title: Involvement of microRNA-24 and DNA methylation in resistance of nasopharyngeal carcinoma to ionizing radiation.
abstract: Nasopharyngeal carcinoma (NPC) is a malignant tumor originating in the epithelium. Radiotherapy is the standard therapy, but tumor resistance to this treatment reduces the 5-year patient survival rate dramatically. Studies are urgently needed to elucidate the mechanism of NPC radioresistance. Epigenetics--particularly microRNAs (miRNA) and DNA methylation--plays an important role in carcinogenesis and oncotherapy. We used qRT-PCR analysis and identified an miRNA signature from differentially expressed miRNAs. Our objectives were to identify the role of miR24 in NPC tumorigenesis and radioresistance and to identify the mechanisms by which miR24 is regulated. We found that miR24 inhibited NPC cell growth, promoted cell apoptosis, and suppressed the growth of NPC xenografts. We showed that miR24 was significantly downregulated in recurrent NPC tissues. When combined with irradiation, miR24 acted as a radiosensitizer in NPC cells. One of the miR24 precursors was embedded in a CpG island. Aberrant DNA methylation was involved in NPC response to radiotherapy, which linked inactivation of miR24 through hypermethylation of its precursor promoter with NPC radioresistance. Treating NPC cells with the DNA-hypomethylating agent 5-aza-2'-deoxycytidine compensated for the reduced miR24 expression. Together, our findings showed that miR24 was negatively regulated by hypermethylation of its precursor promoter in NPC radioresistance. Our findings defined a central role for miR24 as a tumor-suppressive miRNA in NPC and suggested its use in novel strategies for treatment of this cancer.
authors.affiliation: Department of Pathophysiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, Guangdong, P.R. China. Department of Systems Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Sumei
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Pathophysiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, Guangdong, P.R. China. State Key Laboratory of Oncology in South China, Sun Yat-Sen University, Guangzhou, Guangdong, P.R. China.
authors.forename: Rong
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Department of Systems Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas. Experimental Therapeutics Academic Program and Cancer Biology Program, The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas. fxclaret@mdanderson.org hlyangsums@hotmail.com.
authors.forename: Francois X
authors.initials: FX
authors.lastname: Claret
authors.affiliation: Department of Pathophysiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, Guangdong, P.R. China. fxclaret@mdanderson.org hlyangsums@hotmail.com.
authors.forename: Huiling
authors.initials: H
authors.lastname: Yang
mesh_terms: D000818:Animals; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D002277:Carcinoma; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D016000:Cluster Analysis; D019175:DNA Methylation; D000077209:Decitabine; D004195:Disease Models, Animal; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006657:Histones / Q000378:metabolism; D006801:Humans; D008297:Male; D051379:Mice; D035683:MicroRNAs / Q000235:genetics*; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000235:genetics* / Q000473:pathology / Q000532:radiotherapy; D011836:Radiation Tolerance / Q000235:genetics*; D011839:Radiation, Ionizing; D047368:Tumor Burden / Q000235:genetics / Q000528:radiation effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D006657:Histones; C543845:MIRN24 microRNA, human; D035683:MicroRNAs; D000077209:Decitabine; D001374:Azacitidine