Myc proteins have documented oncogenic potential and similar DNA binding properties. Studies indicate that inhibiting N-myc gene expression results in either the suppression of cell proliferation or the induction of differentiation and/or apoptosis. The oncogene v-myc was first identified as the transforming gene of the avian myelocytomatosis retrovirus MC29 (hence the name myc). Five members of the human myc family of nucleus-associated phosphoproteins (c-, N-, L-, B-, and R-myc) are currently known. The N-myc gene gives rise to at least two nuclear phosphoproteins of 64kD and 67kD with a relatively short half life (30 minutes) in vivo and exhibit DNA binding properties in vitro. Amplification of the N-myc gene has been reported in human neuroblastomas and cell lines. For example, amplification of the N-Myc gene is associated with a poor prognosis in some neuroblastomas. Myc proteins are potent transcriptional activators that regulate gene expression by forming heterodimers with Max and binding specifically to CAC(G/A)TG sequence motifs in target genes. Max proteins can also form homodimers that recognize the same DNA motif as the Myc/Max heterodimer. Max homodimers, however, repress transcription. The extent of N-myc amplification correlates well with the stage of neuroblastoma disease.