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    Please use this identifier to cite or link to this item: http://ir.cnu.edu.tw/handle/310902800/28546


    標題: DNMT3B Overexpression by Deregulation of FOXO3a-Mediated Transcription Repression and MDM2 Overexpression in Lung Cancer
    作者: Yang, Yi-Chieh
    Tang, Yen-An
    Shieh, Jiunn-Min
    Lin, Ruo-Kai
    Hsu, Han-Shui
    Wang, Yi-Ching
    貢獻者: 通識教育中心
    關鍵字: DNMT3B
    FOXO3a
    MDM2
    Doxorubicin
    Nutlin-3
    Prognosis
    Lung cancer
    日期: 2014-09
    上傳時間: 2015-05-06 21:20:11 (UTC+8)
    出版者: Lippincott Williams & Wilkins
    摘要: Introduction: DNA methyltransferase 3B (DNMT3B) contributes to de novo DNA methylation and its overexpression promotes tumorigenesis. However, whether DNMT3B is upregulated by transcriptional deregulation remains unclear. Methods: We studied the transcriptional repression of DNMT3B by forkhead O transcription factor 3a (FOXO3a) in lung cancer cell, animal, and clinical models. Results: The results of luciferase reporter assay showed that FOXO3a negatively regulated DNMT3B promoter activity by preferentially interacting with the binding element FOXO3a-E (+166 to +173) of DNMT3B promoter. Ectopically overexpressed FOXO3a or combined treatment with doxorubicin to induce FOXO3a nuclear accumulation further bound at the distal site, FOXO3a-P (-249 to -242) by chromatin-immunoprecipitation assay. Knockdown of FOXO3a resulted in an open chromatin structure and high DNMT3B mRNA and protein expression. Abundant FOXO3a repressed DNMT3B promoter by establishing a repressed chromatin structure. Note that FOXO3a is a degradation substrate of MDM2 E3-ligase. Cotreatment with doxorubicin and MDM2 inhibitor, Nutlin-3, further enforced abundant nuclear accumulation of FOXO3a resulting in decrease expression of DNMT3B leading to synergistic inhibition of tumor growth and decrease of methylation status on tumor suppressor genes in xenograft specimens. Clinically, lung cancer patients with DNMT3B high, FOXO3a low, and MDM2 high expression profile correlated with poor prognosis examined by immunohistochemistry and Kaplan-Meier survival analysis. Conclusions: We reveal a new mechanism that FOXO3a transcriptionally represses DNMT3B expression and this regulation can be attenuated by MDM2 overexpression in human lung cancer model. Cotreatment with doxorubicin and Nutlin-3 is a novel therapeutic strategy through epigenetic modulation.
    Appears in Collections:[通識教育中心] 期刊論文

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