There may be a close relationship between myc oncogenes and carcinogenesis of human neuroblastoma. In previous studies

we were able to induce differentiation of certain neuroblastoma cell lines with NGF. In order to study gene regulation during differentiation

N-myc and c-myc cDNA probe were hybridized with RNA extracted from different cell lines before and after NGF treatment. It was found that cell lines which expressed N-myc did not express c-myc while those with c-myc did not express N-myc except for SHEP cell line which had neither c-myc nor N-myc expression. In NGF-induced differentiated neuroblastoma cells

c-myc oncogene was down-regulated in comparison with the control samples. The time course of c-myc down-regulation was concomitant with the appearance of morphological differentiation. In situ hybridization also showed remarkable reduction of c-myc oncogene expression in NGF-induced differentiated cells as compared with the untreated control cells. These results indicate that down-regulation of c-myc oncogene may be a key event during NGF-induced differentiation and overexpression of c-myc oncogene may

at least partially

be responsible for the genesis of neuroblastoma.