title: Epigenetic silencing of microRNA-218 via EZH2-mediated H3K27 trimethylation is involved in malignant transformation of HBE cells induced by cigarette smoke extract.
abstract: Abnormal expression of miRNAs has been implicated in the pathogenesis of human lung cancers, most of which are attributable to cigarette smoke. The mechanisms of action, however, remain obscure. Here, we report that there are decreased expression of miR-218 and increased expression of EZH2 and H3K27me3 during cigarette smoke extract (CSE)-induced transformation of human bronchial epithelial (HBE) cells. Depletion of EZH2 by siRNA or by the EZH2 inhibitor, 3-deazaneplanocin A, attenuated CSE-induced decreases of miR-218 levels and increases of H3K27me3, which epigenetically controls gene transcription, and BMI1, an oncogene. Furthermore, ChIP assays demonstrated that EZH2 and H3K27me3 are enriched at the miR-218-1 promoter in HBE cells exposed to CSE, indicating that EZH2 mediates epigenetic silencing of miR-218 via histone methylation. In addition, miR-218 directly targeted BMI1, through which miR-218 ablates cancer stem cells (CSCs) self-renewal in transformed HBE cells. In CSE-transformed HBE cells, the protein level of Oct-4 and mRNA levels of CD133 and CD44, indicators of the acquisition of CSC-like properties, were reduced by over-expression of miR-218, and over-expression of miR-218 decreased the malignancy of transformed HBE cells. Thus, we conclude that epigenetic silencing of miR-218 via EZH2-mediated H3K27 trimethylation is involved in the acquisition of CSC-like properties and malignant transformation of HBE cells induced by CSE and thereby contributes to the carcinogenesis of cigarette smoke.
authors.affiliation: Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, 211166, Jiangsu, People's Republic of China.|The Key Laboratory of Modern Toxicology, Ministry of Education, School of Public Health, Nanjing Medical University, Nanjing, 211166, Jiangsu, People's Republic of China.
authors.forename: Bairu
authors.initials: B
authors.lastname: Wang
authors.affiliation: Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, 211166, Jiangsu, People's Republic of China.|The Key Laboratory of Modern Toxicology, Ministry of Education, School of Public Health, Nanjing Medical University, Nanjing, 211166, Jiangsu, People's Republic of China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, 211166, Jiangsu, People's Republic of China.|The Key Laboratory of Modern Toxicology, Ministry of Education, School of Public Health, Nanjing Medical University, Nanjing, 211166, Jiangsu, People's Republic of China.
authors.forename: Fei
authors.initials: F
authors.lastname: Luo
authors.affiliation: Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, 211166, Jiangsu, People's Republic of China.|The Key Laboratory of Modern Toxicology, Ministry of Education, School of Public Health, Nanjing Medical University, Nanjing, 211166, Jiangsu, People's Republic of China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Jiangsu Center for Disease Control and Prevention, Nanjing, 210009, Jiangsu, People's Republic of China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Qin
authors.affiliation: Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, 211166, Jiangsu, People's Republic of China.|The Key Laboratory of Modern Toxicology, Ministry of Education, School of Public Health, Nanjing Medical University, Nanjing, 211166, Jiangsu, People's Republic of China.
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Lu
authors.affiliation: Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, 211166, Jiangsu, People's Republic of China.|The Key Laboratory of Modern Toxicology, Ministry of Education, School of Public Health, Nanjing Medical University, Nanjing, 211166, Jiangsu, People's Republic of China.
authors.forename: Wenchao
authors.initials: W
authors.lastname: Xu
authors.affiliation: Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, 211166, Jiangsu, People's Republic of China.|The Key Laboratory of Modern Toxicology, Ministry of Education, School of Public Health, Nanjing Medical University, Nanjing, 211166, Jiangsu, People's Republic of China.
authors.forename: Le
authors.initials: L
authors.lastname: Shi
authors.affiliation: Institute of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, 211166, Jiangsu, People's Republic of China. drqzliu@hotmail.com.|The Key Laboratory of Modern Toxicology, Ministry of Education, School of Public Health, Nanjing Medical University, Nanjing, 211166, Jiangsu, People's Republic of China. drqzliu@hotmail.com.
authors.forename: Qizhan
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Jiangsu Center for Disease Control and Prevention, Nanjing, 210009, Jiangsu, People's Republic of China. xiangquanyongcdc@163.com.
authors.forename: Quanyong
authors.initials: Q
authors.lastname: Xiang
mesh_terms: D001980:Bronchi / Q000166:cytology; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000235:genetics*; D000071221:Enhancer of Zeste Homolog 2 Protein / Q000235:genetics / Q000378:metabolism*; D044127:Epigenesis, Genetic / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006657:Histones / Q000378:metabolism; D006801:Humans; D008175:Lung Neoplasms / Q000139:chemically induced / Q000473:pathology; D008239:Lysine / Q000378:metabolism; D008745:Methylation / Q000187:drug effects; D035683:MicroRNAs / Q000235:genetics*; D048054:Mitogen-Activated Protein Kinase 7 / Q000235:genetics / Q000378:metabolism; D012907:Smoking / Q000009:adverse effects*
chemical_list: D006657:Histones; C547471:MIRN218 microRNA, human; D035683:MicroRNAs; C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein; C481581:MAPK7 protein, human; D048054:Mitogen-Activated Protein Kinase 7; D008239:Lysine
keywords: Cancer stem cell-like properties; Carcinogenesis; Cigarette smoke extract (CSE); Epigenetic silencing; miR-218