title: Interrupted E2F1-miR-34c-SCF negative feedback loop by hyper-methylation promotes colorectal cancer cell proliferation.
abstract: Tumour suppressor miR-34c deficiency resulted from hyper-methylation in its promoter is believed to be one of the main causes of colorectal cancer (CRC). Till date, miR-34c has been validated as a direct target of p53; but previous evidence suggested other transcription factor(s) must be involved in miR-34c transcription. In the present study, we in the first place identified a core promoter region (-1118 to -883 bp) of pre-miR-34c which was embedded within a hyper-methylated CpG island. Secondly, E2F1 promoted miR-34c transcription by physical interaction with the miR-34c promoter at site -897 to -889 bp. The transcriptional activating effect of E2F1 on miR-34c was in a p53 independent manner but profoundly promoted in the presence of p53 with exposure to 5-aza-2'-deoxycytidine (DAC). Thirdly, stem cell factor (SCF), a miR-34c target, was specifically reduced upon an introduction of E2F1 which lead to suppression of CRC cell proliferation. The E2F1-suppressed cell proliferation was partially abrogated by additional miR-34c inhibitor, indicating that the anti-proliferation effect of E2F1 was probably through activating miR-34c-SCF axis. Finally, SCF/KIT signalling increased E2F1 production by reducing its proteosomal degradation dependent on PI3K/Akt-GSK3β pathway. In conclusion, our results suggested the existence of E2F1-miR-34c-SCF negative feedback loop which was interrupted by the hyper-methylation of miR-34c promoter in CRC cells and increased cell proliferation.
authors.affiliation: Department of Histology and Embryology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, P.R. China Beijing Key Laboratory of Cancer Invasion and Metastasis Research, Beijing 100069, P.R. China Cancer Institute of Capital Medical University, Beijing 100069, P.R. China.
authors.forename: Shu
authors.initials: S
authors.lastname: Yang
authors.affiliation: Department of Histology and Embryology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, P.R. China Beijing Key Laboratory of Cancer Invasion and Metastasis Research, Beijing 100069, P.R. China Cancer Institute of Capital Medical University, Beijing 100069, P.R. China.
authors.forename: Bo
authors.initials: B
authors.lastname: Wu
authors.affiliation: Department of Histology and Embryology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, P.R. China Beijing Key Laboratory of Cancer Invasion and Metastasis Research, Beijing 100069, P.R. China Cancer Institute of Capital Medical University, Beijing 100069, P.R. China.
authors.forename: Haimei
authors.initials: H
authors.lastname: Sun
authors.affiliation: Department of Histology and Embryology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, P.R. China Beijing Key Laboratory of Cancer Invasion and Metastasis Research, Beijing 100069, P.R. China Cancer Institute of Capital Medical University, Beijing 100069, P.R. China.
authors.forename: Fengqing
authors.initials: F
authors.lastname: Ji
authors.affiliation: Department of Histology and Embryology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, P.R. China Beijing Key Laboratory of Cancer Invasion and Metastasis Research, Beijing 100069, P.R. China Cancer Institute of Capital Medical University, Beijing 100069, P.R. China.
authors.forename: Tingyi
authors.initials: T
authors.lastname: Sun
authors.affiliation: Clinical Research Centre for Autoimmune Liver Disease, Beijing YouAn Hospital, Capital Medical University, Beijing 100069, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Department of Histology and Embryology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, P.R. China Beijing Key Laboratory of Cancer Invasion and Metastasis Research, Beijing 100069, P.R. China Cancer Institute of Capital Medical University, Beijing 100069, P.R. China zhoudeshan2008@163.com.
authors.forename: Deshan
authors.initials: D
authors.lastname: Zhou
mesh_terms: D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism*; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000235:genetics / Q000378:metabolism*; D050687:E2F1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism*; D020218:Response Elements; D015398:Signal Transduction; D019089:Stem Cell Factor / Q000235:genetics / Q000378:metabolism*
chemical_list: D004273:DNA, Neoplasm; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; C522425:MIRN34 microRNA, human; D035683:MicroRNAs; D009363:Neoplasm Proteins; D012334:RNA, Neoplasm; D019089:Stem Cell Factor
keywords: E2F1; colorectal cancer; hyper-methylation; miR-34c; p53; stem cell factor (SCF)