title: The MYCN enigma: significance of MYCN expression in neuroblastoma.
abstract: MYCN amplification strongly predicts adverse outcome of neuroblastoma. However, the significance of MYCN expression in the clinical and biological behavior of neuroblastoma has been unclear. To address this question, we first examined the expression of MYCN in combination with TrkA (a favorable prognostic indicator of neuroblastoma) in 91 primary neuroblastoma by quantitative reverse transcription-PCR and investigated the relationship among patient survival, MYCN, and TrkA expressions. Three subsets of neuroblastoma were defined based on MYCN and TrkA expression. Neuroblastoma expressing the highest level of MYCN but little TrkA were MYCN-amplified cases, which had a 5-year survival of 9.3%. Interestingly, MYCN and TrkA expression showed a linear correlation (r = 0.5664, P < 0.00005) in neuroblastoma lacking MYCN amplification, and the 5-year survival of neuroblastoma patients with low MYCN and low TrkA expressions was 63.7%, whereas those with high expression of both had a 5-year survival of 88.1% (P < 0.00005). This nonlinear distribution of disease outcome relative to MYCN expression in neuroblastoma explains why MYCN expression is not predictive of neuroblastoma disease outcome by dichotomous division of the neuroblastoma cohort. However, high-level MYCN expression is associated with favorable outcome in neuroblastoma lacking MYCN amplification. Furthermore, forced expression of MYCN significantly suppresses growth of neuroblastoma cells lacking MYCN amplification by inducing apoptosis and enhancing favorable neuroblastoma gene expression. Collectively, these data suggest that high-level MYCN expression in neuroblastoma lacking MYCN amplification results in a benign phenotype. Thus, the high MYCN expression confers the opposite biological consequence in neuroblastoma, depending on whether or not MYCN is amplified.
authors.affiliation: AFLAC Cancer Center, Department of Pediatrics and Children's Healthcare of Atlanta, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: Xao X
authors.initials: XX
authors.lastname: Tang
authors.forename: Huaqing
authors.initials: H
authors.lastname: Zhao
authors.forename: Bing
authors.initials: B
authors.lastname: Kung
authors.forename: David Y
authors.initials: DY
authors.lastname: Kim
authors.forename: Sakeenah L
authors.initials: SL
authors.lastname: Hicks
authors.forename: Susan L
authors.initials: SL
authors.lastname: Cohn
authors.forename: Nai-Kong
authors.initials: NK
authors.lastname: Cheung
authors.forename: Robert C
authors.initials: RC
authors.lastname: Seeger
authors.forename: Audrey E
authors.initials: AE
authors.lastname: Evans
authors.forename: Naohiko
authors.initials: N
authors.lastname: Ikegaki
mesh_terms: D000367:Age Factors; D045744:Cell Line, Tumor; D015331:Cohort Studies; D005784:Gene Amplification; D006801:Humans; D000071447:N-Myc Proto-Oncogene Protein; D009367:Neoplasm Staging; D009447:Neuroblastoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000235:genetics; D015513:Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics; D011379:Prognosis; D020917:Receptor, trkA / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C459801:MYCN protein, human; D000071447:N-Myc Proto-Oncogene Protein; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D020917:Receptor, trkA