title: DNA methylome analysis identifies epigenetic silencing of FHIT as a determining factor for radiosensitivity in oral cancer: an outcome-predicting and treatment-implicating study.
abstract: Radioresistance is still an emerging problem for radiotherapy of oral cancer. Aberrant epigenetic alterations play an important role in cancer development, yet the role of such alterations in radioresistance of oral cancer is not fully explored. Using a methylation microarray, we identified promoter hypermethylation of FHIT (fragile histidine triad) in radioresistant OML1-R cells, established from hypo-fractionated irradiation of parental OML1 radiosensitive oral cancer cells. Further analysis confirmed that transcriptional repression of FHIT was due to promoter hypermethylation, H3K27me3 and overexpression of methyltransferase EZH2 in OML1-R cells. Epigenetic interventions or depletion of EZH2 restored FHIT expression. Ectopic expression of FHIT inhibited tumor growth in both in vitro and in vivo models, while also resensitizing radioresistant cancer cells to irradiation, by restoring Chk2 phosphorylation and G2/M arrest. Clinically, promoter hypermethylation of FHIT inversely correlated with its expression and independently predicted both locoregional control and overall survival in 40 match-paired oral cancer patient samples. Further in vivo therapeutic experiments confirmed that inhibition of DNA methylation significantly resensitized radioresistant oral cancer cell xenograft tumors. These results show that epigenetic silencing of FHIT contributes partially to radioresistance and predicts clinical outcomes in irradiated oral cancer. The radiosensitizing effect of epigenetic interventions warrants further clinical investigation.
authors.affiliation: Department of Radiation Oncology, Buddhist Dalin Tzu Chi General Hospital, Taiwan, ROC.|School of Medicine, Tzu Chi University, Hualien, Taiwan, ROC.|Institute of Molecular Biology, National Chung Cheng University, Min-Hsiung, Chia-Yi, Taiwan, ROC.
authors.forename: Hon-Yi
authors.initials: HY
authors.lastname: Lin
authors.affiliation: Department of Radiation Oncology, Buddhist Dalin Tzu Chi General Hospital, Taiwan, ROC.|School of Medicine, Tzu Chi University, Hualien, Taiwan, ROC.
authors.forename: Shih-Kai
authors.initials: SK
authors.lastname: Hung
authors.affiliation: Department of Radiation Oncology, Buddhist Dalin Tzu Chi General Hospital, Taiwan, ROC.|School of Medicine, Tzu Chi University, Hualien, Taiwan, ROC.
authors.forename: Moon-Sing
authors.initials: MS
authors.lastname: Lee
authors.affiliation: Department of Radiation Oncology, Buddhist Dalin Tzu Chi General Hospital, Taiwan, ROC.|School of Medicine, Tzu Chi University, Hualien, Taiwan, ROC.
authors.forename: Wen-Yen
authors.initials: WY
authors.lastname: Chiou
authors.affiliation: Department of Oral and Maxillofacial Surgery, Buddhist Dalin Tzu Chi General Hospital, Taiwan, ROC.|School of Medicine, Tzu Chi University, Hualien, Taiwan, ROC.|Institute of Oral Medicine, National Cheng Kung University, Tainan, Taiwan, ROC.
authors.forename: Tze-Ta
authors.initials: TT
authors.lastname: Huang
authors.affiliation: Department of Anatomic Pathology, Buddhist Dalin Tzu Chi General Hospital, Taiwan, ROC.|School of Medicine, Tzu Chi University, Hualien, Taiwan, ROC.
authors.forename: Chih-En
authors.initials: CE
authors.lastname: Tseng
authors.affiliation: Department of Anatomic Pathology, Buddhist Dalin Tzu Chi General Hospital, Taiwan, ROC.|School of Medicine, Tzu Chi University, Hualien, Taiwan, ROC.
authors.forename: Liang-Yu
authors.initials: LY
authors.lastname: Shih
authors.affiliation: Department of Radiation Oncology, Buddhist Dalin Tzu Chi General Hospital, Taiwan, ROC.|School of Medicine, Tzu Chi University, Hualien, Taiwan, ROC.|Institute of Molecular Biology, National Chung Cheng University, Min-Hsiung, Chia-Yi, Taiwan, ROC.
authors.forename: Ru-Inn
authors.initials: RI
authors.lastname: Lin
authors.affiliation: Institute of Molecular Biology, National Chung Cheng University, Min-Hsiung, Chia-Yi, Taiwan, ROC.|Department of Life Science, National Chung Cheng University, Min-Hsiung, Chia-Yi, Taiwan, ROC.
authors.forename: Jora M J
authors.initials: JM
authors.lastname: Lin
authors.affiliation: Institute of Molecular Biology, National Chung Cheng University, Min-Hsiung, Chia-Yi, Taiwan, ROC.|Department of Life Science, National Chung Cheng University, Min-Hsiung, Chia-Yi, Taiwan, ROC.
authors.forename: Yi-Hui
authors.initials: YH
authors.lastname: Lai
authors.affiliation: Institute of Molecular Biology, National Chung Cheng University, Min-Hsiung, Chia-Yi, Taiwan, ROC.|Department of Life Science, National Chung Cheng University, Min-Hsiung, Chia-Yi, Taiwan, ROC.
authors.forename: Chia-Bin
authors.initials: CB
authors.lastname: Chang
authors.affiliation: Department of Radiation Oncology, Buddhist Dalin Tzu Chi General Hospital, Taiwan, ROC.
authors.forename: Feng-Chun
authors.initials: FC
authors.lastname: Hsu
authors.affiliation: Department of Radiation Oncology, Buddhist Dalin Tzu Chi General Hospital, Taiwan, ROC.
authors.forename: Liang-Cheng
authors.initials: LC
authors.lastname: Chen
authors.affiliation: Department of Radiation Oncology, Buddhist Dalin Tzu Chi General Hospital, Taiwan, ROC.
authors.forename: Shiang-Jiun
authors.initials: SJ
authors.lastname: Tsai
authors.affiliation: Department of Hematology-Oncology, Buddhist Dalin Tzu Chi General Hospital, Taiwan, ROC.|School of Medicine, Tzu Chi University, Hualien, Taiwan, ROC.
authors.forename: Yu-Chieh
authors.initials: YC
authors.lastname: Su
authors.affiliation: Department of Hematology-Oncology, Buddhist Dalin Tzu Chi General Hospital, Taiwan, ROC.|School of Medicine, Tzu Chi University, Hualien, Taiwan, ROC.
authors.forename: Szu-Chi
authors.initials: SC
authors.lastname: Li
authors.affiliation: Department of Hematology-Oncology, Buddhist Dalin Tzu Chi General Hospital, Taiwan, ROC.|School of Medicine, Tzu Chi University, Hualien, Taiwan, ROC.
authors.forename: Hung-Chih
authors.initials: HC
authors.lastname: Lai
authors.affiliation: Department of Radiation Oncology, Buddhist Tzu Chi General Hospital, Hualien, Taiwan, ROC.|School of Medicine, Tzu Chi University, Hualien, Taiwan, ROC.
authors.forename: Wen-Lin
authors.initials: WL
authors.lastname: Hsu
authors.affiliation: Department of Radiation Oncology, Buddhist Tzu Chi General Hospital, Hualien, Taiwan, ROC.|School of Medicine, Tzu Chi University, Hualien, Taiwan, ROC.
authors.forename: Dai-Wei
authors.initials: DW
authors.lastname: Liu
authors.affiliation: Institute of Molecular Biology, National Chung Cheng University, Min-Hsiung, Chia-Yi, Taiwan, ROC.|Department of Life Science, National Chung Cheng University, Min-Hsiung, Chia-Yi, Taiwan, ROC.
authors.forename: Chien-Kuo
authors.initials: CK
authors.lastname: Tai
authors.affiliation: Institute of Molecular Biology, National Chung Cheng University, Min-Hsiung, Chia-Yi, Taiwan, ROC.|Department of Life Science, National Chung Cheng University, Min-Hsiung, Chia-Yi, Taiwan, ROC.
authors.forename: Shu-Fen
authors.initials: SF
authors.lastname: Wu
authors.affiliation: Institute of Molecular Biology, National Chung Cheng University, Min-Hsiung, Chia-Yi, Taiwan, ROC.Department of Life Science, National Chung Cheng University, Min-Hsiung, Chia-Yi, Taiwan, ROC.Human Epigenomics Center, National Chung Cheng University, Min-Hsiung, Chia-Yi, Taiwan, ROC.
authors.forename: Michael W Y
authors.initials: MW
authors.lastname: Chan
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D045744:Cell Line, Tumor; D019175:DNA Methylation; D000071221:Enhancer of Zeste Homolog 2 Protein; D044127:Epigenesis, Genetic; D005260:Female; D020868:Gene Silencing; D057809:HEK293 Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008745:Methylation; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008875:Middle Aged; D009062:Mouth Neoplasms / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy*; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D017063:Outcome Assessment, Health Care / Q000379:methods; D063151:Polycomb Repressive Complex 2 / Q000235:genetics / Q000378:metabolism; D011379:Prognosis; D011836:Radiation Tolerance / Q000235:genetics*; D047368:Tumor Burden / Q000235:genetics / Q000528:radiation effects; D023041:Xenograft Model Antitumor Assays / Q000379:methods*; D000099170:Bis(5'-adenosyl)triphosphatase
chemical_list: D017766:Acid Anhydride Hydrolases; D000071221:Enhancer of Zeste Homolog 2 Protein; D006657:Histones; D009363:Neoplasm Proteins; D063151:Polycomb Repressive Complex 2; D000099170:Bis(5'-adenosyl)triphosphatase; C498409:EZH2 protein, human