Effect of forced N-myc gene expression on src gene expression in neuroblastoma cells

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NB69N which is a clonal subline of neuroblastoma cell line NB69, has a neuroblastic characteristic and an ability to differentiate by retinoic acid. S1 nuclease protection assay showed that NB69N expressed not only nonneuronal c-src but neuronal c-srcN1 and c-srcN2 mRNA.Because NB69N cell has a single copy of N-myc gene and does not express N-myc mRNA, we introduced N-myc expression vector into the NB69N cells by an electroporation method. We cloned 7 N-myc transfectants (NB69N41 - 47) and one control transfectant NB69NR.In 7 N-myc transfectants, the exogenous N-myc DNA was integrated in genomic DNA, and N-myc mRNA and protein products from the introduced N-myc were expressed. NB69N cells had no advantage of growth activity in a normal culture medium, but acquired a resistance to serum starvation. Furthermore, NB69N47 cells were able to form 6 times colonies to compare with NB69NR in soft agar. No difference of c-src mRNA splicing and expression levels was observed between NB69N47 and NB69NR by S1 nuclease protection assays. The forced expression of N-myc gene possibly conferred a malignant potential to the neuroblastoma cells independent of the c-src mRNA expression.