p53 is a direct transcriptional target of MYCN in neuroblastoma.
MYCN amplification occurs in approximately 25% of neuroblastomas, where it is associated with rapid tumor progression and poor prognosis. MYCN plays a paradoxical role in driving cellular proliferation and inducing apoptosis. Based on observations of nuclear p53 accumulation in neuroblastoma, we hypothesized that MYCN may regulate p53 in this setting. Immunohistochemical analysis of 82 neuroblastoma tumors showed an association of high p53 expression with MYCN expression and amplification. In a panel of 5 MYCN-amplified and 5 nonamplified neuroblastoma cell lines, and also in the Tet21N-regulatable MYCN expression system, we further documented a correlation between the expression of MYCN and p53. In MYCN-amplified neuroblastoma cell lines, MYCN knockdown decreased p53 expression. In Tet21N MYCN+ cells, higher levels of p53 transcription, mRNA, and protein were observed relative to Tet21N MYCN- cells. In chromatin immunoprecipitation and reporter gene assays, MYCN bound directly to a Myc E-Box DNA binding motif located close to the transcriptional start site within the p53 promoter, where it could initiate transcription. E-Box mutation decreased MYCN-driven transcriptional activation. Microarray analysis of Tet21N MYCN+/- cells identified several p53-regulated genes that were upregulated in the presence of MYCN, including MDM2 and PUMA, the levels of which were reduced by MYCN knockdown. We concluded that MYCN transcriptionally upregulates p53 in neuroblastoma and uses p53 to mediate a key mechanism of apoptosis.
Northern Institute for Cancer Research, Newcastle University, Department of Cellular Pathology, Royal Victoria Infirmary, Newcastle upon Tyne NE2 4H, United Kingdom.
Lindi
L
Chen
Nunzio
N
Iraci
Samuele
S
Gherardi
Laura D
LD
Gamble
Katrina M
KM
Wood
Giovanni
G
Perini
John
J
Lunec
Deborah A
DA
Tweddle
D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D001932:Brain Neoplasms / Q000235:genetics* / Q000378:metabolism; D005784:Gene Amplification; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D016158:Genes, p53; D006801:Humans; D000071447:N-Myc Proto-Oncogene Protein; D009447:Neuroblastoma / Q000235:genetics* / Q000378:metabolism; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis; D015513:Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000502:physiology; D034741:RNA, Small Interfering / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
C459801:MYCN protein, human; D000071447:N-Myc Proto-Oncogene Protein; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53