The biological effects of antisense N-myc expression in human neuroblastoma

Although N-myc amplification and overexpression are believed to play an important role in determining the clinical behavior of neuroblastoma (NB), the exact function of N-myc in NB cell growth and differentiation remains unknown. To better understand the function of N-myc, an established human NB cell line was transfected with N-myc antisense (AS) complementary DNA in an effort to down-regulate N-myc gene expression. Five clones expressing AS N-myc RNA have been maintained in culture for over 2 years. Compared to control cells, a 30-69% decrease in the quantity of N-myc protein was demonstrated by Western blot analysis in 4 of the 5 AS clones. All 5 of the AS clones exhibited a 50-75% decrease in colony formation in soft agar assays compared to control cells. In addition, all 5 AS clones expressed a 3.2-kilobase protein kinase C-alpha transcript, whereas this message was not detected by Northern blot analysis in any of the control clones. These results suggest that N-myc may play an important role in NB cell growth and that antisense N-myc expression is associated with an induction of protein kinase C-alpha RNA expression. Further characterization of the AS clones may provide insight into the function of N-myc and may thus lead to a better understanding of the role that N-myc plays in determining the clinical behavior of this childhood neoplasm.