In this report, the upstream region of mouse N-myc gene was ligated to pSVPCAT, which carries the simian virus 40 (SV40) promoter and bacterial chloramphenicol acetyltransferase (CAT) gene, and transcriptional activities were examined by CAT and S1 protection assays after transfection of the DNAs into human cervical carcinoma HeLa or neuroblastoma IMR32 cells.
We have used the polymerase chain reaction (PCR) to detect amplification of the MYCN oncogene in neuroblastoma cell lines and to distinguish primary tumors with a single copy from those with MYCN amplification using DNA extracted from frozen sections.
Applying this technique, we followed the metaphase location and interphase position of amplified DNA sequences corresponding to the SAMK, MYC, and MYCN genes in four cell lines derived from human tumors: two gastric carcinoma lines (KATO III and SNU-16), a neuroblastoma (NUB-7), and a neuroepithelioma (NUB-20) line.
In our investigation of 14 neuroblastoma patients, we could demonstrate N-myc gene amplification in the bone marrow of 5 patients with neuroblastoma stage IV disease and in bone marrow infiltration without enrichment of neuroblastoma cells.
To study the regulation of N-myc, we have subcloned fragments of the 5' flanking region of the human N-myc gene upstream of the chloramphenicol acetyl transferase (CAT) reporter gene, and assayed for promoter activity in transient transfections into neuroblastoma and other cell lines.
Our results demonstrate that enhanced MYCN expression confers to neuroblastoma cells the ability to respond to bFGF, possibly by inducing functional FGF receptors.
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.
One, favorable neuroblastoma, is associated with young age and early stage at diagnosis, triploid karyotypes, no 1p abnormalities or N-myc gene amplification, more mature catecholamine synthesis and excretion, and excellent clinical outcome despite no or minimal therapy.
Transfected clones were isolated and found to express the N-myc gene at levels similar to those seen in a tumor cell line (neuroblastoma LA-N-1) which contains an amplified N-myc gene.
We conclude that the immunohistochemical detection of N-myc protein expression is one of the most unfavorable prognostic factors in neuroblastoma patients.
These results suggest that the down-modulation of the MHC class I expression may be associated with the high level of expression and amplification of N-myc gene in the advanced stage of neuroblastoma.
Expression of protein kinase C-alpha (PKC-alpha) and MYCN mRNAs in human neuroblastoma cells and modulation during morphological differentiation induced by retinoic acid.
We assessed tumor cell DNA content (ploidy) and N-myc gene copy number as predictors of long-term disease-free survival in 298 children with neuroblastoma.
Because N-myc protein is thought to have a regulatory role, prolongation of the half-life of this protein may be an important factor in the regulation of growth in NBs which lack N-myc amplification and rapidly progress.
To investigate the interrelationships between these two parameters, tumor samples from 18 patients with neuroblastoma were analyzed for both total DNA and N-myc gene content.
These results demonstrate that enhanced MYCN expression contributes to malignant progression of human neuroblastoma cells, conceivably by stimulating the expression of autocrine growth factor activity.