA sequences in cancers

Amplification of genes other than known oncogenes was analyzed using an in-gel DNA renaturation method, in which a mixture of restriction fragments of radioactively labelled tracer DNA and unlabelled driver DNA was electrophoresed and amplified DNA fragments were visualized after two cycles of denaturation and renaturation in the gel. Different DNA fragments were found to be amplified more than 400 fold in NB1, a neuroblastoma cell line, in Y79, a retinoblastoma cell line and in H69, a small cell lung carcinoma cell line, in addition to 120 to 160-fold amplification of N-myc gene in these three cell lines.