title: MYCN and MYC regulate tumor proliferation and tumorigenesis directly through BMI1 in human neuroblastomas.
abstract: The BMI1 gene is overexpressed in ≈ 90% of human neuroblastomas. However, little is known about the regulation of BMI1 expression. Using microarray and immunohistochemical analysis, we show that BMI1 expression correlated with MYCN levels in MYCN-amplified human neuroblastomas, and with MYC levels in the MYCN-nonamplified group. We further demonstrated that BMI1 is a direct target gene of MYCN/MYC in 3 neuroblastoma cell lines: BE (2)-C, LAN1, and SH-SY5Y. Overexpression of MYCN or MYC transactivated the BMI1 promoter and up-regulated BMI1 gene expression. shRNA-mediated knockdown of MYCN or MYC decreased BMI1 gene expression. Chromatin immunoprecipitation and point-mutation assays revealed that both MYCN and MYC bind to the E-box within the BMI1 promoter. Overexpression of BMI1, MYCN, and MYC independently increased both cell proliferation and tumor growth. Conversely, specific inhibition of BMI1, MYCN, and MYC decreased tumor cell proliferation and tumor growth. Interestingly, BMI1 suppression in MYCN/MYC-overexpressing cells resulted in significantly greater inhibition compared to that in mock-transduced and parental cells. Our results indicate that MYCN and MYC regulate BMI1 gene expression at the transcriptional level and that dysregulation of the BMI1 gene mediated by MYCN or MYC overexpression, confers increased cell proliferation during neuroblastoma genesis and tumor progression.
authors.affiliation: Department of Neurology, Memorial Sloan Kettering Cancer Center, 1275 York Ave., New York, NY 10065, USA.
authors.forename: Ruimin
authors.initials: R
authors.lastname: Huang
authors.forename: Nai-Kong V
authors.initials: NK
authors.lastname: Cheung
authors.forename: Jelena
authors.initials: J
authors.lastname: Vider
authors.forename: Irene Y
authors.initials: IY
authors.lastname: Cheung
authors.forename: William L
authors.initials: WL
authors.lastname: Gerald
authors.forename: Satish K
authors.initials: SK
authors.lastname: Tickoo
authors.forename: Eric C
authors.initials: EC
authors.lastname: Holland
authors.forename: Ronald G
authors.initials: RG
authors.lastname: Blasberg
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D005260:Female; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D016259:Genes, myc; D006801:Humans; D007223:Infant; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D000071447:N-Myc Proto-Oncogene Protein; D009368:Neoplasm Transplantation; D009447:Neuroblastoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D015513:Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D063150:Polycomb Repressive Complex 1; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation; D014183:Transplantation, Heterologous
chemical_list: C069077:BMI1 protein, human; C489427:MYC protein, human; C459801:MYCN protein, human; D000071447:N-Myc Proto-Oncogene Protein; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D011518:Proto-Oncogene Proteins; D016271:Proto-Oncogene Proteins c-myc; D034741:RNA, Small Interfering; D012097:Repressor Proteins; D063150:Polycomb Repressive Complex 1