MYCN amplification strongly correlates with unfavorable outcomes in patients with neuroblastoma. The aim of this study was to investigate the role of MYCN in neuroblastoma cell differentiation and apoptosis. We used the technique of RNA interference to inhibit MYCN gene expression in neuroblastoma cells with variable expression of MYCN. Our results showed that inhibition of MYCN gene expression in MYCN amplified cells induced apoptosis and suppressed cell growth; neuronal differentiation also occurred after MYCN gene silencing. Moreover, N-myc downregulation was associated with decreased Bcl-xL protein levels and caspase-3 activation. These data show that small interfering RNA directed to MYCN, which plays a crucial role in neuroblastoma cell survival, may provide a potential novel therapeutic option for aggressive neuroblastomas. (c) 2006 Elsevier Inc. All rights reserved.