title: HDM2 impairs Noxa transcription and affects apoptotic cell death in a p53/p73-dependent manner in neuroblastoma.
abstract: HDM2, a human homologue of MDM2, is a major negative regulator of p53 function, and increased expression of HDM2 by its promoter polymorphism SNP309 resulted in p53 inactivation and an increased risk of several tumours, including neuroblastoma (NB). Herein, we show that increased expression of HDM2 is related to a worse prognosis in MYCN-amplified NB patients. HDM2 plays an important role in the expression of Noxa, a pro-apoptotic molecule of the Bcl-2 family, which induces NB cell apoptotic death after doxorubcin (Doxo) treatment. Knockdown of HDM2 by siRNA resulted in the upregulation of Noxa at mRNA/protein levels and improved the sensitivity of Doxo-resistant NB cells, although these were not observed in p53-mutant NB cells. Noxa-knockdown abolished the recovered Doxo-induced cell death by HDM2 reduction. Intriguingly, resistance to Doxo was up-regulated by over-expression of HDM2 in Doxo-sensitive NB cells. By HDM2 expression, p53 was inactivated but its degradation was not accelerated, suggesting that p53 was degraded in a proteasome-independent manner in NB cells; downstream effectors of p53, p21(Cip1/Waf1) and Noxa were suppressed by HDM2. Noxa transcription was considerably regulated by both p53 and p73 in NB cells. Furthermore, in vivo binding of p53 and p73 to Noxa promoter was suppressed and Noxa promoter activation was inhibited by HDM2. Taken together, our results may indicate that the HDM2-related resistance to chemotherapeutic drugs of NB is regulated by p53/p73-dependent Noxa expression in NB.
authors.affiliation: Division of Biochemistry and Molecular Carcinogenesis, Chiba Cancer Center Research Institute, 666-2 Nitona, Chuoh-ku, Chiba 260-8717, Japan.
authors.forename: Yun
authors.initials: Y
authors.lastname: Shi
authors.forename: Hisanori
authors.initials: H
authors.lastname: Takenobu
authors.forename: Kenji
authors.initials: K
authors.lastname: Kurata
authors.forename: Yohko
authors.initials: Y
authors.lastname: Yamaguchi
authors.forename: Ryu
authors.initials: R
authors.lastname: Yanagisawa
authors.forename: Miki
authors.initials: M
authors.lastname: Ohira
authors.forename: Kenichi
authors.initials: K
authors.lastname: Koike
authors.forename: Akira
authors.initials: A
authors.lastname: Nakagawara
authors.forename: Ling Ling
authors.initials: LL
authors.lastname: Jiang
authors.forename: Takehiko
authors.initials: T
authors.lastname: Kamijo
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000627:therapeutic use; D017209:Apoptosis / Q000502:physiology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004317:Doxorubicin / Q000627:therapeutic use; D019008:Drug Resistance, Neoplasm; D006801:Humans; D007150:Immunohistochemistry; D053208:Kaplan-Meier Estimate; D009447:Neuroblastoma / Q000188:drug therapy / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D051736:Proto-Oncogene Proteins c-mdm2 / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014407:Tumor Cells, Cultured; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D000903:Antibiotics, Antineoplastic; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C498702:PMAIP1 protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; C000606460:TP73 protein, human; D014157:Transcription Factors; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D004317:Doxorubicin; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2